Toward performance improvement of supersulfated cement by nano silica: Asynchronous regulation on the hydration kinetics of silicate and aluminate

Supersulfated cement (SSC) is a traditional low-carbon cement, but its slow hydration and strength development has limited its practical applications. Nano silica (NS) was used to activate the hydration of SSC by taking advantage of its ability to regulate silicate and aluminate reactions. The mechanical performance of various mixes was determined, as a function of sulfation degree and NS addition, as pore structure, phase assemblage, hydration degree, and microstructure. Results showed that NS improves the hydration degree of slag, densifies the microstructure, and significantly increases both early- and late-age compressive strength. The enhancement was attributed to its effects on the hydration of slag in SSC: delaying ettringite formation, but promoting C-(A)-SH precipitation, reducing microporosity. This study reveals the critical role of the regulation of hydration kinetics of silicate and aluminate in controlling the performance of SSC as NS does.