Synergistic action of nano silica and w/b ratio on accelerated durability performance of concrete

Cement, which is a primary component of concrete and the manufacture of which generates a significant amount of CO2, has an adverse effect on the environment. The environmental effect of manufacturing cement may be decreased by focusing on improving their durability criteria. Sufficient number of nanoparticles may be incorporated to the concrete mix to change the cementitious materials' nano-structure and increase concrete's durability as well. The present article examines the synergistic influence of nano silica (NS) and water-binder (w/b) ratio on concrete subjected to aggressive chemical environment and thus examines the durability of the mix. To study the tendency of binary mix concrete with NS subjected to aggressive environment; acid test, sulphate test and chloride resistance test have been conducted in laboratory. To meet the research objectives the concrete specimen was exposed to 5% sulphuric acid, 5% sodium sulphate and 5% sodium chloride respectively for 60 days. To perform this study, eighteen mix proportion were prepared for M35 concrete by six partial replacement level of cement with NS, viz. 0, 0.5, 1.0, 1.5, 2.0 and 2.5% and three dissimilar w/b ratio, viz. 0.36, 0.40 and 0.44. The percentage drop in weight and compressive strength of concrete specimen after the chemical attack has been measured. The test results showed that there is significant effect of NS and w/b ratio on improving the resistance of concrete towards chemical attack. But the effect of NS inclusion was more prominent than w/b ratio. To gain extra insights for the durability of the mix, flexural tensile test and split tensile strength test was performed. To investigate the morphology and properties of the mix at microscopic level scanning electron microscope (SEM) test was also performed.