The Influence of Gypsum Dihydrate and Plasticizing Additives on the Properties of Sulfoaluminate Cements

Within the framework of the conducted research, a comprehensive assessment of the influence of chemical plasticizing additives of differ-ent natures on the rheological and physico-mechanical properties of special cement systems based on calcium sulfoaluminate clinker was performed. The objects of the study were the polycarboxylate ether-based superplasticizer MELMENT F10 and the new generation hyper-plasticizer MELFLUX 4930F. The study involved varying two key parameters: the type and dosage of the plasticizing additive, and the amount of dihydrate gypsum (CaSO₄·2H₂O) introduced into the binder composition. Gypsum plays a critical role in regulating the hardening kinetics and the formation of the final structure of calcium sulfoaluminate cement. As a result of the experiments, a clear dependence between the nature of the additive and the construction-technical characteristics of the composites was established. The hyperplasticizer MELFLUX 4930F demonstrated significantly higher efficiency compared to the superplasticizer MELMENT F10. Its application provided a significant reduction in the water demand of the mixtures while simultaneously improving workability, which positively affected the density and strength of the hardened paste. Based on the totality of the obtained data (compressive and flexural strength, standard consistency of cement paste, setting times), the optimal formulation composition was determined. The best results were recorded for the composition containing 5% dihydrate gypsum by weight of the binder and 0.5% hyperplasticizer MELFLUX 4930F. This particular combination ensured the formation of a cement paste with maximum strength indicators at early and late hardening ages, as well as high density and durability.