The effect of different water/binder ratio and nano-silica dosage on the fresh and hardened properties of self-compacting concrete

This paper aims to study the effect of increasing water/binder ratio on the fresh and hardened properties of self-compacting concrete containing nano-silica with different dosages, focusing on the mixes with high w/b ratios that are produced in the field in places with hot weather. 12 mixes were designed with a total binder content of 350 kg/m3, three different water/binder (w/b) ratios of 0.41, 0.45 and 0.5 and 0%, 0.25%, 0.5% and 0.75% (by weight) replacement of cement by nano-silica. Self-compacting concrete was examined concerning fresh state properties and hardened state properties (mechanical and durability properties). Also, the densification of the microstructure of hardened concrete was verified by SEM examinations. The results showed that the effect of a certain nano-silica dosage on compressive strength of concrete with high w/b is greater than that on concrete with low w/b. While concerning durability, the results proved that the influence of a certain nano-silica dosage on low w/b mixes is greater than that on high w/b mixes. Also, the results showed that for mixes with high w/b, the nano-silica cannot compensate the significant decrease in durability caused by increasing w/b but can compensate only the strength reduction and segregation.