The incorporation of nano-silica (NS) into high-strength concrete has emerged as an effective approach to enhancing both mechanical and durability properties of cement-based materials. Owing to its extremely fine particle size and high specific surface area, nano-silica significantly influences the hydration process and microstructural development of concrete. This study investigates the effect of varying nano-silica contents on the fresh, mechanical, and durability properties of high-strength concrete. Nano-silica acts as a highly reactive pozzolanic material, accelerating cement hydration and promoting the formation of additional calcium silicate hydrate (C–S–H) gel, which leads to a denser and more refined microstructure. As a result, notable improvements in compressive strength, tensile strength, and flexural strength are observed, particularly at early curing ages. The presence of nano-silica also enhances the interfacial transition zone between aggregates and the cement matrix, reducing microcracks and porosity. This refinement contributes to improved resistance against water permeability, chloride ion penetration, and chemical attack, thereby significantly improving the durability performance of high-strength concrete. Additionally, nano-silica reduces bleeding and segregation, improving the homogeneity of the mix, although careful control of dosage and dispersion is required to prevent agglomeration and excessive water demand. Experimental observations indicate that an optimum nano-silica content exists beyond which strength and workability may be adversely affected.
Janardhan et al. (Thu,) studied this question.