Roads in Africa have often been challenging to travel on because of the different types of pavement failures. With the help of the Council for Scientific and Industrial Research’s (CSIR) world-class bituminous binders laboratory, US-based science company, DuPont, is changing how roads are built in Africa with its DuPont™ Elvaloy® Reactive Elastomeric Terpolymers (RET) bitumen modifier technology. The tests conducted by the CSIR set the scene for the uptake of Elvaloy® RET and the advancement of bitumen specifications in Africa.
Elvaloy® RET is a bitumen modifier that creates a strong chemical bond between the polymer and asphalt part, enabling roads modified with Elvaloy® RET to have improved performance properties, like greater rutting resistance and fuel resistance. Elvaloy® RET helps roads withstand increasing heavy traffic, extends the life time of the pavement and minimises maintenance costs.
Even though the technology has been utilised in many parts of the world since the early 1990s and has been known to modify bitumen for better roads, Elvaloy® RET only entered the South African market in the past decade. For years, bitumen in South Africa was evaluated based on empirical specifications like softening point and elastic recovery. Although these specifications showed the required consistency conformance, they did not show how different modified bitumen products cope in long-term performance.
“After three years of repeated testing and evaluation, we only had a handful of formulations that met the available South African empirical specifications,” notes DuPont’s Account Manager, Richard Ntombela. “It all changed with ‘rheology’, which is a science that deals with the deformation and flow of matter and correctly reflects how the pavement will perform in the long term.”
At the time, the CSIR was the only organisation with a Dynamic Shear Rheometer (DSR) instrument dedicated to measuring the rheological properties of bitumen in Southern Africa. DSR is used to characterise the viscous and elastic behaviour of asphalt binders at medium-to-high temperatures and results obtained corresponds to road performance better than any other test method.
“While working with CSIR to evaluate the rheological properties of our products, we obtained better relationships to actual performance,” said Ntombela. “It became evident that local bitumen modified with Elvaloy® RET compared favourably in a number of properties against other modified bitumen products.”
Georges Mturi, a CSIR senior scientist, said, “This shows that if we look at material challenges from a scientific point of view, we are able to open up industries to a wider range of alternative materials and improved innovations. At this stage, the performance of bitumen modified with Elvaloy® RET complemented field performance observed in a number of DuPont’s projects across the continent. The combination of these factors convinced the local industry that empirical specifications were discouraging an innovative product.”
Nowadays, almost every lab in South Africa has a DSR. Countries on the continent have also started purchasing these instruments. Rheology has become a common word and rheological properties now form the basis of new bitumen specifications.
“The CSIR had quite the foresight,” says Ntombela. “This proves that no one organisation can single-handedly address the African infrastructure challenges, we need collaborations such as the one we have with the CSIR, which resulted in this technology being accepted by road industries throughout the continent,” concludes Ntombela.
In South Africa, Elvaloy® RET has been used for chip seals and asphalt projects in Mpumalanga, the Free State and Eastern Cape provinces. In the rest of Africa, countries like Tanzania, Ghana, Zambia, Namibia and Mozambique are already using the technology across major cross-border road networks.