LAUSR

Abstract Coal washing waste was studied as supplementary cementitious material to evaluate it as new raw materials for ecocements. The influence of temperature (room temperature, 450, 650, and 800 °C) and residence time in the muffle furnace (1, 2, and 3 h) on the mineralogy and pozzolanic properties of coal washing waste was analyzed. Different characterization techniques such as PSD, XRF, XRD, FTIR, and elemental analysis were employed. In addition, the degree of structural order–disorder of the kaolinite and the amount of amorphous material in each calcined sample were determined. Subsequently, blended cements were prepared by replacing 20% with calcined waste, and their physical and mechanical behavior were analyzed (water demand, setting time, expansion, pozzolanicity, and compressive strength). The results obtained show that despite the low kaolinite content in the coal waste (14%), it is possible to obtain optimal eco-pozzolans when they are subjected to a thermal activation process above 600 °C, with an optimal temperature around 800 °C. The blended cements comply with the specifications for Type II/A cements, reaching relative compressive strength up to 0.99%. A good correlation between the compressive strengths and amorphous content of the thermally activated waste was obtained.