Effects of aphthitalite on the formation of clinker minerals and hydration properties

This paper aims to explore the mechanisms of aphthitalite in clinker sintering and hydration process, in order that wastes containing sulfates can be effectively utilized in cement production. TG-DTA, XRD, XRF and SEM were applied to investigate the sintering process, mineral composition, polymorphs and hydration products of clinker. Hydration reactivity of sintered clinker was analyzed by TA. Results show that aphthitalite increases the initial decomposition temperature of CaCO3 and the viscosity of liquid phase. Aphthitalite negatively affects the reaction of CaO and C2S into C3S. β-C2S is detected and R-C3S is transformed into the T1, M3, and T2 along with M2-C3S as the aphthitalite content rises. The morphology of clinker with different aphthitalite content show clearly heterogeneous characteristic. The early hydration of clinker is suppressed, but the induction period is shortened as the aphthitalite is introduced. Moreover, hydration of clinker in the acceleration period is increased by aphthitalite. Portlandite shows earlier after the induction period in the hydration of clinker as the aphthitalite content increases.