Recycling coal ash for road construction
In a first for South Africa, Eskom is piloting the recycling of legacy coal ash for use in road construction. This innovative initiative, launched by Eskom Rotek Industries (ERI) at the utility’s Kusile Power Station in Mpumalanga, aims to enhance operational efficiency and it reinforces Eskom’s commitment to sustainability.
The new access road at Kusile Power Station is designed to support the daily passage of up to 1 600 trucks, each weighing ~34 tonnes.
At the power station, Eskom has built a new access road, stretching 759 meters across two sections. The road is designed to support the heavy-duty daily passage of 1 200 to 1 600 trucks, each weighing ~34 tonnes, during the construction of a new coal conveyor belt.
As part of the Research, Testing and Development (RT&D) initiative, Eskom is using around 2 904 tonnes of legacy coal ash per kilometre of road, adhering to conventional road-building standards. By replacing traditional cement with recycled ash, the project contributes to a reduction in carbon dioxide emissions as every tonne of cement avoided means less carbon dioxide (CO2) produced.
Eskom’s Research Division has explored geopolymerisation, a chemical process that transforms aluminosilicate ash into geopolymer concrete. This material serves as a sustainable and durable alternative to traditional cement, and it is this technology that was used in the construction of the Kusile West Access Road.
Legacy ash, a by-product of coal-fired power generation, comprises weathered fly and bottom ash. By using it in road construction – and thus reducing a reliance on conventional cement and mitigating carbon emissions – Eskom is marking a significant milestone in its sustainability journey. The use of this technology will open new revenue streams for Eskom and alleviate the costs associated with legacy ash management.
Working in partnership with the Mpumalanga government, Eskom is focusing on ash beneficiation to foster job creation and stimulate regional growth. Under Waste Exclusion Regulations, Eskom is authorised to use coal ash in various applications, including road construction and brick manufacturing, which have the potential to yield significant economic and environmental advantages.
Currently, the utility produces about 34 million tonnes of coal ash annually, of which only 7% to 10% is beneficiated and the remainder is stored in ash disposal facilities (ADF). Classified as Type 3 hazardous waste, coal ash management presents significant environmental and financial liabilities. By contrast, the innovative use of legacy ash minimises ash volumes in dumps, reducing both environmental impacts and costs. Additionally, replacing cement with ash allows Eskom to earn carbon credits.
Eskom is working towards expanding the commercial use of coal ash produced during electricity generation. By transforming ash from a waste product into a valuable resource, it can support local economic growth, job creation, and business development. Around 10% of the ash from Eskom’s coal-fired power stations is currently being repurposed by various industries, fostering local economic activity.
Finding additional applications for coal ash will further reduce the environmental footprint of the ash disposal facilities and reduce fugitive dust. As Eskom seeks new uses for fine fly ash from its newer power stations, the potential environmental and socio-economic benefits continue to grow. This builds on the legacy of earlier power station closures that repurposed clinker ash for bricks to construct many homes; these dumps are now almost depleted.
The pilot road construction project represents a significant step forward for Eskom as it transitions towards greater levels of sustainability.
For more information visit: www.eskom.co.za
