Use of Unprocessed Coal Bottom Ash as Partial Fine Aggregate Replacement in Concrete

Abstract

This paper investigates the use of unprocessed coal bottom ash as fine aggregate replacement in structural concrete in an attempt to contribute to a sound management of coal ash on the island of Mauritius. The coal bottom ash was obtained from FUEL thermal power station and had a loss of ignition of 11%. Experiments were conducted by replacing fine aggregate with bottom ash by weight in varying percentages (20%, 30%, 40%, 60%, and 80% respectively). The results showed that an increase in bottom ash content causes workability and plastic density to decrease and bleeding to increase. Moreover, above 40% replacement of bottom ash, compressive strength, flexural strength, and modulus of elasticity decreased sharply. In addition, an increase in bottom ash content improved the drying shrinkage performance of the concrete. The research also shows that 20% is the optimum percentage replacement to achieve favorable strength and good strength development pattern as a normal concrete mix with time. Unprocessed bottom ash from FUEL power station can thus be used as fine aggregate replacement in concrete for that specific percentage replacement. However, investigation should be carried out on the durability of the concrete.

Keywords: unprocessed bottom ash, fine aggregate replacement, structural concrete