Effect of Calcium Hydroxide on the Microstructure and Performance of Super Sulfated Cement

Abstract

The effects of a 0, 0.2 wt. %, 0.6 wt. %, 1.0 wt. %, 1.4 wt. % and 1.8 wt. % calcium hydroxide content on the microstructure and performance of super sulfated cement (SSC) were investigated. The results showed that the setting time of SSC could be reduced by the calcium hydroxide content to less than 7 hours. The variation in the setting time did not affect the working performance of the SSC. The mechanical properties of the SSC can be consistently and gradually enhanced by calcium hydroxide. The SSC, with a 3-day compressive strength of 22.3 MPa and a 28-day compressive strength of 45.1 MPa, was prepared by introducing 0.6 wt. % calcium hydroxide into the system. A microanalysis revealed that the reaction mechanism of the SSC was influenced by the calcium hydroxide, which led to changes in the hydration products as well as the structure. In particular, large amounts of ettringite (AFt) were prompted in the SSC prepared with the raw materials at the early stage. The change in the structure of the hydration products led to a significant improvement in the mechanical properties.