65 / 2021-09-11 05:07:10

Performance of calcium sulfoaluminate cement-based grouts at cold temperatures

calcium sulfoaluminate cement; grouts; cold temperatures; permafrost

About 50% of Canada’s landmass is classified as the permafrost region. When applied in permafrost regions, Ordinary Portland Cement (OPC)-based grouts may fail to function owing to the slow strength development at cold temperatures. Substituting calcium sulfoaluminate (CSA) cement for OPC may help improve the performance of grouts used in permafrost regions since CSA cement has the features of rapid set and fast strength development. However, no research has been conducted to understand the performance of CSA cement-based grouts cured at cold temperatures, especially in a permafrost environment. To this end, this study developed an innovative curing mode—curing samples in cold sands—to mimic the influence of permafrost and evaluated the performance of CSA-based grouts cured in cold sands with different temperatures (10 ℃, 0 ℃, -10 ℃). Another group of samples were cured at 20 ℃ in the air as a reference. In this study, temperature recording and X-ray diffraction (XRD) tests were carried out to understand the hydration reaction of CSA cement-based grouts curd at cold temperatures. Unconfined compressive strength (UCS) tests were conducted to investigate the strength development of grouts. The results showed that the peak temperature in the center of the sample cured at -10 °C could reach about 30 °C within 20 minutes, which means that the hydration of grouts was fast and intense even at -10 °C. Under the fast and intense hydration at early ages, the UCS of samples cured at -10 °C reached 6.5 MPa at 2 hours, which is almost 50% of UCS at 28 days. The XRD test results revealed that the amount of hydration products (e.g., ettringite) in samples increased with the rise of curing temperature. As a result, the 2-hour UCS of samples increased from 6.5 MPa to 12 MPa, 12.3 MPa, and the 28-day UCS increased from 14.9 MPa to 19 MPa, 30.6 MPa when the curing temperature increased from -10 ℃ to 0 ℃, 10 ℃. In summary, CSA cement-based grouts can achieve fast strength development at cold temperatures, so they can be used to replace OPC-based grouts for permafrost region applications.