Double-sided tuning effects of lactic acid on the hydration, microstructure and strength of supersulfated cement

In this study, hemihydrate gypsum was employed to produce supersulfated cement (SSC), and lactic acid was used to address the poor workability induced. The results indicated that lactic acid significantly improved the fluidity and setting time of SSC. In addition, lactic acid exerted a double-sided tuning effect on the hydration process of SSC. At the early stage, the hydration heat release decreased and fewer hydration products were generated, which led to a lower mortar strength. However, a greater number of hydration products formed after long-term curing that included a compact microstructure with less porosity, which contributed to the strength. This was attributed to the higher hydration degree of slag caused by chelation with lactic acid. Overall, SSC mixtures with moderate lactic acid content can obtain desirable properties in terms of both early-stage workability and long-term strength. The findings of this study facilitate a broader design and application of SSC mixtures.