The CSIR and Much Asphalt Pty Ltd used locally available micro-fillers and recycled tyres to pave a 200-m long section of road as part of a controlled trial in Roodepoort, Gauteng.

This followed ongoing research to provide alternative sustainable solutions for the asphalt pavement industry and a year of combined laboratory development and evaluation. The CSIR has been investigating locally available alternative additives that would be cheaper than conventionally imported additives, as well as creating sustainable use of recycled materials that have an economical benefit for the industry, while resolving an environmental challenge for the country.

The trail section included a 60 mm modified high modulus asphalt base layer, known as enrobés à module élevé, and 40 mm modified bitumen rubber surfacing layer that was constructed over a cleaned gravel base layer treated with a bituminous emulsion prior to paving. The findings of the trial were that no edge-breaking was present where heavy vehicles were moving onto and off of the surfacing; no permanent deformation was present on the surfacing, with a particular focus at stopping locations or where vehicle turning took place; and, to date, there had been no signs of any deflection or temperature induced crack formation.

For bitumen users, asphalt manufacturers or any other intermediary bitumen suppliers, this outcome could indicate an easier means of correcting poor bitumen to comply with performance specifications or improving the performance of standard bitumen from one grade to another, in the event of national bitumen shortages. The benefits of this invention for the country would be an increase in the recycling of waste tyres in the road industry, as well as better-performing roads.