Strengthening Mechanism for the Mechanical Properties of Cement-Based Materials after Internal Nano-SiO(2) Production

This study focuses on overcoming the agglomeration issue of nano-SiO(2) powder in cement, facilitating the strengthening mechanism of cement-based materials. A nano-SiO(2) precursor solution (NSPS) was added to cement-based materials to replace nano-SiO(2) powder. The influencing laws of the alkalinity and dosage of the NSPS on the mechanical properties of cement were investigated. Further, the strengthening mechanism of the mechanical properties of cement-based materials after internal nano-SiO(2) production was analysed. The results show that (1) when the alkalinity of the precursor solution is a weak acid (pH = 6), the compressive strength of cement-based materials after internal nano-SiO(2) production is 25%~36% higher than that of pure cement-based materials and 16%~22% higher than that of cement-based materials with silica fume; (2) when the solid content of SiO(2) in the current displacement solution is about 0.16% of the cement mass, the compressive strength of the prepared cement-based material is the highest. With the continuous increase in the solid content of SiO(2) in the precursor solution, the compressive strength of cement-based materials after internal nano-SiO(2) production decreases but is always greater than the compressive strength of the cement-based material mixed with nano-SiO(2) micro powder. According to a microstructural analysis, nano-SiO(2) particles that precipitate from the precursor solution can facilitate the hydration process of cement and enrich the gel products formed on the cement particle surface. In addition, new network structures among cement particles are formed, and precipitated nano-SiO(2) particles fill in the spaces among these cement particles as crystal nuclei to connect the cement particles more tightly and compact the cement-based materials. This reinforces the mechanical properties of cement-based materials.