roads bridges specification 2008 june 9 bun.pdf

8/19/2019 Roads Bridges Specification 2008 June 9 BUN.pdf

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GENERAL SPECIFICATION

FOR

ROADS AND BRIDGES

VOLUME II

June 2008


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GENERAL SPECIFICATION

FOR

ROADS AND BRIDGES

VOLUME II

June 2008


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GENERAL SPECIFICATION ROADS AND BRIDGES

CONTENTS Page

1. GENERAL SPECIFICATIONS 1 1.1 Definition of Engineering Terms 1 1.2 Alignment 1 1.3 The Carriageway 1 1.4 Horizontal Curves and Super Elevation 2 1.5 Office for Engineer’s Representative 2 1.6 Assistance for Engineer’s Representative 3 1.7 Name Boards 3 1.8 Datum 3 1.9 Taking Over Of Site By Contractor 4 1.10 Contractor Not To Enter Neighbouring Land 4 1.11 Notice Of Operations 4 1.12 Weather Conditions 4 1.13 Precautions Against Pollution Of Streams 4 1.14 Copies Of Orders 4 1.15 Work During Period Of Maintenance 5

2. SITE CLEARANCE 6 2.1 Clearance Of Trees, Bushes And Vegetation 6 2.2 Limits of Clearance For Road Works 6 2.3 Removal Of Top Soil and Unsuitable Materials 6

3. ROAD MATERIALS 8 3.1 Quality of Materials 8 3.2 Supply of Materials 8 3.3 Defective Materials 8 3.4 Handling and Storage of Materials 8 3.5 Liquid Limit, Plasticity Index and Linear Shrinkage 8

3.6 Local Materials – Naturally Occurring Materials 9

4. MANUFACTURED MATERIALS 16 4.1 Cement 16 4.2 Lime for Base-Course Stabilization 16 4.3 Bitumen 16 4.4 Steel Reinforcement 16 4.5 Structural Steel Work 17 4.6 Bolts and Washers 17 4.7 Steel Tubing 17 4.8 Galvanised Corrugated Metal Pipe 17 4.9 Mould Oil 18 4.10 Expansion Joint Filler 18 4.11 Expansion Joint Sealing Compound 18 4.12 Concrete Admixtures 18 4.13 Water Bars 18 4.14 Flexible Bridge Bearings 18 4.15 Pile Shoes 18 4.16 Road Marking Materials 18 4.17 Road Signs 19

5. TESTS FOR MATERIALS AND CONSTRUCTION 20 5.1 Sampling of Materials – Trial Pits 20 5.2 Sampling of Materials – Stockpiles 20 5.3 Borrow Pits 20 5.4 Tests for the Selection of Road Materials 20


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5.5 Test for the Selection of Cement Content in Base-Course and Sub-Base 22 5.6 Tests for Selection of Lime Content in Base-Course and Sub-Base 22 5.7 Tests for Selection of Sand Content in Base-Course and Sub-Base 23 5.8 Tests for Selecting Methods and Conditions for Compaction 23 5.9 Tests For The Control of Compaction 23 5.10 Field Control For Soil Cement 24

6. EARTHWORKS AND DRAINAGE 26 6.1 General 26 6.2 Sandfill 26 6.3 Formation Where There Is No Imported Base 28 6.4 Formation Where There Is Imported Base 28 6.5 Cuttings 28 6.6 Embankments 28 6.7 Widening of Embankments 28 6.8 Embankments In Bad Ground 29 6.9 Tolerances Allowable on Formation 29 6.10 Soiling of Side Slopes 29 6.11 Side Drains 29 6.12 Scour of Drains and Verges 29 6.13 Interceptor Drains 30 6.14 Turnouts 30 6.15 Laying of Pitching 30

7. BASE-COURSE AND SUB-BASE 32 7.1 Sub-Base 32 7.2 Tolerance on Sub-Base 32 7.3 Base-Course – Natural Material 32 7.4 Base-Course – Sand Stabilised 32 7.5 Base-Course – Cement Stabilised 32 7.6 Base-Course – Lime Stabilised 33 7.7

Base-Course – Width on Curves 33

7.8 Tolerance on Base-Course 33 7.9 Hard Shoulders and Verges 33

8. CONCRETE 34 8.1 Fixings and Cavities 34 8.2 Gauge Boxes 34 8.3 Proportions of Concrete Mix 34 8.4 Water Cement Ratio 35 8.5 Preliminary Testing of Concrete 35 8.6 Concrete Test Cubes 35 8.7 Standard of Acceptance for Cube Tests 36 8.8 Unsatisfactory Test Results 36

8.9 Consistency of Concrete – Slump Test 37 8.10 Mixing Concrete 37 8.11 Transport and Placing of Concrete 37 8.12 Compaction of Concrete 38 8.13 Construction Joints 39 8.14 Curing of Concrete 40 8.15 Removal of Shuttering 40 8.16 Finishes 41 8.17 Defects in Concrete 41 8.18 Termination of Concrete Pour 41 8.19 Approval Before Concreting 42 8.20 Placing Under Water 42 8.21 Mass Concrete Backing to Masonry or Brickwork 42


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8.22 Displacers 42 8.23 Delays Due To Defective Concrete 42 8.24 Cement Mortar Mixing 42 8.25 Cement Mortar Proportions 43 8.26 Concrete Mixes for Different Types of Construction 44 8.27 Precast Concrete Units 46

9. PRESTRESSED CONCRETE 48 9.1 Cement 48 9.2 Aggregates 48 9.3 Water 49 9.4 Untensioned Reinforcement 49 9.5 Pre-Stressing Steel 49 9.6 Sheathing 51 9.7 Concrete Proportions 51 9.8 Field Tests 52 9.9 Batching and Mixing 52 9.10 Placing of Concrete 53 9.11 Curing of Concrete 53 9.12 Removal of Shuttering 53 9.13 Surface Finish 53 9.14 Tolerances 54 9.15 Pre-stressing 54 9.16 Tensioning 55 9.17 Grouting 56 9.18 Pre-Tensioning 56 9.19 Transverse Pre-Stressing 57 9.20 Additional Requirements 57 9.21 Lifting and Handling 58 9.22 Concrete Mixes 59

10.

CONCRETE PILES 60 10.1 Pre-Cast Concrete Piles 60

10.2 Shuttering for Pre-Cast Piles 61 10.3 Test Piles 61 10.4 Procedure for Testing Piles 61 10.5 Stripping Heads of Piles 62 10.6 Splicing of Piles 62 10.7 Pile Shoes 62 10.8 Cased Piles (British Steel Piling or other approved) 62

11. CULVERTS AND BRIDGES 64 11.1 Minor Culverts 64

12. STEEL REINFORCEMENT AND SHUTTERING 69 12.1 Bending Reinforcement 69 12.2 Fixing Reinforcement 70 12.3 Concrete Cover to Reinforcement 70 12.4 Spacing of Bars 70 12.5 Construction of Shuttering 71 12.6 Erection of Shuttering 71 12.7 Shuttering for Pre-Cast Piles 71

13. STRUCTURAL STEELWORK 72 13.1 Supply, Transport and Erection of Structural Steelwork 72 13.2 Steel Sheet Piling 74 13.3 Hand Railing 75


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14. BITUMINOUS SURFACING 76 14.1 Prime Coat 76 14.2 Seal Coat Surface Dressing 77 14.3 Heating of Cutback Bitumen 78 14.4 Spraying of Cut-Back Bitumen 78 14.5 Spreading of Blinding Material 79 14.6 “Take” of Blinding Aggregate 79 14.7 Rain Damage 79 14.8 Tolerance of Finished Surface 79

15. MISCELLANEOUS 80 15.1 Grassing 80 15.2 Removal of Concrete in Existing Structures 80 15.3 Tree Planting 80


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C:\USERS\PATRICK.KOLAWOLE\DESKTOP\POKSPECIFICATION\CODES\ROADS BRIDGES SPECIFICATION 2008 JUNE 9BUN.DOC

Page 1

1. GENERAL SPECIFICATIONS

1.1 Definition of Engineering Terms

All terms and expressions referred to in this Specification shall have the meaning assigned tothem in B.S. 892, unless the context clearly indicates a different meaning. Some of theseterms are repeated below, amplified where necessary:

a] Carriageway: the portion of the road surface which is formed for the use ofvehicles. It includes the pavement and hard shoulders.

b] Pavement: A term applied specifically to the whole construction of the centralstrip of the road, on which vehicles normally run, and includes all materials abovethe formation.

c] Hard Shoulders: The paved or unpaved portions of the outer edge of thecarriageway, which are designed to contain the pavement and for the occasionaluse of vehicles.

d] Formation: The surface of the ground in its final shape after the completion of theearthworks, immediately below the base-course (or sub-base if any).

e] Formation Level: The level of the formation along the centre line of the road.

f] Formation Profile: The cross section profile of the formation at any particularpoint along the road.

g] Sub-Grade: The natural foundation or the fill, which directly receives the loadsfrom the pavement.

h] Sub-base: A layer of material sometime provided between the formation and thebase to aid strength to the formation or to reduce the cost of the base.

i] Base-course: (Or base). The layer in a road construction, which provides the

principal support to the surfacing.

1.2 Alignment

In the case of reconstruction of an existing road and where the contract drawings do not showthe plan of the new alignment of the reconstructed road, the contractor must allow in thisTender for the expenses incurred in eliminating kinks or bends in the road as shown in theSchedule of Works. Except where otherwise directed, on the drawing, or by Engineer’sRepresentative, no horizontal curve on a reconstructed road will have radius less than 350metres.

1.3 The Carriageway

The carriageway shall conform, in cross-section to the drawings. Horizontal curves shall becircular. On curves of less than 350 metres radius, the pavement shall be widened by 600mm.Where such curves are in cutting or on embankment this shall be increased by 600mm. Theincrease of width on curves shall be applied uniformly over a distance of 30 meters on thestraight road at each end of the curve, and shall be applied to the inner edge of the curve only.

Horizontal curves of 3 000 metres radius or less shall be super elevated at the rates shownbelow. The inner edge of the pavement will follow the grade line. Super elevation will beconstant throughout the circular curve and will be applied uniformly from zero to maximumthroughout the transition lengths shown below:


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1.4 Horizontal Curves and Super Elevation

The radii of Horizontal curves and Super Elevation rates shall comply with the followingformula:

E = V 2

226.9RWhere V = Design speed in km/hr

R = Radius of circular curve in metres

E = Super Elevation rate in metres/metre subject to a maximum of 0.08m/m and aminimum of 0.025m/m

Design Speed km/hr 100 80 65

Maximum Gradient of Super elevation run-offrelative to centre line of road (percent)

0.45 0.50 0.58

Minimum length of Super Elevation run-off(in metres)

55 45 40

Rate of Super Elevation run-off within thecurve (circular)

20% - 33%

1.5 Office for Engineer’s Representative

The Contractor shall, if instructed, provide a suitable office for the sole use of the Engineer’sRepresentative and his staff. If in the opinion of the Engineer the office can conveniently andsubsequently be sued as a road camp, it shall consist of 4 rooms, built to the Federal Ministryof Works approved standard design. Otherwise it shall be of a temporary nature and on thecompletion the contraction and be at least 12.00 metres long and 4 500 metres wide, with 2.4

metre headroom internally, partitioned so as to provide two rooms of equal size, and with a1.800 metre wide covered varandah. The building shall be waterproof, with adequate light,and ventilation, secure against burglary, and shall have a smooth concrete or timber floor.

The Contractor shall supply for the duration of the Contract the following furniture for theoffices, all to approved design:

• Office desk, 1.800m x 1.500m with lockable drawers

• Plan table, 2.700m x 0.900m x 0.825m internal measurements, with stool and footrest.

• Lockable cupboard.

• Table, 1.800m x 0.900m.

• Office chair with arms.

• 4 No. Office chairs, armless.

• Typist table, 1.050m x 0.600m.

• Steel filing cabinet.

• Two drawing boards complete with tables.

• Two T-squares, two sets of setsquares, and one set of railway curves.

• Washbasin, stand and towel.


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The Contractor shall supply for the duration of the Contract, suitable separate latrines for theEngineer’s Representative and for this office staff, constructed to the satisfaction of theEngineer’s Representative, and shall ensure adequate clearing and cleaning of the latrines.

1.6 Assistance for Engineer’s Representative

The Contractor shall provide at all times during the continuance of the Contract all suchworkmen and instruments, etc. for the exclusive use of the Engineer’s Representative as thelatter may deem to be necessary for the carrying out of his duties in connection with theContract. The instruments shall be kept in good working order.

The items to be provided shall include the following:

• 1 x Theodolite and tripod

• 2 x Levels and tripods

• 2 x Levelling staffs

• 2 x Surveyors 30 metre steel tapes

• 4 x Plumb bobs• An adequate number of ranging rods and drop arrows

• 2 Surveyors’ 100 metre steel bands

• An adequate number of cross fall templates and straight edges

1.7 Name Boards

At the commencement of the work two name boards shall be erected, one at either end of thelength of road under construction. These boards shall be moved and re-erected as directed inorder that they are in close proximity to the site of the work under construction. The boardsshall be painted with 2 coats of approved weatherproof paint and shall be maintained in goodcondition for the period of the contract. The boards shall be removed by the end of the periodof maintenance.

The letters shall be black on a yellow background and the wording shall be “Ministry ofWorks” in 100mm high letters with the contract title in 75mm high letters, and the Contractormay place his name and address below the job title in 50mm high letters.

The cost of such boards shall be included in the contract rates.

1.8 DatumThe Datum on which the various levels are based shall be the Nigerian National datum asestablished by the Federal Surveys. The concrete beacons at the intersection points of curvesare to be used as Temporary Bench Marks during the progress of the contract. Values for theTemporary Bench Marks are shown on the drawings but the Contractor at the commencementof the contract must check the Employer will take these values and no responsibility for theaccuracy of the levels of Temporary Bench Marks given on the drawings.


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1.9 Taking Over Of Site By Contractor

The date on which the site is handed over to the Contractor shall be recorded and certified inwriting by both the Engineer and the Contractor’s Agent and from the date on which the site istaken over the Contractor shall be responsible for maintaining that portion of road in goodcondition and for repairing damage of an kind to the road culverts or bridges from whatever

cause arising whether caused by constructional traffic or not.

1.10 Contractor Not To Enter Neighbouring Land

Where it is necessary to enter onto land during the course of construction or maintenance forthe purpose of making temporary road diversions, winning construction or maintenancematerials or for any other reason, the landowner or occupier shall first be consulted by theContractors, and his written permission obtained. In the event of the owner of occupierwithholding his permission full circumstances of the case shall be referred to the Engineer andno further action shall be taken until his instructions are received.

Under no circumstances is land to be interfered with until the compensation, if any, has beenpaid by the Contractors.

When permission has been obtained and work is carried out, care shall be taken to ensure thatno unnecessary damage is caused to the land and that all reasonable precautions are taken toprevent soil erosion, and mosquito breeding. On completion of the work, all land shall be leftin a tidy condition with the sides of all borrow pits battered down to a reasonable slope asdirected by the Engineer’s Representative. All borrow pits shall be adequately drained to as toprevent storm water collecting in them. No compensation will be paid to the Contractors forany delays due to negotiations with the owners of the land. Any costs incurred in complyingwith the requirements of this Item shall be deemed to be included in the tendered rates andprices.

1.11 Notice Of Operations

No important operation and particularly no blocking or cutting of any road, water pipe orother services shall be carried out without the consent in writing of the Engineer no withoutfull and complete notice being given to him also in writing, sufficiently in advance of the timeof operation so as to enable him to make such arrangements as may be deemed necessary forits inspection and the provision of all relevant safety precautions.

1.12 Weather Conditions

The Contractor shall be deemed to have taken weather conditions into account when preparinghis Tender and he shall not be entitled to extension of time by reason of the occurrence ofdelays due to weather unless he can show that such conditions could not have been reasonablyforeseen in the area of the site.

1.13 Precautions Against Pollution Of StreamsThe Contractor shall take all necessary precautions to secure the efficient protection of allditches, streams and waterways against pollution.

1.14 Copies Of Orders

The Contractor and Sub-contractors shall provide the Engineer’s Representative with copiesof all order, which they may place for the supply of materials or goods required in connectionwith the Works.


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1.15 Work During Period Of Maintenance

After the commencement of the period of maintenance the Contractor shall do nothing, whichmight endanger the safety of the public, and he shall obey all instructions of the Engineer orother duly authorised person or authority in this regard.

Throughout the Period of Maintenance the Contractor shall notify the Engineer’sRepresentative what work or operations it is intended to carry out on the Site, and he shallobey any instructions which the Engineer’s Representative may give as to times and mannerof working so that any inconvenience to the Public is kept to a minimum.


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2. SITE CLEARANCE

2.1 Clearance Of Trees, Bushes And Vegetation

This work shall consist of clearing of grubbing necessary for the performance of work coveredby the Contract, in accordance with these specifications. The area to be cleared and/orgrubbed, shall be staked, shown on the plan or designated by the Engineer’s Representativeand as outlined below.

The clearing and grubbing shall consist of clearing the designated area of all trees of girths notexceeding 1.00m. logs, stumps, bushes, vegetation, topsoil, rubbish and all object ionalmaterials and shall include digging up of stumps and roots, and disposal of all spoil materialsresulting from the clearing and grubbing for the width as detailed in Item 2.2 or as directed bythe Engineer’s Representative.

The girth of trees shall be measured 1 metre above ground level, or in the case of buttressedtrees, immediately above the buttress.

In areas under roadway embankments from which topsoil or unsuitable materials aredesignated to be compacted, all stumps and roots shall be removed to a depth of at least150mm below the original ground surface.

Holes made by any of these operations, shall be filled in with approved material which shallbe laid in layers not exceeding 300mm and thoroughly compacted to 100% M.D.D./W.A.S.C.

2.2 Limits of Clearance For Road WorksClearance shall normally be within the limits of the areas as defined hereunder:

• Between the top of the side drains and 1 metre outside the drain on both sides

• 1 metre beyond the top edges of cuttings

• Between the toes of embankmentsClearance shall also be carried out over the top width of cut-off drains and turnouts, plus450mm on either side of such drain or turnout. Clearance shall also be carried out beyond thelimits denoted above, on the inside of bends, in order to obtain and unobstructed sight distanceof 150 metres.

The cost of all operations in Item 2.1 and 2.2 shall be included in the rate for site clearanceand shall be measured in hectares of cleared area.

2.3 Removal Of Top Soil and Unsuitable Materials

Topsoil is defined as any layer of soil adjacent to the existing surface, which contains or isdiscoloured by roots or other organic matter, which in the opinion of the Engineer will affectthe stability of any super, imposed construction.

Topsoil shall be removed to a depth of 300mm or such depth as may be directed, within thelimits of the side drains, toes of embankments or such limits as be directed by the Engineerexcept over embankments area where the height of the embankment exceeds 1 metre.


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The excavated soil shall either be stacked for re-use on side slopes or margins when sodirected, or shall be deposited and spread evenly not less than the clearance limits defined inItem 2.2

Whether stacked for re-use or deposited outside the drains measurement for this item shall bein cubic meters of material measured in-situ before excavation by means of cross-sections


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3. ROAD MATERIALS

3.1 Quality of Materials

All materials used in the Works shall be new and have the quality and kind specified. Theyshall comply with the requirements, unless modified herein, of the current amended editions,at the date of invitation to tender, of the British Standards (hereinafter abbreviated to B.S.)published by the British Standards Institution, or any other recognised Standards, which maybe quoted. All materials may be checked at both the source and on site and approval of anymaterial at its source does not necessarily imply that it will be approved on site.

3.2 Supply of Materials

The Suppliers of all manufactured materials shall be subject to approval and whereverpossible such materials shall be manufactured in Nigeria. All imported materials shall beshipped wherever possible to Nigeria in Nigerian ships.

3.3 Defective MaterialsAll materials, which do not comply with the requirements of this Specification, shall berejected and the Contractor, at his expense, whether in place or not, shall immediately removeall such materials, from site.

3.4 Handling and Storage of Materials

a. The Contractor shall make his own arrangements for storage space or yards and shall notmake use of Government or Local Government facilities.

b. All materials for use in the Works shall be handled with due care and whenever not forimmediate use, shall, subject to (d) and (e) below, be stored in well ventilated, water-tightbuildings with raised floors. In the case of cement and hydrated line, each consignmentshall be kept separately and the Contractor shall use the consignments in the order inwhich they are received. The siting of these buildings shall be approved beforeconstruction commences and on completion of the Works they shall be removed.

c. All store buildings shall be adequate for the complete protection of the materials to bekept therein and precautions shall be taken against damage by fire, particularly in the caseof inflammable materials.

d. Approved materials may be stockpiled at approved locations and prior to stockpiling, thesite shall be cleared, cleaned and levelled by the Contractor who shall, if required, also laysuitable hard surfacing or racks, depending on the type of materials to be stored.

e. The Contractor may use bulk storage for bitumen, cement and lime provided he couldsatisfy the Engineer’s Representative that adequate suppliers are available and also thatsuitable bulk storage facilities can be provided on site.

3.5 Liquid Limit, Plasticity Index and Linear Shrinkage

Wherever a Liquid Limit, Plasticity Index or Linear Shrinkage requirement is specifiedhereinafter, it shall refer to the property of the fraction of the material passing the No. 36Sieve.


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3.6 Local Materials – Naturally Occurring Materials

3.6.1 Fill Materials

All fill material shall be obtained from sites approved by the Engineer’s Representative, afterthe satisfactory completion of the following tests:

• Maximum Dry Density Greater than 1.500kg / cm 3

• Optimum Moisture Content Less than 18%

• Liquid Limit Less than 40%

• Plasticity Index Less than 20%

• C.B.R. value at O.M.C/W.A.S.Compaction after soaking Minimum of 15%

The material shall be capable of being readily compacted, shall be without pockets of clay orsand, and shall be free from trees, stumps, standing or matted bush, roots, rubbish or largestones. Stones larger than 150mm in greatest dimension may be required to be removed.

3.6.2 Sub-Base Material

Sub-base material shall be the nearest approved available material which complies with thefollowing tests:

• Liquid Limit Less than 35%

• Plasticity Index Less than 16%

• C.B.R. value at O.M.C/W.A.S.Compaction after soaking Minimum of 25%

The material shall be free from all deleterious matter as in Item 3.6.1 above and stones with

any larger dimensions than 50mm shall be removed.

3.6.3 Verges, Side Slopes and Margins – Surface Material

Surfacing material for side slopes and margins shall consist of the nearest approved material,which complies with the following tests:

• Liquid Limit 20 - 50%

• Plasticity Index 10 - 20%

The material shall be free from logs or stones of more than 50mm greatest dimension. Asmall amount of vegetation matter will be accepted, so long as the amount is approved.


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3.6.4 Base Course Material

a. Granular Base Course

This may be gravel, gravel-sand-clay or crushed stone or gravel or anycombination thereof, which shall have a uniform grade lying within andapproximately parallel to the limits shown in the appropriate column of thefollowing table:

Grading (Metricequivalent ofImperial B.S.

Sieves

Granular Base

38.10mm maxsize

25.40mm maxsize

19.05mm maxsize

38.10mm 100 - -

25.40mm 70 – 100 100 -

19.05mm 60 – 100 70 – 100 100

12.70mm - 60 – 100 -9.52mm 45 – 80 50 – 90 60 – 100

4.76mm 37 – 60 35 – 70 40 – 75

No.7 (2.40mm) 23 – 50 25 – 55 27 – 60

36 10 – 50 15 – 35 15 – 35

200 5 - 15 5 - 15 5 – 15

This material shall be either in-situ material or soil imported from the nearestavailable source, which shall be approved by the Engineer and comply withthe following tests:• Grading As above

• Liquid Limit Not exceeding 30%

• Plasticity Index Not exceeding 10%

• C.B.R. value at O.M.C/W.A.S. Minimum of 80%

b. Sand-Clay Base Course

The sand-clay material shall have a uniform grade, lying within andapproximately parallel to the limits shown in the following table:


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Sieve Size

Percentage Passing

Nominal Max 9.52mm Nominal Max 4.76mm

9.52mm 100 -

4.76mm 80 – 100 100

No. 7 (2.40mm) 50 – 100 80 – 100

No. 14 35 – 90 40 – 90

No. 36 24 – 70 25 – 70

No. 200 5 - 25 7 – 25

The material shall comply with the following tests and requirements:

• Grading As above




In certain areas, where the sand-clay material to be used is detailed by theEngineer, the C.B.R. value may be reduced as directed.

c. Sand Stabilised Base Course

The material used for this shall be the nearest available material, which whenmixed with 0-80% of approved coarse sand, shall comply with the followingtests and requirements.

• Grading As in (a) or (b)




d. Cement Stabilised Base Course

Material for use in cement stabilised base-course, shall contain not more than2% of organic matter. It shall be the nearest such available material which,when stabilised with 6.81kg – 22.72kg of cement per square metre/150mm

compacted depth, meets the following cylinder penetration ratio specification:Mix in Place Plant Mix

Laboratory tests on material mixedin laboratory

140% 120%

Laboratory or field control test onmaterial mixed each in field(average)

80% 80%


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This specification shall be obtained on samples tested after six days curingfollowed by 24 hours soaking.

With silt and clay soils, further samples will be tested at 7 days and 14 dayssoaking, to examine the resistance to weathering. There should not be anymore than 5% drop in C.B.R. value.

e. Lime Stabilised Base Course

As for (d) with “Lime” instead of “cement”.

f. General

Base-course material shall be free from logs, or stones more than 50mmgreatest dimension, vegetation or any other deleterious matter.

3.6.5 Sand for Sand Bitumen Carpet

The sand shall consist of hard, durable, rough surfaced grains, free from lumps of clay, loam,and other foreign matter for from a coating of any injurious material, which will preventadhesion of the bitumen. The sand shall comply with the following:

• Clay content Not exceeding 5%• Amount passing 200 sieve Between 3% and 10%

When mixed with the specified grade of bitumen, the minimum acceptable stability of thesand-asphalt as given by the Hubbard-Field test, shall be decided by the Engineer, but shallnot be less than 400kg.

3.6.6 Blinding for Prime Coat

The blinding material shall consist of clear, granular material matter, free from all vegetationmatter, and shall comply with the following gradation:

• Maximum size 6.35mm

• Passing No. 200 sieve 0-20%

3.6.7 Coarse Aggregate for Seal Coat

It shall consist of screened, washed natural gravel or crushed stone chipping, clean and freefrom dust and from vegetation matter, or any other matter, which will prevent the adhesion ofthe bitumen to the aggregate.

The aggregate shall comply with the following requirements:


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Gradation “Single Size” (B.S. 1984)

B.S. Sieve

Percentage Passing

Nominal Single Size

19.05mm 12.70mm 9.52mm

25.40mm 100 - -

19.05mm 85 – 100 100 -

12.70mm 0 – 35 85 – 100 100

9.52mm 0 – 7 0 – 45 85 – 100

6.35mm - 0 – 7 0 – 40

4.76mm - - 0 – 2

No. 7 (2.04mm) 0 - 2 0 - 2 0 - 2

Aggregate crushing value not exceeding 25%.

3.6.8 Aggregate for Concrete

a. All aggregates, either fine or coarse, shall be free from loam, vegetable matter, dust or anyother impurity that will adversely affect the strength of the concrete or attack thereinforcement (if present). If required by the Engineer’s Representative, the Contractorshall wash the aggregate at his own expenses.

b. Fine Aggregate

Fine Aggregate shall consist of natural sand, crushed stone or gravel sand and shall be

clean and sharp and as in (a) above. It shall comply with the requirements of B.S. 882,particularly in regard to the grading prescribed in Zones 1, 2 or 3 of the Table of the 1973edition and B.S. 182.

c. Coarse Aggregate

Coarse Aggregate shall consist of natural gravel, crushed gravel or crushed stone and shallbe clean, angular or rounded in shape, and shall have granular, crystalline or smooth (butnot glassy) non-powdery surfaces.

Friable, flaky or laminated pieces of mica and shale shall only be present in suchquantities as not to adversely affect the strength and durability of the concrete. The coarseaggregate shall meet with the requirements of B.S. 882 and 812 and the test cubes be asspecified in B.S. 1881. The aggregate crushing value shall not exceed 25 percent.


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d. Combined Aggregate

The combined coarse and fine aggregate shall have a grading within the limits given in thefollowing table:

B.S. Sieve Max. 9.52mm Max. 19.05mm Max. 38.10mm38.10mm 100 100 97 – 100

19.05mm 100 97 – 100 50 – 75

9.52mm 95 – 100 45 – 75 36 – 60

4.76mm 30 – 60 30 – 48 24 – 47

No. 7 20 – 46 23 – 42 18 – 38

No. 14 16 – 37 16 – 24 12 – 30

No. 25 12 – 28 9 – 27 7 – 23

No. 52 4 – 14 2 – 12 3 – 15No. 100 0 - 3 0 - 15 2 – 5

The grading of the combined aggregate shall be parallel to the above limits and be nearerthe lower limit than the higher.

The combined grading can be obtained by the use of two parts of coarse aggregate withone part of the fine aggregate.

3.6.9 Pitching (of Embankments etc.)

If of concrete blocks, the concrete shall be 1:3:6 in accordance with Specification Item 8.3 and

8.26. If of stone, this shall be durable stone of approved quality, sound, hard and free fromseams, cracks or other structural defects.

80% Of the blocks or stones shall be approximately 300mm x 300mm x 225mm thick, but inno case shall a surface dimension be less than 200mm or a surface area less than 500 squaremetre nor the weight of each stone less than 30kg.

At least one stone per square metre shall be 450mm thick.

3.6.10 Rubble Filling

It shall consist of broken stone, concrete or well-burned brick, of a quality approved by theEngineer’s Representative. The rubble shall be graded 150mm to 50mm and shall be rejectedif it contains more than 20% of material by volume passing a 50mm square sieve.

3.6.11 Water

Water used in the works shall be clean and fresh and free from any matter injurious to theworks, and shall only be used with the approval of Engineer’s Representative. If required, theContractor will arrange for an approved tester to analyse samples of water.

Water used for concrete, grout, mortar or cement stabilization shall comply with therequirements of B.S. 3148 and shall be tested if necessary.


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3.6.12 Grass

The grass used for sowing verges, margins and slopes of embankments and cuttings etc., shallbe approved Dhub or Bahama grass. Tall, quick grown or “tussock” grasses shall not be usedunless specified.


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4. MANUFACTURED MATERIALS

4.1 Cement

Cement shall be delivered to the site in the manufacturer’s original bags with unbroken seal,or, if in bulk, in approved tankers. Each variety of cement used on a site, shall be keptseparate and no mixing will be allowed.

Any bag, package or container that has been damaged, or any container of cement that showssigns of deteriorated, shall be rejected.

The cement shall be of normal Portland type and shall comply in every respect with B.S. 12 of1971 Rapid Hardening Cement and cements other than normal Portland, shall only be usedwhen specifically required or permitted by the Engineer.

Note The Contractor’s attention is drawn to the fact that “Nigercem” cement usually has thequalities of both Ordinary and Rapid Hardening Portland Cement, as required by B.S. 12 andif this is so, may be used where either type is specified.

4.2 Lime for Base-Course Stabilization

Lime shall be “hydrated lime” as specified in B.S. 890, and shall be delivered in themanufacturer’s original bags with unbroken seals, or if in bulk, in approved tankers.

4.3 Bitumena. For Prime Coats

The bituminous binder shall e a cut-back of approved manufacture and having viscositymeasured by the Furol Viscometer as shown in the following table.

The symbols M.C.O., M.C.1 and M.C.2 are those of the American Asphalt InstituteSpecifications.

Grade Viscosity

M.C.O. 75/150 seconds at 77°F

M.C.1 75/150 seconds at 122°F

M.C.2 100/200 seconds at 140°F

b. For Seal Coats

With crushed stone or gravel, cutback bitumen of approved manufacture, having aviscosity of 100/150 seconds at 40°C, measured by the standard Tar Viscometer shall be

used.

4.4 Steel Reinforcement

Steel for normal reinforced concrete shall be free from oil, paint, grease, excessive rust andscale, or any other coating that may damage its bond with the concrete. It shall comply withthe following specifications:

• Hot rolled steel bars B.S. 4449.

• Cold worked steel bards B.S. 4461


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• Steel fabric B.S. 4483

• Structural use of concrete, Code of Practice 110 of 1972.

For each consignment of steel reinforcement used in the work, the Contractor shall supply acertificate giving ultimate strength, yield stress and elongation and the result of the cold bendtest described in the appropriate B.S. If no test data are supplied by the Contractor, theEngineer reserves the right to select pieces of steel for testing at the Contractor’s expense.

4.5 Structural Steel WorkStructural steel shall comply with B.S. 4360 of 1972.

All sections shall comply with B.S. dimensions and weights and the Contractor must supplythe manufacturer’s certificate that the steel complies with all the appropriate tests for theparticular type of steel.

4.6 Bolts and Washers

All bolts shall be supplied with washers and in the case of high strength friction grip bolts;washers shall be placed under the head and above the nut. The bolts shall comply with thefollowing specifications.

• Black bolts B.S. 916

• Turned bolts shall be made from steel complying with B.S. 4360 and shall be finishedto provide a driving fit.

• High Strength Friction Bolts, B.S. 4395.

4.7 Steel TubingSteel tubes for hand railing, drains through concrete and toggle holes for precast pipes, shallbe made form Heavy tube that complies with the requirements of B.S. 1387. The galvanisingshall comply with the appropriate tests in B.S. 729. If required the Contractor shall providemanufacturer’s certificates to this effect.

4.8 Galvanised Corrugated Metal Pipe

Galvanised corrugated metal pipes shall be supplied by the Contractor, to the specifieddimensions and gauges, as shown on the drawing and in the Bill of Quantities. They shall beof nestable or multi-plate type of construction and shall be of “Armco” or other manufacture,approved by the Engineer. They shall be supplied on site complete with all necessary boltsetc. for fixing and painted in accordance with the Engineer’s instructions.

4.8.1 Galvanised Corrugated Metal Arch

These shall be of multi-plate type, otherwise as per Item 4.8.

4.8.2 Painting of Structural Steel

All exposed structural steel work shall be painted every five years. All the paint used on thework shall be ready mixed in sealed drums. The primer shall be Lexide Penetrating Primer orsimilar paint approved by the Engineers. The finishing paint shall be a heat and exposureresistant aluminium paints. The paint shall be used exactly as received from the manufacturerand without any admixture whatsoever. Before the paint drums are opened, they shall beinverted for the purpose of loosening the deposit at the bottom, and the paint shall be


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thoroughly stirred before pouring into smaller containers for use. During the application, thepaint shall be kept thoroughly stirred.

4.8.3 Painting of Hand Rails

This shall be as per Item 4.8.2.

4.9 Mould Oil

All faces of shuttering and moulds in contact with wet concrete shall be treated with mould oilor other approved coating, to prevent adherence of the concrete. Such coatings shall beinsoluble in water, non-staining, not injurious to the concrete and shall not become flaky norbe removable by rain or wash water.

4.10 Expansion Joint Filler

Performed joint filler to expansion joints in concrete, shall be “Flexcell” or other approvedimpregnated fibreboard. The filler shall be compressible, elastic, durable, rot-proof andsufficiently rigid to facilitate its support during construction.

4.11 Expansion Joint Sealing Compound

Compound the sealing expansion joints in concrete shall be a rubber – bitumen compound ofapproved make. The compound shall have a good adhesion to concrete, be readily extensiblewithout fracture, and be durable and resistant to the ingress of grit. The compound shall notflow either into or along the joint in the normal high temperatures on site. The Contractormust if required produce a certificate to this effect from the manufacturer of the compound.

4.12 Concrete Admixtures

Admixtures of any kind for accelerating the setting of cement, plasticisers, waterproofingagents, retarders etc. shall not be used except with the written permission of the Engineer.Samples of the proposed admixture shall, if required, be submitted to an approved testingauthority by the Contractor, to ascertain its suitability for use of the works.

4.13 Water Bars

Water bars shall be as specified on the drawings. Samples shall be submitted for approval bythe Engineer.

4.14 Flexible Bridge Bearings

These shall be of the type shown on the drawings and shall be supplied by an approvedmanufacturer.

4.15 Pile Shoes

The Contractor shall submit for the approval of the Engineer, his pattern for pile shoes madeto the dimensions shown on the drawings.

4.16 Road Marking Materialsa. White Line Paint

It shall be of an approved manufacture and comply with B.S. 2086.


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b. Thermoplastic Materials

They shall be of an approved manufacture and comply with B.S. 3262.

4.17 Road Signs

All road signs shall be in accordance with the approved International Signs, as modified foruse in Nigeria.


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5. TESTS FOR MATERIALS AND CONSTRUCTION

5.1 Sampling of Materials – Trial Pits

Trial pits shall be at least 1.00 metre square, dug to such a depth that the full extent of thematerial intended for corporation in the works is exposed to view.

Materials for testing shall not be taken from the spoil of the trial pit but shall be made up ofincrements taken from each side of the pit. The four increments shall be taken from differentlevels of the trail pit, and the resulting large sample shall be thoroughly mixed by hand beforebeing quartered or riffled down to the size required for testing.

5.2 Sampling of Materials – Stockpiles

The surface material of a stockpile shall be removed before sampling. At least twelve samplesshall be taken from different parts of the stockpile and the resulting large sample shall bethoroughly mixed by hand before being quartered down to the required size.

5.3 Borrow Pits

The Contractor shall be fully responsible for obtaining and working his own borrow pits, andshall not use existing Ministry of Works borrow pits without the approval of the Engineer orhis Representative.

Borrow pits shall be excavated to a regular shape only on that side of the road where thenatural slope of the ground is away from the road and the nearest edge of the pit shall be notless than 15.00 metres from the central line of the new road nor less than 5.00 metres from anyside drain or toe of a embankment, whichever is the greater distance.

The Contractor may be allowed to form side borrow pits for fill material providing such pitsare self-draining having a minimum fall along the line of the road of 1:120 and maximumdepth as directed by the Engineer’s Representative. All pits shall be properly drained to thesatisfaction of the Engineer’s Representative by the construction of turnouts or other approvedmethods.

No borrow pits shall be abandoned until the sides have been battered to a slope of 1:1 so thatanimals may not be trapped.

The Contractor must observe regulations under the Mineral Ordinances.

Government shall make no payment for clearing overburden, or for compensating owners forthe use of or for making access roads to borrow pits.

5.4 Tests for the Selection of Road Materials

The Contractor shall carry out the following tests on materials proposed for use as fill or sub-base or base-course or verge materials:

• Plasticity Test

• Grading Test

• Density/Moisture Content Compaction Test

• Laboratory C.B.R. Test


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5.4.1 Plasticity Test

This test shall be carried out in accordance with B.S. 1377 of 1975 with the followingmodifications:

a. Materials for testing shall be moisturised and sealed in an airtight tin or jar for a minimumperiod of twelve hours before testing.

b. For the method of determining the Liquid Limit as laid down in B.S. 1377 of 1975 tests,at least five points in the range 10-50 blows, evenly distributed when plotted on alogarithmic scale, shall be made. Consecutive tests with respect to moisture content shallform a drying and not a wetting curve.

c. The one point method of determining the Liquid Limit shall not be used.

d. The Plastic Limit of material shall be taken as the mean of at least three tests carried outin accordance with B.S. 1377 of 1975.

5.4.2 Grading Test


a. Of the material passing the 4.76mm sieve, a representative portion shall be obtained ofapproximately 250 – 300 grams. This portion shall be oven-dried to constant weight, anda portion of exactly 200 grams will then be weighed from this dry material. This will beplaced in a mortar and a small quantity of water shall be added. This mixture shall thenpestle, after which the whole shall be transferred to a No. 200 sieve.

The material on the sieve shall be thoroughly washed through with a moderate jet ofwater, until the water passing though the sieve is clean. The washing shall take not lessthan five minutes. The material remaining on No. 200 sieve shall be dried and re-weighed, and the loss in weight shall be recorded as the portion passing the No. 200 sieveshall be dry sieved through the following sieves, No’s 7, 14, 25, 36, 52, 72 and 100 andeach increment shall be separately weighed.

b. Material retained on the 4.76mm B.S. sieve shall also be wet-sieve as described in theparagraph above, full allowance being made for the air-dry moisture content.

c. Pre-treatment and the analysis of the fraction passing No. 200 sieve may be omitted.

5.4.3 Density/Moisture Content – Compaction Test


a. A fresh sample of material shall be taken at each moisture content.

b. Tests shall be made for at least five moisture contents and the material for testing shall bemoisturised and sealed in airtight tins for a minimum period of 12 hours before testing.

c. The test shall be carried out in a mould of 150mm internal diameter and 1250mm internalheight. The material shall be compacted in five layers, each layer being subjected to 25blows of a 4.45kg hammer falling freely through 450mm (West African StandardCompaction).

d. At least three moisture contents shall be taken from the mould after each test and a meanmoisture content calculated. Where the terms maximum dry density (M.D.D.) andOptimum moisture content are used in this specification, they shall mean the maximumdry density and optimum moisture content as determined by the above test.


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5.4.4 Laboratory C.B.R. Test

This test shall be carried out in accordance with the California Bearing Ratio test as outlinedin B.S. 1377 of 1975, subject to the following modifications:

a. The samples shall be prepared by dynamic compaction to optimum moisture content andmaximum dry density.

b. The material for test shall be moisturised and sealed in an airtight tin for a minimumperiod of 12 hours before testing.

c. The compacted sample for fill material shall be totally immersed in water for the specifiedperiod of soaking, following by 15 minutes draining before testing. Sub-base, base andverge materials, which are normally 1 metre above flood or water table level, will not beimmersed or soaked before testing.

The Contractor shall ensure that the results of the selection tests for road materials aresubmitted to the Engineer in good time and the cost of any delay to the works caused by latesubmission of test results will be borne by the Contractor. No material shall be used for fill orsub-base or base-course or verges, without the prior approval of the Engineer’sRepresentative.

5.5 Test for the Selection of Cement Content in Base-Course and Sub-BaseThe Contractor shall provide equipment, labour and such assistance as may be required by theEngineer’s Representative for him to carry out the following tests for the selection and controlof the cement content necessary to stabilise the base-course material:

• Grading

• Density/Moisture Content Compaction Test

• Laboratory C.B.R. Test

Samples of any material proposed by the Contractor for stabilization to form the base-course,

together with a copy of the road materials selection test results shall be submitted to theEngineer for determination of the cement content at least six weeks before the material isrequired for incorporation in the works.

Test No. 1 and 2 shall be carried out in accordance with Item 5.4.4 with paragraph (b) of theDensity/Moisture Content Compaction Test deemed to read:

“Tests shall be made at least five moisture contents and the material for testing shall bemoisturised, mixed and sealed in airtight tins for a minimum period of 12 hours. Therequired proportion of cement is then added and mixed thoroughly before testing”.

Test No. 3 shall be carried out in accordance with B.S. 1924 of 1967 with the followingmodifications:

a. For selection purposes all stabilised soil samples for testing shall be compacted at theoptimum moisture content to the maximum dry density. Samples shall be cured bycoating with wax. The Contractor should allow for the provision of 100m x 50mm and150mm x 125mm moulds and the provision of a 3000kg compression-testing machine.

5.6 Tests for Selection of Lime Content in Base-Course and Sub-BaseAs I tem 5.5 , except that lime will be used as the stabilising agent.


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5.7 Tests for Selection of Sand Content in Base-Course and Sub-Base

Where a sand stabilised base-course is to be constructed, the Contractor shall submit thepreliminary roads materials selection test results to the Engineer’s Representative fordetermination of the required sand content, at least 4 weeks before the material is required inthe works.

The Contractor shall provide such samples of materials and such equipment, labour andassistance as may be required by the Engineer’s Representative for him to carry out the testsdetailed in Item 5.4 for the determination of the sand content necessary.

5.8 Tests for Selecting Methods and Conditions for Compaction

The degree of compaction shall be measured by expressing the in-situ dry density of thecompacted materials as a percentage of the maximum dry density, as calculated at WestAfrican Standards Compaction (M.D.D./W.A.S.C.) for natural materials and at B.S.Compaction for stabilised materials.

Before any road material may be incorporated in the works, tests will be carried out by theContractor, under the supervision of the Engineer’s Representative, to select the most suitablemethod of compacting the soil. For each material, three test areas each 10.0 metre long by8.25 metre wide, will be prepared on the actual site of construction, from which the top soilhas been removed. The material to be used will be spread over one area, in three strips 2.75metre wide, the depth of the loose material in the strips varying from 150mm to 300mm. Themoisture content of the material tested shall be its natural moisture content.

The test area shall be compacted with the plant which the Contractor intends to use on theworks, and the mean dry density of the full depth of each strip determined after 4, 8 and 12passes for all types of plant, except for sheep foot rollers, for which the measurements of drydensity shall be made after 4, 8 and 16 passes. The dry densities of the soil shall bedetermined by the sand replacement method, and the mean of five determinations shall betaken for each soil condition.

The tests will be repeated at the other areas, the materials in the second are being at optimummoisture content, and in the third area at moisture content intermediate between this value andthe natural moisture content of the soil.

The tests will determine the most economical combination of type of plant, soil moisturecontent, number of passes and thickness of layer for obtaining the required compaction, andthe Contractor shall carry out the work in accordance with the test results.

Tests for the control of compaction shall be carried out by the Engineer’s Representative, on abasis of 1 test (the average of 5 test results staggered over the area) for each 1000 squaremetre. The dry densities as determined by the tests shall not be less than the M.D.D. of thematerial at its optimum moisture content.

Where tests carried out by the Engineer’s Representative show an unsatisfactory degree ofcompaction, the Contractor shall, at this own expense, scarify the re-compact the area to thesatisfaction of the Engineer’s Representative.

The Contractor shall allow in his construction programme, time for all tests and it is assumedthat his tender rates reflect the cost of tests.

5.9 Tests For The Control of Compaction

The Contractor shall provide equipment, labour and such assistance as may be required by theEngineer’s Representative for him to carry out the following tests on materials used in filling,sub-base, base-course and on verges, including existing sub-grade material:


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1. Laboratory C.B.R. tests (stabilised material).

2. Moisture Content Test (all materials).

3. In-Situ Dry Density Test (all materials).

All tests will be carried out in accordance with B.S. 1377 of 1975, with such modifications as

may appertain to this Province. Measurement of the in-situ dry density shall be by the sandreplacement method and moisture content of soil cement (or lime) mix before rolling shall bedetermined by means of a “Speedy Moisture Tester” or any other method the Engineerapproves.

No layer of compacted materials may be sealed, or covered by a succeeding layer until theEngineer’s Representative has approved the degree to which it has been compacted.

5.10 Field Control For Soil Cement

The following list of check items is given as a guide in obtaining the best results in soilcement construction.

1. Inspection of formation for correct shape and compaction.

2. Inspection of Base-course material for correct type of soil (as tested) and correct shape.

3. Adequate pulverisation.

4. Checking cement spread.

5. Correct moisture content.

6. Uniformity of mix.

7. Correct depth and width of stabilisation.

8. Degree of compaction

9. Proper finishing

10. Adequate curing.

The following are details of the above items 1 – 10

1. It is essential that all soft spots in the formation are correct and that the specifiedcompaction is obtained over the whole area.

2. After the base-course material has been tested for amount of cement required forstabilisation, it is essential that the same type of material be used, so far as it is available.

3. To obtain an even mix of the required strength it is essential that the plant available givesadequate pulverisation of the soil cement mix before compaction. 80% of the mix shouldpass a 4.76mm sieve and 100% pass the 25.40mm sieve.

4. After the amount of cement per square yard for the required depth, has been decided, it isessential to keep a constant check on cement spreading operations, on a square yard basis,or on the area covered by a truckload or know number of bags of cement.

5. Correct moisture content is one of the basic control factors and it is essential that frequentmoisture content tests be taken from before stabilisation commences, until finalcompaction is obtained. Generally optimum moisture plus 2% is satisfactory forcommencing the operation. Should there be noticeable evaporation losses, additionalmoisture should be added.


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6. Uniformity of mix can be checked by digging short trenches at regular intervals, to thefull depth of the stabilised mix. When the mixture is of uniform colour over the wholeexposed face, the mix is satisfactory. When the mixture has a streaky or patchedappearance, more mixing is required.

7. This can be checked while carrying out the examination for uniformity.

8. Compaction will be checked in accordance with Item 5.9.

9. A satisfactory finish must be smooth, dense and free of ridges, cracks and surfacecompaction planes. It is essential that satisfactory compaction and surface finish must beobtained in as short a time as possible, as detailed in Item 7.3. Allowance should bemade, sot that the finished smooth and correctly shaped base-course if of the requireddepth.

10. Adequate curing of the soil-cement base, as detailed in Item 7.5 is essential.


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6. EARTHWORKS AND DRAINAGE

6.1 General

The materials used in the works shall be new and / or of the qualities and kinds specified, andno materials shall be used in the works unless approved. Materials delivered to the worksshall be equal to the approved samples. Deliveries shall be made sufficiently in advance ofconstructional requirements to enable samples to be selected by the Engineer’s Representativefor testing before using the materials in the Works. Materials failing to comply with theSpecification shall be immediately removed from the Works at the Contractor’s expense.

These Specifications on materials shall be read in conjunction with latest amended report of“The Lagos Materials Testing Conference “, a copy of which will be made available to theContractor on request.

No material shall be used until it has been approved by the Engineer or his Representative.Permission to use any material shall not be construed as an approval of its source nor anyacceptance as continued acceptance.

In no case will material which contains organic matter or other deleterious substance be used.

Material for filling in the embankment shall be obtained from sources approved by theEngineer’s Representative and no slurry, mud or soft or otherwise unsuitable materials shallon any account or under any circumstances be placed in embankments. Large pieces of rock,clay or other materials shall be properly broken up and beaten down and no accumulation atthe foot of side slopes of embankments of boulders or lumps having no cohesion will underany circumstances be permitted. The Engineer’s decision regarding the suitability of anymaterial shall be final, and any material of which more than 35% passes the No. 200 B.S.sieve may be rejected depending on the plasticity characteristics of this material and itsdisposition within the Works.

6.2 Sandfill

Where sand fill, either hydraulic or otherwise, is specified, it shall be obtained from a sourceor sources approved by the Engineer. Where such sources occur in waters or areas under the

jurisdiction o the Nigerian Ports Authority or the Inland Waterway Department of the FederalMinistry of Transport or other appropriate Authority, then the Contractor shall first obtainwritten permission to remove material from the Authority concerned and shall comply, in allrespects with all regulations laid down by such an Authority.

The quality of the material intended for use as sand fill shall be subject to the approval of theEngineer. For hydraulic sand fill the grading of the material shall be such that not more than15% passes the No. 200 B.S. sieve, and in no case will isolated pockets or layers of silt, clayor other organic impurities be accepted. For sand fill placed by any method other than thehydraulic, the grading shall be such that not more than 30% passes the No. 200 B.S. sieve and

in no case will isolated pockets or layers of silt, clay or other organic impurities be accepted.The relative density of hydraulic sand fill placed in embankment shall be as follows:

(A) Top 600mm 90%

(B) Next 600mm 80%

(C) Below the top 1200mm 70%


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Sand fill placed by any method other than the hydraulic shall be compacted in layers by amethod approved by the Engineer’s Representative to a density of not less than 100% of themaximum dry density obtained in the British Standard Compaction Test.

In the case of hydraulic sand fill the Contractor shall construct all drains, ditches, spillways,marginal bunds necessary for the proper protection of the Works. Such drains, marginal

bunds etc., shall be constructed sufficiently in advance of the deposit of the sand fill so as toeffectively drain and retain the sand fill and to prevent any of the material from flowing intoany harbours, creeks, canals, drains etc., or from causing any damage or nuisance to personsor property. The Contractor shall be responsible for any slips or settlements which may occurduring the construction of the sand fill or the bunds, drains, etc., and shall also be responsiblefor same during the maintenance period. The Contractor shall make good such slips andsettlements to the satisfaction of the Engineer’s Representative. The Contractor shall beresponsible for the full and efficient drainage of water resulting from the hydraulic sand filloperation and shall construct such open drains as may be necessary to drain all surface andrainwater, so as to avoid all ponding. The Contractor shall make due allowance for settlementand drying-out of the sand fill and for the making good of same.

Before any hydraulic sand fill is commenced, the Contractor shall, in conjunction with the

Engineer’s Representative, survey the Site and mutually agree the surface levels, and suchagreement shall be recorded in writing by both parties.

The levels shall be taken on a grid with points at not exceeding 15 metre centres and theContractor shall construct concrete pilot-pillars to the satisfaction of the Engineer’sRepresentative to enable the grid lines to be located during the filling operations. TheContractor shall construct sufficient tell-tales, consisting of a 50.8 x 50.9.4 mm angle ofadequate length with a flange of 1 metre in diameter fixed at one end, all in non-corrosivemetal, to the satisfaction of the Engineer’s Representative, to enable any subsidence of theoriginal ground level to be measured. The method of measurement of hydraulic sand fill shallbe on the basis of the volume of material placed as determined from the area filled and thedepth of fill to the finished level from the original ground level for the subsided originalground level, as applicable. Should any dispute arise as to the subsided original ground level,as indicated by the tell-tales, then the same shall be determined by the taking of borings or bythe digging of trial pits.

Hydraulic sand fill shall be deposited in layers as directed by the Engineer, but in any case thethickness of such layers shall not exceed the limits stipulated as follows:

(A) First layer - not exceeding 450mm in thickness

(B) Second layer - not exceeding 750mm in thickness

(C) All Subsequent Layers - not exceeding 1 metre in thickness

The finished level shall be as shown on the drawings or as directed by the Engineer, and shallbe agreed as the result of a joint survey carried out by the Contractor and the Engineer’sRepresentative. A tolerance of 75mm above or below the finished level may be permittedduring pumping operations, but the same shall be made good by subsequent grading or dozingto the satisfaction of the Engineer’s Representative and to the tolerances stipulated for the sub-grade. Without limiting his commitments under the terms of the Contract the contractor shallnot be required to make good any normal expected settlement of the original ground level aftercompletion of the sand fill. The contractor shall be deemed to have allowed for all theforegoing provisions in his rates and prices for sand filling. Should the Engineer so desire theContractor shall place stock-piles of material in quantities and areas as directed. Payment forthese stockpiles shall be made at the Tendered Rates and Prices for Hydraulic Sand fill.


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6.3 Formation Where There Is No Imported Base

After site clearance, removal of unsuitable soil, and filling of holes with suitable material inaccordance with Item 2.1, 2.2 and 2.3 , the existing sub-grade shall be shaped to give aformation profile as shown in the drawings and compacted in 150m layers to 100%M.D.D./W.A.S.C. in accordance with provisions of Item 5.8, over the formation width, to a

minimum depth of 450mm or the depth stated in the Bill of Quantities. Any compactionrequired beyond a depth of 450mm would be in 225mm layers and to 95% M.D.D./W.A.S.C.to the depth stated in the Bill of Quantities.

6.4 Formation Where There Is Imported Base

1. After site clearance, removal of unsuitable soil and filling of holes with suitable materialin accordance with Item 2.1 and 2.2, the existing sub-grade shall be scarified for a leastthe top 150mm and re-compacted to refusal at natural moisture content of sub-grade soilto a cross-section profile as shown on the drawings.

2. Where fill material is required, it shall be spread, shaped and compacted to the sameprofile as above. The maximum depth of any layer of fill shall be 225mm (compacted)

and every effort must be made to ensure that the fill material is spread in layers over thefull width of the formation.

3. Every layer of material shall be adequately keyed into the layer above.

4. The depth of fill that when added to any base or sub-base will total 450mm, shall becompacted to 100% M.D.D./W.A.S.C., over the formation width and 95% below thatdepth, all in accordance with provisions of Item 5.8.

5. Including the imported base and sub-base depths, a minimum depth of 450mm will becompacted to at least 100% M.D.D./W.A.S.C.

6.5 CuttingsThe bottom width of cuttings shall be as shown on the drawings.

The normal side slopes of cuttings shall be 1 to 2 but may be either increased or decreased, asdirected by the Engineer’s Representative.

6.6 Embankments

Selected fill materials, as specified in Item 3.6.1 shall be spread evenly in horizontal layers ofnot more than 225mm compacted over the full width of the embankment, and compacted inaccordance with the results obtained from the tests carried out under Item 5.8 of thisSpecification, and in accordance with Item 6.4. The embankment shall be constructed asshown in the drawings. The side slopes shall be 1 vertical to 2 horizontal, except whereotherwise directed y the Engineer’s Representative. Adequate bond shall be formed betweensuccessive layers of fill material and between the existing sub-soil and the fil l material.

6.7 Widening of Embankments

Where alignment permits, existing embankments shall be widened on one side only to the newprofile shown on the drawing by cutting out approved steps in the existing slope of bylevelling the existing embankment to fill the lower limits of the profile.

Selected fill material shall be placed and compacted within the profile. All exposed horizontalsurfaces, shall be compacted to 95% M.D.D./W.A.S.C. to a depth of 15cm. All new fillmaterial shall be spread in layers, adequately bonded to the previous layer, and compacted in


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accordance with the results obtained from the tests carried out under Item 5.8 of thisSpecification, and in accordance with Item 6.4 .

6.8 Embankments In Bad Ground

The Contractor shall bring to the notice of the Engineer’s Representative cases whereembankments are required to be sited over swamp of unsuitable ground. Where suchconditions exist the Engineer’s Representative may direct that the first lift of fill materialbefore compaction shall be increased to 1m in order to establish firm ground for compactingplant. This may not be done without the approval of the Engineer’s Representative and evenif such approval is given, the Contractor is not relieved of his responsibilities to provide a wellcompacted stable embankment of the same standard as the rest of the works.

6.9 Tolerances Allowable on FormationThe finished surface of the sub-grade at formation level shall be left as smooth as possible,and the accuracy of finish in the longitudinal direction, shall be such that there shall not beany variation greater then 12mm from 3m straight edge, placed in any position on the finished

surface, parallel to the centre line.The formation profile shall not vary more than 12mm from the edge of a correctly shapedtemplate placed across the road at right angles to the centre line.

The finished formation centre line levels shall not be less or more than 5cm for the levelsshown on the drawings or the levels as directed by the Engineer’s Representative.

6.10 Soiling of Side Slopes

Where it is directed that the side slopes of embankments or back slope of cuttings shall becovered with a layer of topsoil, such topsoil shall be laid to a compacted thickness of 15cm. Itshall be compacted to 95% M.D.D./W.A.S.C.

6.11 Side Drains

Side drains shall normally be constructed on either side of the road expect where the road isbuilt on embankment or where the Engineer’s Representative directs that a drain isunnecessary.

The drains shall be constructed in accordance with the types shown on the drawings, asdirected by the Engineer’s Representative. The side, shallow drain shall be excavated bymachine and the soil spread over the formation as directed. The narrow type drain shall beconstruction either by manual excavation or by machine.

Drain inverts shall be finished smooth, and to a steady fall of not less than 1:120. This fallshall, in all cases, be toward a culvert or turnout.

Material excavated from drains, if unsuitable for re-use as fill material, shall be depositedaway from the road, at least 1m clear of the drain, or of the top of cutting.

See Item 6.12 for the action required to obviate scouring in drains in cuttings.

6.12 Scour of Drains and VergesWhere the longitudinal gradient of the verge or drain exceeds 1:33 1 ⁄ 3 and where directed by theEngineer’s Representative the Contractor shall take steps to prevent scour by:

a. Paving the drain inverts and side slopes with 75mm thick concrete quality 6A.


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b. Constructing small weirs across the side drains as directed.

c. Extending the surface dressing over the full width between drains.

Such work will only be done on the instruction of the Engineer’s Representative.

6.13 Interceptor DrainsWhere the road is in cutting and the natural fall of the adjacent ground is towards the road,interceptor drains of type A shall be formed behind the top edge of the cutting and parallel tothe road to prevent run-off into the cutting. The top of the inside edge of the interceptor drainshall be not less than 5m from the top of the cutting.

Where the adjacent ground has a cross-fall, interceptor drains shall be formed, as directed bythe Engineer’s Representative, on the high side of the road to prevent run-off into the road.

6.14 TurnoutsTurnout drains shall be constructed to discharge freely the water carried by the side drain onto lower ground falling away from the road, so that the side drain water does not adverselyaffect the road formation. As a guide, the spacing of such turnouts is found from the formula3√S where “S” is the distance in metres along the road in which it falls 1m. Normally themaximum distance part of turnouts shall be 30m, but where due to the surroundingtopography this cannot be achieved, special consideration will be given to enlarging and/orconcreting the side drains or putting in additional culverts.

The minimum base width of a turnout drain shall be 300mm but they shall be constructed tothe width directed by the Engineer and the side slopes shall be 1 horizontal to 2 vertical. Theinvert of a turnout shall fall away from the road, at a slope not less than 1:120 and not greaterthen 1:20. The drain shall terminate where the invert coincides with the natural ground level,but it is essential that the natural ground continue to fall away to avoid the drain backing up in

times of storms.Turnouts must be constructed in such places where their discharge is not likely to cause landerosion or harm to property, and in order to prevent such erosion or harm, the Engineer maydirect that open or covered concrete turnouts or other works be constructed.

6.15 Laying of Pitching

The pitching shall be in accordance with Item 3.6.9. The blocks or stones when laid shall beclean and have no weak points, or projections more than 25mm beyond the expose surfaceplans. Selected stones roughly squared, shall be used at the edges and ends of the pitching.Stones shall be laid with the minimum practical amount of space between them in such amanner as to break joints with those immediately below, and so that their weight is carried bythe embankment material as well as the adjacent stones.

No pitching shall be laid until the embankment has been properly compacted in accordancewith the specification and no pitching shall be laid at a steeper slope than 1 vertical or 1horizontal. After the stones have been laid, the spaces between them may be filled with cleanrock fragments from the stone dressing that will not pass 18mm sieve.

Grout for grouted pitching shall be 1-part cement to 3-parts sand, with sufficient water toensure a good mix and the right consistency. The interstices between the stones shall becompletely fitted with grout through the entire thickness of the pitching after which thesurface shall be swept with a stiff broom.


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Grouting operations shall progress from the bottom of the slope towards the top.


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7. BASE-COURSE AND SUB-BASE

7.1 Sub-Base

On completion and finishing of the formation, and if directed by the Engineer’sRepresentative a sub-base of approved material shall be laid on the formation. The sub-basematerial shall comply with the requirements of Item 3.6.2 and shall be provided and laid to thedimensions on the drawings or as directed by the Engineer’s Representative.

The sub-base shall be compacted in accordance with the test results under Item 5.8 and shallbe compacted in 150mm (compacted) layers to 100% M.D.D./W/A.S.C. Adequate bond shallbe ensured between the sub-base and formation.

On curves of less than 300m radius, the width of the sub-base shall be increased by 600mmsuch increase being applied to the inside of the curve, gradually over a distance of 30m on thestraight road at each end of the curve in accordance with Item 1.3.

7.2 Tolerance on Sub-Base

The finished surface of the sub-base shall meet the same tolerance requirements as stated inItem 6.9 for the formation.

7.3 Base-Course – Natural MaterialThe base-course shall be laid to width and depth as shown on the drawings or as directed, andshall be compacted in accordance with tests carried out under Item 5.8 of this specification.The material forming the base-course shall comply with the provisions of Item 3.6.4 (a) or (b)and shall be compacted to 100% M.D.D./W.A.S.C. Adequate bond shall be ensured betweenthe base-course and the sub-base (if any) or formation.

7.4 Base-Course – Sand Stabilised

Where sand stabilised base-course is specified, the materials used shall comply with theprovisions of Item 3.6.4. The Engineer’s Representative shall direct the width and depth ofthe stabilised strip.

The selected base-course material shall be stabilised with a percentage of sand as directed bythe Engineer’s Representative, determined from the tests outlined in Item 5.7.

The stabilised material shall be brought to optimum moisture content and compacted to 100%M.D.D./W.A.S.C.

The Engineer’s Representative in accordance with specification Item 5.9 and 5.10 will carryout tests for control of mixing and compaction. The average of a series of control tests mustnot be less than the laboratory tests results set out in Item 3.6.4 [c ] and the minimum test

result must be no more than 2% lower than the laboratory test and occur less frequently thanin 10 tests. If this average is not obtained the Contractor shall at his own expense, scarify, re-stabilise and re-compact the area from which the particular tests were made.

7.5 Base-Course – Cement Stabilised

Where cement stabilised base-course is specified, the materials to be used shall comply withthe provisions of Item 3.6.4 (d) and 4.1. The width and depth of the stabilised strip shall be asshown on the drawings or as directed by the Engineer’s Representative.


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The selected base-course material shall be stabilised with a percentage of cement as directedby the Engineer’s Representative, determined from the tests outlined in Item 5.5 . Thestabilised material shall be compacted to 100% M.D.D./B.S.C. at O.M.C. The methodadopted and plant used must ensure an adequate mixture and compaction of the material, tothe satisfaction of the Engineer’s Representative and the maximum period between mixing inof the cement and the completion of compaction of the stabilised material shall be 2 hours.After compaction, the base-course shall be cured for 7 days and kept free of all traffic. It shallbe cured with M.C.1. or M.C.2 at the rate of approximately 5 square metre per 4.5 litre, thetype of bitumen to be as decided by the Engineer. Great care must be taken to remove all dirtbefore applying the bitumen, and not to damage the surface. Alternatively if required, by theEngineer, the clean surface may be covered with a 50mm layer of sand, kept moist for 7 days.All transverse and longitudinal joints in the base-course shall be cut back to ensure thatadequate bond is obtained and uniformity of construction is maintained.

The Engineer’s Representative in accordance with Item 4.9 and 4.10 will carry out tests forthe control of mixing and compaction. The average of a series of control tests must not beless than the laboratory tests results set out in Item 3.6.4 (d) and the minimum test result mustbe no more than 2% lower than the laboratory test and occur less frequently than 1 in 10 tests.

If this average is not obtained by the Contractor he shall, at his own expense, scarify andremove the unsatisfactory stabilised base, re-shape and re-compact the sub-base or formation,supply, spread and compact the new base-course material and stabilise and compact as before.If conditions are suitable, the Engineer may agree to 100mm stabilised base on top of the sub-standard stabilised base instead of replacing the original base.

7.6 Base-Course – Lime Stabilised

Where a lime-stabilised base is used, the material to be used shall comply with Item 3.6.4 (e) and 4.2. The specification for a cement-stabilised base shall apply except that the maximumtime between mixing in of the lime and completion of the compaction of the stabilisedmaterial shall be 24 hours.

7.7 Base-Course – Width on CurvesOn curves of less than 300mm radius, the width of the base-course material shall be increasedby 600mm such increase being applied to the inside of the curve and being applied graduallyover a distance of 30m on the straight road at each end of the curve in accordance with Item1.3.

7.8 Tolerance on Base-Course

The finished surface of the base-course shall conform to the same accuracy as required for theformation profile (Item 6.9) except that the limit of tolerance shall be 10mm.

7.9 Hard Shoulders and VergesOn roads with a minimum pavement width of 5.4m material as per Item 3.6.3 shall be spreadacross the shoulders and verges and compacted to 100% M.D.D./W.A.S.C. The cross falls ofthe shoulders and verges shall be the same as the base-course i.e. 1:32. In urban areas orroads with a high traffic intensity, 1m wide reinforced concrete shoulders or reinforcedconcrete kerbing as shown on the drawings shall be used where directed by the Engineer’sRepresentative.

See Item 6.12 regarding action to be taken to prevent scour where the longitudinal gradient isexcessive.


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8. CONCRETE

8.1 Fixings and CavitiesNo holes or ot

roads bridges specification 2008 june 9 bun.pdf

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