Study on hydration properties and products of Portland cement/calcium aluminate cement blends in negative temperature

Abstract

In the negative temperature environment of permafrost, the low temperature will hinder the hydration of cement. It is necessary to solve the hydration problem of cement under negative temperatures. Therefore, this paper studies the hardening and strength development of the composite system of Portland cement (OPC) and calcium aluminate cement (CAC) with different proportions at −10°C. The hydration products and their microstructure were analyzed by XRD, TG, and SEM. The results show that adding 10% ~ 30% CAC can promote the setting of OPC at −10°C, improve the compressive strength at the early hydration stage, but slow down the strength growth at the later hydration stage. At −10°C, NO2-AFM crystal and C-S-H gel were generated in the early hydration stage of the composite system to make the paste set and generate strength. However, Ca(OH)2 crystals were generated only in the composite system with a CAC content of 10% at the late hydration stage to make the microstructure denser and improve its strength. Its 28d compressive strength reaches 32.4 MPa.