Influence of external environment on early-age expansion characteristics of calcium sulfoaluminate cement-based binders

Calcium sulfoaluminate (CSA) cements are widely being promoted as alternative low CO2 binders. CSA cements can also be expansive and designed to be shrinkage-compensating. The main phase of CSA cement is ye’elimite, which hydrates in the presence of calcium sulfate to form ettringite as the main hydration product. The availability of calcium sulfate can be used to control the hydration kinetics of ye’elimite, which affects the expansion characteristics of CSA cement. Sulfates in the form of gypsum or anhydrite are usually blended with CSA cement in the manufacturing stage. The presence of sulfates in the external environment also affects the expansion characteristics of CSA cement. This study aims to understand the effect of different exposure conditions on the expansion characteristics of CSA-based blended cement. The expansion of the specimens exposed to calcium sulfate solution was found to increase with the amount of calcium sulfate. The addition of CSA cement to Portland cement was found to have a significant influence on the early age expansion characteristics of the system, without affecting the mechanical properties such as compressive strength and dynamic modulus