The performance of calcium sulfoaluminate cement for preventing early-age frost damage

This study aims to explore the possibility of using calcium sulfoaluminate (CSA) cement to prevent early-age frost damage. CSA-based and ordinary Portland cement (OPC)-based mortars with and without calcium nitrate were exposed to -10 degrees C for 3 days, then re-cured at 23 degrees C until 28 days. Another group of mortars was directly cured at 23 degrees C as references. Thermogravimetric analysis (TGA) and unconfined compressive strength (UCS) tests were conducted at various ages; mercury intrusion porosimetry (MIP) and scanning electron microscopy (SEM) were performed at 28 days. TGA results presented that the hydration of CSA cement was faster than that of OPC, enabling rapid strength development even at -10 degrees C. The MIP and SEM results showed that the -10 degrees C exposure had a negligible influence on CSA-based mortar without calcium nitrate (CSA Mix), while noticeably increased the porosity and cracks in OPC-based mortars. At 28 days, re-cured OPC-based mortars only achieved about half of the UCS of their references, indicating severe early-age frost damage. However, re-cured CSA Mix achieved 117% of the UCS of its reference, showing high resistance to early-age frost damage. In addition, calcium nitrate retarded strength development of CSA cement at -10 degrees C, consequently decreased the resistance to early-age frost damage. In conclusion, CSA cement can be used in frozen temperatures to prevent early-age frost damage. (C) 2020 Elsevier Ltd. All rights reserved.