Effect of fly ash on properties of high strength concrete

Abstract

In high rise structures, high strength concrete has been successfully used in various countries across the world. High-strength concrete is used for resisting high compressive load and improved strength. But, the Cement content of the mix proportion for high-strength concrete is particularly high compared with conventional concrete strength. On the other hand, the production of cement involves the emission of large amounts of carbon-dioxide gas into the atmosphere; which aggravates global warming. So, because of this adverse impact on the environment, it needs to see another cementitious material. Fly ash is by product of coal burning, such material are used as partial replacement of cement in high strength concrete which reduce carbon-dioxide gas emission in to atmosphere and also minimizing the negative impact on the environment which released from industrial waste disposal as land fill. The objective of this study was to investigate the effect of fly ash on high strength concrete properties. Experimental laboratory tests were conducted. Slump height is measured to determine the workability of fresh concrete. The Cube size is (150mmx150mmx150mm) which is used for testing compressive strength for the age of 7, 14 and 28 days of curing. The percentage replacement of cement with fly ash varies from 0% to 30% by the increment of 5%. The total numbers of samples conducted are one hundred twenty six (126). The result of the study shows that the replacement of cement by fly ash up to10% increases the slump values. However, the replacement of cement beyond 10% by fly ash decreases the workability of fresh concrete. Regarding density and compressive strength, the replacement of cement by fly ash decreased the density of concrete. Besides, the compressive strength of concrete becomes improved and increased when the cement is replaced by fly ash up to 10%. At the curing age of 28th days, the concrete containing 5% and 10% fly ash as cement, gained 1.66% and 2.97% of strength respectively. So, this study suggests that partial replacement of cement by fly ash up to 10% increases the capacity of high strength concrete and workability of fresh concrete, So that the optimum percentage of fly ash to replace cement is 10% for high strength concrete.