What Happens When the Fly Ash Runs Out?
1 National Customer Technical Support Manager, Cement Australia
For many years, the replacement of cement with fly ash in pavement concrete mixes has been mandated by infrastructure asset owners. In NSW, R82 requires a minimum 40% replacement level whereas in R83, the minimum level is 20% but typically, replacement levels are actually 60% & 25% respectively. Historically, the benefits of replacing cement with fly ash have been the mitigation of ASR, reduced permeability and reduced mix costs - but things are about to change.
The drive towards net carbon zero by 2050 in the construction industry is forcing specifiers, designers and suppliers to come to terms with evaluating alternative types of binder in low carbon concrete mixes of the future. Cement itself is perceived by the Federal Government as being a major emitter and as such, the four Portland cement clinker manufacturing sites in Australia are all listed amongst the 215 major emitters in their Safeguard Mechanism policy.
The paper will cover the steps being taken by Australia’s biggest cement & fly ash supplier to address cement emissions at source as well as the search for alternatives when the decommissioning of coal fired power generation begins to cease the ability to generate fly ash for the replacement of cement in pavement concrete mixes. Such alternatives include lithium and bauxite by-products, calcined clays and dam ash recovered from coal combustion products storage areas. Also included will be exciting innovations that mitigate the negative impact on strength development in concrete mixes with higher levels of fly ash and slag.
Bruce Perry is graduate chemist and holds the Diploma in Advanced Concrete Technology. His current area of focus at Cement Australia is the implementation of technologies that assist concrete producers in reducing their levels of embodied carbon in concrete mixes though the adaptation of new admixture technologies.
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