Study on strength durability and bond characteristics of concrete containing nano silica

Abstract

Concrete has come a long way since its birth during the Egyptian era. With the help of concrete technology, we have started making concrete that are durable and strong. Concrete, being a porous material, is susceptible to damage by infiltration of harmful substances through its external surface and their advancement through the pore system leading to various durability problems. The passage of water in the pore structure of concrete plays an important role in the deterioration of concrete structure. Durable reinforced concrete is the need of the hour. The financial losses due to the durability problem have made researchers work on ways to make superior and resilient concrete. Several techniques have been developed to assess the residual life time in existing constructions and to evaluate their corrosion resistance capability. When Nano Silica (NS) is added with the concrete mix, it reacts with free calcium hydroxide, increasing the quantity of calcium silicate hydrate and resulting in a higher densification of the matrix, which increases the strength and durability. This research work is principally concerned with the strength and durability properties of the concrete containing NS and also intends to study the effect of corrosion on the pull-out and flexural bond strength of concrete containing NS. The effect on water demand was first confirmed by consistency tests on cement paste with NS and without NS. The consistency test showed an increase in water demand with the increase in NS content. Then slump test was conducted on the designed mix proportion and a slump of 98 mm was achieved. In the designed mix proportion, NS was added at 0.5% by weight of cement and the slump was 79 mm. So, superplasticizer was added by trial and error method till the desired slump value (nearly 100 mm) was achieved. Concrete cubes, cylinders, prisms, cylindrical disks, cylinder for corrosion test and beams for flexural bond test were cast. After curing, compression test, flexure test, split tensile strength test, modulus of elasticity test and ultrasonic pulse velocity test were conducted to find the mechanical properties of the concrete. A chipped off piece from the cube specimens was taken after 180 days from casting and it was subjected to an analysis under Scanning Electronic Microscope (SEM) to study the micro structure of the mortar. The durability properties were studied through sorptivity, Rapid Chloride Penetration Test (RCPT), acid attack, sulphate resistance and corrosion resistance tests. Pull-out and flexural bond strength was tested between concrete and steel when NS was used. Effect of corrosion on the bond strength was also tested. newline