The effects of silanized rubber and nano-SiO2 on microstructure and frost resistance characteristics of concrete using response surface methodology (RSM)

•The effects of different content of silanized rubber and nano-SiO2 on the frost resistance concrete were evaluated.•Pore structure, microstructure, and components were conducted on the freeze–thaw evolution of concrete.•The composite concrete with 5% silanized rubber and 3% nano-SiO2 has the best frost resistance and mechanical properties. Waste rubber powder can be used to enhance the frost resistance of cement concrete. Conventionally, only the rubber powder is directly mixed into concrete, but its mechanical properties are reduced significantly. However, mixing modified rubber, nanometer materials, lime ash, and cement concrete can improve the frost resistance and compressive strength of concrete at the same time. The main objective of this paper is to evaluate the potentiality of utilizing silanized rubber (SR) powder and nano-SiO2 (NS) to develop frost-resistant concretes. Determination of the frost-resistant effect of concrete mixture incorporated with SR and NS on the pore structure and mechanical characteristics was performed by response surface methodology (RSM). Results of scanning electron microscopy (SEM) tests along with Fourier transform infrared spectroscopy (FT-IR) are reported to evaluate the effect of frost resistance from microstructure. Results of the conducted tests show that the combination of SR and NS has a synergistic effect, which makes the distribution of voids in concrete more uniform, and the damage of mass loss rate and relative dynamic modulus of elastic (RDME) after a freeze–thaw cycle is lower. At the optimum content of designed concrete, there is a high correlation between frost resistance and void structure.