Abstract: To overcome the problem of low early strength of supersulfated cement (SSC), the regulation effects and mechanisms of nano-SiO₂(NS) on the hydration hardening performance of SSC were explored. The effects of NS on the mechanical properties, chemical compositions, microstructure, morphology, and pore structure of SSC were studied. The results show that the incorporation of NS significantly improves the mechanical properties of SCC, in which the 3 d compressive strength increases by 32%, the 3 d flexural strength increases by 28%, and the 90 d compressive strength is nearly doubled. Meanwhile, NS significantly densifies the pore structure of SSC, reducing its critical pore diameter from 72.8 nm to 6.5 nm. The enhancement mechanism of NS is mainly to promote the hydration of slag and increase the formation amount and polymerization degree of C-(A)-S-H gel in the product. This work proves the feasibility of NS to improve the hydration hardening performance of SSC and provides a new idea for the performance enhancement of low-carbon SSC.

Key words: supersulfated cement, nano-SiO₂, early strength, hydration of slag, C-(A)-S-H gel, critical pore diameter