qcs 2010 part 6.06 concrete road pavements

8/10/2019 QCS 2010 Part 6.06 Concrete Road Pavements

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QCS 2010 Section 6 Part 6 Concrete Road Pavements Page 1

6.

CONCRETE ROAD PAVEMENTS.................................................................3

6.1

GENERAL REQUIREMENTS........................................................................3

6.1.1

Scope 3

6.1.2

References 3

6.1.3

Quality Control of Concrete Strength 3

6.2

TRIAL LENGTH .............................................................................................4

6.2.1

General Requirements for Trial Length 4

6.2.2

Assessment of Trial Length 5

6.2.3

Approval and Acceptance of Trial Length 6

6.3

REQUIREMENTS FOR PAVEMENT QUALITY CONCRETE........................6

6.3.1

Materials and Mix Designs for Pavement Quality Concrete 6

6.3.2

Workability of Pavement Quality Concrete 6

6.3.3

Trial Mixes 7

6.3.4

Separation Membrane 7

6.3.5

General Requirements for Steel Reinforcement 7

6.3.6

Jointed Reinforced Concrete Slabs 8

6.3.7

Continuously Reinforced Concrete Slabs (CRCP or CRCR) 8

6.3.8

General Requirements for Transverse Joints 9

6.3.9

Transverse Contraction Joints 9

6.3.10

Transverse Expansion Joints 9

6.3.11

Transverse Warping Joints 10

6.3.12

Transverse Construction Joints 10

6.3.13

General Requirements for Longitudinal Joints 10

6.3.14

Longitudinal Construction Joints 116.3.15

Dowel Bars 11

6.3.16

Tie Bars 12

6.3.17

Joint Grooves 14

6.3.18

Groove Formers and Bottom Crack Inducers 14

6.3.19

Joint Filler Board 15

6.3.20

Preparation and Sealing of Joint Grooves 15

6.3.21

Sealing with Applied Sealants 16

6.3.22

Sealing with Compression Seals 17

6.3.23

Joint Seals 17

6.3.24

Joints at Manhole and Gully Slabs 18

6.3.25

Inspection of Dowel Bars 18

6.3.26

Side Forms, Rails and Guide Wires 19

6.3.27

Delivery, Storage and Batching of Concreting Materials 19

6.3.28

Mixing Concrete 20

6.3.29

Transport and Delivery 20

6.3.30

General Requirements for Construction by Machine 20

6.3.31

Construction by Fixed Form Paving Machines 21

6.3.32

Construction by Slip-Form Paving Machine 21

6.3.33

Construction by Small Paving Machines or Hand Guided Methods 22

6.3.34

Surface Textures 23

6.3.35

Curing 23

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6.4

REQUIREMENTS FOR WET LEAN CONCRETE .......................................24

6.4.1

Materials and Mix Designs 24

6.4.2

Placing 24

6.4.3

Compaction 24

6.4.4

Joints 24

6.4.5

Strength 24

6.4.6

Trial Mixes 25

6.4.7

Trial Length 25

6.4.8

Surface Finish 25

6.5

REQUIREMENTS FOR CEMENT BOUND MATERIALS ............................25

6.5.1

General Requirements for Cement Bound Materials 25

6.5.2

Batching and Mixing 26

6.5.3

Transporting 27

6.5.4

Laying 27

6.5.5

Compacting 27

6.5.6

Curing 27

6.5.7

Preliminary Trial 28

6.5.8

Cement Bound Material Category 1 (CBM1) 28

6.5.9


6.5.10


6.5.11


6.5.12

Testing of Cement Bound Materials 30

6.5.13

Special Requirements for Cement Bound Materials 30

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6. CONCRETE ROAD PAVEMENTS

6.1 GENERAL REQUIREMENTS

6.1.1 Scope

1 This part of the specification covers the; materials, mix designs, production and laying ofpavement quality concrete, lean mix concrete and cement bound materials.

2 Related Sections and Parts are:

This Section

Part 3 - EarthworksPart 4 - Unbound Pavement MaterialsPart 5 - Asphalt Works

Section 5 - ConcretePart 16 - Miscellaneous - Pavement Quality Concrete

6.1.2 References

1 The following standards are referred to in this part of the specification

BS 1377: Part 9 Methods of testing soils in-situ testsBS 1881 Methods of testing concrete -BS 1924: Part 1 & 2 Stabilised materials for civil engineering purposesBS 2499 & BS EN 14188 Hot applied joint sealants for road pavementsBS 2752 Chloroprene rubber compoundsBS 3900: Part F12 Determination of resistance to neutral salt sprayBS 3963 Method for testing the performance of concrete mixersBS EN ISO 11600 Two part polysulphide sealantsBS 4449 Reinforcing barsBS 4482 Cold drawn steel wire for reinforcing concreteBS 4483 Reinforcing meshBS 5212: Part 1 & 2 Cold applied joint sealants for concrete pavementsBS EN 206 & BS 8500 Supply of concreteBS 7542 Methods for test of curing compounds for concreteBS 812 Testing methods for aggregates

ASTM D3406 Specification for joint sealant - hot applied elastomeric typesASTM 7116 Specification for joint sealant - hot applied elastomeric types (jet

fuel resistant)ASTM D2628-91 Specification for preformed joint seals

DTP Manual of contract documents for highway works -Volume 1specification for highway works

6.1.3 Quality Contro l of Concrete Strength

1 Sampling and testing for, and compliance with the specified characteristics strength ofdesigned mixes shall be in accordance with BS EN 206 & BS 8500, except that it shall be atthe following rates of sampling and testing and meet the following requirements:

(a) Concrete cubes of the appropriate size shall be made, cured and tested inaccordance with BS 1881 respectively from concrete delivered to the paving plant,each group being from a different delivery of concrete. At least 3 cubes shall be madeper group for each 600 m

2 of concrete slab and not less than 6 groups shall be

made each day, for each type of mix. For areas less than 600

m2

, at least 4 cubesshall be made for each 100 m

2 or less. This rate of sampling and testing may be

reduced at the Engineer's discretion.

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(b) For areas of 600 m2or more, one cube shall be tested in compression at 7 days and

the other two at 28 days after mixing. Groups of four consecutive results at 28 daysshall be used for assessing the strength for compliance with BS EN 206 & BS 8500.For areas less than 600 m

2, two cubes shall be tested at 7 days and two tested at 28

days and assessed in accordance with BS EN 206 & BS 8500.(c) The ratio R between 7 and 28 day strengths shall be established for the mix to be

used in the slab by testing pairs of cubes at each age on at least six batches of theproposed mix or it shall be quoted by the supplier of the concrete. The averagestrength of the 7 day pair of cubes shall be divided by the average strength of the 28-day pair of cubes for each batch and the ratio R shall be the average of these sixvalues. The ratio R shall be expressed to three decimal places.

(d) If during the construction of the trial length or during normal working, the averagevalue of any 4 consecutive 7 day test results falls below the strengths required thenthe cement content of the concrete shall be increased by 5 % by mass or by anamount agreed by the Engineer. The increased cement content shall be maintainedat least until the four corresponding 28-day tests have been assessed. If the cementcontent is increased, the concrete mix shall be adjusted to maintain the requiredworkability.

(e) The values in columns 3 and 4 of Table 6.1 may only be used with the permission of

the Engineer when sufficient test results on trial mixes for calculating the ratio are notavailable. Once sufficient results are available from normal working the ratio R shallbe calculated from the results available on Site.

(f) To assess the time for use of a concrete slab by traffic, the strength development ratemay be predetermined by trial mixes. Alternatively pairs of cubes shall be made foreach 600 m

2or less and stored alongside the pavement in containers or in such a

way that their sides are well insulated. If thermal insulation is used for acceleratedcuring the cubes shall be similarly insulated. Pairs of cubes shall be tested atintervals decided by the Engineer. Tests for compliance with the specified strengthshall be made in the normal way.

Table 6.1

7 Day Cube Strength

Grade of Concrete All Mixes, Ravailable

PC Mixes, R notavailable

PFA or ggbs mixes, Rnot available N/mm

2

C40 43R 35 29C30 33R 27 22C20 22R 18 14C15 17R 13 11C10 10R 8 7C7.5 7R 5.5 4.5

6.2 TRIAL LENGTH

6.2.1 General Requirements for Trial Length

1 Except in rapid construction projects, at least one month prior to the construction of the triallength of surface slabs or CRCR (Continuously Reinforced Concrete Road Base) theContractor shall submit for the Engineer's approval a detailed description of the proposedmaterials, mix proportions, plant, equipment and construction methods.

2 No trials of new materials, plants, equipment or construction methods; nor any developmentof them shall be permitted either during the construction of the trial length or in anysubsequent paving work, unless they form part of further approved trials.

3 The Contractor shall demonstrate the materials, mix proportions, plant, equipment andmethod of construction that are proposed for concrete paving, by first constructing a trial

length of slab, at least 150m but not more than 300

m, long for mechanised construction,and at least 30m long for hand guided methods, or otherwise as directed by the Engineer.

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4 The mix proportions decided by trial mixes may be adjusted during the trial but shall not bechanged once the trial length has been approved except with the agreement of the Engineer.

5 The trial length shall be constructed in two parts over a period comprising at least part of twoseparate working days, with a minimum of half the proposed trial lengths constructed eachday. The trial length shall be constructed at a similar rate to that which is proposed for the

main construction in the permanent works.

6 At least two transverse joints and one longitudinal joint of each type that are proposed forunreinforced concrete slabs and jointed reinforced concrete slabs in the main construction inthe permanent works shall be constructed and assessed in the trial length.

7 If in the trial length expansion joints are not demonstrated, the first 2 expansion joints and at

least the first 150 m of longitudinal construction joint for mechanised paving, or 30 m forhand guided method of construction laid in the main construction in the permanent works,shall be considered the trial length for these joints.

8 One construction joint shall be demonstrated in each trial length of CRCP or CRCR.

6.2.2 Assessment of Trial Length

1 The trial length shall comply with the Specification in all respects, with the following additionsand exceptions provided in (a) through (d) below.

(a) Surface Levels and irregularity(i) in checking for compliance the levels shall be taken at intervals of not more than

2.5 m along any line or lines parallel to the longitudinal centre line of the triallength.

(ii) The maximum number of permitted irregularities of pavement surfaces shallcomply with the requirements for asphalt pavements as per Part 5for 300 m lengths. Shorter trial lengths shall be assessed pro-rata based onvalues for a 300 m length.

(b) Joints(i) At least 3 cores of minimum diameter 100 mm shall be taken from the slab at

joints to check the lateral and vertical location of joint grooves and bottom crackinducers.

(ii) After a minimum of 24 hours following construction the removable part of thejoint groove former shall be taken out and at least three joints and the sides ofthe groove shall be inspected for compaction. If there are voids the size andnumber should be compared with a similar size section of the photograph for3% excess voidage in BS 1881. If there is excess voidage, additionalcompaction shall be provided and further joints inspected. The joints soexposed shall be temporarily or permanently sealed

(iii) Alignment of dowel bars shall be inspected in any two consecutive transverse

joints. If the position or alignment of the dowel bars at one of these joints doesnot comply after the next 3 consecutive joints of the same type have beeninspected then the method of placing dowels shall be deemed to be

satisfactory.(iv) If there are deficiencies in the first expansion joint constructed as a trial,

the next expansion joint shall be a trial joint. Should this also be deficient furthertrial expansion joints shall be made as part of a trial length which shall not formpart of the Permanent Works, unless agreed by the Engineer.

(c) Density(i) Density shall be assessed from at least 3 cores drilled from each part of the trial

length.

(d) Position of Reinforcement and Tie Bars

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(i) Compliance for the position of steel reinforcement and for the position andalignment of tie bars shall be checked by drilling additional cores from the slabunless they can be determined from cores taken for density assessment.

6.2.3 Approval and Acceptance of Trial Length

1 Approval of the materials, mix proportions, plant, equipment and construction methods willbe given when a trial length complies with the specifications. The Contractor shall notproceed with normal working until the trial length has been approved and any earlierdefective trial lengths have been removed, unless they can be remedied to the satisfaction ofthe Engineer.

2 When approval has been given, the materials, mix proportions, plant, equipment andconstruction methods shall not thereafter be changed, without the approval of the Engineerexcept for maintenance of plant. Any changes in materials, mix proportions, plant,equipment, and construction methods shall entitle the Engineer to require the Contractor tolay a further trial length as described in this Clause to demonstrate that these changes willnot adversely affect the permanent works.

3 Trial lengths which do not comply with the Specification, with the exception of areas withinthe pavement surface which can be remedied shall be removed immediately uponnotification of deficiencies by the Engineer and the Contractor shall construct a further triallength.

6.3 REQUIREMENTS FOR PAVEMENT QUALITY CONCRETE

6.3.1 Materials and Mix Designs for Pavement Quality Concrete

1 The constituent materials and mix designs for pavement quality control shall be as perSection 5: Part 16.

6.3.2 Workabil ity of Pavement Quality Concrete

1 The workability of the concrete at the point of placing shall enable the concrete to be fullycompacted and finished without undue flow. The optimum workability for the mix to suit thepaving plant being used shall be determined by the Contractor and approved by theEngineer.

2 The workability shall be determined by the compacting factor test, or the Vebe test oralternatively for concrete grade C20 or below, by the slump test, all in accordance with BS1881, at the minimum rate of one determination per 300 m

2of slab laid or 6 times per day,

whichever is greater. For areas less than 300 m2 the rate shall be at least one

determination to each 20 m length of slab or at least 3 times per day.

3 Alternatively the volumetric method of determining the Compacting Factor in BS 1881 maybe used. Tests for workability shall be carried out at the point of placing, in conjunction withtests for strength and any tests for air content. The workability shall be maintained at theoptimum within the following tolerances.

Compacting Factor (CF) +0.03Slump +20mmVebe +3 seconds or as agreed by the Engineer as a results of trial mixes.

4 Any alteration to the optimum workability necessitated by a change in conditions shall beagreed beforehand by the Engineer.

5 If any determination of workability gives result outside the tolerance, a further test shall bemade immediately on the next available load of concrete. The average of the twoconsecutive results and the difference between them shall be calculated. If the average isnot within the tolerance or the difference is greater than 0.06 for CF or 20 mm for slump, or

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6 seconds for Vebe or other value agreed with the Engineer, subsequent samples shall betaken from the delivery vehicles, which shall not be allowed to discharge into the Works untilcompliance with the Specification has been established.

6.3.3 Trial Mixes

1 For concrete grades C15 and above the Contractor shall carry out laboratory trials ofdesigned mixes with the materials from all sources to be used in the Works, in accordancewith BS EN 206 & BS 8500 unless recent data relating entirely to the proposed mix isapproved by the Engineer.

2 The trial mixes shall be repeated if necessary until the proportions of ingredients aredetermined which will produce a concrete which complies in all respects with theSpecification.

3 Apart from minor adjustments to the mix as permitted by BS EN 206 & BS 8500 anychanges in sources of materials or mix proportions that are proposed by the Contractorduring the course of the Works shall be assessed by making laboratory trial mixes and theconstruction of a further trial length unless otherwise approval is given by the Engineer.

6.3.4 Separation Membrane

1 A separation membrane shall be used between jointed reinforced concrete surface slabs orunreinforced concrete surface slabs and the sub base.

2 Separation membranes shall be impermeable plastic sheeting 125 microns thick laid flatwithout creases. Where an overlap of plastic sheets is necessary, this shall be at least300 mm. There shall be no standing water on or under the membrane when the concrete isplaced upon it.

3 Under CRCP and CRCR a waterproof membrane shall be provided, which shall be abituminous spray before concreting. Where a bituminous spray has been used to curecement bound material or wet lean concrete then only those areas which have beendamaged shall be resprayed after making good. The waterproof membrane shall bebituminous cutback in accordance with clause 5.12 of this Section.

6.3.5 General Requirements for Steel Reinforcement

1 Reinforcement shall comply with any of the following standards and be in prefabricatedsheets or cages, or bars assembled on site and shall be free from oil, dirt, loose rust andscale:

(a) (Carbon steel bars for the reinforcement of concrete) BS 4449(b) (Cold-reduced steel wire for the reinforcement of concrete) BS 4482(c) (Steel fabric for the reinforcement of concrete) BS 4483

When deformed bars are used they shall conform to Type 2 bond classification of BS 4449.

2 Spacing of bars shall not be less than twice the maximum size of aggregate used. Laps in

longitudinal bars shall be not less than 35 times bar diameters or 450 mm which ever isgreater. In continuously reinforced concrete slabs (CRCP or CRCR) only one third of thelaps may be in any one transverse section, except in single bay width construction where

half the laps may be in any one transverse section. There shall be a minimum of 1.2 mlongitudinally between groups of transverse laps or laps in prefabricated reinforcementsheets. Alternatively the reinforcement may be butt welded by a process approved by theEngineer.

3 Laps in a transverse reinforcement shall be a minimum of 300 mm. Where prefabricated

reinforcement sheets are used and longitudinal and transverse laps would coincide, no lap isrequired in the transverse bars within the lap of the longitudinal reinforcement. These

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transverse bars may be cropped or fabricated shorter so that the requirements for cover aremet.

4 If the reinforcement is positioned prior to concreting, it shall be fixed on approved metalsupports and retained in position at the required depth below the finished surface anddistance from the edge of the slab so as to ensure that the required cover is achieved.

Reinforcement assembled on site shall be tied, or firmly fixed, by a procedure agreed withthe Engineer, at sufficient intersections to provide sufficient rigidity to ensure that thereinforcement remains in the correct position during construction of the slab.

5 Alternatively, when a reinforced concrete slab (JRC, CRCP or CRCR) is constructed in twolayers, the reinforcement in the form of prefabricated sheets may be placed on or into thebottom layer which shall be spread and compacted to such a level that it will support thereinforcement without distortion at the required position in the slab. The sheets shall be tiedtogether at overlaps and after the second layer has been spread and compacted, thereinforcement shall have the required cover.

6 When a reinforced concrete slab is constructed at maximum width the transversereinforcement in the centre of each slab width shall be a minimum of 12 mm nominal

diameter bars at 600

mm centres. This reinforcement shall be at least 600 mm longerthan one third of the width of the slab and be lapped to other transverse reinforcement barsor sheets, or be continuous across the whole width of each slab.

6.3.6 Jointed Reinforced Concrete Slabs

1 The reinforcement shall be so placed that after compaction of the concrete, the cover below

the finished surface of the slab is 50 + 10 mm for slabs less than 200 mm thick, 60 +10 mm for slabs 200 mm or more but less than 270 mm thick and 70+20 mm for slabs

270 mm thick or more.

2 The negative vertical tolerance shall not be permitted beneath road stud recesses.

3 Where traffic signal detector loops are to be installed, the minimum cover to the

reinforcement from the surface shall be 100 mm.

4 The vertical cover between any longitudinal joint groove forming strip and any reinforcement

or tie bars shall be at a minimum of 30 mm.

5 Any transverse bars shall be at right angles to the longitudinal axis of the carriageway. Anytransverse reinforcement shall terminate at 125+25 mm from the edges of the slab andlongitudinal joints, where tie bars are used.

6 No longitudinal bars shall lie within 100 mm of a longitudinal joint. The reinforcement shall

terminate 300 mm + 50 mm from any transverse joint, excluding emergency construction

joints.

6.3.7 Continuously Reinforced Concrete Slabs (CRCP or CRCR)

1 The reinforcement shall be Grade 460 deformed steel bars as detailed on the ContractDrawings.

2 The reinforcement shall consists of bars assembled on site, or of prefabricated sheets.

3 Except where otherwise shown on the Drawings the longitudinal bars shall be parallel to thecentre line of the road.

4 The reinforcement shall be positioned so that, after compaction of the concrete, it shall be at

the mid depth of the specified thickness of the slab + 25

mm. No longitudinal bar shall liewithin 100mm of a longitudinal joint.

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5 In reinforcement assembled on site, longitudinal bars shall be placed immediately above anytransverse bars, which shall be at right angles to the longitudinal axis of the carriageway.

Any transverse reinforcement shall terminate 125+25 mm from the edges of the slab andlongitudinal joints where tie bars are used.

6.3.8 General Requirements for Transverse Join ts

1 Transverse joints shall be provided in unreinforced and jointed reinforced concrete slabs andshall be contraction, expansion or warping joints at the spacing shown on the Drawings suchthat for unreinforced concrete slabs the length/width ratio shall be not greater than 2.0.

2 Joints in the surface slab and sub-base shall be staggered so that they are not coincidentvertically and are at least 1m apart.

3 Transverse joints shall be straight within the following tolerances along the intended line ofthe joint, which is the straight line transverse to the longitudinal axis of the carriageway at theposition proposed by the Contractor and agreed by the Engineer, except at road junctions orroundabouts where the positions shall be as shown on the Drawings:

(a) Deviations of the filler board or bottom crack inducer from the intended line of thejoint shall be not greater than 10 mm.(b) The best fit straight line through the joint groove as constructed shall be not more

than 25 mm from the intended line of the joint.(c) Deviations of the joint groove from the best fit straight line of the joint shall be not

greater than 10 mm.(d) When top groove formers and bottom crack inducers are used, the joint groove

as constructed shall be located vertically above the bottom crack inducer within ahorizontal tolerance of 25 mm.

4 Transverse joints on each side of a longitudinal joint shall be in line with each other and ofthe same type and width. The position of the joints relative to manholes and gullies shall bein accordance with the Drawings.

5 Transverse joints shall have a sealing groove which shall be sealed in compliance withClause 6.3.20 of the specification.

6.3.9 Transverse Contract ion Joints

1 Contraction joints shall consist of:

(a) Either a sawn joint groove, or(b) a wet formed joint groove and a bottom crack inducer(c) dowel bars(d) a sealing groove.

6.3.10 Transverse Expansion Joints

1 Expansion joints shall consist of:

(a) a joint filler board(b) dowel bars(c) a sealing groove.

2 The filler board shall be positioned vertically within the prefabricated joint assemblies alongthe line of the joint and at such depth below the surface as will not impede the passage ofthe finishing beams on the paving machines.

3 The joint filler board together with the sealing groove shall provide a complete separation ofadjacent slabs and any spaces around dowel bars and between the sub-base and the filler

board shall be packed with a suitable compressible material after fixing the joint assembly.

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6.3.11 Transverse Warping Joints

1 Warping joints shall consist of:

(a) Either a sawn joint groove, or(b) a wet formed joint groove and a bottom crack inducer(c) tie bars(d) a sealing groove.

6.3.12 Transverse Construct ion Joints

1 Construction joints made at the end of a working day in unreinforced concrete slabs andjointed reinforced concrete slabs shall be expansion joints or contraction joints. In the eventof mechanical breakdown of the concreting machinery, or at the onset of adverse weather,emergency joints may be formed.

2 Emergency joints in unreinforced concrete slabs shall be either contraction or expansion

joints not less than 2.5 m from the preceding or succeeding joint position.

3 Emergency joints in jointed reinforced concrete slabs shall be not less than 2.5 m from the

preceding or succeeding joint position. The stop end formwork shall be sufficiently rigid toensure that dowel bars, tie bars or reinforcement will be held in position in compliance withthe specification, and placed in such a position that it permits the longitudinal reinforcement

to project through the joint for a distance of at least 750 mm.

4 Construction joints in continuously reinforced concrete slabs (CRCP and CRCR) in an

emergency shall not be constructed within 1.5 m of any lap in the longitudinalreinforcement without the approval of the Engineer. The stop end formwork shall besufficiently rigid to ensure that the longitudinal reinforcement and the tie bars projectingthrough the joint are held in the correct position.

6.3.13 General Requirements for Longi tudinal Joints

1 Longitudinal joints shall be provided in surface slabs between or at the centre of traffic laneswithin the allowable positions as shown on the Drawings, so that bay widths are not greaterthan 4.2 m (or 5.0 m with limestone aggregate) for unreinforced slabs, or 6 m (or 7.6 mwith limestone aggregate) for reinforced concrete surface slabs with transversereinforcement.

2 Longitudinal joints shall be provided in CRCR between lanes or at the centre of lanes, withina tolerance of +150 mm so that bay widths are not greater than 6 m (or 7.6 m withlimestone aggregate).

3 Joints in the surface slab, road base or sub-base shall be staggered so that they are not

coincident vertically and are least 300 mm apart. The positions of all longitudinal joints in

any slab shall be agreed by the Engineer prior to construction of the slab.

4 Wet-formed longitudinal joints shall consists of wet-formed joint grooves, bottom crackinducer and tie bars except where transverse reinforcement is permitted in lieu.

5 Longitudinal joints shall be constructed in the positions agreed by the Engineer within thefollowing tolerances:

(a) Deviations of the bottom crack inducer from the intended line of the joint parallelto the axis of the road shall not be greater than +13 m.

(b) The joint groove shall be located vertically above the bottom crack inducers withina horizontal tolerances of +25 mm.

(c) The best fit line along the constructed joint groove, shall be not more than 25 mmfrom the intended line of the joint.

(d) Deviations of the joint groove from the best fit line of the joint shall be not greaterthan 10 mm.

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6 Tie bars may be replaced by continuous transverse reinforcement across the joints incontinuously reinforced concrete slabs, which are constructed in more than one lane width in

one operation, provided that the transverse reinforcement is a minimum of 12 mm diameterbars at 600 mm centres.

6.3.14 Longitudinal Construction Joints

1 Longitudinal construction joints between separate slabs shall have tie bars with a joint

groove. Alternatively, if split forms are used, the transverse reinforcement, if 12 mmdiameter or more, may be continued across the joint for a minimum of 500 mm or 30 timesthe diameter of the transverse reinforcement bars, whichever is greater.

2 A joint sealing groove is not required in construction joints in continuously reinforcedconcrete road bases. Where the edge of the concrete slab is damaged it shall be madegood to the approval of the Engineer before the adjacent slab is constructed.

6.3.15 Dowel Bars

1 Dowel bars shall be Grade 250 steel complying with BS 4449 and shall be free from oil, dirt,

loose rust and scale. They shall be straight, free of burrs and other irregularities and thesliding ends sawn or, if approved by the Engineer, cropped cleanly with no protrusionsoutside the normal diameter of the bar. For expansion joints, dowel bars shall be 25mmdiameter at 300 mm spacing, 600 mm long for slabs up to 239 mm thick and 32 mm

diameter for slabs 240 mm thick or more. For contraction joints, dowels shall be 20 mm

diameter at 300 mm spacing 400 mm long for slabs up to 239 mm thick and 25 mmdiameter for slabs 240 mm thick or more.

2 Dowel bars shall be supported on cradles in prefabricated joint assemblies positioned priorto construction of the slab. For contraction joints, as an alternative to prefabricatedassemblies, dowel bars may be mechanically inserted with vibration into the concrete by amethod which shall ensure full recompaction of the concrete around the dowel bars and thesurface finished by a diagonal finishing beam. Or a longitudinal oscillating float travellingacross the slab.

3 Dowel bars shall be positioned at mid-depth from the surface level of the slab 20 mm.They shall be aligned parallel to the finished surface of the slab, to the centre line of thecarriageway and to each other within the following tolerances:

(a) for bars supported on cradles prior to construction of the slab and for insertedbars in two layers construction prior to placing the top layer:(i) All bars in a joint shall be within 3 mm per 300 mm length of bars.

mm per 300 mm length of bar.(ii) Two thirds of the bars shall be within 2mm per(iii) No bar shall differ in alignment from an adjoining bar by more than 3

mm length of bar in either the horizontal or vertical plane.300(b) for all bars, after construction of the slab:

(i) Twice the tolerances for alignment as in (i) above.(ii) Equally positioned about the intended line of the joint within a tolerance of 25

mm.

4 Cradles supporting dowel bars shall not extend across the line of the joint.

5 Dowel bars, supported on cradles in assemblies, when subjected to a load of 110N appliedat either end and in either the vertical or horizontal direction (upwards and downwards andboth directions horizontally) shall not deflect more than the following limits:

(a) Two thirds of the number of bars of any assembly tested shall not deflect more than2 mm per 300 mm length of bar.

(b) The remainder of the bars in that assembly shall not deflect more than 3 mm per300 mm length of bar.

6 The assembly of dowel bars and supporting cradles, including the joint filler board in thecase of expansion joints shall have the following degree of rigidity when fixed in position:

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(a) For expansion joints the deflection of the top edge of the filler board shall be notgreater than 13 mm, when a load of 1.3 kN is applied perpendicular to the verticalface of the joint filler board and distributed over a length of 600 mm by means ofa bar or timber packing at mid depth and midway between individual fixings, or300 mm from either end of any length of filler board, if a continuous fixing is used.The residual deflection after removal of the load shall be not more than 3 mm.

(b) The joint assembly fixings to the sub-base shall not fail under the 1.3kN loadapplied for testing the rigidity of the assembly but shall fail before the loadreaches 2.6 kN.

(c) The fixings for contraction joints shall not fail under a 1.3 kN load and shall failbefore the load reaches 2.6 kN when applied over a length of 600 mm by meansof a bar or timber packing placed as near to the level of the line of fixings aspracticable.

(d) Failure of the fixings shall be deemed to be when there is displacement of theassemblies by more than 3 mm with any form of fixing, under the test load. Thedisplacement shall be measured at the nearest part of the assembly to the centreof the bar or timber packing.

7 Dowel bars shall be covered by a thin plastic sheath over the whole length of the bar. The

sheath shall be tough, durable and of an average thickness not greater than 1.25 mm. Thesheathed bar shall comply with the following pull out test:

(a) Four bars shall be taken at random from stock and without any specialpreparation shall be covered by sheaths. The dowel bars which have beensheathed shall be cast centrally into concrete specimens 150x150x450 mm,made of the same mix proportions to be used in the pavement, but with amaximum nominal aggregate size of 20 mm and cured in accordance withBS 1881. At 7 days a tensile load shall be applied to achieve a movementof the bar at least 0.25 mm. The average bond stress to achieve this movementshall be not greater than 0.14 N/mm

2.

8 For expansion joints a closely fitting cap 100 mm long consisting of waterproofedcardboard or an approved synthetic material shall be placed over one end of each

dowel bar. An expansion space 10 mm greater than the thickness of the joint filler boardshall be formed between the end of the cap and the end of the dowel bar.

6.3.16 Tie Bars

1 Tie bars in transverse or longitudinal joints shall be Grade 250 steel or Grade 460 deformedsteel bars complying with BS 4449, in accordance with the requirements given below andTable 6.2. Deformed bars shall have Type 2 bond classification. Tie bars shall be free fromoil, dirt, loose rust and scale. Tie bars which are to be cranked and later straightened shallbe Grade 250.

2 Tie bars projecting across a longitudinal joint shall be protected from corrosion by a flexiblepolymeric corrosion resistant coating, bonded onto the previously cleaned centre section,

leaving between 250

mm and 300 mm of each of the bars uncoated.

3 Where tie bars are cranked for construction joints and later straightened the coating shall beshown to be capable of being straightened through 90 degrees without cracking. The coatingshall also be able to withstand 250 hours immersion in a salt fog cabinet complying with BS3900 : Part F12, without showing any visible cracking, or corrosion of the protected part ofthe bar. Any damage observed on the coating after straightening shall be made good beforethe concrete is placed.

4 Tie bars in warping joints and wet-formed longitudinal joints shall be made up into rigidassemblies with adequate supports and fixings to remain firmly in position during theconstruction of the slab.

5 Alternatively, tie bars at longitudinal joints may be mechanically inserted by vibration fromabove using a method which ensures recompaction of the concrete around the tie bars.

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6 At longitudinal construction joints, tie bars may be adequately fixed to side forms or insertedinto the side of the slab by a method which ensures recompaction of the concrete around thetie bars and adequate bond and which shall be approved by the Engineer.

7 Tie bars shall be positioned and remain within the middle third of the slab depth,approximately parallel to the surface and approximately perpendicular to the line of the joint,

with the centre of each bar on the intended line of the joints within a tolerance of 50

mm,and with a minimum cover of 30 mm below any top crack inducer or joint groove for slabs

200 mm thick or more, or 20 mm for slabs up to 200 mm thick.

8 At transverse construction joints in continuously reinforced concrete, tie bars shall be 1.5 mlong and of the same grade and size as the longitudinal reinforcement, and shall be fixed attwice the normal spacing midway between the longitudinal reinforcement bars so that750 mm 50 mm extends each side of the joint at the same level as the longitudinalreinforcement and be tied to the transverse reinforcement. Where paving from a construction

joint is not resumed within 5 days, and extra longitudinal reinforcement bar at 8 m longshall be lapped and tied to each tie bar. These extra bars may be combined with the tie

bars. Where the spacing between longitudinal reinforcement and the extra 8 m long bars isless than 90 mm, the nominal size of aggregate shall be 20 mm for a sufficient number of

concrete batches to complete that section of pavement.

9 Where tie bars are used in longitudinal joints in continuously reinforced concrete they shallbe placed at the same level as the transverse reinforcement and tied to the longitudinalreinforcement.

Table 6.2

Tie Bar Details

Joints Diameter (mm) Grade of Steel Length (mm) Spacing (mm)

Transverseconstruction joints

in continuouslyreinforced concrete

As for mainreinforcement

460 1500

Twice thespacing of

mainreinforcement

Emergencyconstruction joints

in jointedreinforced concreteslabs other than at

contraction or

expansion joints

12250 or

460 deformed1000750

600600

Warping joints 12250 or

460 deformed1000750

300600

Longitudinal.All joints, exceptwhere transversereinforcement ispermitted in lieu

12250 or

460 deformed1000750

600600

Note: The transverse reinforcement may be continued across the joint in reinforcedconcrete with the approval of the Engineer if the bars are of a minimum nominaldiameter of 12 mm and the bars are protected from corrosion and the cover is as

required in this Clause.

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6.3.17 Joint Grooves

1 Transverse contraction or warping joint grooves shall be sawn in the hardened concrete.

2 Transverse joint grooves which are initially constructed less than the full width of the slabshall be completed by sawing through to the edge of the slab and across longitudinal joints

as soon as any forms have been removed and before an induced crack develops at the joint.

3 Sawn transverse joint grooves shall be undertaken as soon as possible after the concretehas hardened sufficiently to enable a sharp edged groove to be produced without disruptingthe concrete and before random cracks develop in the slab. The grooves shall be between1/4 and 1/3 of the specified depth of the slab and of any convenient width not less than3mm. The sealing groove may be constructed at the same time to be sawn to the requiredwidth later. Unless otherwise approved by the Engineer, expansion joint sealing groovesshall be sawn immediately before sealing.

4 Construction Joint Grooves in Surface Slabs shall be formed by fixing a groove-former, stripor cork seal along the top edge of the slab already constructed, before concreting theadjacent slab. Where the edge of the concrete is damaged it shall be ground or made good

to the approval of the Engineer before fixing the groove forming strip.

5 Alternatively the subsequent slab may be placed adjacent to the first and a sealing groovesawn later in the hardened concrete to the minimum depth required in Table 6.3 or to themanufacturer's instructions if greater, and to sufficient width to eliminate minor spalling of thejoint arris, up to a maximum of 25mm for longitudinal joints and 40mm for transverse joints.The joints shall be sealed.

6.3.18 Groove Formers and Bottom Crack Inducers

1 Except where joint grooves are sawn, a bottom crack inducer shall be provided at eachcontraction, warping or longitudinal joint position.

2 The bottom crack inducer shall be an approved triangular or inverted Y-shaped fillet, with abase width not less than the height, made of timber or rigid synthetic material. It shall befirmly fixed to the sub-base so as to remain in position during the whole process ofconstructing the slab.

3 The combined depth of groove formers and bottom crack inducers shall be between 1/4 and1/3 of the depth of the slab and the difference between the depth of the groove former andthe height of the bottom crack inducer shall not be greater than 20mm.

4 The groove former for wet formed transverse joint grooves shall be made of an approvedrigid material of a width not greater than the required width of sealing groove as in Table 6.3.The groove former shall be smooth sides with rounded protrusions no greater than 3mm.Any removable part of the groove former may be tapered with a maximum difference in widthof 2mm in 20mm depth.

5 Groove forming sealing strips for wet formed longitudinal joints shall be of firm compressiblestrips of ethylene vinyl acetate foam of a minimum density of 90kg/m

3, or synthetic rubber, or

equivalent material subject to approval by the Engineer. They shall have a minimumthickness of 5mm and shall be sufficiently rigid to remain vertical and straight in the concretewithout curving or stretching. They shall be inserted continuously along the joint.

6 For CRCP Universal Beam Anchorage Transverse Joints one side of the beam shall beseparated from the CRCP slab by an expansion joint filler board against the vertical face andethylene vinyl acetate foam or similar compressible material, between 5 mm and 10mmthick, stuck under the top flange.

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6.3.19 Joint Filler Board

1 Joint filler board for expansion joints and manhole and gully slab joint shall be 25mmthickness unless otherwise shown in the Drawings, within a tolerance of 1.5mm.

2 It shall be self expanding cork seal or a firm compressible material or a bonded combination

of compressible and rigid materials of sufficient rigidity to resist deformation during thepassage of the concrete paving plant.

3 The depth of the joint filler board for manhole and gully slabs shall be the full depth of theslab minus the depth of the sealing groove. In expansion joints, the filler board shall have aridged top as shown on the Drawings, except where a sealing groove former is permitted bythe Engineer.

4 Holes for dowel bars shall be accurately bored or punched out to form a sliding fit for thesheathed dowel bar.

6.3.20 Preparation and Sealing of Joint Grooves

1 All transverse joints in surface slabs, except for construction joints in CRCP shall be sealedusing one of the joint seals described. Additionally longitudinal joints which are sawn orwidened shall be sealed.

2 Joint grooves shall be prepared in accordance with BS 5212: Part 2 and in compliance with(a) through (g) below:

(a) that part of the groove former used to form the sealing groove or any temporary sealshall be removed cleanly without damaging the joint arises to a minimum depth of25 mm where compression seals are used or otherwise to such depth as will providean applied seal to the dimensions as will provide in Table 6.3.

(b) if joint grooves are not initially constructed to provide the minimum dimensions for thejoint seals as given in Table 6.3, they shall be widened by sawing. Joint grooves

formed by tapered formers need not to be widened. The sealing grooves shall becleaned out immediately after sawing using high pressure water jets, to remove allslurry from the joint, before the slurry hardens.

(c) if rough arrises develop when grooves are made they shall be ground to provide achamfer approximately 5mm wide. If the groove is at an angle up to 10 degrees fromthe perpendicular to the surface, the overhanging edge of the sealing groove shall besawn or ground perpendicular. If spalling occurs or the angle of the former is greaterthan 10 degrees the joint sealing groove shall be sawn wider and perpendicular to thesurface to encompass the defects up to a maximum width, including any chamfer, of40 mm for transverse joints and 25mm for longitudinal joints. If the spalling cannotbe so eliminated then the arris shall be repaired by an approved thin bonded arrisrepair using cementitious materials.

(d) for applied sealants the sides of the joint sealing groove shall be scoured by dry

abrasive blasting. This shall not be carried out before the characteristics compressivestrength of the concrete is expected to reach 15 N/mm

2. When compression seals are

used, the sides of the groove may be ground or wire brushed.(e) for hot and cold applied sealants, compressible caulking material, debonding strip or

tape or cord compatible with the sealant, of a suitable size to fill the width of thesealing groove shall be firmly packed or stuck in the bottom of the sealing groove tosuch a depth so as to provide the correct depth of seal as described in Table 6.3 withthe top of the seal at the correct depth below the surface of the concrete.

(f) all grooves shall be cleaned of any dirt or loose material by air blasting with filtered, oilfree compressed air. The groove shall be clean and dry at the time of priming andsealing.

(g) for applied sealants the joint grooves shall be primed with the relevant primer for thehot or cold applied sealant in accordance with the manufacturer's recommendations

and with BS 5212: Part 2, except that when necessary the joint grooves may be

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primed and sealed earlier than 14 days after construction, as soon as the grooveshave been grit-blasted and cleaned.

6.3.21 Sealing wi th Appl ied Sealants

1 Sealing shall be carried out continuously along the full length of joint in any one rip, exceptfor remedial areas. When hot or cold applied sealants are used the sealant shall be appliedwithin the minimum and maximum drying times of the primer recommended by themanufacturer. Priming and sealing with applied sealants shall not be carried out when the

naturally occurring temperature in the joint groove to be sealed is below 10 C except

between 8 C and 10 C it may be carried out when the temperature is rising.

2 Hot applied sealants shall be heated in and applied from a thermostatically controlled,indirectly heated dispenser with the recirculating pump. The sealant shall not be heated to atemperature higher than the safe heating temperature nor for a period longer than the safeheating period, both as specified by the manufacturer. The dispenser shall be cleaned out atthe end of each day and reheated materials shall not be used.

3 The components of cold-applied sealants shall be thoroughly mixed in the correct

proportions in accordance with the manufacturer's instructions using an automatic meteringand mixing dispenser approved by the Engineer or, for hand application, using a poweroperated paddle mixer for sufficient time to produce homogenous mix without entrapped air.As soon as possible after mixing and within the worklife of the sealant, the material shall bedispensed into the joint, or applied using a caulking gun, to the correct level below theconcrete surface. The tack-free time shall be achieved within 3 hours, for machinedispensed material, or within 12 hours for hand applied material.

4 Test certificates shall be supplied from an approved testing laboratory stating that thesealant complies with the relevant standard. Site testing of cold applied sealants shall be inaccordance with BS 5212: Part 2. Hot-applied sealants shall be sampled at the same rateand checked for dimensions as in BS 5212: Part 2 and by the penetration test of the relevantstandard for the material.

Table 6.3

Dimensions of Applied Joint Seals

Type andSpacing ofJoints (m)

MinimumWidth (mm)

ColdApplied

(mm)

HotApplied

(mm)

ImpregnatedFoam

CompressionStrips (mm)

Depth of SealBelow theConcrete

Surface(mm)

Contraction:

15 and under 13 (Note 2) 13 15 30 5+2Over 15 to 20 20 15 20 30 5+2Over 20 to 25 30 20 25 40 5+2

Expansion All 30 20 25 40 7+2

TransverseWarping

10 10 13 30 5+2

LongitudinalJoints (ifsealed)

10 10 13 30 0 to 5

Gully andManhole Slabs

20 15 20 30 0 to 3

Note: (1) The depth of seal is that part in contact with the vertical face of the joint groove.

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The depth of seal below the surface shall be taken at the centre of an appliedseal relative to a short straight edge, 150mm long, placed centrally across thejoint within 7 days of sealing.

Note: (2) For cork seals other than in construction joints, grooves shall be 20 mm wideand 50 mm deep.

6.3.22 Sealing wi th Compression Seals

1 When compression seals are used, the widths of the seal shall be selected in relation to thewidth of the sealing groove, the bay lengths and manufacturer's recommendations so thatthe estimated maximum width of the joint opening shall be not more than 70% of the originalwidth of the seal, the estimated maximum width being calculated on the basis of amovement of 4mm per 10m run of slab.

2 The maximum calculated width of sealing groove shall be 30mm.

3 The depth of groove shall be such that the contact face of the seal with the side of thegroove shall be not less than 20mm and that the top of the seal shall be a minimum of 3mmbelow the surface of the concrete.

4 Compression seals shall be inserted into the grooves without prior extension or rotation and,where recommended by the manufacturer, with a lubricant adhesive which is compatiblewith the seal and the concrete. The adhesive shall be applied to both sides of the sealinggroove or the seal, or to both. The seal shall be positioned with its axis perpendicular to theconcrete surface. Excess adhesive on top of the seal shall be removed to prevent adhesionof the top faces of the seal under compression.

5 Except when compression seals are used in longitudinal joints the transverse joint seal shallbe continuous across the slab and the longitudinal joint groove forming strips shall be cut tothe required depth after the concrete has hardened for the transverse seal to be inserted.

6 If compression seals are used in longitudinal joints where the grooves have been sawn afterconstruction of the slab they shall be continuous across transverse joints, with thetransverse seals butted and fixed to the longitudinal seals with adhesive.

6.3.23 Joint Seals

1 Joint seals shall consist of hot or cold applied sealants or compression seals or selfexpanding cork seals.

2 Hot-applied sealants shall comply with ASTM Standard D3406, or D7116 (for fuel-resistantsealant).

3 For joints between concrete surface slabs and bituminous surfacing, polymer modified

bitumen sealing strips shall be used and applied in accordance with the manufacturer'sinstructions. Hot-applied sealants complying with BS 2499 & BS EN 14188 may be used forsuch joints and in joints in asphalt kerbs laid on concrete pavements.

4 Cold applied sealants shall be Type N complying with BS 5212: Part 1 except that Type Fshall be used for lay-bys and hardstandings.

5 For joints in kerbs and joints other than in pavements, seals may be any of the pavementsealants if they have the suitable characteristics for the application. Also, gunning gradecold applied plasticised bituminous rubber sealant or gunning grades of two part polysulphid-based sealants complying with BS EN ISO 11600 may be used.

6 Alternatively, polyurethane-based sealing compounds may be used provided their

performance is not inferior to BS EN ISO 11600 material.

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7 Compression seals shall be pre-compressed neoprene impregnated expanding foam sealingstrip, or rubber seals made of polychloroprene elastomers complying with BS 2752 andconforming to the requirements of ASTM Standard D2628-91.

8 Compression seals shall be shaped so that they will remain compressed at all times andshall have a minimum of 20mm contact face with the sides of the sealing groove. If lubricant

adhesive is used, it shall be compatible with the seal and the concrete and shall be resistantto abrasion, oxidisation, fuels and salt.

9 Self Expanding Cork seals may be used in longitudinal joints, joints for manhole and gullyslabs and for transverse joints in short lengths of individual slabs or for replaced slabs.

6.3.24 Joints at Manhole and Gully Slabs

1 Manhole covers, gullies and their frames shall be isolated from the pavement slabs and becontained in separate small slabs, which shall be larger than the exterior of the manhole andgully shafts, including any concrete surround less than 150mm below the underside of thesub-base layer. The joint around the manhole or gully slab shall be vertical and incorporatejoint filler board but without dowel bars and tie bars.

2 Gully slabs in unreinforced concrete slabs shall be adjacent to or straddle a transverse joint,extending the gully slab as necessary to a maximum of 2m. Where this is impractical, anextra tied warping joint shall be provided adjacent to or within the gully slab and at least 2mfrom the next transverse joint. If the edge of an isolator slab is within 1m of any longitudinaljoint the isolator slab shall be extended to that joint.

3 Manhole slabs in unreinforced concrete slabs shall be adjacent to or straddle transverse orlongitudinal joints. If the manhole is within the middle third of the bay length a warping jointshall be constructed on one side of the manhole slab across the whole width of the bay tothe nearest longitudinal joint.

4 Reinforcement as shown on the Drawings shall be placed in the main concrete slabs in the

corners between the manhole and gully slab and the transverse or longitudinal joints. Extrareinforcement as described in the Contract shall be placed in reinforced concrete slabsaround the manhole or gully slabs.

5 Manhole and gully slabs shall have oblique corners, minimum 200mm long, at approximately45 degrees to the axis of the pavement at all corners which are not adjacent to a transverseor longitudinal joint in the main slab.

6 Reinforcement as shown on the Drawings shall be placed in the gully or manhole slab andconcrete grade C40 shall be placed by hand in the space between the main slab and themanhole frame. The concrete shall be fully compacted and finished.

7 A sealing groove shall be made directly above the joint filler board and sealed.

6.3.25 Inspection of Dowel Bars

1 The position and alignment of dowel bars at contraction and expansion joints shall bechecked by measurement relative to the side form or guide wires.

2 When the slab has been constructed, the position and alignment of dowel bars and any fillerboard shall be measured after carefully exposing them across the whole width of the slab.When the joint is an expansion joint the top of the filler board shall first be exposedsufficiently in the plastic concrete to permit measurement of any lateral or verticaldisplacement of the board. During the course of normal working these measurements shallbe carried out at a rate of one joint per 1500m length of slab or one per 5 working days

whichever occurs the sooner. For small areas the rate shall be decided by the Engineer.

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3 If the position or alignment of the bars in a single joint in the slab is unsatisfactory then thenext two joints shall be inspected. If only one joint of the three is defective, the rate ofchecking shall be increased to one joint per day until the Engineer is satisfied thatcompliance is being achieved. In the event of non-compliance in two or more successivejoints, the Contractor shall revert to the construction of trial lengths and make any necessaryalterations to the concrete mix, paving plant or methods until the dowel bar position and

alignment is satisfactory.

4 After the dowel bars have been examined, the remainder of the concrete shall be removed500mm on each side of the line of the joint, and reinstated to the satisfaction of theEngineer. Alternatively if the dowels are examined in the penultimate joint of a day's workthat joint shall be made a construction joint for the next day's work and the remainder of theconcrete in the last slab may be discarded.

6.3.26 Side Forms, Rails and Guide Wires

1 All side forms and rails shall be made of steel and be sufficiently robust and rigid to supportthe weight and pressure caused by the paving equipment. Side forms for use with wheeledpaving machines shall incorporate metal rails firmly fixed at a constant height below the top

of the forms.

2 The forms shall be secured by using not less than three pins for each 3m length having onepin fixed at each side of every joint. Forms shall be tightly joined together by a locked joint,free from play or movement in any direction. Forms shall be cleaned and oiled immediatelybefore each use. The rails or running surface shall be kept clean in front of the wheels of anypaving machine. The forms shall be straight within a tolerance of 3mm in 3m.

3 The forms shall be bedded on low moisture content cement mortar or concrete grade C7.5and set to the pavement surface level as shown on the Drawings within a tolerance of+3mm. The bedding shall not extend under the slab. There shall be no vertical step betweenthe end of adjacent forms greater than 3mm. The horizontal alignment for forms shall be tothe required alignment of the pavement edge as shown on the Drawings within a tolerance

of + 10mm. The mortar or concrete bedding shall be broken out after use.

4 Side forms shall not be removed earlier than 6 hours after the completion of the constructionof the slab. Care shall be taken to prevent damage to the concrete and any projecting tiebars during the removal of the forms. If the removal of forms results in any damage to theconcrete the period of 6 hours shall be increased to that which is necessary to avoid furtherdamage and the Contractor shall make good the damaged areas.

5 Unless otherwise agreed by the Engineer, a guide wire shall be provided along each side ofthe slab to be constructed by slip form paving plant. Each guide wire shall be at a constantheight above and parallel to the required edges of the slab as shown on the Drawings, withina vertical tolerance of + 3mm. Additionally one of the wires shall be at a constant horizontaldistance from the required edge of the pavement as shown in the drawings within a lateraltolerance of + 10mm.

6.3.27 Delivery, Storage and Batching of Concreting Materials

1 Aggregate for roadworks shall be delivered to and stored on the Site in one of the followingways:

(a) in separate nominal single sizes of coarse aggregate and fine aggregate.(b) as graded coarse aggregate of appropriate size and fine aggregate.(c) as all-in aggregate for grades C20 to below.

2 If the Contractor proposes to blend aggregate off the site from two separate sources, heshall obtain the Engineer's approval for the blending process, and for the arrangements for

inspection during the course of the work.

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3 Aggregate brought on to the Site shall be kept free from contact with deleterious matter.Fine aggregate nominally below 5 mm sieve size shall have been deposited at the site for atleast 8 hours before use.

4 Batching plant and storage for aggregate shall comply with the following requirements asappropriate to the method of delivery:

(a) if separate gradings of aggregate are stockpiled, separate accommodation shallbe provided for each nominal size of coarse aggregate or blend of fineaggregate. The base for stockpiles shall be suitably surfaced to preventcontamination of the aggregate. Drainage of the stockpile bases shall beprovided.

(b) aggregate shall be measured by mass and provision shall be made for batchingeach nominal size or blend of aggregate separately, to the tolerances specified inBS EN 206 & BS 8500.

(c) all-in aggregate shall be delivered and stockpiled in such a manner and to aheight that avoids segregation.

6.3.28 Mixing Concrete

1 Mixing concrete shall conform to the requirements of Section 5 Part 7 except as amendedherein.

2 Concrete shall be mixed on site in a stationary batch type mixer in compliance with BS EN206 & BS 8500 unless with the approval of the Engineer, ready mixed concrete is suppliedfrom an approved source.

3 The drums or blades of all mixers shall be operated at the speed using for testing, inaccordance with BS 3963 for the mix proportions required, within a tolerance of 1revolution per minute. The mixing blades of a pan mixer shall be maintained within thetolerances specified by the manufacturers of the mixer and the blades shall be replacedwhen it is no longer possible to maintain the tolerances by adjustment. All drums or panswhich have been out of use for more than 30 minutes shall be thoroughly cleaned before any

fresh concrete is mixed in them.

4 The rated output of the batching and mixing plant shall exceed by at least a third the amountof concrete that is required at a constant rate to enable the paving train to move forwardcontinuously, at the planned rate of progress.

6.3.29 Transport and Delivery

1 Transportation, delivery of concrete shall conform to the requirements of Section 5 Part 8.

6.3.30 General Requirements for Construct ion by Machine

1 The concrete slab shall be constructed in a continuous process by either slip-form or byfixed form paving plant or by small paving machines or hand guided methods.

2 The slab may be constructed in either one or two layers. In two layer construction thethickness of the top layer shall be not less than 50mm or twice the maximum size of thecoarse aggregate whichever is greater, and shall be at least 15 mm thick than the depth ofthe groove former, if used.

3 While the concrete is still plastic its surface shall be brush-textured and the surface andedges shall be cured.

4 The spreading, compacting and finishing of the concrete shall be carried out as rapidly aspossible and the paving operation shall be so arranged as to ensure that the time between

the mixing of the first batch of concrete in any transverse section of the slab and theapplication of the sprayed curing membrane to the surface of that section shall not exceedthose given in Table 6.4.

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5 Each bay in jointed concrete surface slabs shall be consecutively numbered near the vergenext to a transverse joint while the concrete is plastic. In continuously reinforced concretepavement the slab shall be marked with the chainage at intervals not greater than 50mapart.

6.3.31 Construction by Fixed Form Paving Machines

1 A fixed form paving train shall consist of separate, powered machines which spread compactand finish the concrete in a continuous operation.

2 Concrete shall be discharged without segregation into a hopper spreader which is equippedwith the means of controlling its rate of deposition onto the sub-base or onto the lower layer.The concrete shall be spread in each layer without segregation and to a uniformuncompacted density over the whole area of the slab.

3 The deposited concrete shall be struck off to the necessary level by the underside of thehopper as it is traversed across the spreading machine.

4 The machine shall be capable of being rapidly adjusted for changes in average and

differential surcharge necessitated by changes in slab thickness or crossfall. When the slabis constructed in two layers, the spreading of the concrete in the top layer shall follow thecompletion of the bottom layer within the times given in Table 6.4.

5 Prior to being compacted, the surface level of each loose spread layer shall be adjusted tothe correct surcharge by means of rotating strike-off blades or a screw device.

6 The concrete shall be compacted by vibration or by a combination of vibration andmechanical tamping throughout the full depth of the slab. Poker vibrators shall be used ineach layer adjacent to the side forms and the edge of a previously constructed slab.

7 The initial regulation and finish to the surface of the slab shall be effected by means of abeam oscillating transversely or obliquely to the longitudinal axis of the pavement. This

beam shall be readily adjustable for both height and tilt.

8 When grooves are wet-formed the concrete shall be recompacted around the former by ahand held vibrating plate compactor drawn along or on each side of the joint, prior toregulation of the surface by the diagonal finishing beam. Or recompacted and finished if theformer is inserted after the finishing beam.

9 The regulation and finishing of the surface of the slab shall be carried out by a machinewhich incorporates twin oblique oscillating finishing beams which shall be readily adjustablefor both height and tilt. The beams shall weigh not less than 170 kg/m, be of rectangularsection and span the full width of the slab. The leading beam shall be vibrated. The beamsshall be supported on a carriage, the level of which shall be controlled by the average levelof not less than four points evenly spaced over at least 3.5m of the supporting rail, beam orslab, on each side of the slab that is being constructed. After the final regulation and beforetexture is applied any excess concrete on top of the groove former shall be removed.

10 When a concrete slab is constructed in more than one width, flanged wheels on the pavingmachines shall not be run directly on the surface of any completed part of the slab. Thesecond or subsequent slabs shall be constructed either by supporting machines with flangedwheels on flat bottom section rails weighing not less than 15 kg/m laid on the surface of thecompleted slab, or by replacing the flanged wheels on that side of the machines by smoothflangeless wheel.. Flangeless wheels or rails shall be positioned sufficiently far from theedge of the slab to avoid damage to that edge.

6.3.32 Construct ion by Slip-Form Paving Machine

1 A slip-form paving train shall consist of powered machines which spread, compact and finishthe concrete in a continuous operation.

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2 The slip-form paving machine shall compact the concrete by internal vibration and shape itbetween sliding side forms or over fixed side forms by means of either a conforming plate orby vibrating and oscillating finishing beams.

3 The concrete shall be deposited without segregation in front of the slip-form paver across itswhole width and to a height which at all times is in excess of the required surcharge. The

deposited concrete shall be struck off to the necessary average and differential surcharge bymeans of a strike-off plate or a screw auger device extending across the whole width of theslab. The equipment for striking off the concrete shall be capable of being rapidly adjustedfor changes of the average and differential surcharge necessitated by changes in slabthickness or crossfall.

4 The level of the conforming plate and finishing beams shall be controlled automatically fromthe guide wires by sensors attached at the four corners of the slip form paving machine. Thealignment of the paver shall be controlled automatically from the guide wire by at least onesensor attached to the paver. The alignment and level of ancillary machines for finishing,texturing and curing of the concrete shall be automatically controlled relative to the guidewire or to the surface and edge of the slab.

5 Slip-form paving machines shall have a vibration of variable output, with a maximum energyoutput of not less than 2.5 kW per metre width of slab per 300mm depth of slab for a layingspeed of up to 1.5m per minute or pro rata for higher speeds. The machines shall be ofsufficient mass to provide adequate reaction on the traction units to maintain forwardmovements during the placing of concrete in all situations.

6 Where grooves are wet-formed the concrete shall be compacted around the former by aseparate vibrating plate compactor with twin plates. The groove former shall be compactedto the correct level by a vibrating pan which may be included with the transverse jointfinishing beam. In addition a hand held vibrating float, at least 1m wide, shall be drawn overthe surface along the joint. Alternatively the surface shall be regulated with a longitudinaloscillating float travelling across the slab. Any excess concrete on top of the groove formershall be removed before the surface is textured.

7 Where a concrete surface slab is constructed in more than one width or where the edgeneeds to be matched for level to another section of surface slab, and the surface levels atthe edges are not achieved, paving shall be carried out over separate fixed side forms tosupport the edge to the required levels.

6.3.33 Construction by Small Paving Machines or Hand Guided Methods

1 As an alternative to fixed form or slip-form paving trains, the concrete slab may beconstructed using parts of trains, small paving machines, truss type finishing beams or handguided methods. Hand tamping beams may only be used for short lengths or infill bays ortapers. Reinforcement, dowel bars and tie bars shall be supported in position, except wheretwo layer construction is used and reinforcement is placed on the bottom layer in a methodof construction approved by the Engineer.

2 The concrete shall be spread uniformly without segregation or varying degrees ofprecompaction, by conveyor, chute, blade or auger. The concrete shall be struck off by ascreed or auger so that the average and differential surcharge is sufficient for the surface ofthe slab to be at the correct levels after compaction of the concrete.

3 The concrete shall be compacted by vibrating finishing beams across the slab and withvibrating pokers adjacent to the side forms or the edge of a previously constructed slab. Inaddition, internal poker vibration shall be used for slabs thicker than 200mm and may beused for lesser thicknesses. When used, the pokers shall be at points not more than500mm apart over the whole area of the slab, or drawn continuously across the slab in front

of the finishing beams.

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4 The finishing beams shall be metal with a contact face at least 50mm wide. They shall berigid or supported by a frame or truss without sag across the width of slab being paved. Thebeams shall be supported on rails or forms or an adjacent slab and shall be moved forwardat a steady speed of 0.5m to 2m per minute whilst vibrating, to compact the concrete and toproduce a smooth surface finished to the correct crossfalls, crowns and levels relative to thetop of the forms or adjacent slab.

5 Any irregularities at wet-formed joint grooves shall be rectified by means of a vibrating floatat least 1.0 m wide drawn along the line of the joint. The whole area of the slab shall beregulated by two passes of a scraping straight edge not less than 1.8m wide or by a furtherapplication of a twin vibrating finishing beam. All slabs shall be checked for level using astraight edge at least 4m long. Any excess concrete on top of the groove former shall beremoved before the surface is textured.

6 The surface shall be brush textured.

7 The surface shall be cured within the time to completion given in Table 6.4

Table 6.4

Maximum Working Times

Reinforced Concrete SlabsConsumed in Two layers

All other Concrete SlabsTemperature ofconcrete at

discharge fromthe delivery

vehicle

Mixing firstlayer tofinishingconcrete

between layers

Mixing firstlayer tofinishingconcrete

between layersin 2 layer work

Not more than

25 C3 hours 1/2 hour 3 hours 1 1/2 hours

Exceeding25 C

2 hours 1/2 hour 2 hours 1 hour

Exceeding30 C

unacceptablefor paving

unacceptablefor paving

6.3.34 Surface Textures

1 After the final regulation of the surface of the slab and before the application of the curingmembrane, the surface of concrete slabs to be used as running surfaces shall be brushtextured in a direction at right angles to the longitudinal axis of the carriageway.

2 The texture shall be applied evenly across the slab in one direction by a brush not less than450 mm wide. The texture shall be uniform both along and across the slab.

6.3.35 Curing

1 Immediately after the surface treatment, the surface and exposed edges of surface slabsshall be cured for a minimum period of 7 days (unless the Engineer agrees to a shorterperiod). This will be by the application of an approved resin based aluminised curingcompound, or polythene sheeting or an approved sprayed plastic film which hardens into apeelable plastic sheet. It shall be removed before road marking and opening to traffic.

2 Resin based aluminised curing compound shall contain sufficient flake aluminium in finelydivided dispersion to produce a complete coverage of the sprayed surface with a metallic

finish. The compound shall become stable and impervious to evaporation of water from the

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concrete surface within 560 minutes of application and shall have an efficiency index of 90%when tested as described in BS 7542.

3 The curing compound shall not react chemically with the concrete to be cured and shall notcrack, peel or disintegrate within three weeks after application.

4 Prior to application, the contents of any containers shall be thoroughly agitated. The curingcompound shall be mechanically applied using a fine spray onto the surface at a rate of atleast 0.221L/m

2. For the sides of slip-formed slabs or when the side forms are removed

within 24 hours and for small areas where mechanical application cannot be used, thecompound shall be sprayed by hand lance at a rate of at least 0.271/m

2. The rate of spread

shall be checked during construction of each trial length and subsequently wheneverrequired by the Engineer.

5 The mechanical sprayer shall incorporate an efficient mechanical device for continuousagitation and mixing of the compound in its container during spraying.

6 Continuously reinforced concrete road bases shall also be cured. Wet lean concrete roadbases and sub-bases shall also be cured.

6.4 REQUIREMENTS FOR WET LEAN CONCRETE

6.4.1 Materials and Mix Designs

1 The constituent materials and the grades of concrete for wet lean mix shall comply with therequirements of Section 5: Part 16.

6.4.2 Placing

1 Wet lean concrete shall be spread uniformly without segregation and without varyingdegrees of pre-compaction.

2 The concrete shall be struck off to a level so that the surcharge is sufficient to ensure thatafter compaction the surface is at the required level.

6.4.3 Compaction

1 The spread wet lean concrete shall be compacted using internal or external vibration, orcombination of both to meet the required density.

2 Compaction and finishing to level shall be completed within the times given in Table 6.4.

6.4.4 Joints

1 At transverse and longitudinal construction joints between two separately constructed slabs,the previously laid slab end or edge shall present a vertical face before construction ofsubsequent slabs.

2 Longitudinal joints in wet lean concrete shall be staggered by at least 300mm from theposition of longitudinal joints in any superimposed concrete slab, and by 1m for transversejoints.

6.4.5 Strength

1 From each sample, three cubes of the appropriate size shall be made, cured and tested incompliance with BS 1881.

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2 One of each group shall be tested at 7 days and the other two at 28 days. The cubes shallbe assessed for compliance on groups of four 28-day test results in accordance with BS EN206 & BS 8500 for compliance with the grade required.

3 If the average value of any four consecutive results of tests at 7 days falls below the requiredvalues the cement content of the mix shall be increased by an amount agreed with the

Engineer which shall be maintained until the corresponding 28-day test results have beenassessed.

6.4.6 Trial Mixes

1 Trial mixes complying with the requirements for pavement quality concrete shall be requiredfor designed mixes for Grade C15 and above, unless recent data relating to the proposedmix is approved by the Engineer.

6.4.7 Trial Length

1 At least 10 days before the start of the main wet lean concrete works a trial length of at least400 m

2for mechanised construction and 30m for hand guided methods shall be constructed.

2 The trial length shall be laid to assess the suitability of the proposed material, plant,equipment and construction methods to meet the requirements of the Specification.

3 The main construction in the permanent works shall not start until the trial length has beenapproved by the Engineer.

4 If any trial length does not conform to the Specification another trial length shall beconstructed. Trial lengths not complying with the Specification shall be removed unless theycan be rectified to comply with the Specification to the satisfaction of the Engineer.

5 After approval has been given, the material plant, equipment and construction methods shallnot be changed without the approval of the Engineer.

6 Any proposed changes shall entitle the Engineer to require the Contractor to lay a furthertrial length to assess the suitability of the proposed changes.

6.4.8 Surface Finish

1 The surface of the wet lean concrete after compaction and finishing and before overlayingshall be free from ridges, loose material, pot holes, ruts or other defects.

2 The surface texture shall comply with the sub-Clause for pavement quality concrete, Section5: Part 16.

6.5 REQUIREMENTS FOR CEMENT BOUND MATERIALS

6.5.1 General Requirements for Cement Bound Materials

1 Cement bound materials shall be made and constructed as described in the followingclauses.

2 Cement bound materials shall be tested in accordance with this specification for therequirements of Table 6.5

3 Cement water and aggregates shall comply with the requirements of the Section 5: Part 16.

4 Cement for use in all cement bound materials and aggregates for use in CBM3 and CBM4

shall be delivered and stored in compliance with the requirements of Section 5: Part 16.

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Table 6.5

Cement Bound Materials Field Requirements

Category Mixing Plant

Method of

Batching

Moisture

Content

Minimum

Compaction

CBM 1mix in place ormix in the plant

volume or mass NOTE 1 NOTE 2



CBM 3 mix in the plant mass NOTE 1 NOTE 2



NOTE 1 - to suit the requirements for strength surface, level regularity and finishNOTE 2 - 95% of cube strength

Table 6.6

Cement Bound Materials Specimen Requirements

Minimum 7 days Cube StrengthCategory Curing

CompressiveStrength Testing

Average (Note1)(MPa)

Individual (Note2)(MPa)

CBM 1BS 1924 Part

2 1990

BS 1924 Part 21990 or BS

1881Part 116

4.5 2.5

CBM 2BS 1924 Part2 1990

BS 1924 Part 21990 or BS 1881Part 116

7.0 4.5

CBM 3BS 1881 Part111

BS 1881 Part 116 10.0 6.5

CBM 4 BS 1881 Part 116 15.0 10.0

NOTE 1 The average strength of 5 cubes shall not be less than the stated figureNOTE 2 - The strength of any individual cube shall not be less than the stated figure

6.5.2 Batching and Mixing

1 Batching and mixing shall be carried out in the appropriate manner described in Table 6.5.

2 Where the mix-in plant method is used and materials are batched by mass, the materialsshall be batched and mixed in compliance with BS EN 206 & BS 8500. Where continuousmixers are used and materials are batched by mass, the continuous mixers shall comply andtested in accordance with BS 3963.

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6.5.3 Transporting

1 Plant-mixed cement bound material shall when mixed be removed at once from the mixer,transported directly to the point where it is to be laid and protected from the weather bothduring transit from the mixer to the laying site and whilst awaiting tipping.

6.5.4 Laying

1 All cement bound material shall be placed and spread evenly in such manner as to preventsegregation and drying.

2 Spreading shall be undertaken either concurrently with placing or without delay.

3 Road base cement bound material shall be spread using a paving machine or a spreaderbox approved by the Engineer and operated with a mechanism which levels off the cementbound material to an even depth.

4 Cement bound material shall be spread in one layer so that after compaction the totalthickness is as specified.

5 At longitudinal or transverse construction joints, unless vertical forms are used, the edge ofcompacted cement bound material shall be cut back to a vertical face where the correctthickness of properly compacted cement bound material has been obtained.

6 In the case of cement bound sub bases under a concrete surface slab or continuouslyreinforced concrete road base, longitudinal construction joints in the sub-base shall bestaggered by at least 300mm from the position of the longitudinal joints in the concretesurface slab or continuously reinforced concrete road base, and by 1m for transverse joints.

6.5.5 Compacting

1 Compaction shall be carried out immediately after the cement bound material has beenspread and in such a manner as to prevent segregation.

2 Special care shall be taken to obtain full compaction in the vicinity of both longitudinal andtransverse construction joints.

3 Compaction shall be carried out in compliance with Table 6.5 and be completed within

2 hou

qcs 2010 part 6.06 concrete road pavements

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