Effect of calcium nitrate on hydration properties and strength development of calcium sulfoaluminate cement

Global lithium salt price surges drive up costs for high-performance repair materials, creating demand for cost-effective alternatives. Calcium nitrate (CN), with its low production costs and capacity to enhance early cement strength, emerges as a preferred choice. Limited knowledge on combining calcium sulfoaluminate (CSA) cement and CN prompts further exploration for a potentially cost-effective solution in repair materials. This study investigated the impact of varied CN contents on fluidity, setting time, compressive strength, electrical resistivity, heat of hydration, hydration products, and pore structure of CSA cement. The results show that CN can enhanced fluidity, significantly reduced setting time, accelerated hydration process, shortened the hydration induction period, and promoted the nucleation and growth of ettringite. When CN content was 8%, the compressive strength of samples reached its peak at 40.8 MPa, 44.9 MPa, and 47.3 MPa at 3 d, 7 d, and 28 d, respectively. Exceeding 8% CN content will increase the cumulative heat release which reach the maximum of 314.5 J·g−1 at 72 h. The addition of CN will generate the NO3-AFm phase and improve the stability of ettringite, as well as refine the pore structure of the samples but increase their total porosity.