EFFECT OF NANO SILICA AND SILICA FUME ON DURABILITY PROPERTIES OF HIGH PERFORMANCE CONCRETE

During the manufacturing process of cement, when limestone and clay are crushed and heated at high temperature, there is emission of global warming gasses including carbon dioxide (CO2) into the atmosphere. The current atmospheric concentration of CO2 has reached an alarming high value to the tune of 410 ppm (April, 2017), it has become obligatory to use a Green concrete to decrease CO2 emission from cement industry. Aim of the paper is to highlight the utilization of nano silica in high performance concrete in order to reduce the environmental pollution and to increase the durability properties. In this Experimental work, the cement was partially replaced by nano silica with the percentage of 2%, 3% & 4% and replacement level of silica fume was kept constant at 8% for four different water cement ratios (W/C). The samples were casted and tested for durability properties (Abrasion and Rapid chloride penetration test) of high performance concrete for different ages along with Scanning Electron Microscopy and Energy Dispersive Spectroscopy test. The results were statistically analyzed. The experimental results show that the best results of Abrasion and Rapid chloride penetration test were found at 0.30 W/C ratios and at the replacement level of 4% of nano silica and 8% silica fume for 56 days of curing for 0.30 W/C ratios. The Scanning Electron Microscopy (SEM) and Energy Dispersive Spectroscopy (EDS) test results showing the level of Ca (OH)2 in plain concrete and consumption level of Ca(OH)2 along with level of CSH in concrete containing nano silica & silica fume have also been presented. The results of all the four W/C ratios have been found statically significant. The results show that the use of nano silica and silica fume as replacement of cement not only makes the concrete more durable against the environmental agencies but also reduces the emission of CO2 during the production of cement. It also solves the waste disposal problem along with saving of the natural resources.