dmrb volume 7 section 5 part 3 - hd 38/16 - concrete ...design manual for roads and bridges volume 7...

May 2016

DESIGN MANUAL FOR ROADS AND BRIDGES

VOLUME 7 PAVEMENT DESIGN AND MAINTENANCE

SECTION 5 SURFACING AND SURFACING MATERIALS

PART 3

HD 38/16

CONCRETE SURFACING AND MATERIALS

SUMMARY

This Standard gives advice on the materials andtechniques available for road surfacing to trunk roadsusing concrete.

INSTRUCTIONS FOR USE

1. Remove HD 38/97 from Volume 7, Section 5, Part 3, which is superseded by this Standard and archive as appropriate.

2. Insert HD 38/16 into Volume 7, Section 5, Part 3.

3. Archive this sheet as appropriate.

Note: A quarterly index with a full set of Volume Contents Pages is available separately from The Stationery Office Ltd.


Concrete Surfacing and Materials

SUMMARY

This Standard gives advice on the materials and techniques available for road surfacing to trunk roads using concrete.

HIGHWAYS ENGLAND

TRANSPORT SCOTLAND

WELSH GOVERNMENTLLYWODRAETH CYMRU

DEPARTMENT FOR INFRASTRUCTURE

HD 38/16Volume 7, Section 5,Part 3

May 2016

Registration of AmendmentsVolume 7 Section 5 Part 3 HD 38/16

Amend No Page No Signature & Date of incorporation of amendments


REGISTRATION OF AMENDMENTS

May 2016

Registration of AmendmentsVolume 7 Section 5

Part 3 HD 38/16



REGISTRATION OF AMENDMENTS

May 2016


VOLUME 7 PAVEMENT DESIGN AND MAINTENANCE

SECTION 5 SURFACING AND SURFACING MATERIALS

PART 3

HD 38/16

CONCRETE SURFACING AND MATERIALS

Contents

Chapter

1. Introduction

2. Types of Concrete Pavement

3. Features of Concrete Pavements and Detailing

4. Materials for Concrete Pavements

5. Low Noise Textured Concrete Surfaces

6. Transverse Textured Concrete Surface

7. Exposed Aggregate Concrete Surface

8. References

9. Enquiries

May 2016 1/1

Chapter 1Introduction

Volume 7 Section 5Part 3 HD 38/16

1. INTRODUCTIONGeneral

1.1 This Part of the Design Manual for Roads and Bridges gives requirements and advice on the materials and techniques available for road surfacing to trunk roads using concrete. Similar requirements and advice relating to bituminous surfacing is found in HD 37 (DMRB 7.5.2).

1.2 This Part contains requirements and advice on providing a textured concrete surface finish and Exposed Aggregate Concrete Surface (EACS).

1.3 The requirements and advice given in this document is provided on the basis that the works are constructed in accordance with the HA Manual of Contract Documents for Highway Works.

Implementation

1.4 This document shall be implemented in accordance with GD 1. Safety risk assessments shall be carried out in accordance with GD 4. An assessment as to the applicability of an equality impact assessment (EqIA) shall be carried out for all designs. Where the assessment indicates that an EqIA is required, then the designer shall carry out an EqIA.

This part has been updated for the purposes of EU compliance with additional minor changes throughout. Attention is also drawn to the change in clause 4.11 for construction topped by natural stone slabs.

Mutual Recognition

1.5 Where there is a requirement in this specification for compliance with any part of a British Standard or other technical specification, that requirement may be met by compliance with the Mutual Recognition clause in GD 1.

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Chapter 1Introduction


May 2016 2/1

Chapter 2Types of Concrete Pavement


2. TYPES OF CONCRETE PAVEMENTScope of Guidance

2.1 There are several different types of pavements incorporating concrete and/or hydraulically bound mixtures. Those types of pavement incorporating concrete and/or hydraulically bound mixtures most commonly encountered are:

• CRCP – Continuously reinforced concrete pavement.

• CRCB – Continuously reinforced concrete base.

• JRC – Jointed reinforced concrete pavement.

• URC – Jointed unreinforced concrete pavement.

• Thinly overlaid concrete pavements with less than 50 mm thick flexible “surfacing”.

2.2 The design of the concrete pavement slab is covered in HD26. More guidance on the use of thin bituminous overlays (less than 50mm thick) to provide the running surface can be found in HD32, HD36 and HD37.

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Chapter 2Types of Concrete Pavement


May 2016 3/1

Chapter 3Features of Concrete Pavement Surfaces and Detailing


3. FEATURES OF CONCRETE PAVEMENT SURFACES AND DETAILING

General

3.1 The type of surface of the concrete pavement influences the skid resistance, ride quality and noise levels experienced by the road user and in the wider environment.

3.2 The frictional qualities are determined largely by the micro texture at low speed and by the macro texture at higher speeds (above 30 mph).

3.3 The low speed friction of pavement surfaces is routinely measured by SCRIM and is described in HD 28. The high speed friction is not routinely measured but as a surrogate the texture depth of the surface is monitored.

3.4 Older UK concrete pavements have a brushed finished surface. This finish has been found to eventually wear off after several decades in service, leaving a relatively low textured running surface.

3.5 Transversely brushed, tined and grooved concrete pavement surfaces are generally more than 2dB noisier than worn Hot Rolled Asphalt HRA and are not permitted on new construction without authorization from the Overseeing Organisation. They may still be used where an existing concrete pavement is being repaired or widened.

3.6 In a jointed pavement the trafficked transverse joints at the slab interfaces can add to the vehicle noise and reduce ride quality.

3.7 Designs for new concrete pavement incorporating the use of CRCP construction and the use of quieter road surfaces, such as thin surfacing course system, exposed aggregate, longitudinally grooved or specially formed concrete surfaces have been successfully delivered. These have all provided low maintenance durable surfaces, maintaining ride quality and low noise characteristics.

Detailing

3.8 Drainage features such as gullies and manholes should be constructed outside the structural concrete pavement.

3.9 Structural interruptions in the main concrete slab need to be protected by isolation joints and specifically designed pavement details.

3.10 The connection of a concrete pavement to a flexible pavement requires specifically designed termination features and for CRCP ground anchors.

3.11 The design of slip roads reinforcement continuity requires particular attention.

3.12 Rolling crowns for concrete pavements need specific design and laying techniques.

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Chapter 3Features of Concrete Pavement Surfaces and Detailing


May 2016 4/1

Chapter 4Materials for Concrete Pavements


4. MATERIALS FOR CONCRETE PAVEMENTSMaterials

Cements

4.1 Cements used for the construction of concrete pavements are usually composed of Portland Cement (PC), often in combination with ground granulated blast furnace slag (ggbs) or pulverised fuel ash (pfa).

4.2 The specified minimum cement contents have been shown to provide the concrete with satisfactory long term durability. The limits on ggbs and pfa have been set to give the concrete a resistance to spalling when subjected to de-icing salts. Details of the requirements for concrete constituents can be found in MCHW clause 1001.

Admixtures

4.3 To assist in maintaining the workability of high strength pavement quality concrete mixes, while keeping a low water/cement ratio, plasticisers and super-plasticisers are often used. Where the concrete forms the running surface, air entrainment is required in the top 50mm (40mm in EACS) of a concrete pavement to provide resistance to surface scaling from frost action.

Aggregates

4.4 The coarse aggregate will often be natural material, crushed concrete or air-cooled blast furnace slag. The soundness value will exceed 75 and the maximum size will be 40mm, unless the spacing of the longitudinal reinforcement is less than 90mm, when it will not exceed 20mm.

4.5 White flints should not be used. They can cause pop-outs or can lead to D-shaped cracking. They consist of nodules of cortex or harder flints covered in cortex. Cortex is weathered flint and is porous as are, to some extent, all flint aggregates. The overall porosity of a flint aggregate will depend on the proportion of white flints. Smaller particles tend to have higher adsorption than larger aggregate sizes.

4.6 The acid soluble content of the fine aggregate (sand) is limited to ensure the surface has satisfactory low speed skidding resistance.

Construction

4.7 For a number of years new concrete pavements have been built in both single and 2 layer construction, both of which are permitted by the Specification (MCHW 1) Series 1000. The Contractor may choose the method of construction. More recently 2 layer construction has been used with either 2 separate pavers or a double-decker paving machine. The advantage of 2 layer construction is that only the top layer needs to be air entrained and the lower layer can contain the higher levels of ggbs or pfa and sands with a higher acid soluble content. When using different aggregates in each layer the difference in thermal expansion shall be considered and demonstrated that they will not cause reduced durability in the constructed pavement.

4.8 Both fixed-form and slip-formed pavers have been successfully used. Recent developments have made slip forming more attractive to contractors due to their increased capacity and flexibility on site. Modern slip-form pavers also have the capability of being able to be adapted for 2-layer construction.

4.9 Roller-compacted concrete is laid using a paver with a high-compaction screed. This process is often used in the construction of logistics distribution center and warehouse pavements. It has been used in road

4/2 May 2016

Chapter 4Materials for Concrete Pavements


construction in some European countries and in North America. A demonstration section of pavement utilizing this technology has been laid on a trunk road in England.

Joints

4.10 Jointed construction is only permitted with the approval of the Overseeing Organisation. Joints in concrete pavements have been found to be a frequent source of maintenance. Steps have been taken to both improve the durability, hence the serviceability, and to reduce the number of joints. Now expansion joints are only required at run on slabs at the end of CRCP pavements. In JUC and JRC pavements to improve durability transverse joints shall be sawn contraction joints. Longitudinal joints may be wet formed or sawn. The timing of sawing the hardened concrete is critical. If sawn too early the aggregate will be plucked out, if too late the concrete will have already cracked. With flint gravel aggregates in lower strength concrete pavements cracking may occur before sawing can begin, whereas in pavements of high early strength, flint gravel concrete joints are more likely to be successfully sawn. Dowel bars can be successfully inserted by slip form pavers avoiding possible misalignment.

4.11 The spacing of joints in slabs may be increased if a coarse aggregate with a low coefficient of linear expansion, such as limestone, is used in the concrete slab. If 2-layer construction is used the increased joint spacing may be used if this aggregate is used throughout the lower layer.

Surface finish

Regularity

4.12 The regularity of the surface provides a major contribution to the rolling resistance of that surface and the noise generated by traffic. The micro-texture (dependent on the constituents of the concrete) contributes to the slow-speed skidding resistance and sufficient macro-texture (as measured by the volumetric test) reduces aquaplaning at high speed. Both are essential to produce a safe road. Mega-texture is found to generate tyre/road noise. Both macro and mega-texture are controlled by the oscillating longitudinal float, which is also known as a ‘super smoother’. (For details of micro-, macro- and mega-texture see HD 36).

4.13 The oscillating longitudinal float is an integral part of the paving equipment, playing a vital role in ensuring that a smooth, flat slab is produced. Where the oscillating longitudinal float is part of a separate piece of equipment, as may be the case if rail mounted paving equipment is chosen, it shall be kept close to the rest of the paving train so that it is working on the fresh concrete surface.

Curing

4.14 Immediately after completion of the surface texturing of the slab it should be cured as required by the Specification (MCHW 1) Clause 1027 to reduce initial surface thermal cracking. During the initial period the surface should be protected against precipitation, moisture loss, contamination and dispersal of curing agent to avoid damage to the surface of the slab.

May 2016 5/1

Chapter 5Low Noise Textured Concrete Surface


5. LOW NOISE TEXTURED CONCRETE SURFACEGeneral

5.1 In North America a variety of concrete pavement formed surfaces have been developed that produce low road/tyre noise and provide a smooth ride. These often feature a texture that is applied in the longitudinal direction. Work has also taken place in the UK to retrospectively cut parallel longitudinal grooves into existing concrete road surfaces to reduce road/tyre noise and increase the frictional quality of the pavement.

5.2 A minimum texture depth is specified in MCHW 1 clause 1026 for a new brush finished concrete pavement, to ensure adequate surface water drainage and high speed friction. This texture depth requirement assumes that the applied texture is randomly orientated, as is achieved with a brushed finish. It is not known how the high speed friction provided by a longitudinally applied formed texture will relate to the texture depth as measured by either the volumetric or high speed sensor methods.

5.3 The high speed friction of a road surface can be directly measured by the Pavement Friction Tester and a range of values for in-service concrete pavements has been determined. Research has shown that an average locked wheel friction of 0.3 measured at 90km/hr. is desirable for non-event sections of high speed roads. The procedure for measurement of the average locked wheel friction of the road surface in shall be in accordance with ASTM E274/E274M – 11 (at a speed of 90km/hr rather than 40 mph specified in the test method), using a tyre that complies with ASTM E524 – 08.

5.4 To allow innovation in the development of concrete pavement surfaces a guide to support an application for a departure from MCHW 1 clause 1026 has been developed.

For a departure, evidence shall be supplied to show that the proposed new surface form will:

• Adequately allow for the dissipation of surface water to prevent vehicle aquaplaning.

• Resist the wear and tear imposed by heavy vehicle movements and loading.

• Provide a minimum in-service locked wheel friction of 0.3 measured at 90 km/h.

• Be maintained during bulk construction from any demonstration pavement installation.

• Indicate the anticipated noise level of the surface as defined in table 5/1.

5.5 The designer shall specify the noise level required for the finished surface in the contract specific Appendix 7/1. These levels are the same as for bituminous pavements. Detailed information of the methodology for the assessment of road/tyre noise level is provided in MCHW 1 clause 942. The levels are shown in table 5/5.

5/2 May 2016

Chapter 5Low Noise Textured Concrete Surface


Level Equivalence to HRA Surfacing with 20mm pre coated chips and 2mm texture depth

Road Surface Influence RSI

3 Very quiet surfacing material -3.5 dB(A)2 Quieter than HRA surfacing materials -2.5 dB(A)1 Equivalent to HRA surfacing materials -0.5 dB(A)0 Equivalent to Cold Applied Ultra Thin Surfacing +1.2 dB(A)NR No requirement No requirement

Table 5/5: Road/Tyre Noise Levels

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Chapter 6Transverse Textured Concrete Surface


6. TRANSVERSE TEXTURED CONCRETE SURFACEGeneral

6.1 This Chapter explains the use of transverse textured concrete surface. It gives the background and details for the finish that meets the requirements of the Specification for Highway Works (MCHW 1) Series 1000, though this method shall only be used for replacement and repair of existing concrete pavements. The texture is achieved by transversely brushing or tining the slab after compaction of the concrete is completed and before commencement of the curing process. A brushed or tined surface finish may be applied to Unreinforced Concrete (URC), Jointed Reinforced Concrete (JRC) or Continuously Reinforced Concrete Pavements (CRCP).

6.2 Brushed concrete surfaces have been successfully constructed and have given more than 20 years of trouble free service, provided proper maintenance has been carried out. It has become evident that some brushed concrete surfaces can have high road/tyre noise levels. The advice given in this Chapter is aimed at ensuring that new surfaces are not excessively noisy whilst maintaining adequate skidding resistance. Further advice on the noise generated on concrete surfaces is given in HD 36.

Scope

6.3 The requirements for the materials and the construction of roads with a brushed concrete surface are given in the Specification (MCHW 1) Series 1000. The relevant Clause should be used in conjunction with the associated Appendix 7/1 and the related Notes for Guidance to the Specification for Highway Works (MCHW 2).

Texture

6.4 Macro-texture is applied to the surface of the slab to provide a path for water and air to be dissipated from under the tyres. Texture may be applied by brushing the surface or by dragging burlap and then tining the surface of the wet concrete. Whereas both treatments create suitable macro-textures they can also produce surfaces with high mega-textures, which are unacceptably noisy.

6.5 Brushed textures are applied transversely across the slab while the concrete is still plastic. The texture should be applied evenly with no ridges being formed, particularly where the brush overlaps with previous passes. The pressure of the brush on the road needs to be uniform and consistent and the bristles kept clean to enable a satisfactory finish to be produced.

6.6 Burlap and tined surfaces are widely used in America and now can be used in the UK. The burlap (wet hessian) is dragged over the surface after it has been regulated to precondition the surface and give it a micro-texture. The tined texture is produced using similar equipment to that for applying brushed texture but with the brush head replaced by a head carrying the steel tines which is drawn transversely across the surface. The tines are 3mm wide and spaced apart at one third of those given for texturing hardened surfaces in the Specification (MCHW 1) clause 1029. A trial length shall be used to determine the actual spacing required for the particular materials and plant being used.

6/2 May 2016

Chapter 6Transverse Textured Concrete Surface


May 2016 7/1

Chapter 7Exposed Aggregate Concrete Surface


7. EXPOSED AGGREGATE CONCRETE SURFACEGeneral

7.1 This chapter outlines the use of Exposed Aggregate Concrete Surface (EACS). It draws attention to the design, specification, construction and life of the surface and contains guidance on its design, use and maintenance.

7.2 EACS can provide a long life road surface with lower traffic noise than traditionally brush finished surface roads, offering comparable skid resistance. The exposed aggregate top surface forms a matrix of interconnected paths below the plane running surface through which water can pass, to maintain a high speed skidding resistance, and assist in reducing tyre/road surface noise. There may be a slight reduction in spray generated by high speed vehicles.

7.3 The level of noise emitted at the tyre/road interface on EACS is generally higher than for thin surfacing course systems but lower than for hot rolled asphalt, brushed concrete and surface dressed running surfaces whilst offering comparable skid resistance. EACS is perceived to have better tonal qualities than conventional brushed concrete surfaces. It retains the acoustic properties for longer than bituminous surfaces.

7.4 The appearance of EACS is similar to that of hot rolled asphalt with the surface picking up its colour from the exposed aggregate.

Scope

7.5 Clauses specifying requirements for material properties, testing, laying and exposing the aggregate are given in the specification (MCHW 1) Series 1000. The relevant clauses in the Specification should be used in conjunction with the associated Appendix 7/1 and the related Notes for Guidance to the Specification for Highway Works (MCHW 2). The minimum PSV of the exposed aggregate shall accord with those required in HD 36 which are dependent upon site geometry and features.

Development

7.6 EACS was first trialed in Denmark and developed in Belgium with the aim of producing a safe, long life concrete running surface as an alternative to the conventional brushed finishes used previously. The technique has been successfully used since the 1970s and now EACS is the normal form of surface treatment to CRCP on major Belgian roads. In the late 1980s the environmental problems of tyre/road noise came to the fore in Austria. Anxious to find a low noise concrete road surface that would stand up to studded tyre use in winter, the Austrians refined the Belgian process, discovering that by reducing the size of the chippings in the coarse aggregate at the road surface the tyre/road noise levels could be substantially reduced. Consideration was given in Austria to full depth construction but this would have used large quantities of premium aggregate. Two layer construction was chosen to produce an economic solution. Now this is the normal form of EACS construction in Austria providing an economic, long lasting surface giving measurable noise reduction when compared with conventional concrete pavements. Other countries which have used the EACS include France, the Netherlands, Australia and the USA. In Sweden it has provided a durable surface that stands up to the use of studded tyres in the winter months. EACS roads in Austria were constructed using a smaller sized aggregate, with a lower skidding requirement than specified in the UK. To provide an adequate low and high speed skidding resistance a deeper texture depth and the appropriate aggregate size are specified. Other European countries, apart from Belgium, have chosen to use jointed concrete slabs whereas in the UK, CRCP construction with EACS has been successfully used on UK trunk roads and motorways.

7/2 May 2016



Use

7.7 EACS can be used in most locations, including heavily trafficked roads including inlays to flexible roads.

Durability

7.8 Concrete roads are structurally designed for a traffic life of forty years although the surface will normally require restoration of skid resistance at some point in its life. The special aggregate used in the top mix concrete is durable, with the minimum PSV and maximum AAV specified in Appendix 7/1 of the Specification (MCHW 1). Evidence indicates that no particular durability problems are likely to be encountered.

Noise

7.9 EACS is designed to provide an adequate level of skid resistance, both at high and low speeds, as well as a low level of surface noise. Work by Descornet and Fuchs (1992) has identified the respective roles of micro, macro and megatexture in relation to road/tyre noise. On low speed roads, microtexture, which depends on the roughness or harshness of the aggregate, is of prime importance. On higher speed roads, macrotexture created by procedures such as transverse brushing or exposing the aggregate plays an important role in reducing noise. Megatexture, the variations of amplitude of certain wavelengths in the 50 to 500mm range, is an undesirable irregularity. It can be a major cause of road/tyre noise because it creates radial vibration of the tyre. Megatexture can originate during the course of construction in the form of corrugation or other surface irregularities. The use of the transverse finishing screed in advance of a longitudinal oscillating float as soon as the surface is laid plays a vital role in eliminating these characteristics by constructing the aggregate surface in a level plane and hence resulting in noise reduction.

7.10 This type of surface typically exhibits noise reductions in excess of 2 dB(A) compared with HRA bituminous surfaces and the acoustic properties of EACS are the most durable of all road surfaces.

Structural Capacity

7.11 Depending upon the requirements of the highway scheme EACS may be applied to Jointed Unreinforced (URC), Jointed Reinforced (JRC), and Continuously Reinforced (CRCP) pavements.

Materials and Mixing

7.12 In two layer construction, the Specification (MCHW 800) gives a wide choice of aggregates for the concrete in the lower layer. The aggregate used in the upper layer will need to meet the requirements of HD36.

Batching and Transportation

7.13 The contamination of the concrete for EACS with aggregates or constituents for other concretes shall be prevented. It is preferable that plant used for the batching and mixing of EACS should be separate from that used for other concrete unless the mixing plant has a self-cleaning mechanism.

7.14 Dedicated, clearly identified delivery vehicles shall be used for the transport of the separate mixes. These should be cleaned thoroughly between deliveries of separate mixes. Open tipper trucks should be sheeted.

Construction

7.15 Two layer monolithic construction has been shown to be cost effective and has been successfully used by contractors. The requirements for all types of concrete for road pavements are given in the Specification

May 2016 7/3



(MCHW 1000). The batching output capacity and transport delivery capacity should be sufficient to feed the paving equipment continuously, enabling a constant forward movement to be maintained during the period of paving.

7.16 The oscillating longitudinal float plays a vital role in ensuring that a smooth, flat slab is produced prior to the application of retarder.

7.17 The exposure of the surface is a two stage process including retarding of the surface mortar, and brushing to expose the aggregate.

a) A suitable retarder shall be used which will retard sufficiently the action of the cement at the surface of the top layer so that the target texture depth can be achieved by the brushing operation. Advice of retarder manufacturers may be sought. The retarder shall contain a non-staining dye, for visual identification of adequate coverage. The application system shall atomise the retarder with a fine spray enabling total and even coverage of the slab to be obtained without overdosing with excess retarder flowing over the surface of the slab. From the time that the concrete surface is finished and the retarder is applied the surface of the concrete needs protection from both drying out and rainfall. The protection shall be maintained until immediately before exposing the aggregate. This may be of a physical nature with protective sheeting being tightly stretched across the slab and firmly secured at the edges. An alternative is a system of protection where a chemical substance, compatible with the retarder, is sprayed on to the newly retarded surface which, after some minutes, forms a protective skin which protects the retarder and slab against the elements. For this system temporary tentage is required to protect the surface against rain before the longer term protection becomes operative.

b) The second stage in the creation of the exposed aggregate surface is the brushing. The time to start brushing must be determined from trial installations. Brushing too early will result in chipping loss, and brushing too late will mean the surface texture will be very difficult to achieve. The ideal surface will characteristically not only meet the target texture depth requirements, but also exhibit a ‘shoulder to shoulder’ pattern of chippings. Experience indicates that the more cubic the shape of the chipping, the more likely that close packing will occur.

7.18 Care should be taken to avoid fretting at day joints. This can be aggravated by retarder spray running down the vertical end of the slab. Hand finishing of the concrete can cause problems if excess grout is pulled to the surface, making exposure of the aggregate at this point more difficult.

Surface Texture Depths

7.19 The required surface texture depths are stated in Appendix 7/1 in the Specification (MCHW 700). See also Table NG 10/2 in the Notes for Guidance (MCHW 1000), which gives guidance on the requirements of average, maximum and minimum texture depths for high speed and low speed roads.

Brushing

7.20 The aggregate should be exposed by brushing in a longitudinal direction to give the texture depth as stated in Appendix 7/1 in the Specification (MCHW 700). Brushing should continue until that texture depth is achieved. Provision should be made for effective dust and laitance collection and disposal.

Curing

7.21 After brushing is completed the surface should be dampened prior to the application of the final curing agent.

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Defect Repairs

7.22 If the specified minimum texture depth is not achieved by brushing, retexturing shall be carried out. Failure to achieve the specified minimum texture depths will result in unsatisfactory skid resistance for high speed vehicles. The full extent of any areas still nonconforming following mechanical retexturing shall be removed and replaced.

7.23 Where the specified average texture depth has not been met, remedial measures should be agreed with the Overseeing Organisation.

7.24 Surface defects may be repaired provided:

a) The affected area is cut out to the top of the lower layer concrete;

b) A bonding agent is used; and

c) The same mix design used for the replacement concrete.

The aggregate should be exposed in such manner as to achieve a texture similar to that in an adjacent compliant slab.

Renewal of Skid Resistance

7.25 After a period of decades it may be necessary to restore the skid resistance to the EACS. Remedial measures shall be agreed with the Overseeing Organization.

Winter Maintenance

7.26 There are no special winter maintenance requirements.

Road Markings

7.27 There are no problems associated with applying markings to an exposed aggregate surface.

May 2016 8/1

Chapter 8References


8. REFERENCESNORMATIVE

BS EN 197-1.

HD 37 (DMRB 7.5.2) Bituminous Materials.

HD 36 (DMRB 7.5.1) Surfacing Materials for New and Maintenance Construction.

Specification for Highway Works (MCHW 1) 700 Series.




INFORMATIVE

ASTM E274/E274M – 11.

ASTM E524 – 08.

HD 26 (DMRB 7.2.3) Pavement Design.

HD 28 (DMRB 7.3.1) Skidding Resistance.

HD 32 (DMRB 7.3.3) Maintenance of Concrete Pavements.

Descornet, G. and Fuchs, F., Concrete Paving Texture, Proceedings of the PIARC workshop “Noise Reducing Concrete Surfaces”, Vienna, pp 54 – 60, 1992.

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Chapter 8References

May 2016 9/1

Chapter 9Enquiries


9. ENQUIRIESApproval of this document for publication is given by:

Highways England Temple Quay House The Square Temple Quay Bristol M WILSONBS1 6HA Chief Highways Engineer

Transport Scotland 8th Floor, Buchanan House 58 Port Dundas Road R BRANNEN Glasgow DirectorG4 0HF Trunk Road and Bus Operations

Welsh Government Transport S HAGUE Cardiff Deputy Director CF10 3NQ Network Management Division

Department for Infrastructure Clarence Court 10-18 Adelaide Street Belfast P B DOHERTY BT2 8GB Director of Engineering

All technical enquiries or comments on this Standard should be sent to [email protected]

This document was notified in draft to the European Commission in accordance with Technical Standards and Regulations Directive 2015/1535/EU.

9/2 May 2016


Chapter 9 Enquiries