A Novel SiO<sub>2</sub>@CLDH Core-Shell Nanocomposite Strategy for Enhanced Early Strength and Chloride Resistance in High-Volume Slag Cement-Based Materials

To reduce environmental impact and CO2 footprint, ground granulated blast furnace slag (GGBS) is extensively used to replace cement in cementitious materials. High-volume GGBS systems enhance chloride transport resistance but significantly reduce early-age strength, limiting application in chloride-laden environments. This paper aims to enhance early strength and chloride resistance in high-volume GGBS composites through novel nano-SiO2@CLDH core-shell additives. Nano-SiO2@CLDH core-shell material was synthesized via in situ coprecipitation of layered double hydroxide (LDH) on nano-SiO2 followed by calcination. Results show SiO2@CLDH exhibits greater specific surface area than pure CLDH. Compared to individual nano-SiO2 or CLDH, SiO2@CLDH incorporation more significantly enhances early strength in high-volume GGBS composites. Chloride migration coefficients are also more substantially reduced. This enhancement mechanism involves accelerated cement hydration, improved chloride-binding capacity, and microstructural densification induced by SiO2@CLDH.