Abstract:

Volume deformation caused by chemical shrinkage readily leads to material cracking， compromising structural integrity. As a novel low-carbon cementitious material， supersulfated cement exhibits significant differences in its hydration process and chemical shrinkage characteristics compared to traditional Portland cement. This study employed granulated blast furnace slag， phosphogypsum and cement clinker to prepare phosphogypsum-based supersulfated cement （SSC）， investigating the effects of phosphogypsum modification， phosphogypsum content， clinker content and water-binder ratio on SSC chemical shrinkage. The influence mechanisms were explored through microscopic testing characterisation. The results indicate that the chemical shrinkage value of SSC is approximately 0.046 mL/g at 7 d， accounting for roughly 77% of ordinary Portland cement （OPC）. Calcined phosphogypsum-based supersulfated cement （CSSC） exhibits a 17.39% reduction in chemical shrinkage value compared to SSC， while lime-neutralized phosphogypsum-based supersulfated cement （NSSC） shows the 65.21% increase in chemical shrinkage value relative to SSC. With increasing phosphogypsum content， the chemical shrinkage of SSC increases， reaching its minimum at 13% （mass fraction， the same below） phosphogypsum content. As the clinker content increases， the chemical shrinkage value of SSC initially decreases and then increases. The chemical shrinkage value is minimal at a 5% （mass fraction） clinker content. For SSC， chemical shrinkage value decreases with increasing water-binder ratio. The synergistic effect of 15% phosphogypsum and 5% clinker achieves optimal matching between ettringite formation and calcium silicate hydrate （C-S-H） gel structure， thereby attaining the optimum value for chemical shrinkage control.

Key words: supersulfated cement, chemical shrinkage, mechanism, phosphogypsum modification, phosphogypsum content, clinker content