In the past fly ash was generally released into the

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In the past, fly ash was generally released into the atmosphere as it is difficult to decompose, but air pollution control standards now require that it be captured prior to release by fitting pollution control equipment. Fly ash is generally stored at coal power plants or placed in landfills. Due to the presence of pozzolanic activities, which is responsible for setting of concrete and provide concrete with more protection from wet conditions and chemical attack, fly ash can be used as a partial replacement for cement. Moreover, cement industry is the major contributor of pollution by releasing carbon dioxide. 1 ton of cement produces approximately 1 ton of carbon dioxide. So by partially replacing cement with pozzolanic material such as fly ash, the cement industry can serve both the purposes of meeting the demands of construction industry and at the same time producing green and clean environment. Fly ash is of two types class F and C. Class F fly ash is produced by burning of harder, older anthracite and bituminous coals. This fly ash is pozzolanic in nature and contains less than 7% lime (CaO). However, class C fly ash is produced by burning of younger lignite sub-bituminous coal. It possesses pozzolanic as well as self-cementing properties. In the presence of water, class C fly ash hardens and gets stronger over time. It generally contains more than 20% lime (CaO). 2. LITERATURE REVIEW The present study aims to study the effect of fly ash on concrete by partial replacement of cement with 0%, 10%, 20% and 30% of fly ash. Various research works have already been conducted to study the effect of fly ash on various properties of concrete at different ages and for different grades of concrete. Some research works were reviewed and are presented in this paper. C. Marthong [1] studied the effect of fly ash additive on concrete properties and found that the normal consistency increases with increase in the grade of cement and fly ash content. It was also concluded that the use of fly ash improves the workability of concrete. Moreover, it was also
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International Research Journal of Engineering and Technology (IRJET) e-ISSN: 2395 -0056 Volume: 04 Issue: 02 | Feb -2017 www.irjet.net p-ISSN: 2395-0072 © 2017, IRJET | Impact Factor value: 5.181 | ISO 9001:2008 Certified Journal | Page 316 observed that the compressive strength of concrete increases with the grade of cement. As the fly ash content increases in all grades of OPC there is reduction in the strength of concrete. The reduction is more at earlier ages as compared to later ages. Fly ash concrete was also found to be more durable as compared to normal OPC concrete. Aman Jatale [2] studied the effects on compressive strength when cement is partially replaced by fly ash and observed that the use of fly ash slightly retards the setting time of concrete. It was also found that the rate of strength development at various ages is related to the w/c ratio and percentages of fly ash in the concrete mix. Moreover, the modulus of elasticity of fly ash concrete also reduced with the increase in fly ash percentage for a given w/c ratio.
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