Durability testing for belitic calcium sulfoaluminate cement: equivalent hydration

The durability of calcium sulfoaluminate (CSA) cements is disputed in the literature. The significant variance in CSA types and mix designs across studies lead to fundamental chemical differences, making direct comparisons untenable. In addition, standard protocols do not allow for sufficient time for belite hydration, thus leading to inaccurate assessments of the in-service performance of belite-rich cements. In this study, a commercial belitic CSA was used to produce specimens for exposure to different curing conditions with the aim of achieving an ‘equivalent hydration’ comparable to that of a Portland cement cured for 28 days. Specimens were subsequently exposed to carbonation and elevated temperature (80°C) for 1 year, after which their residual mechanical performance was evaluated. It was found that, when cured at 20°C, an increased curing period of 91 days reduced the depth of carbonation by approximately 35% and mitigated strength loss from exposure to elevated temperature by 10%. A similar improvement in performance was also observed when the curing temperature was increased to 40°C for only 28 days. These results, along with the general strength evolution observed for the tested specimens, indicate that ensuring a higher degree of hydration within curing protocols lead to improved long-term physical and mechanical performance.