For small openings a proprietary C32/40 site-batched concrete may be used.
Considerations related to pavement details
Concrete pavements can be classified as jointed unreinforced concrete (URC), jointed reinforced concrete (JRC) and continuous reinforced concrete pavement (CRCP). URC slabs are typically up to 5 m long, JRC slabs are typically between 5 m and 25 m, and CRCP has no joints but will develop fine transverse cracks at 2 m to 3 m intervals. Dowel bars are used to transfer traffic load across transverse joints and tie bars are used in longitudinal joints between lanes.
Reinforcement for long trenches with a length to width ratio greater than 3:2 is typically located between 60 mm and 90 mm below the concrete surface and comprises steel mesh (typically A393 for roads). This mesh minimises the potential for cracking during curing and is not a structural mesh. Shallower (lower cover) reinforcement requires consideration of potential corrosion associated with chlorides. Sources of chlorides include the use of de-icing salt during winter maintenance. Guidance can be found in BS 8500-1.
Additional reinforcement in the concrete surround, should be considered around ironwork and other features to reduce the risk of sympathetic cracking within the reinstatement (see MCHW Volume 3 Series C for guidance).
It is envisaged that the requirement to include transverse joints within the reinstatement would be needed for works that cut across 5 or more concrete bays, or where there is a concern that the dowelled reinstatement will lock up the concrete pavement (i.e. prevent the pavement from contracting and expanding normally) increasing the risk of cracking associated with loading or sympathetic cracking.