Hydration evolution and compressive strength of calcium sulphoaluminate cement constantly cured over the temperature range of 0 to 80 degrees C

摘要

Curing temperature plays a critical role in the properties and hydration of cement pastes. The influence of curing temperature (0-80 degrees C) on the hydration evolution and compressive strength of calcium sulphoaluminate (CSA) cement has been studied in this paper. It was investigated by a combination of XRD, DSC-TGA and BSE-IA. The experimental results indicate that various curing temperatures do not change the type of hydration products but do affect their amounts. The maximum amounts of AFt and AFm appear at 20 degrees C and 40 degrees C respectively. Elevated temperatures promote the hydration. The 1 d-hydration degree increases from 20.3% at 0 degrees C to 53.0% at 80 degrees C. However, low temperature (< 20 degrees C) is in favor of a denser and more homogeneous matrix due to continuous substantial hydration. The early-age compressive strength increases at elevated temperatures. But at 40 degrees C and 80 degrees C, the compressive strength decreases since 7 days. It has some connections with the hydration evolution. Before reaching a critical degree of hydration (about 53% in this study), the compressive strength is controlled by hydration degree. After that, it is dominated by AFt/AFm ratio and microstructure.