Replacement of Cement by Fly Ash in Concrete

From the very beginning of the nineteenth century,it has been come to light that Fly Ash may substitute cement in concrete industry. It may be mentioned here that Fly Ash amounting to 15% to 25 % by mass has been used as cementitious material in concrete. The compressive strength of concrete was examined by replacing different proportions of cement with Fly Ash. However, the actual amount to be used mainly depends on the properties of Fly Ash, methods of applications as well as the Geographic location and climatic condition of the area concerned. A various numbers of research works in regards to use Fly Ash as additive in cement, admixture, n concrete and cement replacement material were done. But most of the research works were related to few percentages of cement replacement for the concrete of lower grades.In this context, an experiment is carried out to examine the effects of Fly Ash on compressive strength of different high grade concrete for different quantity of Fly Ash, taking into account different curing periods. An investigation has also been conducted to examine the effects of Fly Ash on mechanical properties of fresh and hardened concrete by mixing different grades of concrete with varying percentage of Fly Ash. The compressive strength of concrete was measured by 7, 28 and 60 days and the compaction factor was taken from the measurement of workability. Considering the different rate and strength as parameters a comparative study has been conducted .By replacing different proportions of cement with Fly Ash ,the compressive strength of cement has been checked and the results have been found effective and applicable. This paper analyses vividly the effects of Fly Ash as partial replacement of cement in concrete and to ascertain the use of optimum quantity of Fly Ash for different qualities of concrete which will be acceptable , applicable and economical. Here it is also explained the variation in compressive strength of different qualities of concrete at different percentage of Fly Ash at various curing periods.