Research on optimizing performance of desulfurization-gypsum-based composite cementitious materials based on response surface method

[Display omitted] •Properties of desulfurized gypsum-based composite cementitious materials were studied by RSM.•Mechanical properties and water resistance of composite cementitious materials were studied.•The regression models for mechanical properties and water resistance were established.•The good fitting effects of the regression models were verified by experimental data. Desulfurization-gypsum-based composite cementitious materials were prepared by adding certain proportions of sulfoaluminate cement, mineral powder quick lime, retarder, and water reducer into the original desulfurization gypsum and semi-hydrated desulfurization gypsum. Based on the Box–Behnken design of the response surface methodology (RSM), regression models were established to evaluate the influences of various variables and the interactions between variables on the mechanical properties and water resistance of these composites. The significance of the fitted models was revealed by comparing the predicted results with experimental data. Additionally, the composition of the hydration products and the micromorphology of the hardened body were investigated by X-ray diffraction and scanning electron microscopy to explain the influence mechanism. The results showed that the strength and water resistance of the desulfurization-gypsum-based composite cementitious materials were affected by single factors as well as the interactions of pairs of factors. The analysis of variance and fitting precision also showed that the fitting effects of the established polynomial models were all high. The optimal contents of sulfoaluminate cement, mineral powder, and quicklime were 7.82%, 21%, and 5.22%, respectively, under which the composites exhibited excellent strengths and water resistance.