Effects of colloidal nano-silica on fresh and hardened properties of self-compacting lightweight concrete

The aim of this study is to investigate the effects of different levels of colloidal nano-silica (CS) on fresh and hardened properties of self-compacting lightweight concrete (SCLC). For this purpose, two concrete series including 16 concrete mixes with two water to binder (w/b) ratios of 0.35 and 0.45 were considered. The percentage of CS that replaced cement were 0%, 1%, 3% and 5%. Also, mixtures containing 0% and 10% MS were considered. The fresh properties of SCLCs were observed in terms of slump flow diameter and time, J-ring diameter, V-funnel time and U-box tests. The hardened properties were determined through mechanical properties (compressive strength, splitting tensile strength, flexural strength) and non-destructive tests (electrical resistivity and ultrasonic pulse velocity). The results of this work indicate almost all SCLCs satisfied the requirements of EFNARC. The results of hardened properties indicate that combined addition of MS and CS in SCLC was better than adding just one of them. The higher mechanical properties were obtained by ternary mixes containing 10% MS and 3% CS at both w/b ratios of 0.35 and 0.45. Moreover, the improvement of electrical resistivity and ultrasonic pulse velocity in ternary mixes were better than the binary and control mixes.