Of global Gross Domestic Product (GDP), 10% is contributed by the construction industry, which is worth annually about USD 8 trillion. With world annual cement production exceeding 4 billion tonnes and contributing 5 to 8% of global CO2 emissions, there is ample motivation to reduce this figure, partly by using reactive waste. The cement industry has been utilising waste such as coal fly ash and blast furnace slag for many years by blending with Portland cement, hence reducing CO2 emissions by about 30%. In order to reduce such emissions significantly, a shift in binder chemistry is required. Alkali-activated cement (AAC) made from fly ash, metallurgical slags and natural pozzolans could reduce CO2 emissions by at least 80% compared with blended Portland cement (PC).

Although the valorisation of waste utilising AAC technology creates a new value chain, there are substantial barriers to the commercial adoption of AAC, or any alternative binder system. All concrete standards are based on the implicit assumption that PC is the main binder, while some standards like the European standards specify a minimum PC content. Therefore, if no or little PC is used the concrete does not comply with the standards, hence few design engineers and asset owners are prepared to accept the risk. In the absence of a long in-service track record, research is required to validate durability testing methods and improve AAC technology. Even when asset owners and accept the results of durability testing of AAC, a key barrier to entry into an established market is access to a suitable supply of source materials. High profile projects in Australia have demonstrated the vast regulatory, asset management, liability and industry stakeholder engagement process required to commercialise AAC.


Jannie S.J. Van Deventer

Jannie van Deventer was educated in South Africa, where he was Head of Chemical Engineering at the University of ...