Recycled tyre tar test may pave way for better roads
21 October 2020 | Web Article Number: ME202020957
SOUTH Africa may soon adopt a sustainable new kind of road partly made of recycled tyres following a successful trial period on a test stretch of the experimental asphalt.
That’s according to Georges Mturi, senior researcher and manager of the Council for Scientific and Industrial Research’s (CSIR's) Advanced Material Testing Laboratories, who said research aimed at providing more sustainable asphalt products were paying off, paving the way for a more inclusive industry and better roads.
“The CSIR has been focusing on locally available alternative additives that would be much cheaper than the 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.”
Using locally available micro-fillers and sustainably using recycled tyres, the CSIR and Much Asphalt successfully constructed a road section. After just over a years’ worth of combined laboratory development and evaluation efforts the project came to fruition when both products under development were produced and paved into a controlled trial section in Roodepoort, Gauteng.
The 200-metre-long trial section included a 60mm modified enrobés à module élevé (EME) base layer and a 40 mm modified bitumen rubber surfacing layer that was constructed over a cleaned gravel base layer treated with an SS60 tack coat prior to paving.
The location of the trial section, starting from the weighbridge of the Much Asphalt Roodepoort branch to the public road tie-in on the approach to the site, was selected specifically to allow ease of continual performance measurement while having up-to-date details on the type and amount of traffic that moves across the section.
“During both the development and trial phase, several performance characteristics were evaluated as predictors of in-situ performance, which served as the baseline for the in-situ performance evaluation that were set to run on a three-monthly basis for at least the first year after construction,” Mturi said.
“The evaluations and visual inspections have shown that after nine months of traffic and environmental exposure, the layers are performing as expected.”
To date, no edge breaking is present where heavy vehicles are moving onto and off of the surfacing, no permanent deformation is present on the surfacing, with particular focus at stopping locations or where vehicle turning takes place and, to date, there are no signs of any deflection or temperature-induced crack formation taking place.
Joanne Muller, Much Asphalt Regional Laboratory Manager, said, “The developed and trialled technologies, aimed at improving the performance properties of standard 10/20 based EME, as well as having a viable replacement product for standard styrene-butadiene-styrene (SBS) modified A-E2 binder without detracting from pavement performance, are deemed effective and that can assist industry practitioners in the endeavour to provide long-lasting pavements to society”.
Muller said that for bitumen users, asphalt manufacturers or any other intermediary bitumen suppliers, it promises to act as an easier means of correcting poor bitumen to pass performance specifications or improving the performance of standard bitumen from one grade to another, in the event of national bitumen shortages.
“It is also important to highlight that the major benefit of this invention for the country would be an increase in the recycling of waste tyres in the road industry for the beneficial outcome of better-performing roads.”