Properties of concrete containing high volumes of coal bottom ash as fine aggregate

Abstract

Coal fired thermal plants in India produce about 131 million tons of coal ash, which comprises about 25 million tons of coal bottom ash. Utilization of coal bottom ash has environmental advantages also which are of great importance in the present context of sustainability of natural resources. The replacement of river sand with industrial by-products such as coal bottom ash in concrete can prove both technically and economically beneficial to the construction industry. In this study, laboratory tests were conducted to assess the possibility of the use of coal bottom ash as a substitute material of river sand in concrete. River sand was substituted with coal bottom ash by mass in concrete at 0, 30, 50, 75 and 100% replacement level. The test results show that 28 d compressive strength and pulse velocity through concrete were not affected on the use of coal bottom ash in concrete. Water absorption and initial rate of absorption of water by capillary action increased on incorporation of coal bottom ash in concrete manufacturing. However, the secondary rate of absorption of water was constant for all concrete mixtures. Water absorption varied between 4.68 and 5.56% for all concrete mixtures at curing period of 28 d. With increasing age, bottom ash concrete mixtures showed significant reduction in permeable pore space and water absorption. Abrasion resistance was measured in terms of average depth of wear. Bottom ash concrete mixtures displayed marginally lesser resistance to abrasion than control concrete. All the concrete mixtures showed decrease in the average depth of wear with increasing age, in other words increase in resistance to abrasion.