The Johannesburg Roads Agency (JRA) is testing the use of reclaimed asphalt products as a paving material for both new roads and the maintenance of existing ones across the city.
The JRA is the municipal entity responsible for the design, maintenance, and repair of Joburg’s road network and stormwater infrastructure, including bridges, culverts, traffic lights and signage.
The agency’s operations manager for strategic assets, Langeriwa Mthombeni, said that reclaimed asphalt roads are beneficial as they are typically less harmful to the environment and are cheaper to make.
“The JRA benefits from producing cost-effective and eco-friendly materials by creating a production cycle that uses reclaimed asphalt from existing road infrastructure,” he said.
“Another notable benefit is that the public’s money is used effectively, with existing pavement reclaimed for further use and more materials made available to be allocated for various other applications, such as filling of embankments and new road projects,” he said.
Mthombeni said the reclaimed asphalt product is made through the process of milling out used asphalt from an old pavement and reprocessing it by separating its constituent materials.
The JRA recovers constituents of asphalt products, also known as bitumen, to reproduce virgin asphalt material to either resurface a road or pavement and to patch potholes.
The process requires the repurposing of old surface pavement materials as bound matter, which gets unbounded into individual particles that are further evaluated for suitability and appropriateness in asphalt mix designs.
Mthombeni said that the reclaimed asphalt material is then repurposed by a crusher machine plant through gradation and separation of binders from the aggregates.
Reclaimed asphalt materials are also assessed for the optimum portion of asphalt that can be added without compromising the performance and quality of the final product.
Mthombeni said the consistency of repurposing reclaimed asphalt materials can be a challenge, which requires stringent laboratory testing and analysis due to the infiltration of dust pollution.
However, its advantages outweigh the challenges, he said.
“The benefits of reclaimed asphalt products include an eco-friendly or green focus due to less energy used during production. It is also more cost-effective owing to decreased usage of bitumen, which is the most expensive constituent material in asphalt production,” Mthombeni said.
Reclaimed asphalt products can also be used on pavements, such as the base layer after pulverisation. Additional advantages are that it can be used in the production of cold mix, which is usually deployed to fill broken materials on embankments. It also provides an opportunity for innovation, he said.
“The civil engineering sector is moving in the direction of developing sustainable and eco-friendly construction materials, and we want to lead that process on the continent. Cold mix, warm mix, and hot mix asphalt are key in the development of new products with reclaimed asphalt product and the use of waste products such as plastics, fly ash, and rubber.”
At the current rate of development in Joburg, he hopes the JRA will register its engineering professionals with the Engineering Council of South Africa to enhance the application of quality civil engineering practices.
“I foresee the asphalt plant producing a variety of asphalt products supported by the South African National Accreditation System (SANAS) and applied on all our roads. Through research and development, the JRA will be conducting various rehabilitation interventions using the latest technology,” said Mthombeni.
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