Characterisation and hydration kinetics of β-C2S synthesised with K2SO4 as dopant

Abstract

In this study, a protocol for synthesising β-C2S using K2SO4 as a dopant has been reported. Quantitative X-Ray diffraction was used to characterise synthesised samples. It was observed that it is possible to synthesise β-C2S with high purity (>96 wt%) and limit the formation of free lime to below 0.5 wt% using this protocol. Unreactive γ-C2S was the main secondary phase present in the sintered samples. Isothermal calorimetry studies were conducted to understand the reaction kinetics which showed that β-C2S reacts slowly but produces similar calorimetric curve profiles as that of C3S. The C-S-H formed from the hydration of C2S was observed to be morphologically and compositionally identical to the C-S-H produced from the hydration of C3S. The hydration kinetics of β-C2S was seen to be affected by the presence of aluminosilicate pozzolan, such as calcined clay, which can have practical implications while producing blended cements with belitic clinkers.