Coupling limestone powder with CFSH/PCE to enhance supersulfated cement: Hydration, microstructure and carbonation resistance.

Supersulfated cement (SSC) has the advantage of low carbon emissions, but its application is limited due to the limited availability of high-quality slag and slow early hydration. This study aims to balance SSC performance and economy by using limestone powder (LP) and CFSH/PCE. In this work, LP was used to replace slag at levels of 5%, 10%, and 15%, and 1.0% CFSH/PCE was introduced. Their effects on hydration kinetics, mechanical properties, phase assemblage, microstructure, and carbonation resistance of SSC were investigated in detail. The results show that the combined incorporation of LP and CFSH/PCE produced a significant synergistic enhancement compared with their individual use. This synergy can be attributed to the filler and nucleation effects of LP, which provided additional growth sites for the hydration products rapidly induced by CFSH/PCE, thereby reducing localized accumulation. With the combined addition of LP and CFSH/PCE, the 12 h compressive strength increased by 533-833%, while the 28 d compressive strength increased by approximately 8%. In addition, the pore structure is refined and the porosity is reduced, thereby improving the carbonation resistance. Among them, L10-F (10% LP + 1.0% CFSH/PCE) showed the lowest strength loss rate (i.e., 14.3%) after 28 d of accelerated carbonization. This study provides a feasible strategy for the application and performance improvement of ultrafine particles in SSC.