Nano-Silicon Dioxide-Optimized Cementitious Composite Material in the Restoration of Concrete Cracks in House Building

Abstract

This study aimed to investigate the restoration performance of nanocomposite materials used in house building. The ethyl orthosilicate was used as raw material, the sol–gel method was adopted to synthesize nano-silicon dioxide (SiO2), and the doped nano-SiO2 cementitious composite material was prepared. Then, the mechanical properties of the cementitious composite material based on different nano-SiO2 content was analysed through the characterization and performance test. The results showed that the nano-SiO2 prepared this time had regular crystal phases, small particle size, and certain thermal stability, with fully developed crystal grains. By analysing the mechanical properties of nano-SiO2 doped cementitious composites, it was found that the initial setting time and final setting time both showed an upward trend when the doped content of nano-SiO2 was less than 3%. Besides, the initial setting time and final setting time of cementitious composites decreased when the content was 3%–5%. The fluidity analysis indicated that the fluidity of cementified composites gradually dropped with the growth of nano-SiO2 content. The test results of mechanical properties of cementitious composites doped with nano-SiO2 revealed that the flexural strength and compressive strength of cementitious composites presented a trend of first rising and then falling, as the nano-SiO2 content rose. Shrinkage test results showed that the shrinkage rate of the gel composites increased with the growth of duration. The specific surface area and pore ratio measurement results indicated that the specific surface area of the cementitious composite doped with nano-SiO2 was 33.42 m2/g, and the porosity was small. In conclusion, the nano-SiO2-doped cementitious composite material synthesized in this study had good mechanical properties and could be applied in the repair of concrete cracks in house building.