Retread (Carriageway/Footway Shallow Depth Insitu Recycling)

This is a recycling process where the existing aggregate in the carriageway, footway or other infrastructure is planed, regraded, and reprofiled, before hot-applied bitumen emulsion is added, and recompacted to the required line and level.

Retread has been successfully carried out for many years in urban and rural locations; for carriageways, footways, car parks and low-speed HGV parking plus storage/yard areas.

This innovative and environmentally-friendly process provides significant reductions in resource, carbon, cost, time and inconvenience to stakeholders, compared to traditional resurfacing solutions.

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The Carriageway Retread Process

The process involves scarification (planing) of the existing carriageway by up to 100mm deep and the re-introduction of fresh, hot bitumen emulsion (5 – 6% of the total mix volume) into the recycled material. BS 434-2:2006 Bitumen Road emulsions –Part 2: Code of practice for the use of Cationic bitumen emulsions on roads and other paved areas, applies to this.

Once sufficient bitumen has been mixed into the carriageway, a final re-profiling and re-compaction is completed before the carriageway is sealed with a light surface dressing and reopened to traffic. Depending on end-use, the Retread surface can be surface dressed (racked-in double dressing is recommended) or an asphalt/macadam surface course can be laid to a nominal 40mm compacted thickness.

Benefits include:

  • Significantly reduced or eliminated exportation of materials from site.
  • Minimal landfill costs with tar-bound material retained (locked-in) on site.
  • Potential to import and lock-in extra tar-bound material from other sites to create a revenue stream and/or contract savings.
  • Allows re-profiling of cracked/deformed carriageway and footway surfaces.

Up to 50%

cost savings compared to traditional plane-out and re-lay solutions


carbon reduction – reduced energy consumption and wagon movements


importation of quarried materials, asphalt and/or bitumen macadam

Relatively quick

process – potential for each section of carriageway/footway to be reopened at the end of each shift to minimise disruption

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