Effect of Incorporation of Nano-Silica on Mechanical Properties of Mortar and Concrete

There are a number of applications of nanotechnology, particularly in concrete. The addition of nano-silica improves both the mechanical and durability properties of concrete. During the hydration process, the reaction of nano-silica with calcium hydroxide creates an additional calcium silicate hydrate bond, which improves the mechanical characteristics of concrete. The effect of the inclusion of nano-silica on the mechanical properties of paste, mortar and concrete is investigated in this study. Nano-silica was introduced as a replacement of cement from 1 to 5% with an increase of 1%. Various mechanical properties and setting time of different mixes were evaluated and compared with the control mix. The cement paste’s consistency increased while the setting time of the paste was reduced by 8 and 47%, respectively, due to the inclusion of nano-silica. The optimum dosage of the addition of nano-silica was 3%. At 3% of nano-silica, the compressive strength of the mortar specimen was higher than control mortar by 15 and 28% at 7 and 28 days, respectively. Above three percentages of nano-silica, the strength will be reduced. Similarly, in concrete, the inclusion of nano-silica by 3% led to an increase in compressive strength by 15 and 20%, respectively, at 7 days and 28 days over control concrete. Flexural and split tensile strength was also increased by 3% nano-silica by 15 and 22%, respectively. Nano-silica did not produce a significant change in the modulus of elasticity of concrete.