surface dressing manual - may 2005

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Government of the Republic of Ghana

Ministry of Road Transport

SURFACE DRESSING MANUAL

May 2005

First Edition

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Ministry of Road Transport Surface Dr essing Manual 1

TABLE OF CONTENTS

1. INTRODUCTION 1

1.1 SCOPE 1

1.2 SURFACE DRESSING 1

1.3 THE GHANA NETWORK 1

1.4 SURFACE DRESSED PAVEMENTS 1

1.5 RESEALING 3

2. BITUMINOUS MATERIALS 4

2.1 GENERAL 4 Description 4 Types of Bitumen Binders 4 Selection of Type and Grade 4 Bitumen in Ghana 4 Viscosity 5 Methods to Change Viscosity 5 Polymer Modified Bitumen (PMB) 5

2.2 BITUMEN 6 Base Crudes 6 Production 6 Standard Classification 6 Specification Requirements 6 Physical Properties of Bitumen 7

2.3 CUTBACK BITUMEN 10 Production 10 Grades and Applications of Cutback in Ghana 10 Setting Up 10

2.4 BITUMEN EMULSION 12 Description 12 Types 12 Composition 13 Production 13 Standard Grades 13 Special Products 14 Specification 14 Breaking of an Emulsion 14 Handling and Storage 16 Mixing Emulsions 16 Field Behaviour 16 Co-efficient of Expansion 17

2.5 POLYMER MODIFIED BINDERS (PMB’s) 17 General 17 Adhesion and Cohesion Characteristics 18

2.6 ADDITIVES 18 General 18

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Cutter Oil 18 Adhesion Agent 18

3. CHIPPINGS 19

3.1 GENERAL 19 Source Rock 19 Types of Chippings in Ghana 19

3.2 CHIPPING REQUIREMENTS 19 Material and Shape Requirements 19 Wearing Qualities 19 Adhesion 20 Shape 20 Grading 22 One Sized Chippings 22 Average Least Dimension (ALD) 23

3.3 PRECOATING OF CHIPPINGS 25 General 25 Precoating Materials 25

3.4 GEOTEXTILES 26 General 26 Choice of Geotextile 26

4. TYPES OF TREATMENT 27

4.1 GENERAL 27

4.2 CLASSIFICATION OF TREATMENTS 27 Initial treatments 27 Seals 28 Reseals 28 Types of Seals and Reseals 29 Other Treatments 29

5. DESIGN 30

5.1 GENERAL 30 Definitions 30

5.2 DESIGN OF PRIMES 30 General 30 Design Procedure 31 Application Rates 31

5.3 DESIGN OF PRIMERSEALS 34 General 34 Design Procedure 34

5.4 DESIGN OF SEALS AND RESEALS 38 General 38 Single Application Seals 38 Double Application Seals 38 Binder 39 Chipping Size 39

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Chipping ALD 39 Curing of Primerseals 39 Seal and Reseal Design Procedure 40 Chipping Design Procedures 42 Design Calculation Sheet 43

5.5 DESIGN OF BITUMEN EMULSION SEALS 48 General 49 Binder Design – Primersealing 49 Binder Design –Seals and Reseals 49 Emulsion Calculations 49 Maximum Allowable Rates 50 Design Calculation Sheet 50 Chipping Design Procedures 50

5.6 DESIGN EXAMPLES 52 Primerseal 52 Seal 53 Double Seal – Hot Applied Bitumen 56

5.7 DESIGN SHEETS 59 Prime Design 59 Primerseal Design for Cutback Bitumen 60 Primerseal Design for Bitumen Emulsion ( 70% Bitumen) 60 Seal and Reseal Design for Hot Applied Bitumen Binder 61 Double Seal Design for Hot Applied Bitumen Binder 62 Seal and Reseal Design for Bitumen Emulsion 64

5.8 DETERMINING AVERAGE LEAST DIMENSION (ALD) 65 General 65 Apparatus 65 Sampling 65 Procedure 65 Calculation 66

5.9 SAND TEXTURE TEST 68 Equipment 68 Test Sites 68 Test Procedure 68 Calculate Surface Texture Depth (T) 69

5.10 BALL PENETRATION TEST 71 Definitions 71 Apparatus 71 Procedure 71

5.11 RESISTANCE TO STRIPPING OF CHIPPINGS 74 Apparatus 75 Test Samples 76 Preparation Of Test Samples 76 Test Procedure 77 Calculations 78 Reporting 79

6. CONSTRUCTION PRACTICE 80

6.1 PREPARATIONS FOR SEALING 80 General 80 Inspections 80

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Site Preparation 81 Supply of Binder 81 Supply and Precoating of Chippings 81 Sampling of Chippings 84 Plant Requirements 84 Spray Gang 85 Traffic Control Strategy 85 Job Instructions 86 Repairing Pavement before Sealing 86

6.2 HANDLING HOT BITUMINOUS MATERIALS 87 General 87 Transferring Material 87 Heating 88 Mixing Bituminous Materials 88 Storage 92

6.3 PREPARATION OF PAVEMENT SURFACE 94 General 94 Primers and Primerseals 94 Seals and Reseals 95

6.4 SPRAYING OPERATIONS 95 Setting Out 96 Spray Width 96 Quantity of Binder to be Sprayed 96 Loading the Distributor 96 Spraying 97 Spray Nozzles 97 Measurement of Binder Quantity 97 Binder Temperature 97 Traffic Control 97 Cut Off Paper 97 Positioning the Distributor and Chipping Trucks 97 Commence Spraying 98 Remove Cut Off Paper 98 Determine Binder Application Rate 98 Overlap Longitudinal Joints 99

6.5 CHIPPING OPERATIONS 99 Loading 99 Spreading 99 Rolling Chippings 101 Sweeping 102

6.6 TRAFFIC CONTROL 103 General 103 Spraying Operation 104 Protection of New Bituminous Seals 104

6.7 PRIMING 104 Spraying Temperature 104 Primer Set Up 104 Covering Primes 105 After Care 105

6.8 PRIMERSEALING 105 Spraying Primerbinder 105 Trafficking the Primerseal 106

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6.9 SEALING AND RESEALING 106 Curing of Primes and Primerseals 106 Spraying Binder 106 Trafficking Seals and Reseals 106 After Care 106

6.10 EMULSION SEALING AND RESEALING 107 General 107 Type of Emulsion 107 Precoating Chippings 108 Pavement Preparation 108 Heating Emulsion 108 Spraying 108 Chip Spreading 108 Scatter Coat 108 Rolling 108 Traffic on the Fresh Seal 109 Sweeping 109

6.11 SITE INSPECTION SHEETS 110 Site Visit Checklist 110 Surface Texture Assessment 112

6.12 DAILY SPRAY RECORD SHEET 113

6.13 CHECK SHEET FOR TRAY TESTING BITUMEN SPRAY RATE 113

7. MAJOR PLANT ITEMS 115

7.1 GENERAL 115

7.2 BITUMEN STORAGES AND ROAD TANKERS 115

7.3 BITUMEN DISTRIBUTOR 115 Calibration 116 Spraying Certificate and Table 117 Spraying Jets 117

7.4 CHIPPING LOADER 121

7.5 CHIPPING SPREADERS 121

7.6 ROLLERS 121

7.7 BROOM 122

8. FAILURES AND REMEDIES 123

8.1 GENERAL 123

8.2 DEFECTS IN TREATMENTS 123 Initial Treatments 123 Retreatments 124

8.3 REMEDIES 124 Priming 124 Primersealing 124 Sealing 125

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9. TRAFFIC MANAGEMENT 127

9.1 GENERAL 127 Basic Requirements 127

9.2 SIGNING THE WORKSITE 127 Planning 127 Design 128 Installation 128 Operation 129 Removal 129

9.3 TRAFFIC CONTROLLERS 130 Functions of a Traffic Controller 130 Equipment 130 Instructions 130 Approach Tapers 131

10. SAFETY 134

10.1 GENERAL 134 Storage and Blending Areas 134

10.2 PERSONNEL 135 Manual Handling 135 Falls 135 Protective gear 136 Burns Treatment (see Bitumen Burn Card) 136 Shock 136 Fumes 136 Hydrogen Sulphide 137 Skin Exposure 137 Public Safety 137 Contractors / Subcontractors 137

10.3 ROAD TANKERS 138 Loading and Unloading 138 Transfer 138 Blending 138 Heating 139 Using LPG 139 Blockages 140 Distributors 140 Brooms 140 Trucks 141 Roller Operators 141 Drum Cleaning and Filling 141 Drum Handling-Loading / Unloading Vehicles 141 Drum Opening Decanting 142 Fire 142 Testing - Sampling 142 Office 142 Supervisor instructions 143

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1. INTRODUCTION

1.1 SCOPE

This manual has been prepared to assist personnel involved in surface dressing in Ghana. It provides a reliable approach to all aspects of surface dressing including design and practice. The information provided is based on the current best practice of overseas road authorities and the experience of road agency staff of Ghana.

1.2 SURFACE DRESSING Surface dressing is the common name given to the method of applying a bituminous film that water proofs the surface, and acts as a binder to hold the stone chips in place. The stone chips then provide the wearing surface for traffic. Surface dressing however, is also known as sprayed sealing. The main objectives of surface dressing are: • To waterproof the pavement thereby protecting the pavement from traffic

abrasion and weather • To provide a surface with good riding qualities for road users • To reduce vehicle operating and maintenance costs. The choice of a surface dressing over asphalt depends on many factors including the operating environment and financial considerations. On a flexible pavement in rural locations, surface dressing will generally be selected unless other factors notably traffic volume dictate a higher class pavement and surfacing.

1.3 THE GHANA NETWORK The Ministry of Road Transport is responsible for approximately 48,000 km of roads of which about 6,900 km or 14% are surfaced dressed, or 1,600 km or 3.3 %, surfaced in asphalt or concrete, with the remaining 39,500 km being gravel. Delivery of services for the construction and maintenance work on the road network is generally performed by contracts managed by the road agencies, namely Ghana Highway Authority, Department of Feeder Roads, and Department of Urban Roads.

1.4 SURFACE DRESSED PAVEMENTS

Pavements which are to be surface dressed in Ghana are often made up of naturally occurring materials. On the more heavily trafficked roads a mechanically stabilised rock or manufactured crushed material is often used for the road base.

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To prepare a pavement for initial sealing (the first sprayed seal ) the top of the pavement is watered, rolled and graded to provide a surface with a smooth tight and uniform texture. The surface dressing is then applied to the prepared surface. While there are various techniques, essentially they are all a sprayed layer of bitumen with stone chips rolled into the bitumen. Proper preparation of the pavement surface is essential to achieve a first class surface dressing. Therefore the pavement must properly designed and constructed to withstand the expected traffic loading before sealing is done.

The traffic runs on top of the stone chippings and the tyres do not come into contact with the bitumen. A sketch of the basic arrangement of a sprayed seal is shown in Figure 1.1. The stone chippings are one sized and must be clean and durable. They must also be precoated with a mixture of diesel fuel oil and bitumen before being spread onto the bitumen.

Note: Bitumen rises around chippings and holds it in place Bitumen does not come into contact with tyre

Figure 1.1 Sketch Showing Tyre Contacting the Chip pings and Clearance to the Bitumen

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1.5 RESEALING As surface dressing is very thin, it requires regular maintenance to quickly repair tears to the surface and pot holes. Pavements surfaced with surface dressing are normally treated by resealing on a regular basis. After the pavement has been treated initially, it should be resealed every 6-10 years as part of a periodic maintenance program. Resealing restores the surface texture, and water proofs the pavement. As a seal ages, the bitumen oxidizes resulting in loss of chippings. The bitumen then tears and pot holes form in the pavement from traffic abrasion. The oxidization also causes cracking in the seal which allows water to enter the pavement resulting in pavement failure.

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2. BITUMINOUS MATERIALS

2.1 GENERAL

Description The basic material used as a binder for bituminous surfacing work is residual bitumen, obtained by processing the residual from the refining of naturally occurring crude petroleum. Types of Bitumen Binders Various grades of bitumen binders are generally prepared and used in one of the following forms: • Bitumen • Cutback Bitumen – using kerosene as a solvent (cutter) • Bitumen Emulsion • Polymer Modified Bitumen or PMB (by the addition of natural rubber or other

polymers) • Fluxed bitumen – using diesel as a solvent (not used in Ghana)

Selection of Type and Grade The choice and type of grade of binder selection include:

• The nature of the work • Climatic conditions • Traffic • The loads to be carried • Type and size of chippings used For economy, a binder should have as long a life as possible and be resistant to hardening by weathering. To achieve this, the binder used should contain the largest proportion of the softest practical grade of bitumen to perform in the service conditions expected Bitumen in Ghana The bitumen used for surface dressing in Ghana is grade AC–10 as discussed below. It is also proposed to introduce polymer modified bitumen in the future for use in special circumstances, such as areas subject to high speed traffic, and to minimise crack reflection in distressed pavements or to improve chipping retention.

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Viscosity Viscosity is the main property used to classify grades of bitumen. It gives an indication of the state of the bitumen at various temperatures. The variation in viscosity of grade AC–10 bitumen with temperature is shown in Table 2.1.

Table 2.1

Variation in Viscosity with Temperature of Grade AC -10 Bitumen

Temperature °C

Approx. Viscosity Poise

Condition

25 60 70

135 185

500,000 1000 300 1.5 0.8

Very Viscous, semi-solid

Heavy Liquid Free flowing liquid

Methods to Change Viscosity The viscosity of grade AC-10 bitumen at ambient temperatures is very high which means that it is very viscous or semi solid. Bitumen cannot be used in this condition. To change the viscosity of a binder into a condition suitable for the particular type of work, one or a combination of the following methods may be used: • Heating • Cutting back • Emulsification The most common method of reducing viscosity is by heating. Heating to the specified temperature reduces the viscosity so that it is suitable for spraying. Polymer Modified Bitumen (PMB) It may at times be necessary to enhance the properties of the bitumen (e.g. elasticity, toughness, adhesion) by the addition of special materials. Polymer modified binders are mainly used to minimise crack reflection in sprayed seal work over cracked pavements or to improve chipping retention in high stress areas such as on winding alignments.

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2.2 BITUMEN Base Crudes Deposits of crude petroleum occur all over the world in varying quantities and qualities. The bitumen used in Ghana is supplied by the oil refinery in Cote D′Ivoire. The refinery imports the crude petroleum from Venezuela which is one of the world’s most important oil producing areas. The crude petroleum found in Nigeria is unsuitable for the production of bitumen. Bitumen is also found in naturally occurring deposits but these cannot compete economically with refinery-produced bitumen and are not generally used in the road industry. Production Crude petroleum is a mixture of a large number of individual hydrocarbons, many of them closely related to each other, with boiling ranges which extends continuously from far below 0°C to above 300°C. At the refinery crude oil, is distilled by heating with the lighter fractions evaporating off leaving a residue. This residue is processed to produce a soft bitumen. The various grades of bitumen are produced by blowing air through the soft bitumen to oxidise it and make it harder or by combining soft and harder grades. The end product is known as residual bitumen.

A sketch of the distillation process is shown in Figure. 1.2.

Standard Classification

The residual bitumen is classified into grades mainly on the basis of viscosity measured at 60°C. The grade of bitumen specified by the Road Agencies for use in sealing work in Ghana is grade AC–10 which has a viscosity of 1000±200 Poise at 60°C. Specification Requirements

Grade AC -10 bitumen must conform to the properties of ASTM D3381.92 as shown in Table 2.2 .

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Figure 1.2 Sketch Showing Crude Oil Distillation Pr ocess

Table 2.2 Properties of Bitumen ASTM D3381.92

Test AC-2.5 AC-5 AC-10 AC-20 AC-40

Viscosity 60°C Poise Viscosity 135°C cst Penetration 100g 5min Flash point Cleveland Open cup Solubility in Trichloro- Ethylene min % Tests on residue form Thin film oven test Ductility 25 cm/min

250±50 80 200 163 99.0 1250 100

500±100 110 120 177 99.0 2500 100

1000±200 150 70 219 99.0 5000 50

2000±400 210 40 232 99.0 10000 20

4000±800 300 20 232 99.0 20000 10

Physical Properties of Bitumen The physical properties of residual bitumen to be considered when heating and handling are as follows:

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(a) Specific Gravity

The specific gravity (SG) of a material may be taken as the mass of a volume of that material compared to the volume of mass of an equal volume of water. The specific gravity of bituminous materials is normally given at 150C.

Using the fact that 1 tonne = 1000 kilogram and that 1 litre of water has a mass of approximately 1 kilogram, the volume of material delivered can be calculated from the known mass.

For convenience the specific gravity, mass per litre, and litres per tonne that may be used for conversion from mass to volume are tabulated in Table 2.3

(b) Co-efficient of Expansion

Bitumen expands when heated and contracts when cooled from a given temperature. The rate of expansion or contraction is uniform and is expressed as the co-efficient of expansion. For convenience, the multiplier to be used to correct volumes for any temperature between 15°C and 200°C are shown in Table 2.4

Table 2.3

Mass and Litres Conversion Table

Material Specific Gravity

Kilograms per Litre

Litres per Tonne

Grade AC-10 bitumen Cutback Bitumen AMC 00 AMC 0 AMC 1 AMC 2 AMC 3 AMC 4 Bitumen Emulsion

Flux Oil

Cutter

Adhesion Agent

1.030

0.90 0.92 0.94 0.96 0.98 1.00

1.00

0.84

0.78

0.95

1.030

0.90 0.92 0.94 0.96 0.98 1.00

1.00

0.84

0.78

0.95

970

1115 1085 1060 1040 1020 1000

1000

1190

1285

1055

Approximate Average at 15°C

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Table 2.4

Bitumen Volume Correction Tables

BITUMEN VOLUME CORRECTION TABLES

COLD BITUMEN to HOT BITUMEN at 150C HOT BITUMEN to COLD BITUMEN at 150C

Temperature Multiplier Temperature MultiplierC -celsius C -celsius

15 1.0000 15 1.000020 1.0034 20 0.997025 1.0068 25 0.994030 1.0102 30 0.991035 1.0137 35 0.988040 1.0171 40 0.985045 1.0205 45 0.982050 1.0239 50 0.979055 1.0273 55 0.976060 1.0307 60 0.973065 1.0341 65 0.970170 1.0376 70 0.967175 1.0410 75 0.964180 1.0444 80 0.961185 1.0478 85 0.958190 1.0512 90 0.955195 1.0546 95 0.9521100 1.0580 100 0.9491105 1.0615 105 0.9461110 1.0649 110 0.9431115 1.0683 115 0.9401120 1.0717 120 0.9371125 1.0751 125 0.9341130 1.0785 130 0.9311135 1.0819 135 0.9281140 1.0854 140 0.9251145 1.0888 145 0.9221150 1.0922 150 0.9191155 1.0956 155 0.9161160 1.0990 160 0.9131165 1.1024 165 0.9102170 1.1058 170 0.9072175 1.1093 175 0.9042180 1.1127 180 0.9012185 1.1161 185 0.8982190 1.1195 190 0.8952195 1.1229 195 0.8922200 1.1263 200 0.8892205 1.1298 205 0.8862210 1.1332 210 0.8832215 1.1366 215 0.8802220 1.1400 220 0.8772

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2.3 CUTBACK BITUMEN Production

Cutback bitumen is manufactured from refinery produced bitumen, cut back (thinned) with petroleum solvents of selected volatility to produce products which are more fluid and of easily worked viscosities. The distillation range of the solvent used determines the curing characteristics and the types that may be made. Grades and Applications of Cutback in Ghana The grades of cutback bitumen produced fall into three main categories: • Standard Grades

These grades were originally divided into grades based on viscosity as detailed in Table 2.5. However, following a review in 1998, it was decided to include a second grading system to extend the viscosity range. The two grading systems are detailed in Table 2.6. The grade of cutback bitumen specified for primersealing is AMC4 which contains 16 % cutter by volume. • Proprietary Grades

These grades were also divided based on viscosity, but using refinery residues and/or different cutters to the standard grades. They may or may not comply with the Standard Grades. • Field Produced Grades

These grades are produced in the field by mixing AC-10 bitumen, and cutter to produce grades which are broadly equivalent in performance to the standard grades.

Setting Up Cutbacks set up or thicken and increase in viscosity after spraying by three processes: • Reduction in temperature • Loss of the light oils by evaporation • Selective absorption of the oils by the fines in the pavement material.


Table 2.5

Grades of Cutback Bitumen Originally Specified

MC-30 MC-70 MC-250 MC-800 MC-3000 Min. Max. Min. Max. Min. Max. Min. Max. Min. Max. Kinematic Viscocity at 60C (140F) (See Note 1) centistokes Flash point (Tag. open-cup). degrees C (F) Water, percent Distillation test: Distillate, percentage by volume of total distillate to 360 C (680 F) to 225 C (437 F) to 260 C (500 F) to 315 C (600 F) Residue from distillation to 360 C (680 F) Volume percentage of sample difference Tests on residue from distillation: Absolute viscosity at 60C (140 F) poises Ductility,5cm/min,cm(See Note 2) Solubility in Trichloroethylene. - % Spot test (See Note 3) with:

30 38

(100) - -

40 75

50

300 100 99.0

60 -

0.2

25 70 93 -

1200 - -

70 38

(100) -

0 20 65

55

300 100 99.0

140

-

0.2

20 60 90 -

1200 - -

250 66

(150) -

0 15 60

67

300 100 99.0

500

-

0.2

10 55 87 -

1200 - -

800 66

(150) - - 0 45

75

300 100 99.0

1,600

-

0.2 -

35 80 -

1,200 - -

3,000

66 (150)

- - 0

15

80

300 100 99.0

6,000

-

0.2 -

15 75 -

1,200 - -

Standard naphtha Negative for all Grades Naphtha-xylene solvent - percent xylene Negative for all Grades Heptane-xylane solvet, - percent xylene Negative for all Grades

NOTE 1 - As an alternate, Saybolt-Furol viscosities may be specified as follows Grade MC-70 - Furol viscosity at 50 C (122 F) - 60 to 120 sec. Grade MC-73 - Furol viscoity at 25C (77F) - 75 to 150 sec. Grade MC-250 - Furol viscoity at 60C (140F) - 125 to 250 sec. Grade MC-800 - Furol viscoity at 82.2C (180 F) - 100 to 200 sec.

Grade MC-3000 - Furol viscoity at 82. 2C (77F) - 300 to 600 sec.

NOTE 2 - If the ductitlity at 25 C (77 F) is less than 100, the material will be acceptable if ductility at 15.5 C (60 F) is more than 100.

NOTE 3 - The use of the spot test is optional. When specified, the Engineer shall indicate whether the standard naphtha solvent, the naphtha xylene solvent, or the heptane xylene solvent will be used in determining compliance with the requirement, and also, in the case of the xylene solvents, the percentage of xylene to be used.


Table 2.6

Grades of Cutback Bitumen Currently Specified

Classification Additional Grade

Approx. ASTM Grade

Viscos ity Cst % Kerosene by volume

Priming AMC00 AMC0 AMC1

MC30 MC70

8-20 30-60

70-140

56 44 34

Primerseal AMC2 AMC3 AMC4

MC250 MC800

250-500 500-1500 1500-5000

27 21 16

Seal AMC5 AMC6 AMC7

MC3000 5000-12000 12000-32000

11 7 3

2.4 BITUMEN EMULSION Description Bitumen emulsion is a liquid product in which a substantial amount of very finely divided bitumen is suspended in water by means of one or more emulsifying and stabilising agents. Types The nature and type of emulsifying agents control the type of the bitumen emulsion that is produced. The types of bitumen emulsion manufactured for road making purposes are: (a) Anionic

Anionic emulsion is one in which the suspended bitumen particles are negatively charged.

(b) Cationic

Cationic emulsion is one in which the suspended bitumen particles are positively charged.

(c) Non Ionic

Non-ionic emulsion is an inverted bitumen emulsion, which is basically droplets of water dispersed in bitumen, and the bitumen has no electrical charge. These emulsions are not commonly used.


Composition

Bitumen emulsions are manufactured from three components, which may be varied in proportion in the mixture to provide specific properties. The components are: • Binder - generally AC-10 bitumen, but other grades may also be used. • Water • Emulsifier Emulsions can also be made from polymer modified binders.

Production

Bitumen emulsion is commonly manufactured using a colloid mill. In a colloid mill the bitumen is subjected to a shearing force by means of two discs or cylinders rotating in opposite directions, or in the same direction at different speeds, with only small clearance between them. The shearing force from the mill produces fine droplets of bitumen. The size of the droplets can be varied, by adjusting the clearance in the mill. The two phases, bitumen and water plus emulsifier, are introduced into the mill together. The mixture from the mill, is usually discharged into a holding tank fitted with a mechanical stirrer to continue mixing the components and prevent sedimentation. Standard Grades

Bitumen emulsions are produced to conform to specific grades which are defined according to the time it takes the emulsion to break, i.e. the time it takes to form a continuous film of bitumen over the surface to which the emulsion is applied. The standard grades are shown in Table 2.7.


Table 2.7 Standard Grades of Bitumen Emulsion

Type of emulsion Grade Anionic ARS = rapid setting

AMS = medium setting ASS = slow setting

Cationic CRS = rapid setting CMS = medium setting CSS = slow setting CAM = aggregate mixing

Special Products Polymer Modified Binder (PMB) emulsions are special products that are currently not available for use in Ghana. They are generally designed to suit particular applications, for example, polymers may be added to improve the early strength, produce a binder for a Strain Alleviating Membrane (SAM), a High Strength Seal (HSS) or reduce temperature susceptibility. Specification

Emulsions used in sealing and resealing work are normally the rapid setting type. They are also predominantly cationic emulsions because they can be used with a wider range of chippings and better tolerate the presence of water than anionic emulsions. The properties required of the cationic standard grades of bitumen emulsion produced are given in Table 2.8. Breaking of an Emulsion A bitumen emulsion is said “to break" when the bitumen and water separate out and the bitumen forms a film on the surfaces to which the emulsion is applied. “Breaking” can be seen by the emulsion changing colour from brown to black. The time taken to break cannot be exactly predicted as it is influenced by the prevailing weather conditions and the chippings. Rapid setting emulsion will break more quickly under the same conditions than a medium or slow setting grade. The types of bitumen emulsion produced break by different actions. (a) Anionic Emulsion

The breaking of an anionic emulsion normally occurs when the water is lost by evaporation or absorption. The breaking of an anionic emulsion is therefore more influenced by the prevailing weather conditions.


R E Q U IR E M E N TS F O R C A TIO N IC E M U LS IF IE D B ITU M E N TA B L E 2 .8

TY P EG R A D E

TE S TS m in m ax m in m a x m in m a x m in m ax m in m ax m in m ax

V iscos ity,S a ybo lt fu ro l a t 25 o C s 20 1 00 2 0 10 0V iscos ity,S a ybo lt fu ro l a t 50 o C s 2 0 10 0 100 400 5 0 450 50 45 0S to ra ge S tab ility tes t 24 h , % 1 1C lass ifica tio n tes tC oa ting ab ility a nd W ate r re s is tanceC oa ting o f d ry a ggrega teC oa ting a fte r sp ra yingC oa ting w e t ag greg a teP artic le ch a rg e tes tS ieve te s t 0 .1 0 .1 0 .1 0 .1 0 .1 0 .1B re ak ing In dex (w ith s ilica fille r) gD is tilla tionO il d is tilla te by vo lu m e o f E m u ls io n % 3 3 1 2 12R es idue % 6 0 6 5 6 5 65 57 5 7Tes t o n res idue fro m d is tilla tio n te s tP en e tra tion 25 oC , 10 0g 5s 8 0 12 0 8 0 120 8 0 120 40 90 80 1 20 4 0 90D uc tility 25 oC 5 cm /m in , cm 4 0 4 0 4 0 40 40 4 0S o lu b ility in T rich lo roe thy lene % 97 .5 97 .5 97 .5 9 7 .5 9 7 .5 97 .5

P os itive P o s itiveP os itive P os itive

< 10 0 <1 00 80 -14 0 80-140 >12 0 > 120

R A P ID S E TTIN G M E D IU M S E TTIN G S LO W S E TTIN G

F a irP os itiveP os itive

F a ir

G o od G o odF a irF a irF a ir

F a ir

C S S -1 C S S -1h

P a sses P asses

C R S -1 C R S -2 C M S -1 M S -2h


(b) Cationic Emulsion

Cationic emulsions break for the same reason, but the positive charge on the bitumen particles also reacts with the negative surface charge on the chippings which gives a more rapid break and good adhesion. This is an important advantage in the use of cationic emulsions as it makes them less dependent on evaporation.

Handling and Storage

Emulsion has a finite life in storage. The extent of the life depends on the formulation, handling and storage. As bitumen is heavier than water the fine droplets will settle out in time. This is known as sedimentation, which can be minimised by periodic agitation of the emulsion. When the droplets stick together and form lumps this is known as coagulation. Coagulation is a partial or complete breakdown of the emulsion and is serious because it cannot be corrected in the field. The whole of the emulsion in the container becomes useless. To overcome sedimentation it is recommended that drums be stored upright in a sheltered position and turned end for end once a fortnight. Bulk storage tanks are fitted with an automatic control electric heater and agitator, usually a mechanical stirrer, to keep the emulsion warm and the bitumen droplets in suspension. Mixing Emulsions

Anionic and cationic emulsion must not be mixed because when they come into contact, the emulsions will break. Care is required when changing from one type to another. It is essential to remove all traces of the material last used by flushing out all tanks, hoses, etc. with clean water. If the emulsion has broken and a bitumen residue is left in the equipment this may be removed using kerosene or distillate followed by thorough flushing with clean water.

Field Behaviour

Cationic rather than anionic emulsions are commonly used in Ghana because they are compatible with the chippings which generally have a negative surface charge. However, the type of chippings to be used and whether the surface is positive or negatively charged should be determined before the type of emulsion is chosen.

Bitumen emulsions should achieve results similar to cutback bitumen. An emulsion primer is required to soak into and bind the pavement surface the same way as a cutback bitumen prime. An emulsion primerseal is also required to soak into and bind the surface of the pavement yet have sufficient binder remaining to hold the chippings and waterproof the pavement, in the same way as a cutback bitumen primerseal.


Co-efficient of Expansion Bitumen emulsion expands when heated and contracts when cooled from a given temperature. The rate of expansion or contraction is uniform and is expressed as the co-efficient of expansion. For convenience, the multiplier to be used to correct volumes for any temperature between 15°C and 85°C are shown in Table 2.9.

Table 2.9

Volume Correction Tables – Bitumen Emulsion

Part A Part B Table for calculating the volume of bitumen emulsion at a temperature above 15°C to its volume at 15°C

Table for calculating the volume of bitumen emulsion at a temperature above 15°C from its volume at 15°C

Temperature °C Multiplier Temperature °C Multiplie r 15 1.000 15 1.0000 20 0.9980 20 1.0020 25 0.9956 25 1.0043 30 0.9935 30 1.0065 35 0.9913 35 1.0088 40 0.9890 40 1.0111 45 0.9868 45 1.0134 50 0.9845 50 1.0157 55 0.9823 55 1.0181 60 0.9800 60 1.0204 65 0.9778 65 1.0228 70 0.9755 70 1.0251 75 0.9733 75 1.0274 80 0.9710 80 1.0297 85 0.9688 85 1.0320

3. POLYMER MODIFIED BINDERS (PMB’s) General Polymer modified binders, PMB’s are currently not available for use in Ghana but have been included for completeness. They are used in surface dressing to:

• Provide a more robust binder than grade AC-10 bitumen • To improve ability to resist crack reflection, waterproofing and chipping

retention properties Common polymer materials used in surface dressing work include:

• Granular Scrap Tyre Rubber • Styrene Butadiene Styrene (SBS) • Ethylene Vinyl Acetate (EVA)


Adhesion and Cohesion Characteristics When a polymer is added to bitumen, the fluid characteristics of the end product are very different from those of the bitumen. Generally the cohesive (internal strength) characteristics increase, and the adhesive (ability to stick to other materials) characteristics decrease. PMB’s are therefore more resilient, viscous and cohesive and consequently less able to wet the chipping stones (except PMB emulsions). For sprayed work using PMB’s, an adhesion agent should be added to the bitumen binder at all times, and the chippings pre-coated with bitumen based pre-coat. With high concentrations of polymer, adhesion to the chipping becomes more difficult, even when the chippings are pre-coated.

3.1 ADDITIVES General

Additives are used to temporarily or permanently alter some of the physical properties of bitumen. The common additives are: Cutter Adhesion agent Flux oil (or diesel which is not used in Ghana) Other additives are: Polymers (Granular scrap tyre rubber, SBS, and EVA as discussed above) Anti-foaming agents (Not used in Ghana) Cutter Oil Cutter oil, which is more commonly known as kerosene, is used to temporarily reduce the viscosity of grade AC-10 bitumen. In Ghana cutter oil is mainly used in the field to produce cutback bitumen for primer sealing. It is also used to flush and clean out bitumen from tanks, spray bitumen hoses, equipment etc.

Adhesion Agent Adhesion agents are generally made from tallow, fish oil, sunflower oil or similar material, which improves the adhesion between the binder and chippings. It is generally added directly to the bitumen but may also be added to the chipping pre-coating material, or both. A typical adhesion agent is Redicote 422N which is available in Ghana.


4. CHIPPINGS

4.1 GENERAL The name commonly used for stone chips in Ghana is “chippings”. However, chippings are also known as aggregate. In sprayed sealing the function of the chippings is to provide the surface for traffic to travel on and to transmit the wheel loads to the base pavement material. Source Rock The material from which crushed chippings are produced should be either clean quarried spalls of approved igneous, metamorphic or sedimentary rock free from bedding planes or lines of weakness which would affect the product, or hard clean gravel. It should be free from clay, organic matter, unsound rock and elongated flat particles. Types of Chippings in Ghana The chippings used in Ghana are produced mainly from the granitic rock family. That is, granite, granodiorite, tonalite, and gneiss.

4.2 CHIPPING REQUIREMENTS Chippings should be clean, durable, and possess the necessary hardness, toughness, wearing resistance, crushing strength and polishing resistance. Material and Shape Requirements The material and shape requirements of chippings are specified in Table 3.1. As chippings are a critical component of surface dressing, it is important that all of these requirements are met. Stripping deficiencies however, may be improved by the addition of adhesion agents into the binder. Wearing Qualities The best indicator of the wearing qualities of a material is the Los Angeles Abrasion (LAA) Test result. This test requires a sample of chippings and a number of steel balls to be placed in a cylinder. The inside of the cylinder is fitted with shelves to lift and drop the chippings and steel balls as it is rotated at a constant speed for a set number of revolutions. The wearing quality of the chippings is measured by the amount of breakdown during the test. The greater the amount of material broken down, the poorer the quality of the chippings.


Adhesion Adhesion between bitumen and chippings varies depending on the type and charge of the stone. Adhesion values are determined by a laboratory test for the assessment of resistance to stripping in the presence of moisture on samples of chippings.

Shape Chippings should be cubic in shape with crushed angular faces but not flat or flaky. In practice a quantity of flat particles is always present. A flat particle is defined as a particle having its least dimension (thickness) less than 0.6 of its mean dimension. The quantity of flat particles is determined by the Flakiness Index test which measures the percentage by volume of flat particles in the sample. In practice testing and calculations are carried out on a "per mass" basis. The lower the Flakiness Index the better the shape of the chippings, that is, the higher the percentage of cubical stones as shown in Figure 3.1 (a) and 3.1 (b) In Ghana the maximum permissible Flakiness Index for Size 14mm is 25% and for Size 7 and Size 10 mm is 30%. A good quality chipping is in the range of 20 to 25%.

Chippings with good cubical shape - low flakiness index

Figure 3.1 (a) Sketch Showing Chipping with Go od Shape


Chippings with poor shape - high flakiness index

Figure 3.1 (b) Sketch Showing Chippings with Poor Shape

Table 3.1

Material and Shape Requirements of Chippings

Test Limit

Los Angeles Abrasion (LAA) Max %

Aggregate Crushing Value (ACV) Max %

Sodium Sulphate Soundness (SSS) Max %

Flakiness Indexes: Max (14mm) (10mm, 7mm) Elongation Indexes: Max

10% Fines Min (dry) KN

Wet / Dry Strength Ratio %

Stripping Test [ASTM D1644-80] Max%

30

25

12

25 30

35

210

75

5


Grading The ideal grading for surface dressing work is one which all the particles of stone are very close to one size. One sized chippings are defined as chippings of which 60 to 70% by mass of the whole material passes a sieve of a specified size and is retained on a sieve having an opening of 0.7 of the specified size. For reasons of economy and practicability some variation from the ideal must be allowed, but the range of grading should be limited as much as is reasonably possible. The grading requirements for one sized chippings are specified in Table 3.2.

Table 3.2 Grading of Chippings

One Sized Chippings As noted above only one sized chippings should be used for sealing and primer sealing work. Figure 3.2 illustrates a sprayed seal in which one sized chippings have been used. The figure also tries to show why oversize and undersize materials are undesirable. When a good one-sized chipping is used with the correct quantity of binder, maximum contact and skid resistance are obtained between the tyre and the chipping. Sprayed seals also provide drainage passages between the chipping particles allowing the rapid removal of water between the tyre and road surface. This assists in maintaining skid resistance when the surface is wet as does the tyre tread design, the road cross fall grade and drainage characteristics.

Percentage by Weight Passing Sieve Size (mm)

Nominal Sizes

14mm 10mm 7mm 5mm 26.5 19.0 13.2 9.5 6.7 4.75 2.36 1.18

Min ALD

100

95-100 0-20 0-5

0-0.5 7.0

100 85-100 0-30 0-5

0-0.5 5.0

100 85-100 0-30 0-10 0-0.5 3.5

100 85-100 0-30 0-5 2.5


Figure 3.2 Sprayed Seal with One Sized Chippings Average Least Dimension (ALD)

The first use of the term Average Least Dimension (ALD) is attributed to F. M. Hanson, in the paper 'Bituminous Surface Treatment of Rural Highways' published by the New Zealand Society of Civil Engineers (Incorporated) in 1935. The ALD of a chipping is the average of the thickness of all the individual stones, when they are spread as a single layer on a horizontal surface with their least dimension vertical. A sketch of ALD is shown in Figure 3.3. The ALD can be determined as follows: (i) Direct Measurement Method

This method involves measuring the ALD of each stone chip in a sample by vernier calliper, dial gauge or slotted gauge. The average dimension is then calculated to determine the ALD. Refer to Section 5.8 for details of method.


(ii) Grading Method

The chippings sample may be tested in the laboratory to determine its grading, median size and the flakiness index and then the ALD calculated.

The ALD is expressed in millimetres and is used to calculate the base rates of application of binder in sprayed work.

ALD

ALD = Average Least DimensionBitumen filled voids

Air voids

Figure 3.3 A Sketch of ALD


4.3 PRECOATING OF CHIPPINGS General

All chippings used in sprayed sealing should be pre-coated. A suitable pre-coating material should be selected for the type of chipping material being used.

Pre-coating Materials The purpose of a pre-coating material is to improve the adhesion between the binder and the chipping by: • Minimising the adverse effect of dust • Increasing the ability of the binder to “wet” the chippings. The pre-coating material generally used in Ghana is a diesel and bitumen based material comprising 90% diesel (de-waxed distillate or gas oil) and 10% bitumen. Adhesion agent (0.5%) should be added if available. These proportions however, may be varied to obtain the improved adhesion. Pre-coating of chippings at a nominal rate of 12litres/m³ is recommended in Ghana but again this can be varied by testing to obtain the best uniform coating of the chippings. The bitumen based pre-coating materials provide improved adhesion compared to distillate or other oil based materials.


4.4 GEOTEXTILES General Geotextile fabrics are not currently available for use in Ghana but have been included for completeness. They may be used to reinforce seals and reseals. Choice of Geotextile There are many geotextiles available for use in sprayed bituminous seals. The following characteristics are desirable: • Non woven geotextiles have more uniform elongation, greater resistance to

tearing and superior bitumen/fabric adhesion than woven.

• Needle bonded filaments are more stable than resin bonded joins which may become unstable when in contact with hot bitumen.

• Polyesters fabrics are the most suitable as they do not melt easily, absorb only small amounts of water and are less sensitive to sunlight than other types.

• Polypropylene fabrics may also be used provided that the bitumen spraying temperature is less than the softening point (165°C) of the material. Signs of heat susceptibility include shrinking or melting along the edges of the fabric after being covered with hot bitumen. Polypropylene fabrics are not recommended for use with Polymer Modified Binders (PMB’s) because of the required spraying temperatures. However, where the binder is a Polymer Modified Binders (PMB) emulsion, sprayed at temperatures below 90°C, the fabric can be used without risk.

• Geotextiles should be stored in dry areas in their shipping bags.

The properties of geotextiles suitable for sprayed seals are given in Table 3.3. Table 3.3 Properties of Geotextiles

Property Mass Thickness Elongation Bitumen Saturation Melting Point Roll width Roll Length

Typical Values 140gm/sq metre 0.6mm 25-30% 0.9 litre/sq. metre 250°C 4 m 150 or 300m


5. TYPES OF TREATMENT

5.1 GENERAL Bituminous surface dressing is the term generally used to describe the method of surfacing where the binder is sprayed onto the prepared road surface and covered with chippings. The other treatments are primes and surface enrichments where no chipping is applied. The main objectives when applying a sprayed bituminous surface dressing are: (a) To provide an economical, durable, skid resistant, and non glare surface on

which it is safe and comfortable to travel under all weather conditions (b) Waterproof the pavement surface, that is, stop rain and surface runoff

reaching the pavement (c) Provide a wearing surface resistant to abrasion by vehicles

5.2 CLASSIFICATION OF TREATMENTS Sprayed work can be broadly divided into four groups: initial treatments, seals, reseals, and other treatments. Initial treatments Initial treatments are applied to unsealed surfaces (new or reconstructed) and are either a Prime, or a Primerseal. The functions of the initial treatment are: (a) Prime

The function of the prime is to provide a short life weatherproof surface which bonds tightly to the unsealed surface by penetrating the pavement. It also provides a uniform surface for the application of the seal.

The material used for priming in Ghana is cutback bitumen. The grade of cutback is selected so it penetrates 5 to 10 mm into the pavement surface. The harder and more compact the pavement surface the lower the viscosity of the cutback (and higher percentage of cutter) required to achieve the penetration.


(b) Primerseal

The function of a primerseal is to provide a light weatherproof wearing surface incorporating chippings. A primerseal uses a cutback binder which is intended to act as a primer and penetrate the pavement surface, and binder to retain the chippings.

The cutback generally used for primersealing in Ghana is cutback grade AMC4 with 16% cutter (kerosene). This cutback has been selected to achieve penetration of 2-3 mm into the surface of the pavement. The use of emulsion for primerseals is being carried out on limited basis and performance is being monitored.

(c) Selection of Initial Treatment

The criteria for selection of an initial treatment are related to its function. The following criteria should be used to select the particular type of initial treatment:

(i) Prime

This treatment is used when the surface is not trafficked or only subject to light construction traffic before sealing.

(ii) Primerseal

This treatment is used when the surface is to be trafficked immediately.

The Ministry of Road Transport policy is that all initial treatments will be primerseals.

Seals Seals are applied to primed or primersealed surfaces. The function of the seal is to provide a lasting weatherproof surface. It is designed for compatibility with the surface underneath (without penetration) and for chipping retention. Reseals A reseal is applied directly over an existing sealed surface. Where the existing surface has a variable texture or is bleeding, flushing, or stripped, remedial pre-treatment should be undertaken. In some circumstances, such as an old seal cracking due to pavement movement, or high heavy vehicle traffic volumes, a polymer modified binder (using crumb rubber or other polymer), a geotextile reinforced seal, or double application seal may be necessary.


Types of Seals and Reseals There is a large range of sprayed seals possible but in Ghana the majority of sprayed seal work utilizes a single (may also be called a single/single) seal or reseal. Less common are double (or double/double) seals or reseals. (a) Single Seals

Single seals comprise a single application of grade AC-10 bitumen binder and a single application of chippings over a primed or primersealed surface.

(b) Single Reseal

A reseal is the utilisation of a single seal to an existing bituminous surface to restore a previously sealed surface to a satisfactory condition.

(c) Double Seals

A double seal consists of two applications of binder and chippings. The chippings in the second application are normally no more than half the size of the first, and the spread rate is just sufficient to fill the voids in the first application.

Other Treatments (a) Dust Suppression

A dusty road surface can be treated by the application of a low viscosity, slow curing oil, or a diluted bitumen emulsion.

(b) Surface Enrichment

Surface enrichment is a light application of bituminous emulsion, to an existing bituminous surface, to increase the binder content around at the surface. This is generally done without the addition of chippings but may be done using a light covering of dust to minimise delay to traffic. Usually suited to low traffic areas or where traffic may be detoured.


6. DESIGN

6.1 GENERAL The success of a sprayed seal depends on many factors, some of which are beyond the direct control of the designer. The most important factor that can be controlled is the design which involves selection of : (a) the type, grade and rate of application of prime, primerbinder, or binder (b) the type, size and rate of application of chipping if part of the treatment. All design binder application rates and additive mixing rates are measured and expressed at 15OC. For conversion to rates at higher temperatures for spraying operations see Table 2.4 Application rates for primes and primerseals are expressed as mixtures. All other rates are expressed in terms of residual binder. Definitions The following definitions apply: Seal : A seal is the first seal applied over a primed or primersealed surface. Reseal : A reseal is the application of a sprayed seal over an existing

bituminous surface.

6.2 DESIGN OF PRIMES General Priming is the application of a primer to a prepared pavement prior to the application of a sprayed seal. The function of priming is to assist in achieving and maintaining an interfacial bond between the pavement and the sprayed seal. A primer should therefore penetrate, and strengthen the pavement near its surface. The selection of the type and grade of primer, and the rate of application, is based on the type of pavement material, the degree of compaction, moisture content, the prevailing conditions and the life expected of the primer.


Design Procedure A prime is designed to penetrate the surface by 5 to 10 mm. The best practice is to use an application rate that has been determined from previous field trails or from previous priming experience with the base material. However, if this is not available, the design method to determine the rates of application for priming is as follows: (i) Evaluate the surface type – refer to Table 5.1. (ii) Select primer grade and application rate – refer to Table 5.2. Once an application rate has been determined it should be tested on a small area of the job to confirm the penetration and application rate. The final result should be a hard, dry, black surface with the desired penetration. Application Rates (a) Low Rates

In practice where a seal is to be applied on the same day or shortly after the primer, the application rates specified can be reduced. However, this practice is not desirable.

For example, if a light primer (56% cutback) has been selected, the rate of application can be reduced to 0.30-0.60 Litres/square metre (L/m2). When using light rates of application followed by sealing in the one day, it is also necessary to consider absorption of the seal binder into the lightly primed pavement.

Some of the low viscosity primer may also have a cutting back effect on the binder. In such cases it is necessary to increase the binder rate and decrease the amount of cutter in the binder. This should be based on experience as it is difficult to estimate.

It is suggested that rather than use a light primer at a low rate of application to allow early application of the seal coat, that a primerseal be applied.

(b) Normal Rates

Where a primer of the correct viscosity for tightly bonded and fine surface conditions has been selected the normal rate of application should be about 1.0 -1.1 L/m2 as shown in Table 5.3. This usually results in a uniformly primed surface. If it appears that a heavier rate of application is required, it is preferable to use a heavier grade of primer at the normal rate of application (sandstones, limestones and other very porous pavement excepted).

The rate of application should be varied according to the compaction of the pavement and the moisture content of the surface. In general the rate of


application should be 0.8 to 1.3 L/m2. Except in special cases, a rate below 0.8 L/m2 does not adequately prime the surface or fill the pores in the pavement surface and could lead to a stripped seal due to absorption of binder into the surface.

(c) Heavy Rates

On sandstone, limestone and other very porous pavements, the normal rate of application should be about 1.3 to1.5 L/m2 of a heavy viscosity primer.

To minimise absorption, provide a uniformly primed surface and avoid undue delay to traffic, it is preferable to apply the heavy rates in two separate applications, generally about two or three days apart.

If the rate of application is in excess of 1.5 L/m2, then the pavement is unsuitable for priming and should be treated by other means, e.g. primersealing.

Table 5.1

Evaluation of Surface Type

Surface Type Description

Tightly Bonded

Hard and dense when compacted Exhibits a high degree of resonance when struck with a heavy implement

Fine

Does not ring when struck with a heavy implement but appears to be firm Does not compact to a tight and resilient surface

Coarse

Very porous and open grained surfaces with little or no binding material Difficult to compact – forms a weak, open textured surface


Table 5.2

Typical Primer, Grades and Rates of Application

Surface Type Primer

Basic Primer Application Rates

AMC Grade Cutback Bitumen (%)

Pavement Application Surface Rate @ 150C Condition (L/m2) of mixture

Tightly Bonded Light Primer

AMC00 Field prepared

AMC0

(56%) 50% (44%)

Dry 0.6 – 1.1 Damp 0.5 – 0.8

Fine Medium Primer

AMC0 Field prepared

(44%) 40%

Dry 0.8 -1.1 Damp 0.5 – 0.8

Coarse Heavy Primer

AMC1 Field prepared

(34%) 30%

Dry 0.9 – 1.3 Damp 0.5 – 0.8

Table 5.3.

Surface Type, Primer Grades and Application Rates

Residual Prime Mixture Hot Sprayed Prime Mixture Cold Spray Rate- . Residual bitumen 15°C* Hot Spray Rate

Pavement Tightly Bonded Pavement Tightly Bond (Hard/Dense) (Hard/Dense)

% Cutter MC30-MC70 (56-44%) % Cutter MC30-MC70 (56-44%)- at 60°°°°C Surface Condit. Dry Wet Surface Condit. Dry Wet

Range Minimum Optimum Minimum maximum Range Minimum Optimum Minimum Maximum

Litre/m2 0.6 1.1 0.5 0.8 Litre/m2 0.62 1.13 0.51 0.82 Pavement Fine Pavement Fine

(Soft/Porous) (Soft/Porous) % Cutter MC70 (44%) % Cutter MC70 (44%)-at 85°°°°C

Surface Condit. Dry Wet Surface Condit. Dry Wet Range Minimum Optimum Minimum maximum Range Minimum Optimum Minimum Maximum

Litre/m2 0.8 1.1 0.5 0.8 Litre/m2 0.84 1.15 0.52 0.84 Pavement Coarse Pavement Coarse

(Very Porous) (Very Porous) % Cutter MC250 (34%) % Cutter MC250 (34%)- at 110°°°° C

Surface Condit. Dry Wet Surface Condit. Dry Wet Range Minimum Optimum Minimum Maximum Range Minimum Optimum minimum maximum

Litre/m2 0.9 1.3 0.5 0.8 Litre/m2 0.96 1.38 0.53 0.85 NB: - PRIME mixture of Bitumen, Cutter and Adhesive Agent is to be treated as RESIDUAL. i.e. Spray Rates are inclusive of Bitumen, Cutter and Adhesive Agent. Pavement should be slightly DAMPENED (not wet) after sweeping and just prior to PRIMING Use 1% adhesion agent in PRIMING


6.3 DESIGN OF PRIMERSEALS General Primersealing is the application of a primerbinder to a prepared pavement which is then covered with chippings as a temporary treatment prior to applying the sprayed seal. A primerseal is designed to seal a pavement immediately after construction. The binder used for a primerseal is more viscous than a primer and less viscous than a normal binder and is required to act as both a primer and binder. That is, the binder is required to penetrate the pavement as well as acting as a binder for the chippings. A primerseal must also cure to a very hard surface. Design Procedure A primerseal is designed to penetrate the pavement surface by 2 - 5 mm. The best practice is to adopt an application rate that has been successfully used on previous jobs with the same materials and construction standards. However, if this is not available, the design method to determine the rates of application for priming is as follows: (a) Select Primerbinder

The grade of cutback bitumen specified for use in Ghana for primersealing is AMC4 which contains 16 % cutter by volume.

Cationic rapid setting bitumen emulsion (minimum 70% bitumen content) has been specified for use on a trial basis at the present time.

(b) Select Chipping Size

Size 10 mm chippings are normally selected for both low and high traffic volumes as Size 7 mm chippings are not generally available. However, Size 14 mm chippings maybe selected if traffic volumes are high and contain a high proportion of commercial vehicles.

(c) Select Primerbinder Application Rate – Cutback bitumen (i) Select the Basic Primerbinder Application Rate from Table 5.4 for cutback

bitumen for the traffic volume (vehicles/lane/day). (ii) Add an allowance for the surface condition from Table 5.5 to the Basic

Primerbinder Application Rate to give the Design Application Rate. From experience, the average total allowance is generally about +0.2 to +0.3 L/m2.


(d) Select Chipping Application Rate

Select the chipping application rate from Table 5.4. In primersealing, the chipping quantity spread is approximately 1.5 times the quantity for a seal or reseal using similar chippings.

(e) Design Calculation Sheet

Complete the Design Calculation Sheet which is shown in Section 5.7. (f) Curing Period

A primerseal must be cured to a hard surface before a seal is applied. The cutback bitumen binder is cured by evaporation of the cutter oil and hardening of the bitumen. From experience, the minimum evaporation period in Ghana is three months. However, if the surface is not hard and the seal is applied, the surface texture of the seal may become flushed or bleeding due to embedment of the chippings into the primerseal binder. Field trials are being conducted to determine the minimum period to be allowed for the primerseal seal to harden before the seal is applied. In the interim, to ensure that all primerseals, regardless of primerbinder type are hard and able to be sealed the following minimum period should be allowed before the seal is applied: (i) an absolute minimum period of three months but subject to the surface

having a ball penetration result of less than 2.5 mm.

(ii) a desireable minimum period of six months but also subject to the surface having a ball penetration result of less than 2.5 mm.

(iii) a minimum period of 12 months without a ball penetration test.


Table 5.4

Basic Rates for Primerbinder (Cutback bitumen) and Rates for Chippings

Note:

The application rates given are intended as a guide only. Actual rates should be determined by onsite trials. The above rates do not include any allowance for surface texture, or absorption by the base.

Table 5.5

Surface Condition Allowances for Primerbinders

Allowance (L/m 2) Surface Condition

0.0 to + 0.1

Tightly bonded surfaces

+ 0.1

Fine surfaces

+ 0.2

Coarse surfaces

+ 0.2 to + 0.4

Crushed rock spread and compacted without surface finishing

Chipping Size

Basic Primerbinder Application Rate at 15 0C

(L/m 2) of mixture

Chipping Application

Rate Vehicle/lane/day

(mm)

<300 300-2000 >2000 (m2/m3)

7 1.3

1.2 1.1 150 - 190

10 1.4

1.3 1.2 120 – 150

14 1.5 1.4 1.3 90-110


Table 5.6

Typical Rates of Application of Primerbinder (Cutba ck Bitumen – 16% Cutter)

RESIDUAL PRIMERSEAL MIXTURE HOT SPRAYED PRIMERSEAL MIXTURE (Cold Sprayer Rate. Residual bitumen at 15°C HOT SPRAY RATES at 135°C Pavement Tightly Bonded Pavement Tightly Bond Vehicle/Lane/Day Vehicle/Lane/Day <300 300-

2000 >2000 <300 300-

2000 >2000

Chipping mm Application Rate Litres / m²

Chipping m2 / m3

Chipping mm HotCutback Litres / m²

Chipping m² / m³.

7 1.35 115 7 1.46 115 10 1.35 1.25 1.15 100 10 1.46 1.35 1.24 100 14 1.45 1.35 1.25 80 14 1.56 1.46 1.35 80

Pavement Fine Bonded Pavement Fine Bonded Vehicle/Lane/Day Vehicle/Lane/Day <300 300-

2000 >2000

<300 300-2000

>2000

Chipping mm Cold Cutback Litres / m²

Chipping m2 / m3


Chipping m² / m³.

7 1.4 115 7 1.51 115 10 1.4 1.3 1.2 100 10 1.51 1.40 1.30 100 14 1.5 1.4 1.3 80 14 1.62 1.51 1.40 80

Pavement Coarse Pavement Coarse Vehicle/Lane/Day Vehicle/Lane/Day <300 300-

2000 >2000

<300 300-2000

>2000


Chipping m² / m³.


Chipping m² / m³.

7 1.5 115 7 1.62 115 10 1.5 1.4 1.3 100 10 1.62 1.51 1.40 100 14 1.6 1.5 1.4 80 14 1.73 1.62 1.51 80

Pavement Crushed Rock Pavement Crushed Rock Vehicle/Lane/Day Vehicle/Lane/Day <300 300-

2000 >2000

<300 300-2000

>2000


Chipping m² / m³.


Chipping m² / m³.

7 1.6 115 7 1.73 115 10 1.6 1.5 1.4 100 10 1.73 1.62 1.51 100 14 1.7 1.6 1.5 80 14 1.83 1.73 1.625 80

NB: - PRIMERSEAL mixture of Bitumen, Cutter and Adhesion Agent is to be treated as RESIDUAL. i.e. Spray Rates are inclusive of Bitumen, Cutter and Adhesion agent Pavement should be slightly DAMP (not wet) after sweeping and just prior to Primersealing Use 1% adhesion agent in Primerbinders Recommend 10mm Chipping for Primerseals


6.4 DESIGN OF SEALS AND RESEALS General The design objective is for the residual binder to be about 50 to 60% of the height of the chippings layer two years after construction. The residual binder comprises bitumen, and adhesion agent, but does not include cutter oil or water. The amount of binder required will depend on the size, shape and orientation of the chippings, embedment of chippings into the base, texture of surface onto which the seal is being applied, and absorption of binder into either the pavement or chippings. All application rates determined by this method are stated in L/m2 of residual binder at a temperature of 15°C. In determining the actua l field application rate, allowances must be made for proportion of the cutter oil or water (emulsions) and the volume corrected for the spraying temperature. Single Application Seals The general aim in design of single application sprayed seals is to achieve a single layer of one- sized chippings in continuous interlocked contact, with sufficient binder to hold the chippings in place but at the same time allowing vehicles to travel on top of the chippings. Double Application Seals In certain circumstances, such as at intersections, high stress areas on heavily traffic roads with a high percentage of commercial vehicles etc, double seals may be used. The general aim of the design of double seals is for the chipping in the second application to occupy the spaces between the chipping particles in the first application. The second layer improves interlock and modifies the surface texture of the first layer. It is usual for the chippings for the second application to be half the size of the first, or smaller. The design philosophy of a double seal is such that: The first layer is designed as per single seal or reseal (as appropriate) and the rate of application of binder and chipping spread rate may be reduced if the second application is done within few days of the first; The design of the second layer is based on single seal or reseal (as appropriate), with reduced binder and chipping application rates; The total design binder and chipping application rates are less than the sum of two single seals.


Both layers of a double seal are designed as for single seals except that for the first layer the basic voids factor is reduced (in accordance with Table 5.10 in the Design Method).

The second layer is designed without any surface texture or embedment allowances. As general rule, the total binder required for both layers will be about 70% of that required for the two layers designed as separate reseals. Where the second application is to be delayed by between one week and several months after the first application, but the seal is to be trafficked : The first application should be designed as a single seal or reseal (as appropriate). For the second application, the binder application rate may be reduced to a minimum (i.e. the basic rate without adjustment for surface texture or embedment) and the chipping spread rate reduced by up to 30% (i.e. use 30% less chippings). This should fill the void spaces in the first seal and avoid excessive loss of chippings. Binder The grade of bitumen specified for use in Ghana for sealing and resealing is straight grade AC – 10. Cationic rapid setting bitumen emulsion (minimum 70% bitumen) has been specified for use on a trial basis at the present time. Chipping Size The chipping size is selected based on the surface texture of the primerseal. Generally a Size 14 mm chipping is selected for sealing over a Size 10 mm chipping primerseal. However, the size of chipping may need to be adjusted if during the design process detailed below, it is found that the surface texture allowance is too high. Chipping ALD The design must be based on the ALD of the chippings in stockpile to be used for the work. Curing of Primerseals When a primerseal is to be sealed, it must be sufficiently cured or hard as discussed under the section on Primerseals.


Seal and Reseal Design Procedure Single application seals and reseals (a) Select Basic Voids Factor (Vf)

The Basic Voids Factor (L/m2/mm) is the percentage of the seal mat volume to be filed with binder.

Select Vf for the traffic volume from the mid-line of Figure 5.1a or Figure 5.1b as appropriate.

(b) Determine Adjustments, (Va and Vt)

Determine the appropriate voids factor adjustments for chippings shape (Va) and traffic (Vt) from Tables 5.7 and 5.8 respectively.

For lanes where traffic is channelled into confined wheelpaths, the basic voids factor is decreased by 0.01 L/m2/mm. Examples of applicable situations are single lane bridges, tight radius curves and confined lane widths.

Short term increases in traffic volumes, such as local festivals may occur early in the life of the seal. This effect can be allowed for by a decrease in the basic voids factor to allow for the extra traffic during this critical phase.

(c) Calculate Design Voids Factor (VF) VF = Vf + Va + Vt

Check that the resulting factor is between the upper and lower limits of Figure 5.1a or 5.1b as appropriate. If it is outside the limits, adjust to the nearest limit. Adopt the value obtained as VF.

(d) Measure ALD

Determine the ALD (Average Least Dimension) of the chippings.

(e) Calculate Basic Binder Application Rate (A) A = VF x ALD (L/m2)

(f) Surface Texture Allowance (AT) (i) For a prime, concrete, or asphalt surface


Where the surface to be sealed or resealed is a prime, asphalt, or concrete, determine the following allowances. (The higher allowances are for surfaces with some texture.)

Prime: AT = 0.0 to + 0.2 L/m2

Concrete: AT = + 0.2 to + 0.3 L/m2 Asphalt: AT = 0.0 to + 0.3 L/m2 (ii) For a primerseal or seal

The surface texture depth of an existing primerseal or seal is determined from the sand texture depth test which is carried out in the wheel path areas of the pavement as described in Section 5.9.

Using the surface texture depth, the Surface Texture Allowance (AT) is determined from Table 5.9 and then added to the basic binder application rate (A). It should be noted that Table 5.9 has been designed to prohibit the use of large size chippings over coarse textured surfaces.

The surface texture depth of the existing seal condition is also be defined in the following terms:

Bleeding – free binder on the surface completely covering the chippings.

Flushed – binder near tops of the chippings.

Smooth – minimal texture depth, with proud chipping particles.

Matt – a well textured seal, with the chippings embedded into the binder to

⅔ of the chipping height.

Hungry – chipping embedded into the binder to ⅓ the chipping height. The binder is not visible between the chipping particles.

(g) Chipping Binder Absorption Allowance (ABA)

This allowance is a function of chippings but usually is not applicable in Ghana.

(h) Embedment Allowance (AE)

This step applies to seals, not reseals. The Embedment Allowance (AE) which compensates for loss of voids in the seal under traffic, is determined from Figure 5.2. It is added to the Basic Application Rate.


Surface hardness is measured by the Ball Penetration Test which is described in Section 5.10. The test method includes a temperature correction but is not usually applied in Ghana, because of limited temperature changes.

High ball penetration values indicate that bleeding may occur in subsequent seals. Where ball penetration and traffic volume are both high, alternative treatments should be considered.

(i) Design Binder Application Rate (BD)

The Design Binder Application Rate for conventional binders is calculated in L/m2 of residual bitumen as follows:

BD = A + AT + ABA + AE

Double Seals and Reseals

Both layers of a double seal are designed as for single seals except:

Multiply the Design Voids Factor of the first layer by the amount (Vm) shown in Table 5.10.

The second layer is designed without surface texture or embedment allowances, however Binder Absorption Allowance (ABA) is to be added.

Double Seals with Second Application Delayed

Where the second application is to be applied after 1 week and up to several months after the first, and the seal will be trafficked during this delay:

The first application should be designed as a single seal.

For the second application, the Design Binder Application Rate may be reduced to the minimum and the chipping spread rate may be reduced by up to 30% (that is, 30% less chippings).

Chipping Design Procedures (a) Basic Chipping Spread Rate (F)

Select and calculate the appropriate Basic Chipping Spread Rate (F) from Table 5.11 for 10 & 14mm chippings

(b) Seal Type Factor ( I )

Multiply the basic chipping spread rate by the appropriate factor (I) from Table 5.12. This adjusts the spread rate for double seals.


(c) Double Application Seals and Reseals:

Choose the size of the second application of chippings to occupy the spaces between the chipping particles of the first, thus ensuring that the first chipping is permanently locked by the second. This is usually achieved by choosing the second chipping to be half the nominal size of the first.

In Ghana because Size 7mm chippings are not always readily available, for the second application Size 10mm chippings may be selected.

Design Calculation Sheet The binder application rate is calculated on the Design Calculation Sheet in Section 5.7 .


Figure 5.1a Basic Voids Factor ( V f) Traffic Volume 0-500 vehicles/lane/day

Figure 5.1b Basic Voids Factor ( V f) Traffic Volume 500 – 10,000 vehicles/lane/day


Table 5.7 Chipping Shape Adjustment (V a) to Basic Voids Factor

Chipping Shape

Flakiness Index (%)

Voids Factor Adjustment* (L/m2 /mm)

Flaky Angular average Angular good Cubic

26 to 35 15 to 25 < 15

- 0.01 0.0 + 0.005 + 0.01

Note : Adjustments are applied to the mid-line voids factor from Figure 5.1a or 5.1b, as appropriate.

Table 5.8

Traffic Effects Adjustment (V t) to Basic Voids Factor

Adjustment to Basic Voids Factor (L/m 2/mm)

Traffic Effect Flat or downhill Slow moving – climbing lanes

0-15% HV 0 0

15 - 30% HV

- 0.01 - 0.02

> 30% HV - 0.02 - 0.03

Overtaking lanes (cars only)

+ 0.01 0

Key: HV Heavy Vehicles


Table 5.9

Surface Texture Allowance (A T) L/m 2

For Proposed Seal or Reseal

EXISTING PAVEMENT SEAL PROPOSED NOMINAL SIZE SIZE CONDITION TEXTURE

DEPTH 5mm 7mm 10mm 14mm

5mm Bleeding -- A -0.2 -0.2 -0.2 Flushed <0.7mm A -0.1 0 0 Smooth 0.9mm 0 0 0 0 Matt 1.0mm 0 +0.1 +0.1 +0.1 Hungry 1.4mm +0.2 +0.2 +0.2 +0.2 Very Hungry >1.8mm +0.3 +0.3 +0.3 +0.3

7mm Bleeding -- A -0.2 -0.2 -0.2 Flushed <0.7mm -0.1 -0.1 -0.1 0 Smooth 1.0mm 0 0 0 0 Matt 1.2mm 0 +0.1 +0.15 +0.2 Hungry 1.7mm +0.2 +0.2 +0.25 +0.3 Very Hungry >2.0mm +0.3 +0.3 +0.35 +0.4

10mm Bleeding -- -0.3 -0.2 -0.2 -0.2 Flushed <0.7mm -0.1 -0.1 -0.1 0 Smooth 1.0mm 0 0 +0.1 +0.1 Matt 1.4mm +0.1 +0.2 +0.3 +0.3 Hungry 1.9mm +0.2 +0.3 +0.35 +0.4 Very Hungry >2.2mm +0.3 +0.4 +0.4 N/R

14mm Bleeding -- A -0.3 -0.3 -0.3 Flushed <0.7mm -0.2 -0.1 -0.1 -0.1 Smooth 1.0mm 0 0 +0.1 +0.1 Matt 1.6mm +0.1 +0.15 +0.2 +0.25 Hungry 2.4mm +0.2 +0.25 +0.3 +0.35 Very Hungry >3.2mm +0.3 +0.35 +0.4 +0.4

20mm Bleeding -- A -0.3 -0.3 -0.3 Flushed <0.7mm A -0.1 -0.1 -0.1

Smooth 1.0mm 0 0 +0.1 +0.2 Matt 1.8mm +0.1 +0.15 +0.2 +0.35 Hungry 2.9mm +0.2 +0.25 +0.3 +0.4 Very Hungry >3.5mm +0.3 +0.35 +0.4 N/R Notes: A = Specialised treatment necessary N/R = Consider alternative treatments Note 1 For Absorption >1% add +0.1 Litre/m2 For absorption < 1% add 0 – 0.1 litre/m2

Note 2 Texture allowance for: Seals over primes 0.0 to +0.2litre/m2 Seals over asphalt 0.0 to +0.3 litre/m2


Figure 5.2 Embedment Allowance A E

Table 5.10

Modification to Design Voids Factor for the first layer of Double seal V m

Traffic Volume

(vehicle/lane/day)

Modification to VF

< 500

0.75

500 – 1000

0.80

1001 – 2000

0.85

> 2000

0.90


Table 5.11

Basic Spread Rates for 10 & 14 mm Chippings (F)

Binder type

Very low to low traffic ≤ 750 vehicles per lane

per day (m 2/m3 )

Medium to high traffic

> 750 vehicles per lane per day (m 2/m3)

AC -10

900 ALD

900 ALD

Emulsion

800 ALD

800 ALD

PMB

750 ALD

800 ALD

Note: For shoulder seal/reseal, the basic chipping spread rate (m2/m3) may be increased up to 800/ALD.

Table 5.12 Factor (I) to be applied to Chipping Spread Rates

Obtained from Table 5.11

Note: Factors greater than 1.0 indicate that less chippings are to be used.

6.5 DESIGN OF BITUMEN EMULSION

Type of Seal

Factor to be applied* (I)

Single

1.0 (no adjustment)

Double

• 1st layer • 2nd layer

1.1 1.0 (no adjustment)

Double Delayed application of second layer

• 1st layer • 2nd layer

1.0 (no adjustment) 1.3


SEALS General Cationic rapid setting bitumen emulsions (minimum 70% bitumen) are being used on a limited scale for primersealing and sealing works. The Road Agencies are monitoring their performance. Binder Design – Primersealing For primersealing the required residual binder application rate is determined in accordance with the procedures described in 5.3 except that the Basic Primerbinder Application Rate is selected from Table 5.14. The residual bitumen in Table 5.14 for a bitumen emulsion with 70% bitumen content is the same as that in Table 5.4 for a cutback bitumen with 16% kerosene.

Binder Design –Seals and Reseals Determine the Basic Binder Application Rate (A) in L/m2 of residual bitumen in accordance with 5.4. Select an appropriate Emulsion Factor (EF) from Table 5.13 Then calculate the Design Binder Application Rate (BD) as follows: BD =(A x EF) + AT + ABA + AE Emulsion Calculations The following procedure should be used to determine the equivalent application rate of bitumen emulsion. (a) Convert primerbinder application rates to residual binder application rates.

Primersealing application rates are expressed in terms of cutback bitumen in Section 5.3. These rates must first be converted to residual binder application rates, as follows:

Residual Binder = 100-C x D Application Rate 100 where: C = design cutter oil content (%) D = primerbinder design application rate (L/m2)


(b) Using Residual Binder Application Rates, convert to Equivalent Bitumen Emulsion Application Rates.

Bitumen Emulsion Application Rate = 100 x RB

B where: RB = residual binder application rate (L/m2) B = percentage of bitumen in the emulsion Maximum Allowable Rates Where bitumen emulsion application rates exceed the following, significant run-off may occur. • 1.7 L/m2 for 60% bitumen emulsions • 2.5 L/m2 for 70% bitumen emulsions If a proposed application rate exceeds the above, an alternative treatment should be considered. Design Calculation Sheet The binder application rate is calculated on the Design Calculation Sheet in Section 5.7 and the conversion to bitumen emulsion made at the end of the design process. Chipping Design Procedures (a) For Primerseals

Design in accordance with the procedures in 5.3. (b) For Single Seals, and Reseals

Additionally, a light scatter coat of precoated 7 mm chippings (about 400 m2/m3) is spread before rolling to lock in the larger chippings and reduce its movement during rolling.


Table 5.13

Emulsion Factor (EF)

Product

Emulsion Factor (EF)

Conventional emulsion (60%)

1.0

High Bitumen Content Emulsion (≥67%)

1.1 – 1.2

Table 5.14

Basic Rates for Primerbinder (Bitumen Emulsion – 70 %Bitumen) and Rates for Chippings

Note:

The application rates given are intended as a guide only. Actual rates should be determined by onsite trials. The above rates do not include any allowance for surface texture, or absorption by the base.

Chipping Size

Basic Primerbinder Application Rate at 150C

(L/m 2) of mixture

Chipping Application

Rate

(mm) Vehicle/lane/day

<300 300-2000 >2000

(m2/m3) 7 1.55

1.45 1.30 150 – 190

10 1.70

1.55 1.45 120 – 150

14 1.80 1.70 1.55 90-110


6.6 DESIGN EXAMPLES Primerseal A primerseal is to be placed on a reconstructed section of highway. The job details are as follows: The top layer of pavement has been constructed using a finely bonded gravel. A cutback bitumen binder with 16% cutter and Size 10 mm chippings has been selected. The traffic volume AADT is 3600 vpd but it is assumed that the traffic volume is split 50/50 for each direction of travel. The completed calculation sheet is detailed in Figure 5.3

PRIMERSEAL DESIGN CALCULATION SHEET

JOB No.

ITEM DESCRIPTION RATE

(L/sqm) CHIPPING

Size 10 mm Type Granite Traffic volume v/l/d 1800 BASIC APPLICATION RATE (Litres/sqm) Design Rate – Table 5.4 1.3 ALLOWANCES (Litres/sqm) Surface condition – Table 5.5 0.1 Absorption chippings NA 0.0 DESIGN APPLICATION RATE (litres/sqm) 1.4 LOOSE CHIPPING SPREAD RATE m2/m3 Design Rate – Table 5.4 120-150

Figure 5.3 Primerseal Design Calculation Sheet


Seal (i) Hot applied bitumen

A hot applied bitumen (grade AC-10) seal is to be placed over a primerseal on a section of highway. The job details are as follows: Traffic 380 v/l/d , Heavy vehicles 20% No steep grades Chipping Size 10 mm granite Shape angular average ALD 5.9 mm The existing surface is a size 10 primerseal about one year old with surface texture T = 1.4 mm. Ball penetration results indicate an average embedment of 3.0 mm. The completed calculation sheet is detailed in Figure 5.4 (ii) Bitumen emulsion A bitumen emulsion (Cationic rapid setting with 70% bitumen) seal is to be placed over a primerseal on a section of highway. The job details are as follows: Traffic 930 v/l/d , Heavy vehicles 10% No steep grades Chipping Size 10 mm granite Shape angular average ALD 8.2 mm The existing surface is a size 10 primerseal about one year old with surface texture T = 1.0 mm. Ball penetration results indicate an average embedment of 3.0 mm. The completed calculation sheet is detailed in Figure 5.5.


SEAL AND RESEAL DESIGN CALCULATION SHEET

JOB

ITEM DESCRIPTION VALUE RATE COMMENT

CHIPPING

Size 10 mm

Type Granite

ALD 5.9 mm

Traffic volume v/l/d 380

Basic voids factor V f From Fig 5.1 0.18

ADJUSTMENT FACTORS CHIPPINGS

Chipping Shape Va – Table 5.7 Angular Average 0.00

Commercial Vehicles Vt – Table 5.8 20% -0.01

Climbing lane Vt – Table 5.8 NA 0.00

BASIC APPLICATION RATE

Design Voids Factor VF VF = Vf + Va + Vt 0.17

Stripping/Bleeding Check From Fig 5.1 OK

Basic application rate A A= ALD x VF 1.00

ALLOWANCES (Litres/sqm)

Existing surface size 10 mm

Surface texture AT – Table 5.9 1.4 mm +0.3

Absorption chippings ABA NA 0.0

Embedment AE - Fig 5.2 3 mm 0.0

Total Allowance +0.3 ADOPTED APPLICATION RATE Other factors NA 0.0

DESIGN BINDER APPLICATION RATE BD (litres/sqm) BD = A + AT + ABA + AE

1.30 1.30

CHIPPING DESIGN LOOSE SPREAD RATE m2/m3

Loose Spread Rate F* From Table 5.11 152

* Does not include stockpile waste

Figure 5.4 Seal Design Calculation Sheet


EMULSION SEAL AND RESEAL DESIGN CALCULATION SHEET

JOB No.


Chipping

Size 14 mm

Type Granite

ALD 8.2 mm

Traffic volume v/l/d 930 v/l/d

Basic voids factor V f From Fig 5.1 0.16


Chipping Shape Va - Table 5.7 Angular Average 0.00 Commercial Vehicles Vt – Table 5.8 10% 0.00

Climbing lane Vt - Table 5.8 NA 0.00



Stripping/Bleeding Check From Fig 5.1 OK

Emulsion Factor EF From Table 5.13 1.1

Basic application rate A A = ALD x VF x EF 1.44


Existing surface size 10 mm

Surface texture AT - Table 5.9 1.0 mm +0.1

Absorption chippings ABA NA 0.0

Embedment AE - Fig 5.2 3 mm -0.1

Total Allowance 0.0

Other factors 0.0 BITUMEN DESIGN APPLICATION RATE (litres/sqm) = A + AT + ABA + AE

1.44

ADOPTED APPLICATION RATE Litres/m2 % BITUMEN IN EMULSION 70% 0.70

EMULSION DESIGN APPLICATION RATE* = BITUMEN DESIGN RATE % BITUMEN IN EMULSION

2.06

Say 2.1

* Check Final Rate does not exceed 2.5 litres/sq m OK

DESIGN LOOSE SPREAD RATE m2/m3

Loose Spread Rate F* From Table 5.11 97

* Does not include stockpile waste Figure 5.5 Bitumen Emulsion Seal Design Calculation


Double Seal – Hot Applied Bitumen A hot applied bitumen (grade AC-10) double seal is to be placed over a primerseal on a section of highway. The double seal is to be applied with no delay between applications. The job details are as follows: Traffic 2500 v/l/d, Heavy vehicles 16% No steep grades Chipping Size – first application 14 mm granite ALD 8.6 mm Shape angular average Chipping Size - second application 10 mm granite ALD 6.1 mm Shape angular average The existing surface is a size 10 primerseal about one year old with surface texture T = 1.3 mm. Ball penetration results indicate an average embedment of 1.0 mm. The completed calculation sheet for the first application is detailed in Figure 5.5a, the second application in Figure 5.5b, and the chipping spread rate in Figure 5.5c.


DOUBLE SEAL DESIGN CALCULATION SHEET

ITEM DESCRIPTION VALUE RATE COMMENT JOB NO. First Application Chipping Size 14 mm Type Granite ALD 8.6mm Traffic volume v/l/d 2500

Basic voids factor V f From Fig 5.1 0.14 ADJUSTMENT CHIPPING FACTORS

Chipping Shape Va - Table 5.7 Angular Average 0.00

Commercial Vehicles Vt - Table 5.8 16% -0.10

Climbing lane Vt – Table 5.8 N.A. 0.00 BASIC APPLICATION RATE


Adjustment Factor Vm - Table 5.10 0.9

Basic application rate A A= ALD x VF x Vm 8.6x.13x0.9 1.01 ALLOWANCES (Litres/sqm)

Existing surface size 10mm

Surface texture AT - Table 5.9 1.3 mm + 0.3

Absorption chippings ABA N.A. 0.0

Embedment AE- Fig 5.2 1.0 mm -0.1 ADOPTED APPLICATION RATE

Total Allowance +0.2 DESIGN FIRST LAYER APPLICATION RATE B D (litres/sqm) BD = A + AT + ABA + AE

1.21 1.20 CHECK BD > 0.1 x ALD 0.1x8.6= 0.86 OK

Figure 5.5a First Application of Double Seal



ITEM DESCRIPTION VALUE RATE COMMENT JOB NO. Second Application Chipping Size 10 mm Type Granite ALD 6.1 mm Traffic volume v/l/d 2500

Basic voids factor V f From Fig 5.1 0.14 ADJUSTMENT CHIPPING FACTORS

Shape Va - Table 5.7 Angular Average 0.00

Commercial Vehicles Vt - Table 5.8 16% -0.01

Climbing lane Vt - Table 5.8 N.A. 0.00 BASIC APPLICATION RATE

Design Voids Factor VF VF = Vf + Va + Vt 0.13 Basic Application Rate A A = ALD x VF 0.79 ALLOWANCES (Litres/sqm)

Absorption chippings ABA N.A. 0.0 ADOPTED APPLICATION RATE

Total 0.0

DESIGN SECOND LAYER APPLICATION RATE B D (litres/sqm) BD = A + ABA 0.79 0.80

Figure 5.5b Second Application for Double Seal FIRST LAYER LOOSE CHIPPING SPREAD RATE ALD Basic Rate F From Table 5.11 105 Spread Factor From Table 5.12 1.1 DESIGN LOOSE SPREAD RATE m2/m3 115 115 SECOND LAYER LOOSE CHIPPING SPREAD RATE ALD Basic Rate F From Table 5.11 147 Spread Factor From Table 5.12 1.0 DESIGN LOOSE SPREAD RATE m2/m3 147 147

Figure 5.5c Chipping Spread Rate for Double Seal


6.7 DESIGN SHEETS Prime Design

Job Details Date:……………………………………………

Job / Order No:.………………………………...

Office:…………………………………………..

Road No. / Name:………………………………

Location: Roadloc:………………………………………..

To

…………... km to …………… km from ………………………towards ………………………….. Length ………….mtr.

Width …………...mtr. Area …………sq.mtr. No. of lanes………….

Pavement Surface Type

Table 5.1

Type and Grade of Primer

Table 5.2

Equivalent % of Cutter Oil in Mixture

Table 5.2

%

Adhesive Agent Type / Rate

%

Pavement Surface Condition

Table 5.1

Basic Application Rate (including Cutter) (A)

Table 5.2

L/m²

Adjustments (based on field trial) (B)

L/m²

Design Application Rate (=Sum A+B)

L/m²


Primerseal Design for Cutback Bitumen


JOB No.


(L/sqm) CHIPPING

Size Type Traffic volume v/l/d BASIC APPLICATION RATE (Litres/sqm) Design Rate – Table 5.4 ALLOWANCES (Litres/sqm) Surface condition – Table 5.5 Absorption chippings DESIGN APPLICATION RATE (litres/sqm) LOOSE CHIPPING SPREAD RATE m2/m3 Design Rate – Table 5.4

Primerseal Design for Bitumen Emulsion ( 70% Bitume n)


JOB No.


(L/sqm) CHIPPING

Size Type Traffic volume v/l/d BASIC APPLICATION RATE (Litres/sqm) Design Rate – Table 5.14 ALLOWANCES (Litres/sqm) Surface condition – Table 5.5 Absorption chippings DESIGN APPLICATION RATE (litres/sqm) LOOSE CHIPPING SPREAD RATE m2/m3 Design Rate – Table 5.4


Seal and Reseal Design for Hot Applied Bitumen Bind er SEAL AND RESEAL DESIGN CALCULATION SHEET

JOB


CHIPPING

Size

Type

ALD

Traffic volume v/l/d

Basic voids factor V f From Fig 5.1


Chipping Shape Va – Table 5.7

Commercial Vehicles Vt – Table 5.8

Climbing lane Vt – Table 5.8


Design Voids Factor VF VF = Vf + Va + Vt

Stripping/Bleeding Check From Fig 5.1

Basic application rate A A= ALD x VF


Existing surface size

Surface texture AT – Table 5.9

Absorption chippings ABA

Embedment AE - Fig 5.2

Total Allowance ADOPTED APPLICATION RATE Other factors

DESIGN BINDER APPLICATION RATE BD (litres/sqm) BD = A + AT + ABA + AE

CHIPPING DESIGN LOOSE SPREAD RATE m2/m3

Loose Spread Rate F* From Table 5.11



Double Seal Design for Hot Applied Bitumen Binder First Application


ITEM DESCRIPTION VALUE RATE COMMENT JOB NO. First Application Chipping Size Type ALD Traffic volume v/l/d

Basic voids factor V f From Fig 5.1 ADJUSTMENT CHIPPING FACTORS

Chipping Shape Va - Table 5.7

Commercial Vehicles Vt - Table 5.8

Climbing lane Vt – Table 5.8 BASIC APPLICATION RATE


Adjustment Factor Vm - Table 5.10

Basic application rate A A= ALD x VF x Vm ALLOWANCES (Litres/sqm)


Surface texture AT - Table 5.9


Embedment AE- Fig 5.2 ADOPTED APPLICATION RATE

Total Allowance DESIGN FIRST LAYER APPLICATION RATE B D (litres/sqm) BD = A + AT + ABA + AE

CHECK BD > 0.1 x ALD


Second Application DOUBLE SEAL DESIGN CALCULATION SHEET

ITEM DESCRIPTION VALUE RATE COMMENT JOB NO. Second Application Chipping Size Type ALD Traffic volume v/l/d

Basic voids factor V f From Fig 5.1 ADJUSTMENT CHIPPING FACTORS

Shape Va - Table 5.7

Commercial Vehicles Vt - Table 5.8

Climbing lane Vt - Table 5.8 BASIC APPLICATION RATE

Design Voids Factor VF VF = Vf + Va + Vt Basic Application Rate A A = ALD x VF ALLOWANCES (Litres/sqm)

Absorption chippings ABA ADOPTED APPLICATION RATE

Total

DESIGN SECOND LAYER APPLICATION RATE B D (litres/sqm) BD = A + ABA

Chipping Application FIRST LAYER LOOSE CHIPPING SPREAD RATE ALD Basic Rate F From Table 5.11 Spread Factor From Table 5.12 DESIGN LOOSE SPREAD RATE m2/m3 SECOND LAYER LOOSE CHIPPING SPREAD RATE ALD Basic Rate F From Table 5.11 Spread Factor From Table 5.12 DESIGN LOOSE SPREAD RATE m2/m3


Seal and Reseal Design for Bitumen Emulsion

EMULSION SEAL AND RESEAL DESIGN CALCULATION SHEET

JOB No.


Chipping

Size

Type

ALD

Traffic volume v/l/d

Basic voids factor V f From Fig 5.1


Chipping Shape Va - Table 5.7 Commercial Vehicles Vt – Table 5.8

Climbing lane Vt - Table 5.8



Stripping/Bleeding Check From Fig 5.1

Emulsion Factor EF From Table 5.13

Basic application rate A A = ALD x VF x EF



Surface texture AT - Table 5.9


Embedment AE - Fig 5.2

Total Allowance

Other factors BITUMEN DESIGN APPLICATION RATE (litres/sqm) = A + AT + ABA + AE

ADOPTED APPLICATION RATE Litres/m2 % BITUMEN IN EMULSION

EMULSION DESIGN APPLICATION RATE* = BITUMEN DESIGN RATE % BITUMEN IN EMULSION

* Check Final Rate does not exceed 2.5 litres/sq m

DESIGN LOOSE SPREAD RATE m2/m3

Loose Spread Rate F* From Table 5.11



6.8 DETERMINING AVERAGE LEAST DIMENSION (ALD)

General The direct measurement method is one of the most reliable methods of determining ALD as it is based on actual measurements. The method uses a vernier calliper, a dial gauge, or a slotted gauge, and is applicable to chippings Size 5 mm and larger. Apparatus The following apparatus is required: (a) Vernier callipers, dial gauge or slotted gauge (see (b) below). (b) A slotted gauge consists of a metal frame with slots 2 mm, 4 mm, 6 mm, 8

mm, 10 mm, 12 mm, 14 mm, 16 mm and 18 mm wide arranged consecutively. The tolerance for all slots is ± 0.05 mm.

(c) Containers or metal dishes to hold the various portions of test sample. (d) Sieves-as required, complying with ASTM D1130-90 Sampling The test portion of chippings is prepared as follows: (a) Sieve the sample as per ASTM D75-87 requirements (b) Discard all size fractions where the material is present in an amount of less

than 10 percent of the whole sample. (c) Recombine the remaining size fractions and reduce the size of the sample by

quartering or riffling to obtain the test portion of at least 100 stones.

Procedure General. (a) Spread the stones on a flat surface and turn them such that they lie with their

least dimension in a vertical plane.

(b) Determine the least dimension of each stone by vernier calliper dial gauge, or

slotted gauge method.


(c) Record the least dimension in the appropriate class size (between 0 mm and

20 mm in 2 mm intervals) calculation table.

Vernier Calliper Method.

(a) Set the vernier scale to an opening of 2.0 mm. Record the number of stones

passing through the opening in the minimum dimension orientation in the calculation table. Repeat the procedure for vernier scale openings from 2mm to 18mm.

Dial Gauge Method.

(a) Zero dial gauge to a fixed plane surface. (b) Slide each stone under the dial gauge in the minimum dimension orientation.

Record the minimum dimension obtained for each stone. (c) Separate the stones into class sizes with 2 mm intervals, i.e. between 0 and 2

mm, 2 mm and 4 mm, etc. (d) Count the number of stones in each class size.

Slotted Gauge Method. (a) Slide the stones through the slotted gauges in the minimum dimension

orientation. (b) Separate the stones into class sizes with 2 mm intervals as for the dial gauge

method and then count the number in each class.

Calculation The average least dimension (ALD) based on the class frequency distribution is calculated using Table 5.15.


Table 5.15 Calculation of ALD

Class Size (mm)

Class least Dimension

A

Number of particles

B

A x B

Less than 2

1

a

2 to 4

3

b

4 to 6

5

c

6 to 8

7

d

8 to 10

9

e

10 to 12

11

f

12 to 14

13

g

14 to 16

15

h

16 to 18

17

i

18 to 20

19

j

SUM B =

SUM of A x B =

Average Least Dimensio n (ALD)= (Sum (A x B) ÷ SUM B) to the nearest 0.1mm

Report ALD to the nearest 0.1mm


6.9 SAND TEXTURE TEST The Sand Texture Test is used to assess the surface texture of an existing sprayed seal. That is, the average depth from the top of the chipping to the binder level of a primerseal, seal, or reseal . The surface texture depth is then used to determine the allowances required for the design of seals and reseals. Equipment • 4 litre Plastic Jar for sand • graded sand 100% passing 1.18mm sieve and retained on the 0.600mm sieve.

Or

• graded sand 100% passing 0.600mm sieve and retained on the 0.300mm sieve. • 300 mm ruler • bannister brush • measuring container such as a white film canister which has a known volume

between of 31.8 cc or a small plastic bag with a standard measured volume of sand

Test Sites

Inspect the whole of the job and mark with paint the large scale changes of surface texture. Do not mark small texture changes. Assess each zone with particular attention being paid to traffic volumes,wheel paths, super-elevations, climbing areas and hilly terrain. Be aware of variability of texture across pavement and test and interpolate results.

Test wheel path locations for traffic greater than 1000 vehicles/lane/day and test average texture of lane for traffic less than 1000 vehicles/lane/day.

Test Procedure (a) Select test sites as above.

(b) Install traffic warning signs or devices as appropriate.

(c) Fill standard volume container with sand by dipping into the jar,

tapping the cylinder and striking off excess. (or take measured plastic bag samples of beads or sand)

(d) Pour contents of the container into a small pile on to the area being tested


(e) Use the straight edge or ruler to rotate the sand on the road surface to work the sand down into the surface voids in a circular motion working from the center outwards and forming a uniform diameter sand circle.

(f) Continue to work the sand to form as neat a circle as possible until the diameter of the circle stabilizes and all the sand has migrated into the surface voids.

Figure 5.6 Sketch of Sand Texture Test Procedure (g) Use the ruler to measure the diameter of the circle (mm) in a number of diagonal

directions and average the four readings. (h) A sketch of the test procedure is shown in Figure 5.6. Calculate Surface Texture Depth (T) The surface texture depth is calculated from the formula:

T = 1273 x V

D²


T = Average Surface Texture Depth (mm) V = Volume of sand sample (cc) D = Average diameter of patch (mm)

For convenience, the surface texture depth (T) for sand patch diameters (D) from 100 to 300 mm can be read directly from Table 5.16 where a white film container, which has a known volume (31.8cc) has been used to measure the sand. The surface texture depth is then used to determine the Surface Texture Allowance from Table 5.9 It should be noted that the method is for determination of texture allowances on sealed or asphalt surfaces. It is not applicable for primed or unsealed surfaces.

The texture allowance need only be read to an accuracy of + or - 0.05 L/m2 due to general variability in surface texture. It is better to nominate a range, e.g. 0.2 to 0.3 L/m2., and round off the final application depending on traffic volumes and other allowances.

It may not be necessary to measure surface texture at every site once you have formed a firm opinion based on a number of previous tests however, this opinion needs to be checked against actual measurements on a regular basis.

Table 5.16

Surface Texture Depth

Diameter (mm)

Av Texture

Depth mm

Diameter (mm)

Av Texture

Depth mm

100 4.0 180 1.2

110 3.3 190 1.1

120 2.8 200 1.0

130 2.4 220 0.8

140 2.1 240 0.7

150 1.8 260 0.6

160 1.6 280 0.5

170 1.4 300 0.4


6.10 BALL PENETRATION TEST The Ball Penetration Test is used to determine chipping embedment into the road surface. The test method procedure measures the depth of penetration by a 19 mm diameter steel ball into road surface under the impact of a standard load. Definitions The road surface includes the road base, prime, primerseal and existing seals. Seals are considered to be soft when the ball penetration unit sinks into the surface under its own weight. Apparatus The Ball Penetrometer is shown in Figure 5.7. Procedure (a) To measure Ball Penetration on a typical road surface: 1. Unscrew the ball penetrometer tip from the top of the base and

screw into the bottom of the penetrometer base after removing the keeper screw.

2. Remove the Ball Penetrometer transit pins B&C shown in Figure 5.8. 3. Sit the Ball Penetrometer on an area typical of the road surface to be sealed. 4. Level the Ball Penetrometer with the leveling feet until bubble is approximately

centred. 5. Rest one knee firmly on the unit’s base, at the same time grasp the rear of the

unit near the top. The unit should now be stable and ready for operation. The free hand is used to raise the hammer weight.

6. Zero the direct measurement scale, by adjusting the thumb screw and locking

nut on top of the hammer. Locking the thumb screw is optional. 7. Apply one blow of the hammer by raising the hammer weight to the top of the

unit and allowing it to fall freely. 8. Measure and record the depth of penetration in mm to the nearest 0.5mm.


9. Repeat steps 2 to 8 another 4 times at each location. Average and record the results of the tests to the nearest 0.5mm. Each repeat test should be carried out within a radius of 100mm of the initial test.

NOTE: Hands are to be kept clear of collar around base at all times. (b) To measure Ball Penetration on a soft seal

When it is evident that the hammer will sink into the seal under its own weight, the frame is separated from the penetrometer mechanism.

1. Replace the case hardened screw in ball tip with blank screw-in tip 2. Remove pins A,B and C - see Figure 5.8. 3. Detach base of penetrometer frame by removing the two base screws. The

detached upright section minus the gauge pin, is not used in this part of the procedure.

4. Assemble the depth gauge (from pin of direct measurement scale) by

removing the graduated pin and reinserting perpendicularly in the slot provided.

5. Remove the 19mm case hardened steel ball from the base and place on an

area typical of the road surface to be sealed. 6. Centre the Ball Penetrometer base over the steel ball. 7. Place the assembled depth gauge into the slots of the base sleeve (with the

knurled end facing the steel ball) and measure down to the top of the steel ball by releasing the screw and lowering the knurled end onto the steel ball. Remove the gauge and note the measurement to the nearest 0.5mm.

8. Place the hammer through the collar in the base so that the blank tip contacts

the steel ball. 9. Apply one blow of the hammer by raising the hammer weight to the top of the unit and allowing it to fall freely. 10. Remove the hammer and replace the depth gauge. Measure to the top of the

steel ball. Record the determined difference (penetration) between the first and second readings to the nearest 0.5mm.


Figure 5.7 Ball Penetrometer


Figure 5.8 Ball Penetrometer

6.11 RESISTANCE TO STRIPPING OF


CHIPPINGS GHA test method T230 is used to assess the resistance of chippings to stripping in the presence of moisture with or without precoating and with or without binder adhesion agents. This method is also known as the Plate Test or Stripping Test. It is not applicable to chippings which pass a 9.50 mm BS sieve. Note: When performing this test using modified binders, the softening point must first be determined. Apparatus (a) Zinc or aluminium plates, of nominal size 152 mm by 152 mm, 3 mm thick

with a 6 mm rim turned up on all sides, and an etched upper surface.

(b) Hot plate, electric, with adjustable temperature control. (c) A thermostatically controlled oven with good air circulation, capable of

maintaining a temperature within the range of 60 - 110 + 2°C. (d) A thermostatically controlled oven with good air circulation capable of

maintaining a temperature within the range of 185 + 5°C. This oven is only required where binder adhesion agents are to be tested.

(e) A thermostatically controlled water bath, capable of maintaining water at a

temperature within the range of 50 + 2°C, and being adjustable to maintain a temperature of 24 + 2°C fitted with a water circulating device and racks to support metal plates below water level.

(f) Scales or balance for weighing material up to 6 Kg, readable and accurate to

1 gram. (g) Containers of at least 500 mL capacity, with press-on lids. (h) Pliers, long nose, with hollow-ground tips. (i) Heat insulating gloves and tongs. (j) Spatula or palette knife. (k) 9.5 mm BS sieve.


Test Samples Each chipping test sample shall consist of at least 50 particles of a similar size which are representative of the chippings submitted for testing. In general, five test samples are required. The binder should be a sample of the type and class from the same source of supply or manufacture as the binder proposed for use in the field. The binder may consist of bitumen, scrap rubber bitumen or polymer modified bitumen. Preparation Of Test Samples (a) Chippings

Samples shall be prepared as follows:

• As received

• Clean and Dry

The chipping particles shall be washed and scrubbed to remove adhering dust, and dried to constant mass in an oven at a temperature in the range of 105°C to 110°C.

• Dusty

The chipping particles shall be lightly sprinkled with dried clay screened to pass a .075 mm sieve. Excess dust should be shaken from the particles before applying the chipping particles to plates.

• Saturated Surface Dry

The chipping particles shall be soaked in water at room temperature for 24 hours allowed to drain for about 15 minutes then spread on an absorbent cloth and rolled or patted until all visible films of water are removed. Larger particles may be wiped individually.

• Saturated Surface Wet

The chipping particles shall be soaked in water at room temperature for 24 hours and then allowed to drain for 15 minutes before applying the chipping particles to the plate.


(b) Precoating Material This should be prepared and applied in accordance with the proportions to be used. If a proprietory product it should be applied in accordance with the manufacturers’ recommendations.

The chipping test samples, shall be placed in the 500 mL container and the precoating material added in small increments. After each addition the container should be scaled and shaken or rolled to mix the precoating onto the chipping particles. Continue adding and mixing small increments until the chipping particles have a dull damp appearance without any inundation.

Remove the precoated chippings from the container and stand on a tray or in a flat dish for 24 hours before applying the chippings to the plates.

(c) Adhesion Agent

The adhesion agent should be prepared and applied to the binder in accordance with the manufacturer's recommendations:

Weigh out sufficient binder for the number of plates allowing approximately 35gram for each plate. Determine the mass of binder to the nearest 1gram and calculate the quantity of adhesion agent as a percentage by mass.

Gently warm the binder until fluid and add the adhesion agent. Stir the mixture at frequent intervals until the temperature of the mixture reaches 180°C. Place the mixture in an oven at a temperature within the range of 185 + 5°C. Allow the mixture to remain in the oven for 60 ± 2 minutes. Remove the mixture from the oven and allow to cool to room temperature.

As hot binders can cause burns, samples must be handled with gloves or tongs. Suitable safety glasses and/or face shields are also to be worn.

Test Procedure (a) Gently heat binder on the hotplate until fluid. (b) Place a zinc or aluminium plate on the balance. Pour the fluid binder on to the plate until 30 to 35 grams have been spread.

(c) Remove the plate from the balance and gently heat on a hot plate to ensure a

uniform thickness of the binder film. Allow the plate and binder to cool to room temperature.

(d) Gently hand press the 50 aggregate particles (test portion) into the binder film

on the plate. Place the plate into an oven at 60 + 2°C or at [Binder Softening Point + 20°C + 2°C] whichever is the higher, for 24 hours.


(e) Remove the plate containing the binder and aggregate particles from the oven and immerse in the water bath at 50 ± 2°C for 4 days.

(f) After 4 days the temperature of the water in the water bath shall be lowered to

24 ± 2°C and maintained at this temperature for one hour, or transfer the plate to another container of water at 24 ± 2°C for one hour.

(g) Remove the plate and contents from the water bath and pull the chippings

from the binder with the aid of long-nosed pliers. Use steady vertical pressure when pulling the chipping particles to avoid sliding the particles while manipulating the pliers.

(h) Sort the chipping particles into groups according to the following features:

• Completely Stripped - less than one quarter of the contact area is coated with binder.

• Partly Stripped - between one quarter and three quarters of contact area is

coated with binder.

• Not Stripped - more than three quarters of the contact area is coated with binder.

Note: The black binder on the contact surface may be very thin. To confirm the presence of binder, place a filter paper (Whatman No 1) over the contact area of the inverted chipping particle and apply firm pressure with the index finger. Lift the filter paper by its edges. If the chipping is lifted with the filter paper and remains attached to the paper for greater than 5 seconds a binder film is present. When using scrap rubber bitumen, the binder film remaining on the chipping may be thinner than that usually encountered with other binders. Calculations (a) After visual assessment of each aggregate particle, calculate the percentage

of particles (by number) which have stripped as follows:

• Completely Stripped - count one unit • Partly Stripped - count one-half unit • Not Stripped - count nil

(b) The percent stripping of the sample is the sum of these percentages

calculated to the nearest two percent.


Reporting Report the following: (a) Type and source of chippings. (b) Type, class and source of binder. (c) Softening Point of Binder and oven temperature for 24 hour conditioning. (d) Precoating, material. (c) Type and proportion of binder adhesion agent. (f) Percent Stripped to the nearest 2%. (g) Report any tendency for chipping particles to crumble when being pulled from

plate.

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Ministry of Road Transport Surface Dressing Manual 80

7. CONSTRUCTION PRACTICE

7.1 PREPARATIONS FOR SEALING General It is essential to plan and prepare for bituminous sealing work so as to ensure that a high standard seal is produced at minimal cost. Inspections The site must be inspected well in advance of the planned date of sealing to enable the selection or determination of: (a) sealing treatment (b) remedial treatment required to restore the pavement to a condition suitable

for sealing (c) location of sites for handling and storage of binder and for stockpiling,

precoating and loading of chippings.

The sites should be selected so that they are: (i) near the site of the work and closest to the source of supply.

(ii) on level cleared hard standing ground . (iii) clear of the road formation, drains, side tracks, trees, poles or other

obstructions. (iv) of suitable size and shape for handling and storage of binder or for

stockpiling, precoating and loading of chippings. (d) traffic control strategy for the work.

(e) design of the surfacing treatment.

The site inspection should include an assessment of the pavement condition for the following design parameters:

• Surface Texture Allowance (AT) based on Sand Texture Test .

• Embedment Allowance (AE) based on the Ball Penetration Test .

________________________________________________________________________________________________________________________


The pavement should also be inspected a day or two before the bituminous sealing to ensure that the preparation work has been satisfactorily completed. To ensure that all information is collected during the site inspection, complete the checklists shown in Section 6.11. Site Preparation The sites for Binder Handling and Storage and Chipping Stockpiles should be prepared by:

(a) grading and compacting the surface to provide good drainage (b) clearing all vegetation and rubbish (c) locating storage tanks and other equipment for ease of handling and storage

of binders. Supply of Binder The following actions should be taken to ensure satisfactory delivery of the binder: (a) check that the type of materials are available and acceptable.

(b) determine the manner of supply (eg. road tanker) and requirements relating to

delivery, eg temperature. (c) determine the sampling and testing procedure to be used for the contract. Supply and Precoating of Chippings (a) Supply of Chippings

Whether chippings have been supplied as part of the contract, or have been purchased directly from the quarries, the following action should be taken:

• always test samples of chippings before acceptance and delivery to site

• check quantities and locations of deliveries

• arrange regular sampling and testing

• measure stockpiles

________________________________________________________________________________________________________________________


(b) Stockpiles

For ease of precoating and loading operations, and measurement, stockpiles should be:

• rectangular in shape at base of stockpile.

• of uniform side slopes between 1.5 and 3 horizontal to 1 vertical

• 1.2 metres high (approximately).

A clear space of 10 metres width on at least one end and 3 metres width on at least one side is required.

(c) Precoating Chippings

(i) General

All chippings should be precoated before use in bituminous surfacing work.

(ii) Precoating materials

Precoating materials are described in Section 3. Chippings which have been precoated with diesel fuel oil based precoat should be stockpiled for at least one week before use. If stockpiles are covered to prevent contamination, the chippings may be suitable for use for several months. However, if they have not been used within 6 months light precoating may be required.

(iii) Application rates

The application rates for precoating material are detailed in Section 3.3. However, they should be such that each chipping particle is uniformly coated and has a dull, damp appearance. No free precoating material should be evident.

The following field check may be made to determine whether or not the chippings are correctly precoated:

• Fill a white plastic bag to about one third full with some of the precoated

chippings.

• Close the top of the bag and shake it several times so that the chippings contact the inside surface of the bag.

• If the inside of the bag is dusty, then the precoat has been under applied.

• If the inside of the bag is relatively clean with the exception of a few streaks

of precoat, then the precoating rate is correct.

________________________________________________________________________________________________________________________


• If the inside of the bag is covered with an oily coating, then the precoat has been over applied.

(iv) Method of precoating

Chippings maybe precoated using the following methods:

Quarry Crushing Plant

Where practical, chippings should be precoated by the quarry supplying chippings. The precoating agent is normally applied at the specified rate as the chippings come off the conveyor belts into stockpile or into the trucks for delivery to the job site.

Payloader (front end loader)

Precoating of chippings can be undertaken at stockpile sites using a payloader and bitumen distributor hand distributor.

The chippings should be clean and dry with a minimum of dust. They are loaded into the bucket of the payloader and the precoating fluid sprayed evenly over the chippings. The volume of precoating fluid applied is based on application rate and the volume of the payloader bucket. A stockpile of the partially precoated chippings is constructed and then turned over with the payloader until all chippings are uniformly coated. Large stockpiles of chippings can also be precoated using the same method. The required volume of precoating agent is sprayed onto the stockpile and then the stockpile is turned over until all the chippings are uniformly coated.

(v) Condition of chippings

Chippings should be precoated only when they are dry and clean.

Treat the chippings as follows:

• If the chippings are precoated when damp, they should be allowed to dry before being used for sealing.

• Fines and dust should be removed from chippings before precoating.

(vi) Stockpiled precoated chippings

The following precautions should be taken with stockpiled precoated chippings:

________________________________________________________________________________________________________________________


• If stockpiled precoated chippings are not to be used immediately, cover stockpiles with heavy plastic sheeting or similar material to prevent contamination by water and dust.

• If rain appears imminent, cover the stockpiles of precoated chippings.

• Precoated chippings which have dried out while stockpiled, should be

precoated again before being used for sealing work. Sampling of Chippings Before designing a seal or reseal, the chippings should be sampled from stockpile and the ALD determined. Plant Requirements All necessary items of plant should be on site in good working order before the commencement of sealing operations. The plant used by a typical spray gang includes: • bitumen distributor • heater storage unit • road tanker • chipping precoater • chipping loader • chipping spreader • trucks with or without box spreaders • rollers (self-propelled pneumatic tyred) • drag broom • rotary road broom • tender truck • utility truck (Foreman) Descriptions of the types of sealing plant are given in Section 7

________________________________________________________________________________________________________________________


Spray Gang A spray gang for a normal sealing operation may comprise: • 1 foreman

• 1 ganger (penciler) • 1 road tanker driver • 1 distributor driver • 1 distributor operator • 1 heater attendant • 1 loader operator • 2 roller operators • 3 truck drivers (chipping trucks) • 1 ganger truck driver • 4 labourers The size of the spray gang may need to be increased or decreased depending on the type and extent of the work. Traffic Control Strategy After the site inspection, plan the traffic control strategy for each particular job. The strategy must be prepared in accordance with Ghana Road Traffic Regulations. The traffic control strategy elements include: (a) determining the method of traffic control such as: • single lane only • full width • side track or detour around the site (b) preparing detailed instructions (with plans if necessary of traffic control measures)

________________________________________________________________________________________________________________________


(c) arranging for the required number of Traffic Controllers to be available at the site

(d) arranging for the supply and use of all necessary signs, traffic control devices

and pilot vehicles where necessary. Job Instructions For each section of the work, prepare job instructions for the Foremen or Supervisor who will supervise the work. Information to be included in the job instructions comprises: • details of the location.

• lengths and widths to be sprayed • sources of materials • type(s) of binder • binder application rater(s) • procedures for cutting back binder • nominal size(s) of chippings • chipping spreading rate(s) • type of precoating material(s) and application rate(s) • type of adhesion agent and proportion to be used in binder • sketches and/or plans of the work, if appropriate • details of special procedures to be used for the particular work. Repairing Pavement before Sealing Any pavement defects should be repaired and the pavement restored to a satisfactory condition before sealing. For seal and reseal work any weak or failed areas should be repaired, larger cracks filled with binder, and any rutting or other shape deficiencies corrected. Rutting which is not corrected will often result in flushed or bleeding seals in the wheel paths, particularly on roads carrying heavy traffic.

________________________________________________________________________________________________________________________


Patching should be done with suitable pavement material, compacted, and then sealed. Alternatively, asphalt can be used for patching. It should also be noted that repairs and patching should be done at least 6-8 weeks in advance of sealing to allow time for the volatiles to evaporate. Fresh patches and repairs will often result in unsightly fatty or stripped areas in the seal coat.

7.2 HANDLING HOT BITUMINOUS MATERIALS

General Bitumen and cutback bitumen that comply with the specification should give satisfactory service provided they are handled and stored correctly. Implementation of the following procedures should prevent accidents and damage to, or contamination of, these materials. Transferring Material Bituminous materials are usually handled very hot and require special equipments for storage and application. Serious burns can be caused by the liquid coming into contract with the skin. Water should not be allowed to contact hot bituminous materials, as this will cause boil over and foaming, which may lead to a fire or explosion. The following precautions are to be taken when transferring bituminous materials: • If a hot bituminous material is to be transferred, check the type of material last

used in the tank to be loaded. If unknown or a bitumen emulsion then flush the tank and connecting pipelines with cutter oil to ensure they are free of water. See also section on cleaning tank.

• Always check quantities to be loaded to ensure sufficient volume is available

in the tank to allow for addition of additives and expansion when heated. • Wherever possible transfer materials by suction rather than by pumping under

pressure. If material must be pumped then use the lowest pumping rate possible to avoid excess pressure.

• Never unload heated materials until at least 20 minutes after the heaters are

turned off. • Bitumen emulsion should be pumped with either a purpose made emulsion

pump or else a pump with low shearing action. • Do not load cleaning oil, or cutter oil into an empty hot tank unless the

temperature in the tank is below 100°C.

________________________________________________________________________________________________________________________


• To avoid contamination, always flush pipes, hoses, strainers, etc. with cleaning oil after the loading operations are finished.

Heating (a) Bituminous Material

Bituminous material should not be heated above the maximum temperatures shown in Table 6.1.

(b) Cutback Bitumen

The following precautions should be taken when heating cutback bitumen:

• Extreme care should be taken as the volatile vapours given off are easily ignited.

• Only heat cutback bitumen if its temperature is below the recommended

minimum temperature for spraying.

• Do not heat cutback bitumen at a rate greater than 15°C per hour.

• Only heat cutback bitumen in distributors.

• Circulate cutback bitumen in the distributor during heating and continue circulating for at least 20 minutes after burners have been turned off.

(c) Bitumen Emulsion

The following precautions should be taken when heating emulsion:

• Apply heat gently.

• Use gentle agitation.

• Warm pumps before use.

• Do not apply direct heat to emulsion with a fire or blow torch.

• Do not heat emulsion at a rate greater than 15°C p er hour. Mixing Bituminous Materials (a) Cutter Oil with Bituminous Materials

The most common procedure for adding cutter oil to bituminous material applies to the field production of cutback bitumen. A different procedure is used when adding cutter oil to scrap rubber bitumen.

________________________________________________________________________________________________________________________


Cutback bitumen

The procedure for adding cutter oil or kerosene to bitumen is:

(i) Check for presence of water in cutter oil.

(ii) If there are concerns that water may be present, pour cutter oil into a cut-down 200 L drum before pumping into distributor. If water is present, it can be seen at the bottom of the cut-down drum. Alternatively, use a water-finding paste.

(iii) Pump cutter oil at ambient temperature into the empty distributor tank.

The quantity of cutter oil pumped into the distributor should be predetermined on the basis of the percentage of cutter oil required in the cutback bitumen and the quantity of cutback bitumen to be produced.

(iv) Pump hot bitumen (grade AC-10 bitumen) into the distributor tank, observing all the safety precautions The temperature of the bitumen should be adjusted so that the resultant cutback bitumen is at the required temperature for spraying. This obviates the need to heat the cutback bitumen.

(v) Heating of cutback bitumen should be avoided where possible. (vi) Circulate the mixture of cutter oil and bitumen for at least 15 minutes

before spraying. (b) Adhesion Agents with Bituminous Material

Adhesion agents are usually incorporated into the binder in the field. Adhesion agents are usually dissolved in all binders including primers and primerbinders, except for bitumen emulsions. Bitumen emulsions are manufactured with adhesion agents incorporated and no further addition should be made. Adhesion agents should be thoroughly agitated in their containers before use and when emptied, the interior of the container should be free of sediment. Gloves must be worn by personnel at all times when handling adhesion agents. As most adhesion agents deteriorate if held at high temperatures for long periods, they should be added to hot binders shortly before spraying. When loading the distributor, it should be at least one-third filled with binder before adhesion agent is added. The measured quantity of adhesion agent should then be added.

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If adhesion agent will not pour from the drum, it may be warmed or mixed with a small quantity of cutter to make it fluid. To ensure uniform dispersion of the adhesion agent throughout the binder, the mixture should be circulated for 15 minutes before spraying.

Table 6.1

Maximum Heating Temperatures for Various Bituminous Binders

Type of Material Class or Grade Equivalent % cutter

Max. Heating Temp. (°C)

Bitumen Cutback Bitumen

AC – 10

AMC00 AMC0 AMC1 AMC2 AMC3 AMC4 AMC5 AMC6 AMC7

56 44 34 27 21 16 11 7 3

190

30 55 80

100 115 135 150 160 175

Note: 1. For bitumen emulsion binders, refer to Section 6.10. Cleaning (a) General

Cleaning procedures should minimize the risk of:

• injury to personnel due to fire, explosion or other cause.

• damage to equipment due to fire or explosion.

• contamination of bituminous materials.

(b) Tanks Containing Bituminous Materials

Tanks include road tankers, bitumen distributors, heater storage units, drums and connecting pipe lines. The following procedures and precautions should be taken when cleaning tanks which have stored bituminous materials:

________________________________________________________________________________________________________________________


(i) Changing the type of material in tank

When changing the contents of a tank from one type of bituminous material to another type (bitumen, cutback bitumen or emulsion), the procedure for cleaning out the tank before refilling with a different type of material is as follows: Bitumen or Cutback Bitumen to Bitumen Emulsion or the reverse Drain tank and flush with kerosene or cutter oil. It is particularly important when changing from bitumen emulsion to bitumen or cutback bitumen that all emulsion is flushed from the system as any emulsion left may result in foaming when hot bitumen is next loaded. Cationic to Anionic Emulsion or the reverse Flush out surplus material from tank with water until water is not discoloured and drain tank and lines. Flush with kerosene or cutter oil and drain tank.

Flush out surplus cuter oil with water (about 450 L) and drain tank and lines. Heating the water to about 60°C will assist in flus hing the cutter oil. If cationic emulsion is to be the product for the next load, then the final flush should be carried out with 0.25% to 0.5% of hydrochloric acid added to the water.

(ii) Internal cleaning

Additional precautions to be taken when personnel are working inside tanks used for bituminous materials are: • Degas the tank or flush with boiling water to remove all dangerous fumes

before commencing the cleaning operations.

• Isolate any mixing mechanism with a lock out tag.

• Isolate any valves used to control the delivery of bituminous materials or heat to the tank with a lock out tag.

• Any person who has to work inside the tank must retain the vehicle’s

ignition key the whole time work is in progress inside the tank. Place a large sign *Person working in Tank* on each side of the vehicle.

• Disconnect the vehicle and distributor batteries and any other power

sources which are normally used.

• Any person working in the tank must wear an air supplied respirator.

• Personnel must stand by outside the tank.

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(iii) Completion of the work

After completion of each job, thoroughly clean the tank, pump and pipelines with kerosene or cutter oil to ensure that all bituminous material is removed from the system.

(c) Tanks containing bitumen emulsion

When a cationic emulsion comes into contact with metal it can begin to break. If a pump is not flushed after use or lines are left part full of emulsion, they will clog. To achieve the high performance expected of emulsions, cleaning of the storage tank and pipelines is essential and needs to be carried out thoroughly.

Storage (a) Bituminous Material (i) Hot materials in bulk

Bituminous materials are stored hot in insulated storage tanks to have on hand an adequate supply of materials at or near their working temperatures. When material is stored hot in bulk: • Do not exceed the maximum prescribed temperature for the material as

shown in Table 6.1.

• When the material is required for immediate use keep it within the recommended temperature range for spraying, e.g. bitumen 160 – 190°C

• Do not store the materials hot for any length of time if no demand is

expected, e.g. over a lengthy break. Prolonged hot storage will drive off the lighter oils and increase the viscosity of the material. It is better to let the material cool and heat it in time for use.

(ii) Cold materials in bulk

Bituminous materials may be stored at ambient temperatures without suffering any deterioration.

To avoid settlement when materials are stored cold in bulk and are liquid at the storage temperature, circulate them at regular intervals.

(iii) Materials in drums

Storing and stacking

• Drums containing the same materials should be grouped in the same area.

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• Drums should be stacked in a single layer with the bung uppermost. • Always use the materials in order of receipt, ie. The oldest material should

be used first.

(iv) Protection

Bituminous materials stored in drums should be stacked under cover to protect them from weather and to avoid contamination. It is particularly important to exclude moisture from bituminous materials (except emulsion) and precoat which require heating before use to minimize the risk of foaming

(b) Bitumen Emulsion

Bitumen emulsion only remains stable and usable while the fine particles of bitumen are uniformly suspended in the water phase. Storage procedures should ensure that bitumen droplets do not settle or coagulate during storage.

When an emulsion is stored it has a finite lifetime which is determined by the formulation, method of handling and how it is stored.

(i) Bulk storage

The precautions to be taken when storing bitumen emulsion in bulk are:

• Do not store bitumen emulsion for longer than 90 days. • Circulate bitumen emulsion at regular intervals.

• Circulation should be slow and for limited periods.

• The frequency of circulation depends on the weather and the length of

time the emulsion has been in storage but generally once every 7 days is adopted.

(ii) Storage in drums

The precautions to be taken when storing bitumen emulsion in drums are: • Store drums above ground in an upright position. • Store drums under cover. • Use bitumen emulsion in order of receipt.

• Do not store bitumen emulsion in drums for longer than 90 days. • Gently agitate drums by turning each drum over every 2 weeks.

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The agitation minimises settlement of the fine particles of bitumen.

(c) Cutter Oil

Containers of cutter oil should not be stored on the job for long periods unless they are protected from rain and condensation. If containers are stored in the open for short periods, they are to be placed in such positions as to minimise the possibility of water gaining entry. This may be achieved by storing the drums on their sides.

Cutter oil storage tankers should be separated from other products at the tanker site (eg. Gas cylinders, petrol, oil, etc) by a minimum of 10 metres. If stored in sheds they should be adequately ventilated.

7.3 PREPARATION OF PAVEMENT SURFACE

General It is most important that pavements are properly prepared prior to applying any sprayed treatment as sprayed treatments will not overcome pavement deficiencies. Primers and Primerseals For initial treatment work the pavement should be constructed to line and level, be well compacted with a uniform moisture content with a clear unblemished surface.

Before priming or primersealing, the pavement surface should be prepared by:

(a) Drying

If the voids near the pavement surface are filled with water, allow the surface to dry out by evaporation to a slightly damp condition.

(b) Sweeping

Sweep the pavement surface to remove dust, slurry and other foreign matter using:

• a rotary road broom.

The broom should be adjusted so that it removes the dust without damaging the pavement surface.

• hand brooms, if necessary, in confined areas not swept by the rotary

broom.

Sweeping should extend to at least 300 mm beyond each edge of the area to be sprayed.

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(c) Watering

At the time of priming or primersealing, the pavement should be slightly damp to the required depth of penetration of the primer.

Where the moisture has evaporated from the top 15 mm of the pavement material, the surface should be dampened by a light application of water. This is done by running a water bowser over the surface at a higher speed than normal.

The purpose of watering is to: • kill the dust • improve penetration of primer or primerbinder into the pavement.

Watering should not reduce either the hardness of the pavement surface or the surface penetration of the primer.

If over watered, allow the surface to dry before priming.

Seals and Reseals

Before sealing or resealing on bituminous surfaces, the pavement surface should be prepared by:

(i) Drying

A damp surface should be allowed to dry. Sweeping with a rotary road broom may assist.

When using a bitumen emulsion binder the surface may be left damp.

(ii) Sweeping

Sweep the pavement surface to remove dust, slurry and other foreign matter using a rotary road broom

Supplement with hand brooms, where necessary.

Sweeping should extend to at least 300 mm beyond each edge of the area to be sprayed.

7.4 SPRAYING OPERATIONS

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Setting Out

Set out the area to be sprayed with markings on the pavement (300 mm outside the longitudinal edge).

The guide arm chain of the distributor is then adjusted to the position of the markings.

Spray Width

Full width spraying should be carried out so that there will be no longitudinal joins in the seal. Single lane spraying may be carried out : • Where the maximum length of spray bar is less than the full width for

spraying.

• If unacceptable traffic delays are likely to occur.

• Where the design calls for different binder application rates in adjacent lanes.

• On a rough pavement, where the spray bar height will vary as the distributor moves forward causing variations in the binder application rate.

• On winding roads with small radius curves, where full width spraying would cause varying binder application rates.

Quantity of Binder to be Sprayed

The procedure to be followed is:

(i) Calculate the design application rate of binder at 15°C. Refer to Section 5.

(ii) Convert the designed application rate to the application rate of hot cutback binder using the conversion tables in Section 2.

(iii) Multiply the application rate of hot binder by the area to be sprayed to give the volume of hot binder.

These calculations are carried out on the Daily Spray Record Sheet in Section 6.12 .

Loading the Distributor

Transfer to the distributor, the calculated volume of hot binder plus an allowance of 10% to ensure the distributor pump does not pump air before the end of the run.

The cutter oil and /or adhesion agent is included as part of the distributor loading operation as described above.

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Spraying

Spraying the binder should be undertaken with a calibrated distributor, as described in Section 7. Determine from the spraying table ( refer to Figure 7.3), the forward speed of the distributor and required pump shaft speed for the selected bar width (constant volume distributors only).

Use hand spray equipment to spray small or odd-shaped areas.

Spray Nozzles

The spray nozzles should be of the make and type endorsed on the Distributor Certificate.

The end nozzles may be either intermediate nozzles set with a jig or else purpose made end nozzles.

Measurement of Binder Quantity

Before commencing spraying, park the distributor on level ground, dip the distributor tank and record the quantity of binder on the Daily Spray Record Sheet.

In addition place binder collection trays for checking of spray rate in the wheelpaths on surface to be sprayed

Binder Temperature

At the time of spraying, measure the temperature of the binder. It should be within the allowable temperature range for spraying the binder being used. Refer to Table 6.1.

Traffic Control

Stop or detour all traffic in accordance with traffic management plan before commencing spraying.

Cut Off Paper

Lay a strip of craft paper, 1.2m wide transversely across the pavement at the start and finish of the distributor run. Weigh the paper down with chippings, gravel or other suitable material.

Positioning the Distributor and Chipping Trucks

Position the distributor a minimum of 20 meters behind the start of the run.

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Position the loaded chipping trucks behind the distributor before commencing the distributor run.

Lower the spray bar so that the nozzles are 250 – 300 mm above the pavement.

Commence Spraying

Drive the distributor forward and commence spraying when the spray bar is over the cut off paper. Check that all nozzles are producing a uniform spray pattern.

Stop spraying immediately if any of the nozzles are not operating correctly or any defect develops in the spraying equipment.

Maintain a constant distributor speed to ensure a uniform application rate of binder.

Remove Cut Off Paper

Before the chipping spreading starts, remove the paper and dispose of it correctly.

Determine Binder Application Rate

At the end of the run, park the distributor on level ground, dip the distributor and calculate the actual rate of application of binder on the Daily Spray Record Sheet.

In addition weigh the bitumen collection trays and calculate the actual rate of application of binder on the Spray Check Sheet shown in Section 6.

The actual application rates should be within a tolerance of ± 5% of the ordered application rate. If necessary, adjust the application rate of binder to ensure the ordered application rate is achieved in subsequent runs.

It is more difficult to obtain accuracy on short runs than it is when spraying full loads due to the accuracy of dipping the load and its influence on the overall accuracy when spraying only small quantities.

Always check the rates of application for each run or load sprayed. If in error check the calculations first. Minor corrections to the forward speed of the distributor may be necessary to obtain the desired rate of application. It may not be possible to obtain the desired rates of application due to the following: • the pump is worn • the material being sprayed is at the incorrect temperature • the pump shaft speeds are too low to obtain the correct flow rate • there are restrictions in the valves and pipes • using incorrect or faulty jets • any of the instruments are faulty

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• the dip stick suspension point has been altered or the dip stick has been damaged.

Overlap Longitudinal Joints

Where single lane spraying is used, the overlap at the longitudinal joint of adjacent runs should be 50 mm to 100 mm wide, provided the outer nozzles have been specially set with a jig unless purpose made end nozzles are used.

The overlap should be located under lane lines or outside the normal wheel paths of traffic. They must not be located in the wheel paths of traffic.

7.5 CHIPPING OPERATIONS

Loading

The loading operation is usually carried out with a front end loader. To avoid contamination of the chippings:

• The bucket should not have teeth.

• A thin layer of chippings should be left behind in the stockpile under the loader bucket.

Spreading

(a) General

The aim in spreading chippings is : • To produce a uniform mat of chippings • To spread at the ordered rate

Excess chippings on the surface may crush under the action of rolling and/or traffic.

A deficiency of chippings will not give a tight mat and may result in some stripping. This is because the depth of binder around the chippings is not sufficient to hold them in place.

To ensure a good seal, the spread rate must be controlled.

(b) Spreading Equipment • Self propelled spreaders with rate of chipping discharge linked to road

speed produce the best results.

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• Cockerell (box) spreaders in which the discharge rate is not automatically linked to road speed may also be used.

(c) Preparation for Spreading

The following preparations should be undertaken:

• Check spreaders for correct operation of mechanisms and linkages. • Truck bodies must be clean before chippings are loaded. • Select spreading widths to enable coverage to be achieved in a minimum

number of passes. Narrow spread widths of less than 600 mm should be avoided.

(d) Spreading Procedure • Before spraying commences, have sufficient loaded spreading trucks positioned behind the distributor to cover the area to be sprayed. • Spreading should commence immediately after spraying has started. • The binder must be covered with chippings as quickly as possible and in.

any case within 10 minutes when using grade AC-10 bitumen. • The spreading width is controlled by the number of gates opened. A

square nose shovel may be used for blocking off part of a gate. • Spreading should be carried out at a steady speed. • Adjust gate openings to achieve an even curtain of falling chippings. • If the operation of the truck produces corrugations in the spread chippings,

spreading should be stopped and the spreading truck moved off the affected area. All corrugations should be removed by smoothing out with hand brooms.

• A check should be made on the rate of application using the Daily Spray

Record sheet.

• The appearance of the spread mat before rolling should be uniform, with some binder visible between the stones (except for emulsion sealing).

• When working half widths or lane widths the overlap width of the binder

should be left uncovered. • The spreaders must always be cleaned out when changing from one size

of chipping to another.

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• To reduce the likelihood of damage to a new seal, chippings spreading

trucks and other equipment should not turn on newly spread and rolled chippings. Ensure that the truck tyres do not carry dirt or mud onto the new work.

• If an area has been generally underspread it should have extra chippings added using the spreaders.

(e) Handspreading

Handspreading may be carried out in small or odd shaped areas by shaking chippings off a shovel. Do not throw or broadcast the chippings because this will result in a non uniform cover.

Rolling Chippings

(a) General

Rolling of chippings is undertaken for the following reasons:

• To press the stones into the binder

• To move the stones so that their least dimensions are vertical

• To achieve mechanical interlock between the stones.

(b) Equipment

• Self propelled pneumatic multi tyred rollers having an unballasted mass of about 7 tonnes are preferred.

Tyres are operated at a minimum pressure of 600 kPa.

These rollers do not have to be ballasted.

• Steel wheel rollers are not used because they:

Break down chippings.

Push some chipping particles into the base.

Ride on the high spots, leaving chippings in the low areas unrolled.

• Number of Rollers

Whilst only one roller may be required for small patching work, it is good practice to have two rollers on site to allow for mechanical breakdown and to assist with backrolling. However, as a guide, at least one roller is required for every 1500 m2 of pavement sprayed.

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(c) Procedure

• Rollers must follow as close as is practical behind the spreader. Once chippings are spread, one roller pass must be applied to the whole area as quickly as possible. When this has been completed, rolling should proceed by overlapping each preceding pass by about one third of the effective roller width.

• The full width of the spread chippings must be rolled.

• Rolling should continue until the chippings have been well embedded in the binder and a uniformly textured surface is obtained.

• Rolling should be continuous during the day and should continue for at least one hour after the last chipping has been spread.

• Rollers must be driven at uniform speed to avoid skidding the wheels. Rolling speed should be about 15km/h to move and settle the chipping particles to their correct position.

• At least one pass of the rollers should be completed before traffic is allowed onto the new work.

• Particular attention should be given to rolling the untrafficked areas (centerline, between wheeltracks and outside the wheeltracks on a 2 lane road). Lack of rolling in these areas can lead to stripping.

(d) Backrolling

Backrolling is used to reorientate the stones and reduce the voids between the chipping particles.

• On lightly trafficked roads (say up to – 250 v/l/d), one roller should continue rolling for periods up to half a day behind the spraying operations, ie. 4-5 hours additional rolling after the initial one hour minimum rolling.

• On heavily trafficked roads, traffic can provide the backrolling. To ensure uniform rolling, the traffic should be moved over the area of the seal using traffic control measures.

• On deviations constructed away from traffic, backrolling should be carried out for a number of days. Particular attention should be given to shoulders and to the centerline areas.

Sweeping

(a) Hand Sweeping

This may be used to correct minor irregularities in the spread rate with or without additional chippings.

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Chippings must not be swept in from outside the sprayed area, as this may bring in dust.

(b) Drag Brooming

Drag brooming is undertaken after initial rolling to provide an even cover of chippings. Drag brooming should not be used if the chippings are larger than Size 10 mm as they tend to be dislodged by the broomimg.

Drag brooms should operate at between 5 and 10 km/h.

(c) Removing Loose Chippings

There is always an excess or loose chippings on the road after rolling of the chippings has been completed. As they are a safety hazard to motorists, the loose chippings should be removed by sweeping or suction cleaner if available.

(i) Timing

To ensure that the seal is not damaged, sweeping should be delayed until the chippings have sufficiently adhered to the binder. Generally, when hot applied bitumen AC-10 binder has been used, a light sweeping is carried out the next day. However, for bitumen emulsion binder, sweeping is generally undertaken after the second day.

(ii) Rotary Road Broom

The bristles should be uniform in length to enable setting of the broom to produce uniform sweeping. To prevent gouging of chippings, a low pressure setting is selected.

Sweeping should commence in the centre of the pavement and progress to the edges. Surplus chippings should not necessarily be removed in one pass. A number of light passes are preferable to prevent damage to the new seal.

With a rotary road broom it is preferable to have a roller following to ensure that any disturbed chippings are rolled back into place.

7.6 TRAFFIC CONTROL General

Control of traffic is an important part of sealing work. Traffic must be controlled to ensure that road workers are protected from hazards and that road users can travel safely through or around the work site. Control of traffic is also important to protect the seal from damage when first opened to traffic.

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Spraying Operation

During spraying operations it is essential that traffic be detoured or stopped for short periods. The work should be organized so that any delay to traffic is limited to less than 15 minutes. In order to control vehicle speeds, a temporary 60 km/h speed zone should be established. This zone should extend at least 100 m beyond the limits of the work and should be left in force until after excess aggregate has been removed from the seal.

Figures 9.1 and 9.2 show typical traffic control arrangements for sprayed sealing work. Protection of New Bituminous Seals In its early life surface dressing is susceptible to damage, even if done in favourable conditions. For hot applied cutback and bitumen binder, the first four hours are critical and the next 48 hours very important. For bitumen emulsion binder, which takes longer to set up, the first 48 hours are critical. To protect the work during the initial period, it is therefore essential that traffic control measures to restrict speeds to less than 30 Km/hr are implemented

Measures to restrict traffic speeds are as follows:

• Where possible, close the road and detour traffic • Use vehicles with flashing light, rollers or other plant to lead traffic through the

works at slow speed • Restrict the lane width available to traffic by the use of cones, signs, barriers

or other traffic control devices.

7.7 PRIMING Spraying Temperature • The temperature of the primer at the time of spraying should be within the

range shown in Table 6.2. • Primer should not be held at the spraying temperature for longer than one

hour. If it is held at that temperature for longer, a repeat dose of adhesion agent should be added.

Primer Set Up Priming is a matter of experience and no definite rules can be applied regarding the grade (viscosity) of primer and rate of application to use. A reasonable balance has been achieved between grade and rate of application if the pavement is uniformly well covered with primer, and if all the primer is absorbed

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and dry within the following time limits for the weather conditions shown: • Hot weather 6 to 12 hours • Cool weather 12 to 24 hours • Damp weather 24 to 48 hours

Covering Primes

When primer has been sprayed, the surface must not be immediately covered with dust or sand to mop up the wet primer in order to shorten the drying time. This is a wasteful practice and generally results in a non-uniform poor standard surface. It is preferable to adjust the grade or rate of application so that the primer is dry within the times given. Minimum time to allow absorption before covering with dust/sand should be about 4-6 hours. After Care After spraying primer, the following action should be taken: • Inspect the pavement surface about two hours after spraying. • Where the primer has been selectively absorbed, reprime hungry areas. • Sweep pools of free primer onto adjoining areas.

Table 6.2

Primer Temperature for Spraying

Type of Primer

Grade

Temperature Range for Spraying

(°C) Cutback Bitumen

AMC00

AMC0 AMC1

10 – 20

35 – 55

60 - 80

Bitumen Emulsion

Manufacturer’s recommendation

7.8 PRIMERSEALING Spraying Primerbinder

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• The temperature of the primerbinder at the time of spraying should be within the range shown in Table 6.3.

• Primerbinders should generally not be held at the spraying temperature for longer than one hour as it reduces the cutter content and effectiveness of adhesion agent if used. A repeat dose of adhesion agent may be required.

Trafficking the Primerseal Fresh primerseals have relatively poor stone holding ability under traffic, particularly during the first 4 to 6 hours. During this period protect the primerseal by: • controlling the speed of traffic - refer to Section 6.6. • extending the period of traffic control until chippings are held securely.

7.9 SEALING AND RESEALING Curing of Primes and Primerseals Before sealing is carried out, the prime or primerseal should be cured. The recommended curing periods are: • Primes – one to two weeks • Primerseals – refer to Section 5.3. Spraying Binder The temperature of the binder at the time of spraying should be within the range shown in Table 6.4. Trafficking Seals and Reseals Fresh seals and reseals, particularly when cutback bitumen is used, have relatively poor stone holding ability under traffic on the day of sealing. During this period protect the seal by: • Controlling the speed of traffic refer to Section 6.6. • Extending the period of traffic control until chippings are held securely. After Care The seal should be regularly inspected, particularly during the early part of its life. Defects and failures should be repaired immediately after their appearance.

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Table 6.3

Primerbinder Temperatures for Spraying

Type of

Primerbinder

Grade

Temperature Range

for Spraying ( °C)

Cutback bitumen

AMC4

110 – 135

Bitumen emulsion (70% Bitumen)

Primersealing

75 – 85

Table 6.4.

Binder Temperatures For Spraying

Type of Binder

Grade or Class

Temperature. Range for spraying ( °C)

Bitumen

AC -10

170 – 190

Bitumen Emulsion (70% bitumen)

Sealing

75 – 85

7.10 EMULSION SEALING AND RESEALING

General The procedure used in carrying out an emulsion seal differs from those used in conventional sprayed sealing. Type of Emulsion The technique described in this section is the general practice used for sealing and resealing using high bitumen content (70%+ bitumen) emulsions. Whilst conventional (60% bitumen) emulsions may be used, the maximum application rates achievable without significant runoff restricts the size of chippings which may be used. Emulsions used in sealing and resealing are sprayed undiluted.

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Precoating Chippings Chippings should be precoated approximately 1 week in advance of the work. Freshly precoated chippings with an excess of precoat should not be used, as it may delay the breaking of the emulsion. Chippings which have previously been precoated and are damp at the time of sealing present fewer problems in achieving initial adhesion with the binder than would be the case with conventional sealing. Pavement Preparation The pavement should be cleaned by sweeping as described in Section 6.3. Heating Emulsion Emulsion should be heated slowly (maximum rate 15°C per hour) to between 75°C and 85°C for spraying. Spraying The emulsion is sprayed at the designed rate determined from Section 5. While it is possible to spray at hot application rates up to 2.5 L/m2 , run off may be a problem at higher application rates or on steep grades. Chip Spreading The chippings are spread at a rate to give a uniform single stone thickness with the particles in shoulder to shoulder contact. If a scatter coat is to be spread it is essential that the first chipping is spread uniformly at the designed rate. The scatter coat is spread after the first chipping and before rolling. Scatter Coat When carrying out emulsion sealing using chippings of Size 10 mm or greater, a second chipping applied as a scatter coat, may be used to lock in the chippings. The function of the scatter coat is to prevent the first chipping from rolling and being dislodged as the seal gains strength during the first days of its life. Rolling

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Immediately after the scatter coat is spread, rolling should be carried out. Traffic on the Fresh Seal After 2 or 3 roller passes, traffic may be allowed to use the new seal. The speed of traffic must be restricted to a maximum of 40 km/hour until the seal has gained sufficient strength to be trafficked at higher speeds without chippings being dislodged. The speed restriction is normally required for 4-6 hours. Sweeping Because of the slow strength development of emulsion seals when compared with hot applied bitumen seals, sweeping may have to be delayed for longer until sufficient strength has developed. Sweeping with a rotary road broom may be carried out 48 hours after sealing.

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7.11 SITE INSPECTION SHEETS Site Visit Checklist

Page 1 of 2

Contractor:-……………………………………………………………… Phone No:……Contract No:-…………………………………………………… Mobile No:……

Fax No:..……..

Superintendents Representative:-…………………………………………………………Contractor's Site Representative:-…………………………………………………………

Expected Date of Seal:-……………………………………………………………Duration of Work:-………………………………………………………………

Seal Design by :- ………………………………………………………………

JOB DETAILS 1 2 3 4

Site Location…………………………Length of work :……………………….(meters)Width of work ………………………..(meters)Total area:……………………………(square meters)

SURFACE TREATMENT

Surface Treatment Type (Prime / Primerseal / Seal / Reseal)Bitumen Grade (AC-10 Bitumen)Prime / Primerseal Grade (% - Cutter with AC-10 Bitumen) Emulsion Grade (eg CRS70 etc.)Adhesive Agent Type% of Adhesive Agent (%)

SURFACE DRESSING MATERIALS

Surface Dressing (Single / Double)Quarry SourceType of Chippings Chipping Shape (Angular/ Cubic/ Round)Chipping Test Results Available (Yes / No)Supplied at Stockpile Site by:- (Quarry / Contractor)Haulage Dist - Quarry to Stockpile (Km) Haulage Dist- Stockpile to Worksite ( kms)Stockpile Site Constructed by:- Stockpile Site clean,dry and accessible (Yes / No)Chipping Covered by:- Precoating of Aggregate Precoating LocationPrecoat Brand or MixturePrecoat Rate (litres/cubic metre)Chippings Size (mm)Chipping ALD (Average Least Dimension) (mm)

Spray Seal Site Visit Check List

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Page 2 of 2

SITE CONDITIONS Contractor Road Agency

Traffic Control Plan

Site services identifiedmanholes , overhead power lines, etc

Potholes, shoulders repaired,Trees lopped

Kerbs, gutters, drains and assets protected

Pavement condition ready for surface treatment

CONTRACTOR'S EQUIPMENT Available Number of Capacity

Yes No Items / MenSite Supervisor / EngineerSite Penciller Number of MenPatrol VehicleWater CartTractor BroomFront End LoaderPneumatic Tyre RollerSteel Drum RollerBitumen Sprayer Calibrated Not Calibrated Bitumen TrailerCutter TrailerCrew Truck Spreading TrucksChipping SpreadersSafety ConesBarrier Boards and LegsStop / Slow Bats

Signed By:………………………………………………………… Date:……………CONTRACTOR REPRESENTATIVESigned By:………………………………………………………… Date:……………ROAD AGENCY SUPERINTENDENT'S REPRESENTATIVE

Spray Seal Site Visit Check List

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Surface Texture Assessment

Job Details Date:…………………………………………… Job / Order

No:.……………………………….….. Office:………………………………………….. Road No. /

Name:………………………………… Location: Roadloc:……………………………………….. To:………………………………………………

… …………... km to …………… km from ………………………towards …………………………………… Length ………….mtr. Width …………...mtr. Area …………sq.mtr. No. of

lanes………….. Type of Treatment Single Application Seal Seal (S) or Reseal (RS) Double Application Seal Existing Surface Conditions Bituminous Surfaced Pavement: Primed (P), Primersealed (PS), Sealed (S),

Existing Chipping Size (nominal)

Mm

Asphaltic Concrete (AC) or Cement Concrete (CC) Unit Shoulder Lane

1 Lane 2

Lane 3

Lane 4

Shoulder

Lane Direction or Description Surface Texture Mm Bleeding (B),Flushed F), Smooth (S),

Matt(M),Hungry(H), VeryHungry(VH) Age of Surface Yrs. Standard Ball Penetration mm

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7.12 DAILY SPRAY RECORD SHEET ROAD AGENCY DAILY SPRAY RECORD Date :- Contractor :- Location Type Treatment :- Grade of Bitumen Sprayed :-

Refinery / Emulsion Supplier:- Quarry Supplier:-

ITEM Refer Unit Run 1 Run 2 Run 3 TOTAL

1 Area

2 Length m

3 Width m

4 Area 2x3 m2

5 Size of Load

6 Design Application Rate Cold l/m2

7 Volume Correction for Temp Hot Table 2.4

8 Design Application Rate Hot 6x7 l/m2

9 Volume Required Hot 8x4 lites

10 Total Load Required Hot (Approx) 9 +10% litres

11 Spraying

12 Dip Sprayer Load at Start Hot litres

13 Dip Sprayer Load at Finish Hot litres

14 Volume Sprayed Hot 12 –13 litres

15 Temperature Sprayed 0C

16 Volume Correction for 150C Table 2.4

17 Volume Sprayed Cold 14 x16 litres

18 Spray Application Rate Cold 17div 4 l/m2

19 Over or Under Sprayed Cold 18—6 l/m2

20 Tolerance ( 5%) 6x0.05 l/m2

21 Sprayed Outside Tolerance Cold 20—19 l/m2

22 Chippings

23 Chipping Size mm

24 Chipping Design Rate 25 div 4 m2/m3

25 Design Quantity 4 div 24 M3

26 Ordered Quantity 25 +5% M3

27 Chippings Spread M3

28 Over or Under Spread 27—25 M3

29 Actual Rate 4 div 27 m2/m3 Note : For Primerseals and Emulsions, the Design Application Rate is the total rate of the mixture

7.13 CHECK SHEET FOR TRAY TESTING

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BITUMEN SPRAY RATE

Type of Material: Date:

Test Location: from CH. To CH.

BINDER Test No

1 2 3 Wt. of Tray + Bitumen W1 Kg Wt. of Tray W2 Kg Wt. of Bitumen W1-W2= W3 Kg Sp. Gravity of Bitumen SG

1.03 gm/ml

Vol. of Bitumen V = W3 SG

Litres (L)

Area covered ………A m² Rate of Spread R = V A L/m²

Tested by: __________________________ __________________________ Remarks:

______________________________________________________________ ______________________________________________________________ ______________________________________________________________

Consultant’s Signature ________________ Contractor’s Signature __________

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8. MAJOR PLANT ITEMS

8.1 GENERAL

The main items of plant in sprayed sealing are: (a) Bitumen storages and road tankers - for storage and cartage (b) Bitumen Distributor - for spraying the binder (c) Chipping spreaders - for spreading the chippings (d) Rollers - for rolling the spread chippings

(e) Broom - for sweeping prior to spraying and removing loose chippings

(f) Trucks - for loading/spreading chippings Plant items must be kept well maintained and in good repair, particularly regarding engine and hydraulic oil leaks which will soften the binder and may cause fatty spots or stripping of the aggregate. For safety, the operators should all be properly instructed in the safe use of the plant, in particular the items involved in handling and heating hot bituminous materials.

8.2 BITUMEN STORAGES AND ROAD TANKERS

Storages are purpose built items to store, heat or maintain bitumen at the correct temperature. They may be oil or gas fired or electrically heated, depending on whether they are mobile or fixed units.

Road Tankers as shown in Figure 7.1 are also purpose built to safely transport and handle bituminous materials. They are generally equipped with gas heating and pumping equipment to enable them to be self contained units that can load, heat and transfer bituminous materials on the job sites, and are used to supply materials from refineries/manufacturers to sealing gangs in the field.

8.3 BITUMEN DISTRIBUTOR The bitumen distributor (also known as bitumen sprayer) as shown in Figure 7.2 is one of the key plant items and its standard of operation will affect the standard of work achieved. They are self contained units fitted with pumping and heating equipment that can load, mix, heat and spray bituminous materials.

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Figure 7.1 Bitumen Road Tanker

Figure 7.2 Bitumen Distributor

The bitumen distributor is designed to apply a uniform application of binder at a predetermined rate. This is achieved by providing a uniform constant output from the spraybar, and varying the forward speed of the distributor. Accurate spraying to the design rates of application requires precise control of both these functions. The adaptation of microprocessor controls has provided very accurate control of these two important functions.

Calibration

The Ministry of Road Transport requires bitumen distributors to be inspected and calibrated to ensure that the bitumen pump speed, and spray bar pressure, is satisfactory to achieve the constant spray bar output required.

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The forward speed and distance recording accuracy are also checked by timing the distributor over a measured set distance, generally a kilometre. The distributor must be inspected and calibrated every year, or whenever the distributor has been overhauled or the bitumen pump replaced. Spraying Certificate and Table A spraying certificate and table is issued when a bitumen distributor is tested and calibrated. The table indicates the following information necessary to spray material.

(a) Application rate versus the forward speed of distributor

(b) The pump shaft speed versus number of jets for the width of spray required

(Constant volume distributors).

(c) Actual distance to indicated distance Scale factor. It should be noted that the spraying table is different for each distributor because the pump speed, pump output, and spraybar pressure varies with the spraybar width on each distributor. An example of a spray table is shown in Figure 7.3.

Spraying Jets The spraybars are generally fitted with: (a) Slotted "Copley" jets These jets are spaced at 100 mm centres and the spray bar is set 300 mm above the pavement. The spray from each jet overlaps that of adjacent jets which ensures a uniform transverse distribution as shown in Figure 7.4 For standard work, A4 jets, which have a rated output of 18 litres per minute, are used. As there is no overlap at the ends of the spray bar, there is a small loss in the transverse distribution at this location. This is partially compensated for by the use of special end jets, which have non-uniform slots and direct more material towards the outside. They are designated EA4 and have an output of 36 litres per minute. The standard A4 jet and EA4 end jets are shown in Figure 7.5.

The transverse distribution of a well maintained calibrated distributor is uniform except for about 50mm on the outer edges. It is therefore important to use end jets at all times and overlap adjacent distributor runs by about 50mm. (Alternatively, when end jets are not available, it is common practice to “turn” the standard A4 to an angle of 45 ° to the bar to increase the spray r ate at the end of the bar, and overlap by about 100mm.).

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Smaller and larger jet sizes are available for particular products or conditions, such as large jets to spray viscous bitumen scrap rubber blends.

Jets are made from brass and are machined accurately to ensure a correct spray pattern. They must be carefully handled and maintained to ensure a uniform spray pattern. Only jets of the same size must be fitted in the bar - do not mix different sizes to try and achieve varying application rates across the pavement. Testing has shown this to be poor practice as the rates achieved cannot be checked and the variations are not accurately predictable.

(b) Whirling “Phoenix” Jets Whirling jets give a conical overlap and the spray-bar is set at 450 - 480mm above the pavement. They generally have an output of 11 litres per minute depending on the type of distributor and are suitable for spraying in the range of 0.5 – 2.0 litres/sq m before the speed of the distributor starts to affect the spray pattern. Care needs to be taken with PMB’s as these jets are susceptible to blocking with higher viscosity material. A Whirling jet is shown in Figure 7.6.

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SPRAYING TABLE FOR A4 NOZZLES

Distance Correction Factor: 0.977 Avg Pump Output Ltr/Rev: 2.41

(1) IN CASE OF CONSISTENT OVERSPRAY DECREASE PUMP SPEED SLIGHTLY. IN CASE OF CONSISTENT UNDERSPRAYY, INCREASE PUMP SPEED SLIGHTLY. SPRAYING TABLE SHOULD THEN BE ADJUSTED ACCORDINGLY.

(2) WHEN SPRAYING IN BAR CIRCULATE ENSURE CONTROLS

REMAIN IN BAR CIRCULATE WHEN THE SPRAYBAR IS TURNED ON.

(3) THE INTERMEDIATE NOZZLES ARE SET AT 30° TO THE SPRAY BAR AND PARALLEL TO ONE ANOTHER.

(4) WHEN EA4 END NOZZLES ARE FITTED THE SPRAY WIDTH IS

0.1 METRES WIDER AND THE PUMP SPEEDSHOULD BE INCREASED BY 7 REVS FOR EACH NOZZLE.

(5) IF THE MEASURED OUTPUT IS INCONSISTENT WITH

THIS TABLE, THE DISTRIBUTOR REQUIRES RECALIBRATION.

Figure 7.3 Example of Spraying Table – Constant Volume Distributor

Width

of Sprayer

Run (metres

)

Number

of Nozzles

Pump Drive Gear

Pump Speed

(rpm) (rpm)

Spraying Pressure (kPa)

Pump Output (l/min)

Spraybar Circulate

Spraying

7.8 78 N/A 580 580 180 1404 7.2 72 N/A 540 540 1296 6.6 66 N/A 495 495 150 1188 6.0 60 N/A 450 450 1080 5.4 54 N/A 405 405 130 972 4.8 48 N/A 360 360 864 4.2 42 N/A 315 315 110 756 3.6 36 N/A 270 270 648 3.0 30 N/A 230 230 95 540 2.4 24 N/A 185 185 432 1.8 18 N/A 140 140 85 324 1.2 12 N/A 95 95 216 0.6 6 N/A 50 50 75 108

0.6 6 N/A Bar Circ. 340 180 108 1.2 12 N/A Bar Circ. 400 200 216

Application Rate

(l/min)

Road Speed

indicator (m/min)

0.40 458 0.45 407 0.50 366 0.55 33 0.60 305 0.65 282 0.70 261 0.75 244 0.80 229 0.85 215 0.90 203 0.95 193 1.00 183 1.05 174 1.10 166 1.15 159 1.20 152 1.25 146 1.30 141 1.35 135 1.40 131 1.45 123 1.50 122 1.55 118 1.60 114 1.65 111 1.70 108 1.75 104 1.80 102 1.85 99 1.90 96 1.95 94 2.00 91 2.05 89 2.10 87 2.20 83 2.30 79 2.40 76 2.50 73 2.60 70 2.70 68

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Figure 7.4 Sketch showing transverse distribution o f binder

(a) (b)

Figure 7.5 (a) Standard A4 jet 30, (b) End EA4 jet 45 °°°°

Figure 7.6 Whirling Jet

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8.4 CHIPPING LOADER Chippings that have not been precoated prior to delivery to stockpile require to be precoated on site. Specialised loaders are available which load the chippings from the stockpile site into a revolving screen to remove dust and undersize chippings prior to precoating.

8.5 CHIPPING SPREADERS The most common type of chipping spreader is a cockerell or box spreader which consists of a hopper mounted on the truck tail gate as shown in Figure 7.7. Spread rate is controlled by both gate opening and truck spreading speed. This gives reasonable control for most applications, with experienced operators and truck drivers, but recent investigations have shown that the chipping spread rate has a greater influence than originally thought on the mosaic, texture and performance of a seal coat.

Figure 7.7 Truck with Chipping Box Spreader More complex spreaders with metering rollers and gates, either truck mounted or self propelled, are being increasingly used to achieve more accurate and uniform spreading, often resulting in significant reductions in overspreading chippings.

8.6 ROLLERS Rolling is usually carried out by pneumatic tyred self propelled multi-wheel rollers as shown in Figure 7.8. The aim is not so much compaction, but orienting the chippings particles with their ALD vertical and packed together as closely as possible. Steel rollers tend to roll only the high spots and crush the chipping and are not recommended. Slow moving traffic also provides very good rolling.

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Figure 7.8 Pneumatic Tyred Roller

8.7 BROOM Dust affects the adhesion of the bituminous materials to the pavement and it is most important to clean the pavement by sweeping with a mechanical broom as shown in Figure 7.9. This may be a tractor mounted or drawn rotary broom. The broom is generally made up of plastic or steel wire segments fitted to a steel core, which may be driven hydraulically or mechanically. Care must be taken with the broom core during storage and use to avoid flat spots in the broom core as this will result in non uniform sweeping, i.e. leaving dusty areas on the pavement surface.

Figure 7.9 Tractor Mounted Mechanical Broom

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Ministry of Road Transport Surface Dressing M anual 123

9. FAILURES AND REMEDIES

9.1 GENERAL The aim is to achieve high quality work without a single failure. As a guide to help reduce failures, some of the common causes are listed below: • Condition of the surface to be treated

• Pavement not swept properly • Selection of incorrect treatment for the conditions

• Cold binder • Delays in covering the binder • Incorrect cutting back of the binder

• Wet weather conditions • Poor or incorrect precoating of chippings

• Poor chipping grading and high flakiness index • Over or under spreading of chippings

• No after care treatment, inspections • Insufficient rolling, inadequate traffic control after completing the work

• Incorrectly designed or applied rates of application of binder

9.2 DEFECTS IN TREATMENTS Initial Treatments • Poor pavement preparation

• Incorrect type and/or grade of primerbinder

• Incorrect rate of application of primerbinder • Primer not allowed to cure properly • Poor maintenance of primed/primer sealed surface

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• Absorption of binder into the primed/primersealed surface • No allowance for possible embedment of chipping • Using too large a chipping size for primersealing/final sealing Retreatments • Poor pavement preparation

• Non uniform surface texture, more than 0.2 litre/sq m variation • Patching not done far enough in advance • Failure to seal-off open textured patches • Lack of compaction of patches • Incorrect surface texture classification • Generally too low and incorrect application rate treatment

• Using too large a chippings size

9.3 REMEDIES The quicker a problem is identified and treated, the lower the cost and generally the more successful the result. The following provides a guide on how to deal with the most common failures/problems that occur. Priming • Excess primer is most easily dealt with by covering with clean grit, sand or

quarry dust while still wet. • Where there is insufficient primer lightly re-prime. • Non-uniform primed surface. Small areas may be touched up by

handspraying. If the areas are large, hand spray the worst areas and then lightly reprime.

Primersealing • Excess primerbinder .

If the primerbinder is soft enough, roll in more chippings.If that does not succeed, apply a second primerseal at a reduced rate of application.

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If the primerbinder is not picking up and the condition is not a hazard, wait for the next hot day and try and roll in more chippings. The wetting power of the primerbinder may be improved by a light application of kerosene just before applying the chippings. Chippings may be size 7 or 10mm, depending on the amount of free binder.

• Deficient primerbinder

If there is a minor loss of chippings, the life expectancy will be reduced but no other action may be required.

If there is a significant loss of chippings, a second primerseal should be applied using size 7 chippings. It is preferable to use a bitumen emulsion to minimise potential flushing or bleeding problems.

• Picking up

Primerseals that are placed in cool weather should be watched carefully during the first hot spell as the primerbinder may bleed for the first few days.

If bleeding, roll in size 7 chippings. If chippings are not available, cool the surface by watering lightly.

Pick up may also occur if it rains shortly after application and the primerbinder is emulsified.

Chippings should be spread on the surface in sufficient quantity to keep vehicle tyres from the binder. Up to size 10mm chippings may be used, depending on the primerseal and depth required.

Sealing • Excess binder

If the binder is soft enough, roll in more chippings. However, if the binder is not picking up and the situation is not dangerous, roll in more chippings on a hot day.

If the seal is older and the binder no longer fluid enough, on the next hot day spray about 0.2 litre/sq m of a high grade cutter to temporarily soften the binder, and cover with a clean, good quality, precoated size 7mm chippings.

There are proprietary brands of a hard grade of cutback binder, such as Gilsabind, which may be also used.

If the above does not work, a reseal with a hard grade of PMB, or an emulsion, may be applied using size 10 chippings

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• Deficient binder The seal coat will have a shorter life than normal. If stripping, some remedial treatment will be required.

• Stripping of chippings (i) Loss due to rain

If the chippings are stripping due to rain, traffic should be excluded from the seal if at all possible and the water allowed to evaporate. While drying it may be possible to slowly roll the chippings, or allow slow moving traffic. The traffic should be controlled until the binder has set up.

(ii) Due to deficiency in binder

If only some of the chippings are lost in a random pattern, a surface enrichment may be a suitable option on low traffic roads or where the traffic can be detoured. Otherwise a light reseal with size 7mm chippings, preferably using bitumen emulsion as the binder, may be applied.

Where the chippings have mainly stripped in the wheel-paths, a technique known as "dry matting", using bitumen emulsion, may be used. It basically involves spreading (by hand mostly), at a light spread rate, the same type and size of chippings over the stripped areas and then spraying a light application of bitumen emulsion to hold the chippings in place. A light reseal, or surface enrichment, may then be applied over the full area, if required.

If most of the chippings are lost, it will need resealing to provide some texture. This may use a hard grade of PMB to minimise future bleeding.

(iii) Due to general lack of adhesion

A surface enrichment, or light reseal with say size 7mm chippings may be applied to pin down the chippings and prevent further loss. Bitumen emulsion is the preferred binder if the seal has only recently been applied as this will minimise any future problems in hot weather, due to cutter

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10. TRAFFIC MANAGEMENT

10.1 GENERAL Consideration must be given to the management of traffic at the work site to ensure safety for both the road users and workers, no matter how short the duration of the work. The most important aspects to be addressed include how traffic is to be controlled, selection of the signs and devices to be used, where they are located, and that a consistent credible approach is taken by all who carry out work on or near roads.

Basic Requirements Signs and devices are used to warn traffic of a change in road surface or driving conditions, and that men and plant are engaged in work on the road. The signs and devices to be used must be appropriate and provide a message that instructs, advises or guides traffic through or past the wok site or hazard. To ensure a consistent approach signs and devices must be :

• Erected before work commences at a work site

• Checked regularly for effectiveness and maintained in satisfactory condition

• Removed from the work site when they are no longer applicable. However,

appropriate signs shall remain in place until all work including any bituminous surfacing, removal of loose stones and line-marking has been completed.

10.2 SIGNING THE WORKSITE There are five stages involved in signing a work site:

• Planning • Design • Installation • Operation • Removal Planning Planning for signing of the worksite should consider the type and nature of the works being undertaken, location, likely duration of the work, the speed and volume of traffic involved, and any staging of the work.

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Inconvenience to all lawful traffic movements, should be minimized which may require the use of traffic signals or traffic controllers at various stages of the work It may also be desirable to request traffic control assistance from local police. In order to minimise risks to the public, works should cause minimum disruption and hazard to traffic, with the smallest length of carriageway being closed at any one time. Prior to a detour being planned or constructed consideration of the traffic loads, pavement and surface of the detour must be taken into account.

Design • Signs and devices should be standard signs.

• Signs and devices should be placed such that sufficient advance warning is

provided for correct driver response under the worst conditions.

• When left in place at night signs must have appropriate reflective surfaces.

• Notwithstanding the above the number of signs must be such that if one is knocked over there should be sufficient other signs and devices in place to guide the traffic past the hazard.

• Existing (permanent) signs or devices which are unrelated to the work should be covered or removed while works are in progress.

• Structural barriers may be necessary to provide safety where head on conflict may be a possibility.

• Where pedestrian volumes are significant, it may be necessary to provide specific crossings with barrier boards to direct pedestrian traffic.

Installation • Signs and devices must only be left in place while the work or hazard exists

and must not in themselves cause a hazard or restrict drivers line of sight and are generally placed 1m clear of the traveled path.

• Signs should be erected prior to work starting in the following order:

(i) Advance warning (ii) Other warning (iii) Driving instructions

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• Persons erecting signs should wear appropriate safety vests and signs should be in place warning of the presence of these people.

• Account should be taken as to whether the signs can be seen against the sun

or other distracting background or headlights. • Reflective signs should be turned at an angle of 1 in 10 perpendicular to the

direction of traffic flow to minimise reflective glare from oncoming headlights. • After erection, supervisory personnel should drive through the site at the

normal traffic speed to assess the effectiveness of the signage. Operation • Regular inspections shall be carried out to verify erected signs are still in

place.

• Signs and devices for which the need either temporarily or permanently no longer exists shall be covered or removed.

• Defective signs or devices should be replaced.

• All personnel working adjacent to traffic must wear fluorescent safety vests and light clothes. Appropriate reflective apparel shall be worn at night.

• Occasionally it will be necessary to close the road completely. In such cases the delay shall be kept to a minimum and generally no longer than 15 minutes. If the delay is expected to be longer consideration should be given to the provision of a side track.

• For inadvertent delays longer than 15min because of an unexpected event the supervisor will inform the traffic controllers who in turn will ensure the public is similarly informed.

• In the case where accidents occur the position of all signs and names of witnesses and details of the accident including actual traveled path and weather conditions, shall be recorded and the sign layout photographed and filed for further reference.

Removal • Signs and devices should be removed or concealed from view in the opposite

order to erection, as soon as the activity or hazard ceases to exist.

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10.3 TRAFFIC CONTROLLERS Traffic controllers shall be used when:

• One lane of a two lane single carriageway road is closed only leaving one

lane open to traffic

• On long sections where vehicles may have to pull over onto the shoulder to allow oncoming vehicles to pass.

• Wherever work conditions exist that may cause a hazard.

Functions of a Traffic Controller • Supervisors shall be mindful of the Road Agencies responsibilities to the

public at all times and arrange for clear directions or warnings at all times.

• Supervisors and their workers shall conduct themselves with restraint and courtesy at all times; even at times of abuse and unreasonable antagonistic behavior on the part of any member of the public.

• This will strengthen their position at the time and also in any future action which may occur.

Equipment Traffic safety vests should be worn at all times. Traffic control signs shall be circular with “STOP” on one side and “SLOW” on the other and shall be in good condition. Advance warning signs should indicate that a traffic controller is ahead. Instructions • Traffic controllers must stand where they can be seen from 150 metres away

by both the traffic and other traffic controllers. If traffic controllers cannot see each other then additional controllers shall be employed or radio contact implemented.

• They must also stand in such a position that there is a clear escape route in

the event of an emergency. • As a mark of importance wear a clean traffic safety vest fastened at all times.

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• To stop a vehicle turn bat to STOP and raise the free arm into the stop signal position (with the elbow bent a right angles and the palm of the hand vertical and facing the traffic).

• After stopping the vehicle inform the driver of the reason and possible length of the delay.

• When traffic is to proceed turn the bat to SLOW and with the other hand give the “to go” signal.

• Not leave the post unless directed by the supervisor or replaced by another traffic controller.

• Be courteous to the public and if provoked by unreasonable behaviour exercise restraint.

Approach Tapers

• Where a lane has to be closed a sufficient length of taper of lateral shift markers or cones, must be provided in accordance with Table 9.1.

Table 9.1

Approach Tapers to Lane Closures

Typical Approach (Speed km/h)

Taper (meters)

40 40-60 60-80

80-100 100-120

20 30 40 50 60

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Figure 9.1 Typical Traffic Control Set Up for Singl e Lane Closure

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Figure 9.2 Typical Traffic Control Set Up for Road Closure

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11. SAFETY

11.1 GENERAL • Cleanup rubbish, oily rags.

• Remove items people are likely to trip over and clean up spills

• Keep passageways, walkways and doorways clear of obstructions

• Keep tools and equipment clean and in the right place Storage and Blending Areas

• Eliminate ignition sources - No smoking, welding, naked flames or sparks

• Store at as low a temperature as possible, check recommended temperature range before heating cutbacks

• Remove combustible rubbish from site

• Prevent pipe leakage, clean up any spills immediately

• Keep bitumen (150mm) above heating tubes to prevent possible ignition of vapors, fit fail safe low level cut off switch

• Monitor tank level during filling to prevent overfilling

• No water or contamination. Prevent moisture contamination (steam is 1600 x volume of water) sudden and violent foaming and boil-over is a major hazard

• Ensure dry chemical fire extinguishers are available in an accessible place in the event of a fire

• Keep a pile of sand and shovel handy at all times

• Provide step on safety showers in a close accessible place. The layout of a typical site for blending bitumen with cutter and adhesion agents is shown in Figure 10.1. Note that there are separate heating and blending areas.

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Figure 10.1 Typical site layout for blending

11.2 PERSONNEL Personnel should be trained in the following:

• Potential hazards

• Fire fighting and use of protective and safety equipment

• Safe use of bitumen handling equipment, pumps burners and compressors

• Procedures to follow in emergencies, accidents, fires, evacuation points etc. Manual Handling • Get help if it’s too big or heavy • Warm up before you start • Decide how to hold it • Get a firm footing • Bend knees, keep back straight • Rest frequently • Keep hands and fingers away from pinch points

Falls • Do not jump from moving equipment • Clean up potential trip items and slip areas

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• Keep boots clean of slippery materials Protective gear

• Wear a hat • Distributor operators should wear a face mask while

spraying • Wear long sleeve shirts and long cotton trousers over

boots • Elastic sided safety boots or gumboots inside trousers

and socks (preferably woolen) • Use heat protective long gloves when handling pipes

or hoses • Eye and face shields when in vicinity of pumping or

transfers • Have eye wash equipment available • Ensure a fully stocked first aid kit is close at hand at all

sites • Wear ear muffs in noisy zones ( above 85 dBA) Burns Treatment (see Bitumen Burn Card) • Immerse or flush with cold water for about 20 minutes • Do not pull away clothing which has stuck • Do not pull stiffened bitumen from skin it aids as an antiseptic and assists

healing • When hot bitumen completely encircles a limb it acts like a tourniquet and

must be split longitudinally as it cools. It can be carefully cut using surgical scissors.

• Keep patient comfortable and warm • Leave holes for eyes, nose and mouth • Do not apply ointments • Seek medical attention for burns over the size of 25mm dia • After several days under medical supervision bitumen may be softened and

removed using Johnsons baby oil or similar Shock

• Use mouth to mouth resuscitation if breathing stops • Keep patient warm until medical aid arrives

Fumes • The rate of production of fume doubles for every 10°C increase in

temperature • Fumes from bitumen or cutbacks can have irritant effects

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• Because of the higher handling temperatures there can be higher fuming from polymer modified binders

• Stand upwind of vapours • Don’t enter tanks where vapours may be a hazard. Test prior to entering to

ensure it is gas free. • When entering tanks always have a trained rescue person nearby with

respiratory apparatus available in case of emergencies.

Hydrogen Sulphide

• Can concentrate in vapour spaces in bitumen storage tanks. • Prolonged exposure over 30min at 200ppm can cause serious lung disorders Skin Exposure • Studies have shown that there is no direct evidence to associate bitumen with

skin disorders in man. But cutback bitumens do contain polycyclic aromatic compounds and therefore it is prudent to avoid prolonged skin contact.

• Protective clothing should be worn to prevent splash contact • Wash hands with soap and water prior to eating or drinking or going to the

toilet • Monitor all parts of the skin subject to contamination to ensure no skin

abnormalities are occurring. Public Safety • Use hazard lights on equipment operating in public areas • Use reversing beepers on all reversing equipment • Park all equipment off the road in a safe place at all times when not working. • Ensure all diesel equipment cannot start accidentally and that they are parked

nose to gutter. • Make sure all safety signs are in place and cant be blown over. • Do not carry unauthorised passengers.

Contractors / Subcontractors • Contractors and subcontractors must be informed of hazards and comply with

all safety regulations. • Safety equipment must be used and protective equipment worn as directed • Work must be performed in an efficient and safe manner • Workplaces must be maintained in a clean and tidy condition, waste materials

and debris should be regularly removed as work proceeds.

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11.3 ROAD TANKERS Loading and Unloading • Wear appropriate personal protective gear • Discard worn or damaged hoses • Ensure tanks are free of moisture • Ensure overflow pipes are free and not blocked with a plug of bitumen • Unlatch (but leave closed) hatches to ensure adequate venting • If moisture is suspected load slowly and allow time for the moisture to foam

and boil off. Leave tank for up to 1 hour before proceeding to fill completely Transfer

• Wear appropriate personal protective gear • No source of ignition within 15 m of loading • No person on the ground adjacent to the tank in case of a boilover or spill • To minimise exposure to fumes do not load in a confined space • Allow sufficient room in tanks for future expansion due to heating • Preferably transfer under suction. ie the pump on the receiving tank should

draw from the discharging tank. • A separate flushing connection should be provided to allow flushing of lines

and pumps with solvent to eliminate the need to disconnect hoses unnecessarily.

• Avoid breathing fumes Blending

• Check all valves are correctly set and free from plugs • Manhole covers are unlatched but closed to allow additional venting. • Check that the materials in the tanks are compatible. If the receiving tank has

been used to hold emulsion flush tank with precoat then add cutter and bitumen slowly (up to say 25% of tank volume) to allow for possible foaming. Only continue to add more bitumen when foaming has subsided

• The greatest risks are from fire, explosion and boilovers • The Flash point of power kerosene (cutter) can be less than 50°C. Exercise

caution. • No ignition sources within 15m of blending operations • It is preferable to add cutter prior to bitumen since if the cutter is contaminated

with water there is more likely to be sufficient room in the tank to accommodate foaming and time for the foaming to dissipate as the bitumen is slowly added

• The use of a small quantity of solvent to flush lines at the conclusion of the blending is permissible

• Liquid adhesion agents may be sucked into the distributor through purpose built connections

• Avoid breathing fumes

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Heating

• Wear personal protective gear • Check that there is sufficient room in the tank to allow for expansion (10%)

when heated • Check that the burner tubes are covered by at least 150mm of bitumen as

shown in Figure 10.2 • Position fire extinguishers in an accessible position away from the tanks • Do not heat on sloping ground (one end of the tubes may not be covered) • Ensure the tank is adequately vented. Unlatch but leave closed the hatches. • No ignition sources within 15m • Limit temperature rises to 30°C per hour for bitumen and 15°C for cutbacks &

emulsions • Ensure product is in circulating mode to assist in heat transfer • Where flame tube heaters have been used allow 30min for the tubes to cool

before fully discharging the tank • Remain with equipment at all times when heating is taking place Figure 10.2 Heating binder on level ground Using LPG • LPG is denser than air and will collect in low lying areas in enclosed spaces • Use LPG in well ventilated areas • If an LPG cylinder develops a leak ensure there are no ignition sources in the

vicinity and allow to vent to atmosphere. • If an LPG cylinder catches provided the flame is directed away from the

cylinder. The safest procedure is to keep the cylinder cool by dowsing with water and allow the flame to extinguish itself by burning out.

• If the cylinder is being directly heated by the flame then the LPG inside the cylinder is likely to boil and the cylinder is likely to explode. LPG is not flammable until it is in a vapour phase which could be a considerable distance from the cylinder

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• If at all possible keep the cylinder dowsed with running water to keep it as cool as possible to prevent the LPG inside from reaching boiling point

• Vacate the area and prevent others from approaching the cylinder Blockages • Fire extinguishers must be in an accessible position in the event of a fire • Controlled flame heating using a butane torch should only be used where

there is no other practical alternative. Burning of soaked rags should not be used for this purpose

• Do not use flame heating when the product in the pipe is cutback bitumen or when there is cutback bitumen in the vicinity

• Only trained personnel shall be permitted to flame heat. Full personal protective gear must be worn.

Distributors • Wear appropriate personal protection equipment • No water or contamination. Water in small amounts in a distributor can cause

sudden and violent boilover . Do not allow moisture or condensate to mix with hot bitumen.

• Ensure hatches are water tight. • Kerosene vapours are extremely flammable. All flames and sources of sparks

(static electricity) within 15m must be eliminated. • Violent braking may cause the bitumen to surge and flow out the overflow

pipe. Keep the overflow pipe clear at all times. • Do not kink or damage bitumen hoses • Do not to pump cold bitumen or force pump bitumen - damage to hoses or

plumbing may occur. • Beware of bitumen drift onto nearby cars and property • Burners must be attended at all times. • Ensure there is at least 150mm bitumen above the burners at all times while

heating. Do not heat on sloping sites as one end of the burner tube could be exposed.

• Do not overheat bitumen (it can ignite over 200°C) and ensure cutback bitumens are kept at lower temperatures than the maximum allowable

• Carry a suitable fire extinguisher (dry chemical type) and have it in a safe place while heating or transferring

• Ensure the correct valves and pipework have been opened. • Prior to travel ensure all hatches are latched and that the overflow vent is

clear

Brooms • Triangles must be fixed to the rear of the broom • Wear appropriate personal protective equipment. (eg Face mask, ear muffs)

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• Weight drums are to be securely fixed. Safety chains are to be used Trucks • If it is necessary to back across traffic use a flag man • When backing sound horn or use reversing beeper. • Beware of obstacles overhead when truck body raised • Develop clear sign language communication with spreader operator. Roller Operators • Watch where you drive • Warn your crew members to keep away from working machines • Allow adequate braking distances • Take extreme care on side slopes and steep slopes • The method of operation and effectiveness of the handbrake must be checked

before operating the roller • If leaving machine for any time, turn off engine,engage parking brake, and if

on steep slope use chocks • Wear approved hearing protection when required • Look behind when reversing Drum Cleaning and Filling

• Stack empty drums horizontally with the bottom end ones chocked with wedges (not rocks).

• If stacked mechanically can be 6 high but if manual, 3 high is easier to handle • Full drums should be handled mechanically on pallets where possible and

stacked vertically no more than 4 high with pallets or wood spacers between. • Where handled manually appropriate purpose built wood or metal skids

should be used Drum Handling-Loading / Unloading Vehicles • Use mechanical means where possible and store vertically on the vehicle. • When loading or unloading manually use wood or metal skids. • When unloading empty drums use skids and matting on the ground to absorb

impact. • Unloading empty or full drums by free fall onto tyres, although practical, can

result in damage to the drums and hazard to personnel at ground level and it should be discouraged.

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Drum Opening Decanting • Standard bitumen drums may have the closure lid removed by leverage

without damage to the drum. • Hot method: both ends may be removed and the whole length of the drum

preheated to form an escape channel before heating the whole of the drum to remove the bitumen

• Cold method : during the removal of the bitumen by breaking personal

protection including eye shields should be worn to prevent injury from fling splinters and hard bitumen.

• For large scale handling the drums should be inverted in an oven and decanted into a tank.

Fire • Use only recommended dry powder fire extinguishers • Spray at the seat of the fire in a motion to provide a mat cover to the source

Remember: NO IGNITION SOURCE – NO FIRE, NO OXYGEN – NO FIRE

Testing - Sampling • Wear heat resistant gauntlet gloves • Face mask and safety glasses or face shield • No smoking • Use tongs to hold containers • Stand upwind of fumes • Take sample slowly to avoid splashing • Label samples properly Office • Remove faulty electrical equipment or leads • Watch for fire hazards • Remove debris and keep access and doorways clear • Lift properly bend knees and keep back straight • Open only one drawer in a filing cabinet at one time • Do not balance on unstable items while reaching to high inaccessible

locations • Know where fire extinguishers are and the phone number for the Fire Brigade. • In case of fire evacuation go to known assembly point

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Supervisor instructions • Be sure every employee understands and accepts personal responsibility for

safety • Know the safety rules that apply to the jobs performed by your employees. A

worker should not be injured because you did not know the correct safe procedure for the job involved

• Anticipate risks from new equipment and changed practices • Encourage Safety discussions with workers • Encourage workers to work safely and to look out for the safety of others • Make sure employees wear appropriate safety gear.

Remember:

Accident prevention reduces human suffering.

Safety therefore is one of your prime obligations.

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BITUMEN BURNS

NO ATTEMPT SHOULD BE MADE TO REMOVE THE BITUMEN

"IN THE FIELD"

NOTES FOR THE GUIDANCE OF FIRST AID AND MEDICAL PER SONNELAll persons working with HOT BITUMEN should be familiar with these recommendations.

This TAG should be pinned to the patient's clothing in a prominent position before transportation to the doctor or hospital

TREATMENT FOR BURNS

FIRST AID FURTHER TREATMENT - CIRCUMFERENTIAL BURNSfirst aid and medical care.

*** If hot bitumen contacts the skin , the *** Adherent bitumen should ONLY be *** When hot bitumen completely encircles aburns area should be cooled immediately by removed at a medical facility under limb or other body part , the burn tissuedrenching in cold , preferably running , water. direction of a burns specialist. may swell under the cooled and hardened

bitumen and have a tourniquet effect. Thebitumen should be softened, as described

*** The cooling treatment should be carried out *** Bitumen after cooling which is adherent to above, and the patient referred urgently for until the bitumen has hardened and cooled. blistered skin , should be removed during specialist medical attention.Body Hypothermia must be avoided initial cleansing and debridement.

EYE BURNS

*** Adherent bitumen should not be removed , *** Bitumen adherent to unblistered skin should *** If hot bitumen enters the eye, it should"in the field" be softened by covering with tulle gras and be flushed with water until the bitumen has

gauze soaked in liquid paraffin. Petrolatum cooled. No attempt to remove adherent based antibiotic ointments and petroleum bitumen should be made by unqualifiedjelly may be used. Dressings should be personnel. The patient should be referredchanged daily, when any emulsified bitumen urgently for specialist medical assessment can be gently removed. and treatment.

These notes are taken from the HEALTH COMMITTEE of the AUSTRALIAN INSTITUTE OF PETROLEUM compiled in August 1992.

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BIBLIOGRAPHY

Ghana Ministry of Roads and Highways - Specification for Road and Bridge Works 1991 Roads and Traffic Authority NSW Australia - Sprayed Sealing Guide

VicRoads of Victoria, Australia - Bituminous Sprayed Surfacing Manual 2005

Australian Asphalt Pavement Association - Sprayed Sealing Course Notes

National Association of Australian State Road Authorities - Bitumen Distributors 1989

Australian Institute of Petroleum - Safe Handling of Bitumen Products 1993

Boral Limited of Australia - Safety Handbook, Road Surfacing Division

CSR Limited of Australia - Emoleum Road Services Personal Safety Handbook

New Zealand Contractors Federation - A Guide to Safe Practices for the Handling Transport and Storage of Bitumen

SMEC INTERNATIONAL PTY LTD Australia

SMEC International of Australia, prepared this Bitumen Surface Dressing Sprayed Sealing Manual for the Ministry of Road Transport with the assistance of the Ghana Highway Authority, Departments of Feeder Roads and Department of Urban Roads.

surface dressing manual - may 2005

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