Expansive and non-expansive calcium sulfoaluminate-based cements

Within the curing period 4 hours- 90 days, a dimensionally stable calcium sulfoaluminate (CSA) cement, consisting of 83% CSA clinker and 17% natural gypsum by mass, and an expansive cementitious blend (MIX), composed by 40% CSA clinker, 40% CEM I- class 52.5 R ordinary Portland cement (OPC) and 20% natural gypsum by mass, were submitted to shrinkage and compressive strength tests as well as differential thermal-thermogravimetric analysis (DTA-TG) and mercury intrusion porosimetry (MIP). OPC was also used as a reference term. The early and late mechanical strengths were respectively highest for CSA cement and lowest for MIX cement which, furthermore, showed the minimum shrinkage. These phenomena were attributed to (i) the faster reaction rate of CSA and MIX cements, and (ii) the non-expansive/expansive nature of ettringite respectively formed. Each investigated cement exhibited peculiar features in terms of pore size distribution modalities and threshold pore widths.