The increasing demand for sustainable structures and infrastructure has accelerated research into alternative construction materials. This study explores the use of bagasse ash and red mud as supplementary cementitious materials (SCMs) in concrete.
Investigations were conducted on bagasse ash and red mud sourced from MSF Mills in Gordonvale and Queensland Alumina, respectively, to assess their potential as SCMs. The materials underwent grinding and heat treatment to enhance their reactivity. A variety of advanced material characterisation techniques, including X-ray fluorescence (XRF), X-ray diffraction (XRD), and thermogravimetric analysis (TGA), were performed to evaluate their chemical and mineralogical composition. Pozzolanic reactivity and compressive strength tests were also conducted to determine the optimal replacement levels in cement and concrete.
Specific surface area tests on bagasse ash indicated low water demand, which enables good workability with plasticisers. Pozzolanic reactivity tests showed that bagasse ash has moderate reactivity and performs better than commercial fly ash.
The findings suggest that bagasse ash can replace up to 20% of cement without compromising strength. In contrast, red mud shows promising early-age reactivity but necessitates further optimisation to achieve long-term strength performance. Compressive strength tests on samples with 20% red mud replacement indicated higher early strength gains (3–7 days), but a 20% reduction in strength at 28 days. Heat treatment at temperatures ranging from 600°C to 800°C further diminished the 28-day strength. The optimal replacement level for red mud was found to be 10%, yet even at this level, the 28-day strength was still 12% lower than that of the control sample.
Life Cycle Assessment (LCA) studies indicate that using SCMs can reduce embodied carbon emissions by up to 20% compared to traditional Portland cement.
The findings demonstrate that strategically utilising such recycled materials can significantly reduce carbon emissions, enhance structural integrity, and lower material costs.