S7 Rigid and Modular Roads
S7 Rigid and Modular Roads
1) When the total thickness of any bituminous overlay is 100mm or more, it shall be reinstated as a composite road in accordance with Section S6.
2) Some modern road constructions incorporating special design philosophies are outside the scope of this Specification and reference should be made to Section NG 7.1.
3) The Undertaker shall carry out the reinstatement in accordance with one of the following methods and should endeavour to achieve the greatest degree of immediate permanent reinstatement. Reinstatement methods are listed in Appendix A2.10 Table A2.6.
5) Where the Authority is aware of a carriageway that is either composite or rigid, the detail of construction (i.e. existence of reinforcement, etc.) should be recorded as a Special Engineering Difficulty on the SRWR. Where the Undertaker discovers the existence of such construction which has not been recorded previously, they should inform the appropriate Authority
6) Where the Authority knows of any site with high sulphate levels, dangerous toxins or contaminants it should advise Undertakers in advance of the works so that appropriate measures may be taken. Ideally this information should be stored on the SRWR (as a Special Engineering Difficulty for dangerous toxins and contaminants) where it is available to all Undertakers and Roads Authorities. Similarly where an undertaker discovers any dangerous toxins or contaminants in the ground, it should inform the Local Authority such that they can update the register.
S7.1.1 Method A - All Permanent Reinstatement
The excavation and concrete road slab shall be reinstated to a permanent standard at the first visit. The bituminous overlay shall not be laid until the cured road slab has achieved a crushing strength of 25N/mm2.
S7.1.2 Method B - Permanent Binder Course Reinstatement
S7.1.3 Method C - Permanent Base Reinstatement
S7.1.4 Method D - Permanent Sub-base Reinstatement
1) The backfill and sub-base shall be reinstated to a permanent standard at the first visit.
2) The concrete road slab and overlay (if existing) shall be reinstated, for the interim period only, with a bound material. The interim surfacing shall be a bound material to a thickness of 100mm or 50mm as shown in Appendices A5.0 to A6.3.
3) On the second visit, all interim materials shall be removed to the top of the sub-base and a permanent concrete road slab reinstated. The road slab shall be in accordance with Sections S7.3.1 and S7.3.4. Any overlay may be reinstated, to an interim standard, in accordance with the relevant requirements of Section S6.1.3.
4) Any interim overlay shall be removed at a later date, to the top of the concrete road slab, and a permanent overlay reinstated.
S7.1.5 Method E - Permanent Reinstatement incorporating Interim Surface Overlay
1) Any bituminous surface overlay may be reinstated, to an interim standard, in accordance with the relevant requirements of Section S6.1.3.
2) Any interim bituminous overlay shall be removed at a later date, to the top of the concrete road slab, and a permanent bituminous overlay reinstated.
1) In a rigid road, the sub-base is deemed to be any layer of imported granular or cement bound material existing immediately below the base of the concrete road slab. Where such a sub-base layer exists, a similar or equivalent material shall be laid to match the existing thickness subject to a minimum thickness of 150mm.
2) Permitted options are shown in Appendix A5, subject to the following exceptions:
S7.2.1 Small Reinstatements
A CBGM B sub-base of 150 mm thickness may be used in small excavations and narrow trenches regardless of whether the existing sub-base is cement bound.
S7.2.2 Alternative Reinstatement Materials
Alternative Reinstatement Materials may be laid at sub-base level, in accordance with Appendix A9.
Permitted options are shown in Appendix A5, subject to the following provisions:
1) The concrete road slab shall be reinstated using C32/40 concrete mixed in accordance with SHW Clause 1001, with an air entrainment admixture used in at least the top 50 mm of the road slab.
Exceptionally, where agreed, the concrete road slab may be reinstated using an alternative material, to suit site conditions, e.g. a high early strength mix may be agreed to allow an earlier re-opening of a heavily trafficked road.
2) Where concrete is mixed off site, Quality Assurance Certificates detailing the Specifications against which the concrete has been ordered and supplied should be obtained by the Undertaker for confirmation of material quality. Where possible, the concrete should be obtained from a plant which holds a valid Quality Assurance Certificate.
3) In the case of small excavations, a site-batched proprietary mix, to C32/40 concrete may be used.
All expansion, contraction and warping joints removed or otherwise damaged during the excavation must be replaced or reconstructed to a similar design, using equivalent materials, at the time of permanent reinstatement.
1) Any slip membrane shall be reinstated beneath the road slab and a curing membrane shall be used above the road slab.
2) Impermeable polythene or similar sheeting may be used for both the slip and curing membranes.
3) Sprayed plastic film may be used as a curing membrane by agreement.
1) For small excavations, narrow trenches and other openings less than 1.0m wide, reference shall be made to Section S2.6.1 (2) and Table S2.5.
2) For all other excavations the Road Authority shall be consulted and a method agreed. The finished surface shall comply with Table S2.5.
S7.3.5 Opening to Traffic
The cured road slab may be opened to traffic as soon as a crushing strength of 25 N/mm² has been achieved.
The edges of all excavations in rigid roads shall comply with the following requirements:
Support for the edges of the reinstatement shall comply with one of the following options:
1) Edge Taper Support
a) Where the surface of the road slab is the running surface of the road, the excavation shall be delineated by sawing the pavement to a depth of 30 mm ±10 mm. The remainder of the exposed faces should be rough cut, at an angle of 27o ± 18o to the vertical; see Figure S7.1.
b) In all other cases, the exposed faces should be rough cut, at an angle of 27o ± 18o to the vertical. Delineation by pavement saw, to a depth of 30 mm ± 10 mm, may also be applied.
2) Dowel Bar Support
a) Where the surface of the road slab is the running surface of the road, the excavation shall be delineated by pavement saw, to a minimum depth of 20 mm. Any unsawn section of the slab shall be left roughcut to give an essentially vertical surface; see Figure S7.2.
b) Where the road is of composite construction or has been overlaid, the exposed faces should be prepared as detailed in Figure S7.1.
c) In all excavations, a row of horizontal holes shall be drilled along the centreline of the exposed faces, to provide a sliding fit for 20 mm or 25 mm nominal diameter steel dowel bars.
d) All holes shall be drilled at 600 mm ± 100 mm centres, with the holes along one face offset or staggered, relative to the opposite face, by at least 200 mm when viewed from above; see Figure S7.2. The nominal hole depth shall be equal to 50% of the dowel bar length ± 50 mm.
The maximum dowel bar length shall be 400 mm; minimum dowel bar length shall be equal to the width of the reinstatement less 50 mm.
The edges of the reinstatement shall be trimmed, where necessary over part or all of the thickness of the concrete road slab, to comply with the following requirements:
1) The edge regularity shall comply with the requirements of Section S6.5.2.
2) Any undercutting shall comply with the requirements of Section S126.96.36.199.
3) Cracking within the adjacent road slab, resulting from the excavation operation, shall require the relevant area of the slab to be removed and included within the area to be reinstated.
4) Where, following trimming, the excavation extends to within 300 mm of the road slab edge, joint, other reinstatement or ironwork, the relevant area of the slab shall be removed and included within the area to be reinstated.
5) All edges shall be cleaned and wetted prior to the placement of the concrete.
Where steel reinforcement within the concrete road slab has been cut, new steel reinforcing of equivalent weight shall be provided, in accordance with the following requirements:
1) The new reinforcement shall be lapped and wired or welded to the existing reinforcement.
2) A minimum of 150 mm of the existing reinforcement shall be exposed to allow adequate attachment of the new reinforcement.
3) Where 150 mm of the exposed reinforcement cannot be preserved during the excavation, the concrete road slab shall be trimmed, as necessary, to expose additional reinforcement. This additional trimming shall not supersede the requirement to provide a slab edge taper or dowel bars.
1) Where the surface of the concrete road slab or the modular surface layer is overlaid with a bituminous material or surface treatment, a matching thickness of a similar or equivalent material shall be laid.
2) Wherever practicable, the required surface course thickness should be maintained, by adjustment of the binder course thickness. The surface course and binder course materials shall not be laid to a thickness less than that required by Appendices A2 and A3 for the nominal size of each material laid.
3) Where the surface of the concrete road slab or modular surface has had a surface treatment including overlay, an equivalent surface treatment or overlay shall be applied.
S7.6.1 Surface Reinstatement
1) Edge preparation shall be carried out in accordance with Section S6.5, except that the existing edge of the overlay shall be trimmed by a distance equal to the nominal thickness of the surface course, or 40 mm, whichever is the greater.
2) Surface reinstatement shall be carried out in accordance with the requirements of Section S6.4.
1) Types 0, 1 and 2 modular roads are not included in this Specification and reinstatement designs shall be in accordance with BS 7533:Part 3.
2) The Undertaker shall carry out the reinstatement of Types 3 and 4 modular roads in accordance with one of the following methods and should endeavour to achieve greatest degree of immediate permanent reinstatement.
4) Where modules of natural stone material are present in trafficked roads refer to Appendix A12.
S7.7.1 Method A - All Permanent Reinstatement
The backfill, sub-base (if existing), bedding and modular surface layer shall all be reinstated to a permanent standard at the first visit.
S7.7.2 Method B - Permanent Sub-base Reinstatement
1) The backfill and sub-base shall all be reinstated to a permanent standard at the first visit, together with an interim granular Base and interim bituminous surface course, as per Section S6.1.5.
2) On the second visit, the interim reinstatement shall be removed to the top of the sub-base and a permanent Base, bedding and modular surface layer reinstated.
S7.7.3 Sub-base Reinstatement
2) The sub-base shall be reinstated to match the existing, or its structural equivalent.
S7.7.4 Base Reinstatement
2) The Base shall be reinstated to match the existing, or its structural equivalent.
S7.7.5 Surface Reinstatement