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SPECIFICATION FOR THE REINSTATEMENT OF OPENINGS IN ROADS
S7 Rigid and Modular Roads
S7.1 Reinstatement Methods
S7.1.1 General
1) Rigid roads shall be considered to be composite when the total thickness of any existing bituminous overlay exceeds 100 mm, and shall be reinstated in accordance with Section S6. Where steel reinforcement has been used, it should be replaced in accordance with Section S7.5, unless otherwise agreed with the Authority.
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.
4) Permitted materials and layer thicknesses are specified in Appendices A1, A2, A5, A9, A10 and A11.
5) Where the Authority knows of any site with high sulphate levels, it should advise Undertakers in advance of the works so that appropriate measures may be taken.
S7.1.2 Method A - All Permanent Reinstatement
1) The excavation and concrete road slab shall be reinstated to a permanent standard at the first visit.
S7.1.3 Method B - 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 S6.1.4.
2) Any interim overlay shall be removed at a later date, to the top of the concrete road slab, and a permanent overlay reinstated.
S7.1.4 Method C - 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 an unbound granular material. The interim surfacing may be a deferred set material as shown in Appendix A5.
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 S7.3.2 & S7.3.5. Any overlay may be reinstated, to an interim standard, in accordance with the relevant requirements of Section S6.1.4.
4) Any interim overlay shall be removed at a later date, to the top of the concrete road slab, and a permanent overlay reinstated.
S7.2 Sub-base Reinstatement
S7.2.1 General
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:
S7.2.2 Small Reinstatements
A CBM3 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.
S7.2.3 Alternative Reinstatement Materials
Alternative Reinstatement Materials may be laid at sub-base level, in accordance with Appendix A9.
S7.3 Concrete Road Slab Reinstatement
S7.3.1 General
Permitted options are shown in Appendix A5, subject to the following exceptions:
S7.3.2 Concrete Specification
1) The concrete road slab shall be reinstated using C40 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 equivalent to C40 concrete may be used.
S7.3.3 Joints
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.
S7.3.4 Membranes
1) A slip membrane shall be used 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.
S7.3.5 Opening to Traffic
The cured road slab may be opened to traffic as soon as a crushing strength of 25 N/mm 2 has been achieved.
S7.4 Edge Support and Preparation
The edges of all excavations in rigid roads shall comply with the following requirements:
S7.4.1 Edge Support
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 pavement saw, to a depth of 30 mm 10 mm. The remainder of the exposed faces should be roughcut, at an angle of 27° 18° to the vertical; see Figure S7.1.
b) In all other cases, the exposed faces should be roughcut, at an angle of 27° 18 o to the vertical. Delineation by pavement saw, to a depth of 30 mm 10 mm, may also be applied.
Figure S7.1 - Slab Edge Taper Options
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) In all other cases, the exposed faces should be roughcut to give an essentially vertical surface. Delineation by pavement saw, to a minimum depth of 20 mm, may also be applied.
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.
e) 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.
Figure S7.2 - Dowel Bar Arrangement - Plan View
S7.4.2 Edge Preparation
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 S6.5.2.4.
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.
S7.5 Reinforcement
Where steel reinforcement within the concrete road slab has been cut out, new steel reinforcing mesh of equivalent weight shall be provided, in accordance with the following requirements:
1) The new reinforcement mesh shall be welded or lapped and wired 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.
S7.6 Overlays
S7.6.1 General
1) Where the surface of the concrete road slab or the modular surface layer is overlaid with a bituminous material, 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 Appendix A2 and A3 for the nominal size of each material laid.
S7.6.2 Surface Reinstatement
Permitted options are shown in Appendices A4 and A5, subject to the following exceptions:
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.
S7.7 Modular Roads
S7.7.1 General
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, BS 6717 part 1 & BS 6667 part 1.
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.
3) Permitted materials and layer thicknesses are specified in Appendices A1, A2, A6 and A9 to A12, subject to the following requirements.
S7.7.2 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.
S7.7.3 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 (roadbase) 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 (roadbase) and modular surface layer reinstated.
S7.7.4 Sub-base Reinstatement
1) Permitted options are shown in Appendix A6, subject to the requirements of section S6.2.
2) The sub-base shall be reinstated to match the existing, or its structural equivalent.
S7.7.5 Base (Roadbase) Reinstatement
1) Permitted options are shown in Appendix A6, subject to the requirements of section S6.3.
2) The base (roadbase) shall be reinstated to match the existing, or its structural equivalent.
S7.7.6 Surface Reinstatement
The modular surface layer shall be reinstated in accordance with Appendices A6 and A12. The requirements and recommendations for the provision of replacement modules are shown in Appendix A12.
S7.8 Tolerances
S7.8.1 All performance requirements and tolerances permitted in the reinstatement of rigid and modular roads shall be in accordance with the requirements of Section S2 and Appendix A2.
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