Mechanism of SCMs on the hydration, pore structure, and durability of UHPFRC

To mitigate cement overuse and associated CO₂ emissions, incorporation of supplementary cementitious materials (SCMs) offers a sustainable strategy for producing eco-friendly ultra-high-performance fiber-reinforced concrete (UHPFRC). This study investigates the effects and underlying mechanisms of replacement of ground granulated blast furnace slag (GGBS) and limestone powder (LP) on hydration, pore structure, mechanical properties, and durability of UHPFRC. Results show that GGBS significantly improves durability, with optimal performance at 30 wt%, attributed to enhanced secondary hydration and reduced pore connectivity. In contrast, LP offers strength benefits at 15 wt% but adversely affects chloride resistance due to poor fiber-matrix bonding. Correlation analysis indicates that chloride resistance in UHPFRC is primarily governed by pore structure and fiber-matrix interfacial transition zone refinement, wherein GGBS enhances both through secondary hydration, while LP tends to impair interfacial bonding at elevated replacement levels. The results offer a scientific basis for designing SCM-incorporated UHPFRC with enhanced durability and sustainability.