Effect of aluminum sulfate on the hydration of Portland cement, tricalcium silicate and tricalcium aluminate

Abstract Alkali-free accelerator, mainly composed of aluminum sulfate (AS), is a widely used chemical admixture in the sprayed concrete. Thus, the impact of AS on the cement hydration should be further studied. This research focused on the effect of AS on the hydration reaction of C3S and C3A, illustrated by various measurements, including hydration heat, XRD, TGA, and thermodynamic modeling. Results indicated that AS accelerated the C3S hydration by rapidly generating AFt in induction period, and facilitated the C3A hydration by producing SO4-AFm and OH-AFm after a short hinderance. These facilitations were integrated into the promotion on cement hydration. The findings could provide guidance for the development of accelerator.