Effects of Dual Incorporation of Nano-SiO2 and Nano-CaCO3 on the Abrasion Resistance and Microstructure of Concrete

Seven sets of concrete containing different mass ratios of nano-SiO2 (0%–5.0%) and nano-CaCO3 (0%–1.5%) were designed. A total of 28 concrete cube specimens cured for 7 and 28 days were tested for compressive strength (14 specimens) and split tensile strength (14 specimens), while 7 cylindrical specimens cured for 28 days were tested for impact resistance. The impact resistance of the concrete specimens was quantitatively analyzed by using impact strength (fa) and wear rate (La), and the effect of dual incorporation of nano-SiO2 and nano-CaCO3 on the microstructure of concrete was further investigated by XRD and SEM. The experimental results indicate that the incorporation of 5.0% nano-SiO2 and 1.5% nano-CaCO3 improves the mechanical properties and impact resistance of concrete most significantly, and the compressive strength, split tensile strength, and impact resistance increase by around 37.80%, 35.31%, and 183.36%, respectively, compared with that of ordinary concrete. At the microscopic level, nano-SiO2 reacts with C-H in a secondary hydration reaction to increase the number of C-S-H gels, which improves the pore structure in the matrix and favorably enhances the adhesion between aggregate and cement paste in the weakened layer, thus improving the abrasion resistance of concrete.