Effect of Microsilica and fly ash on the strength of concrete

In present study, concrete has been partially replaced with micro-silica which acts as a by-product in electric furnace and fly- ash which is a by-product in thermal power plants. Both these materials have been partially replaced with cement to economize the production of concrete as well as to have high strength. Apart from economization, this w ill also help in reducing the environmental losses. This replacement w as made by considering water-cement ratio as 0.45 and it has been observed that about 5% replacement of cement by microsilica cement improves compressive strength and flexural strength of the concrete specimens. In today's world, almost all the structures have been found to have concrete as an important building material which is a mixture of sand, cement, coarse aggregate and water. In order to construct bridges, dams, retaining walls, high rise building and chimneys, con- crete has been an important building material. Cement is an im- portant material in concrete, manufacture of which is expensive and a cumbersome process. Moreover, certain materials which have properties similar to cement like fly-ash, slag, micro-silica etc are emitted as a waste product from industries and power plants. These materials can be successfully applied as a replacement to cement and reduce the cost of production to a great extent. These materials also tend to produce huge environmental problems if left exposed and unattended. Therefore, their utilization in making of concrete mix is not only cost effective, but also eco-friendly in nature. In present study, effectiveness of these materials in improvising the strength of concrete has been tested after 7, 14 and 28 days respectively. The porosity and fineness of fly-ash and micro-silica have been found to develop similar compressive strength as in case of cement with a much lower cost. When water is added to the cement paste, chemical reaction takes place as a result, of which hydration lime is generated. This lime has been found to be susceptible to deterioration of strength and weathering effects. These pozzolanic material produce cementitious properties which on reaction to lime, convert to calcium silicate hydrate thereby, providing sufficient strength and durability.