Effect of gypsum addition on acid resistance of ye'elimite rich calcium sulfoaluminate cement

Calcium sulfoaluminate (CSA) cements exhibit useful properties such as shrinkage compensation and rapid strength development. Acid resistance of CSA cement is majorly governed by its phase composition that varies significantly depending on the desired properties. In this study, acid resistance of CSA cement (i.e., non -expansive) and gypsum blended CSA cement (i.e., expansive) is explored. The current work emphasizes that a small change in phase assemblage can cause large difference in the performance under acidic environment. Conventional acid immersion tests with hydrochloric acid (HCl) of 1 % and 2 % conc., and sulfuric acid (H2SO4) of 2.95 % conc. were considered in the study. Furthermore, a recently developed acid consumption method was used to rank the binders with regard to their acid resistance in HCl and H2SO4 environments. It was found that the gypsum-blended CSA cement showed poorer performance than CSA cement in acidic environment despite having marginally higher compressive strength before the acid exposure.