Construction of the road using the new materials
The Council for Scientific and Industrial Research (CSIR) and private company Much Asphalt have successfully constructed a section of road using locally available micro-fillers and recycled tyres.
Following more than a year of combined laboratory development and evaluation efforts between CSIR Smart Mobility and the Much Asphalt Gauteng Regional Laboratory, the project came to fruition when the products under development were produced and paved into a controlled trial section in Roodepoort, Gauteng.
The 200-m-long trial section included a 60-mm 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 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 the development and trial phase several performance characteristics were evaluated as predictors of in-situ performance, which served as the baseline for the performance evaluation that was set to run on a three-monthly basis for at least the first year after construction,” explains CSIR Advanced Material Testing manager Georges Mturi.
“Evaluations and visual inspections have shown that after nine months of traffic and environmental exposure, the layers are performing as expected.”
To date, there is no edge-breaking 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.
“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 modified A-E2 binder, without detracting from pavement performance, are deemed effective,” says Much Asphalt Regional Laboratory manager Joanne Muller.
“[This] can assist industry practitioners in the endeavour to provide long-lasting pavements to society.”
For bitumen users, asphalt manufacturers or any other intermediary bitumen suppliers, it is believed the technology will act as an easier means of correcting poor bitumen to pass performance specifications, or to improve the performance of standard bitumen from one grade to another, in the event of national bitumen shortages.
Another major benefit should be an increase in the recycling of waste tyres in the road industry.
The CSIR says it has been focusing on using locally available alternative additives that would be cheaper than conventionally imported additives, as well as to use recycled materials, which have an economical benefit for the industry, while also resolving an environmental challenge for the country.