Characterisation and understanding of Portland cement mortar with different sizes of bottom ash

Coal combustion residues are produced in large volumes and have been dumped as waste products over many years. The use of bottom ash (BA) as a partial replacement for Portland cement (PC) is an economical use of this thermal power plant by-product. The study reported here aimed to characterise BA of different sizes for use as 10–40% PC replacement. Chemical and physical characteristics such as chemical composition, phase analysis, microstructure, density and compressive strength were examined. With 10% 63 μm BA, the density slightly decreased while the strength was almost identical to that of the control PC mix. Scanning electron microscopy images revealed the flat and hexagonal shapes of calcium silicate hydrate gel. Calcium carbonate enhanced the hydration process of C₃S while the ternary phase diagram of calcium oxide–silicon dioxide–aluminium oxide showed that a mix with 10% BA was in the high-calcium zone.