Utilization of Nano Silica & Fly Ash on the Workability and Compressive Strength of Ordinary Portland Cement

This paper focusses on studying the utilization of nano silica and flyash on the compressive strength of concrete containing different percentage of nano silica (NS) ranging from 0.3 to 1% (by weight) and a fixed proportion of fly ash (20% by weight) as a partial replacement of cement. The compressive strength of concrete is measured at 7 days & 28 days respectively. The effects of NS in microstructure development and pozzolanic reaction of pastes containing above fly ash content are also studied through Field Emission Scanning Electron Microscope (FESEM).Result shows that the maximum compressive strength is obtained with 20% of fly-ash and 0.75% of nano silica by weight of cement for both M20 & M30 grades of ordinary concrete. The strength found to be 20.76 MPa and 27.11 MPa for 7 days and 28 days respectively for M20 grade of nano silica & fly ash mixed concrete while the compressive strength of ordinary concrete of M20 grade comes out to be 15.06 MPa and 24.88 MPa for 7 days and 28 days respectively. Hence the maximum percentage increase in the compressive strength comes out to be 8.96 % for M20 grade of concrete in 28 days also the compressive strength found to be 31.73 MPa and 40.10 MPa for 7 days and 28 days respectively for M30 grade of nano silica & fly ash mixed concrete while the compressive strength of ordinary concrete comes out to be 23.17 MPa and 34.91 MPa for 7 day and 28 days respectively. Hence the maximum percentage increase in the compressive strength comes out to be 14.86 for M30 grade of concrete at 28 days.The test conducted on it shows a considerable increase in early-age compressive strength and a small increase in the overall compressive strength of the ordinary concrete.The FESEM analysis also supports the above findings