A comparative study of nano-SiO2 and nano-Al2O3 on the improvement of concrete properties under low temperature curing conditions (5 °C)

This study systematically investigates the efficacy of nano-silica (NS) and nano-alumina (NA) in mitigating the detrimental effects of low-temperature curing (5 °C) on concrete performance through a multi-scale experimental approach. Macroscopic tests revealed that an incorporation of 2 % NS or 1 % NA not only optimized compressive strength under standard curing but also effectively counteracted the strength reduction induced by low-temperature curing. Microstructural analysis using Scanning Electron Microscopy (SEM), X-ray Diffraction (XRD), and Mercury Intrusion Porosimetry (MIP) revealed that both nanomaterials improve performance by densifying the pore system, speeding up the hydration process, and encouraging the generation of more calcium silicate hydrate (C-S-H) at the expense of calcium hydroxide (CH). Notably, 1 % NA yielded superior microstructural improvement compared to 2 % NS, achieving comparable mechanical enhancement at a 50 % lower dosage. The findings indicate that nano-alumina, owing to its higher efficiency and cost-effectiveness, presents an ideal admixture for producing durable concrete in cold-region applications.