Effect of nano-Al2O3 on the mechanical and microstructural properties of cement-based grouting material

The mechanical properties and microstructure of cement-based grouting materials are important parameters affecting the quality of geotechnical engineering, which are limited by the properties of added materials. At present, the exploration of nanomaterials has become the development trend of cement-based grouting materials. The results showed that NA can significantly improve the strength of NCBS. The most pronounced effect was observed when the dosage of NA was 1%; compared with the control group, the strength increased by up to 45.2%. NA particles accelerate the hydration reaction rate between cement and fly ash, generating a large amount of hydration products to fill the internal voids of NCBS. When the content of NA was 2–4%, the strength gradually decreased with an increase in the amount of NA addition. The catalytic and microaggregate effect of the NA particles were the primary contributors to the improved NCBS mechanical properties. Aggregated NA particles were the main cause of the decrease in strength. Acicular ettringite, fibrous calcium silicate hydrate, and NA particles are the dominant components that effect the strength and microstructure of NCBSs. By comparing the relationship between NA and the strength of NCBS and the relationship between the curing age and the strength of NCBS, it was found that NA can better reflect the compressive strength of NCBS, and the correlation degree of NA to the strength of NCBS is 76% higher than that of the curing age.