A comparative study on the distinct regulatory mechanisms of varied nanomaterials in recycled aggregate concrete

Journal article, 2026

This study systematically investigates the mechanistic distinctions in how the type of nanomaterials regulates the performance of recycled aggregate concrete (RAC) under comparable particle size conditions. Three nanomaterials-nano calcium silicate hydrate (NCSH), nano titanium dioxide (NTO), and nano silica (NS) were each incorporated at 2 wt% to evaluate their effects on mechanical properties, durability, and microstructural evolution. The results reveal pronounced time-dependent efficacy among the nanomaterials. NCSH exhibited the strongest enhancement in early-age mechanical performance, increasing 1-day compressive and splitting tensile strengths by 56.9% and 41.9%, respectively. In contrast, NS demonstrated superior long-term strength development and permeability resistance, achieving a 20.1% reduction in 28-day water absorption and chloride ion penetration. Microstructural analyses indicate that NCSH primarily accelerates early hydration and structural densification through homogeneous nucleation. NS refines the pore structure and reduces calcium hydroxide content via sustained pozzolanic reactions, while NTO contributes mainly through physical filling and microstructural packing. These findings provide a mechanistic basis for the targeted selection and synergistic optimization of nanomaterials in RAC systems tailored to specific performance requirements.