Increased interest in cold-mix techniques

Asphalt contractors in a number of local authority areas signed up to trial different cold-mix bituminous materials during a three-week-long ‘Cold-Mix Tour’ of Britain organized by Nynas. The company employed a KVM mobile cold-mix asphalt plant for the trials for use with their range of specialist bitumen emulsions, designed specifically to be mixed with recycled materials.

Interest in cold-mix techniques is growing because of sustainability, environmental and energy considerations. The cold-mix process, combined with Nynas’ specialized emulsions, allows bituminous materials to be made using recycled planings; traditional hot-mix materials can only be made with up to 40% of recycled planings.

Cold-mix asphalt also offers potential fuel savings and reductions in CO2 emissions, as Nynas’ cold-mix bitumen emulsions can be mixed with recycled planings at temperatures ranging from ambient to 70ºC, compared to 180ºC for hot-mix materials. This translates into a fuel requirement of just one hundredth of that needed for conventional hot-mix asphalts using the KVM plant.

The main cold-mix technique used for road maintenance in the UK has been Foam Mix, which is generally used in base layers. Materials trialed during the Cold-Mix Tour included the use of 100% planings as binder-course materials for carriageways.