Cold recycling is a process in which the reclaimed asphalt pavement (RAP) is mixed with a rejuvenating agent or binder to produce cold mix asphalt. The binder can be bitumen emulsion or foamed bitumen.
Cold asphalt recycling can be done as a plant mix using RAP or in-situ by milling and adding a rejuvenating/stabilising agent. It is generally applicable to roads with low to moderate traffic volumes.
Physical properties of cold recycled asphalt typically lie between hot mix asphalt and cold bitumen stabilised material.
Cold recycling can be carried out as:
Cold recycling at a central plant
Cold in-situ recycling with a single unit
Cold in-situ recycling with a recycling train
As moisture is introduced to the recycled mix as part of the bitumen emulsion rejuvenating agent, it is critical to the long-term performance of cold recycled mix that this moisture is eliminated during the compaction and curing of the finished mix. This means that the mix gains strength slowly. To accelerate this stiffening process, mobile surface heating units have been used successfully.
Cold recycling can be used for deep strength and full depth applications, as well as for recycling of asphalt wearing surfaces.
A cold recycling plant may be either a batch or continuous drum plant.
In environmental and efficiency terms, a cold recycling asphalt plant provides a number of advantages, including:
high production rates can be achieved
mixes with up to 100% RAP can be produced.
Both batch and continuous drum plants may be used for cold asphalt recycling, although the latter is more common.