Over the past 10 years, cold in-situ recycling has become an increasingly popular technique for the Road Engineer to use for the maintenance and rehabilitation of local and regional roads.

Application

The process consists of mixing a bitumen emulsion with the recycled material from the existing pavement, in situ, to create a new cold-mix asphalt layer. From an environmental point of view, in addition to using a "cold" technique, the Road Engineer is also reducing the use of valuable resources, i.e. bitumen and aggregates.

COLAS Contracting performs cold in situ recycling operation in compliance with the IAT Best Practice Advice for Cold in situ Recycling of Low Traffic Volume Roads. The process starts by determining the depth of material to recycle and the taking of samples from the existing pavement, so that a full laboratory design can be performed. The lab design will determine the optimum moisture content and the percentage of emulsion that is required to be added on site. Corrective aggregate may also be required to ensure that maximum density and strength values are achieved.

On site, the recycling operation is carried out by specialist equipment that include the self-propelled recycler, an emulsion tanker, a water tanker, a grader and rollers. The recycler acts to mill up and pulverise the existing pavement material to a specified depth while at the same time, mixes the emulsion to recycled material using computer-controlled pumps and flow meters.
Benefits
  • The re-use of existing valuable road materials, i.e. aggregate and bitumen.
  • A reduction in the disposal of waste products to off-site locations and, consequently, the avoidance of unnecessary truck movements and disruption to road users and residents.
  • As an entirely cold process, there is a reduction in energy use and carbon emissions, when compared to conventional hot-mix asphalt overlays.
  • An improved pavement strength and, hence, the removal of the need to import additional material to increase the pavement thickness.
  • As an emulsion bound material, the new pavement is more flexible, fatigue resistant and not prone to cracking.
  • A surface dressing finish ensures that the newly constructed pavement is resistant to moisture ingress and its damaging effects.