Promoting the use of waste in road construction

Promoting the use of

WASTE IN ROAD CONSTRUCTION

The CSIR’s Case Studies Project Team was a recent finalist at the National Science Technology Forum (NSTF) Awards 2021/2022.

Construction of the road trial section at the University of Pretoria’s Engineering 4.0 facility using bitumen modified with plastic waste in the asphalt surfacing

The CSIR’s entry, entitled ‘The use of waste materials in road construction’, was submitted in the Green Economy Award category.

Led by project leader and principal researcher Georges Mturi, the CSIR team comprises Johan O’Connell, Imraan Akhalwaya, Nonzwakazi Ncolosi, Vincent Ojijo, Tladi Mofokeng, Michandre Smit, Nomashaka Hawes, Theresa George, Ashiel Rampersad, Refiloe Mokoena, Cameron Munsamy, Kele Makamu and John Letwaba. They have been working with partners from the road pavement industry that include AECI Much Asphalt, Dow, WBHO, BSS, Merchelles Collective, Roadspan and Roadmac Surfacing.

To date, the CSIR Case Studies Project Team has been involved in several research initiatives geared towards providing alternative waste material products for use by the asphalt pavement industry in South Africa. The research focus has been centred around creating a more inclusive and sustainable approach to future road construction, particularly through increasing the potential for job creation, creating greater economic benefits, producing better-performing roads, and trying to resolve South Africa’s environmental challenges.

Micro-fillers, plastic waste and recycled tyres

So far, the team has worked on three case studies. The first case study involved the CSIR collaborating with AECI Much Asphalt to use 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 trial section included a 60 mm modified high modulus asphalt base layer that was constructed over a cleaned gravel base layer treated with a bituminous emulsion before paving.

In the second case study, the project team demonstrated the use of plastic waste in asphalt mixes. This was an initiative of the Department of Science and Innovation funded through the Waste RDI Roadmap Implementation Unit led by Professor Linda Godfrey. The addition of plastic waste directly to the aggregate is called the ‘dry modification process’ or ‘dry method’ of plastic asphalt modification.

To prove the feasibility of this technology, a road section was constructed on the P159/1 (R80) highway in Tshwane and subjected to heavy vehicle simulator testing using a mobile laboratory that can simulate 20 years of heavy traffic in less than six months.

Team members involved in the construction of a road trial section at the R80 in Tshwane using plastic waste coated aggregates in the asphalt surfacing

Wet method trails

The third case study (recipient of the Dow Impact Fund) involved the use of plastic waste via the wet method (plastic waste added directly into bitumen) in the asphalt surfacing layer of a 100 m test section at the University of Pretoria’s Engineering 4.0 facility.

WBHO-funded construction started early in June 2022 with the layer works. The asphalt surfacing with plastic waste was paved in mid-July 2022. The section is currently undergoing preparations for heavy vehicle simulator (HVS) testing.

“All these case studies are ongoing research to provide alternative solutions for the road pavement industry,” states Mturi. Adds Ray Govender, director, WBHO: “They demonstrate the potential of sustainable use of recycled materials that have an economic benefit for the industry, while solving environmental challenges for the country.”