Effects of calcium sulfate as activator on mechanical properties of PVA fiber reinforced cementitious composites with high-volume fly ash

In order to study the role of calcium sulfate as activator in cementitious composites, mixtures with different calcium sulfate content ratios were designed. On the basis of satisfying the engineering castability, the effects of calcium sulfate on the mechanical properties of PVA-ECC with high-volume fly ash were investigated by uniaxial compression and tensile tests. The microstructure was analyzed by SEM and XRD. The results show that the addition of calcium sulfate has a certain activation effect and can promote the formation of ettringite. The early strength of PVA-ECC with high-volume fly ash was improved, and the tensile strain decreased by less than 0.92%. The fiber failure mode was analyzed according to the material failure mechanism. The “slip-hardening type” makes ECCs work better with PVA fibers, showing obvious strain hardening and multiple cracking characteristics. Based on the theoretical analysis, the evaluation method of obtaining high tensile strain was established, and the optimal mix ratio and calcium sulfate content of PVA-ECC with high-volume fly ash were proposed.