Study on the mechanical properties and mechanism of cement concrete based on interface modification

In order to improve the mechanical properties of concrete, silica fume, an active admixture, was selected to replace cement and the effect of silica fume on the mechanical properties of cement paste and concrete was investigated. The mechanism of the peritectic effect of silica fume on concrete was investigated by SEM and XRD. The results showed that the incorporation of silica fume did not improve the mechanical properties of cement paste significantly. The 28d compressive strength of cement concrete based on interfacial modification was improved to a greater extent. When the amount of silica fume was 10%, the compressive strength of cement concrete based on interface modification was increased by 26.4 % compared with that of unmodified concrete. Comparing the SEM images of concrete before and after the interface modification, silica fume improved the structure and density of concrete interface, as well as the arrangement of hydration products CH at the interface. The silica fume has the characteristics of filling effect and pozzolanic reaction with CH. As the amount of silica fume increases, the CH content decreases and the C3S and SiO2 increase. By using the physical and chemical interaction between silica fume and hydration products, the effect of concrete interface modification can be achieved.