Investigation on the utilization of coal gasification slag in Portland cement: Reaction kinetics and microstructure

Gasification slag is a solid waste generated by the coal chemical industry which has emerged in recent years. In this paper, the effect of coal gasification slag (CGS) powder content on the reaction kinetics, gel structure and the compressive strength of Portland cement was investigated for the potential application of CGS powders in cementitious materials. The reaction and gel structure of Portland cement blended with CGS was analyzed by using X-ray diffraction, Fourier transform infrared spectroscopy and scanning electron microscopy tests. The results show that the unreacted CGS power exists mainly in an agglomerated state in cement matrix, and a low dosage of CGS powder (10%) can play a role in nucleation and pozzolanic effect in Portland cement, which is conducive to the formation of hydration reactions of Portland cement, shortening the setting time and improving the compressive strength. If the CGS content is >30%, the hydration product content decreases, and the microstructure of the sample becomes loosened. The setting times are significantly prolonged with the increase of CGS content dosing and the compressive strength is considerably reduced as well.