Abstract: To address the issues of high residual carbon content and low reactivity of coal gasification slag,a high-temperature
calcination method was adopted to activate the slag,aiming to enhance its pozzolanic activity and explore its feasibility
for resource utilization in cement-based materials. The phase evolution of coal gasification slag under different calcination temperatures
was analyzed using X-ray diffraction. The calcined slag was then used to replace part of the Portland cement to prepare
composite cementitious materials. The mechanical properties and hydration products of the composites were tested to systematically
evaluate the effect of calcination temperature on the reactivity of the slag. High-temperature calcination effectively
removed the carbonaceous phases from the slag. However,excessively high temperatures induced recrystallization of amorphous
aluminosilicates,reducing reactivity. The slag calcined at 400 °C retained the most amorphous phases and exhibited the highest
pozzolanic activity. The composite cementitious material prepared with slag calcined at this temperature achieved a 28 d compressive
strength higher than that of pure cement mortar,with increased formation of ettringite in hydration products and a denser
microstructure. Coal gasification slag calcined at an appropriate temperature of 400 °C can be used as a high-quality mineral
admixture in cement-based materials,enabling efficient resource utilization.