Sustainability

Advantage 85

Asphalt roads can be reused directly where they are.

In addition to reusing materials derived from existing roads in new materials, the road itself can be reused in-situ, thereby reducing the need to remove materials from the site to other locations for processing and inclusion in fresh asphalt. This has the benefit of reducing haulage movements and associated transport emissions of the materials to be recycled and any that need to be discarded. 

There are a number of processes which can achieve this, using ‘hot’ and reduced temperature technologies. 

“Repave” 
Repave-type processes are characterised by the heating and scarifying of the immediate surface of the road to approximately 20-30mm depth. This thin layer is then re-profiled and any material in excess of that required for the final line and level may be removed. Fresh asphalt material is laid on top of the scarified layer and these are compacted together. The process employs a highly specialised machine, typically of considerable length which may restrict areas on which it can be used. The process will provide a new running surface, primarily to replace a surface which no longer has the required texture or skid resistance properties, but in which the existing surface course material is itself in good condition. 

“Remix” 
The Remix process is similar to Repave, the main difference being that the existing in-situ material after heating and scarifying, is completely mixed with an appropriate amount of fresh material inside the machine itself. The newly mixed material is laid directly onto the hot, scarified, level surface by the machine. 

The new material that is mixed with the existing material from the road is designed so that the resultant blend will be suitable for the site conditions and comply with the appropriate specification. 

“Retread” 
The Retread process is carried out to a greater depth than Repave or Remix, typically around 75mm. The road is cold scarified and the materials homogenised with fresh aggregate and/or binder in the machine before being re-laid to full depth. As this is a cold process, the materials may also require the addition of a bitumen rejuvenator / emulsion in order to enhance the workability before compaction in a relatively thick layer. Retread is likely to be appropriate for in-situ recycling of base or binder course materials prior to being overlaid with fresh surface course. In some cases, it may even be possible to Retread both the surface and binder course together, if specifications and surface characteristics permit it.


Reference:
EAPA Position Paper: Asphalt the 100% recyclable construction product (2014) http://www.eapa.org/userfiles/2/Publications/EAPApaper_Asphalt_the%20100%20_recyclable_construction%20product.pdf