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Stone mastic asphalt (SMA) and thin surface course systems (TSCS)

Where the existing surface course is SMA or a TSCS the road must be reinstated with either SMA surface course or, at the authority’s request, a TSCS or, by agreement, with HRA. These options are subject to the following requirements:
  1. SMA or TSCS must match the existing nominal aggregate size of the existing surface course material with the exception that 10 mm nominal aggregate size must be used to reinstate SMA/TSCS with 20 mm and 14 mm nominal aggregate size in situations where the hand-laying method is adopted.
  2. Preference must be given to the use of TSCS options suitable for the reinstatement works; including consideration of hand installation and compaction.
  3. The standard combined thickness of binder course and SMA surface course shown in Figures A3.1 to A3.5 is 100 mm.
  4. HRA must comply with the requirements of S6.4.2.
Edge and base preparation details for permanent SMA reinstatements are as follows:
  1. All edges must be saw cut or trimmed by saw, to a depth of 40 mm or the thickness of the surface course, before permanent reinstatement.
  2. A certified bond coat (BS 594987, Clause 5.5) must be applied in accordance with S6.8.
  3. An edge sealant must be applied in accordance with S6.8.7.
Where the existing surface is a TSCS and the authority does not want the reinstatement to be completed using SMA, the authority must contact the undertaker and the surfacing material must be agreed in advance.
Where the authority has a policy to grit or otherwise treat newly laid SMA surfaces, it must advise the undertaker of the required method and materials and the undertaker must comply.