Recycling of Coal Ash in Concrete as a Partial Cementitious Resource

Concrete construction offers a great opportunity to replace the cement with a coal-based power plant waste—known as coal bottom ash (CBA)—which offers great environmental and technical benefits. These are significant in sustainable concrete construction. This study aims to recycle CBA in concrete and evaluate its particle fineness influence on workability, compressive and tensile strength of concrete. In this study, a total of 120 specimens were prepared, in which ground CBA with a different fineness was used as a partial cement replacement of 0% to 30% the weight of cement. It was noticed that workability was decreased due to an increased amount of ground CBA, because it absorbed more water in the concrete mix. The growth in the compressive and tensile strength of concrete with ground CBA was not significant at the early ages. At 28 days, a targeted compressive strength of 35 MPa was achieved with the 10% ground CBA. However, it required a longer time to achieve a 44.5 MPa strength of control mix. This shows that the pozzolanic reaction was not initiated up to 28 days. It was experimentally explored that 10% ground CBA—having particle fineness around 65% to 75% and passed through 63 µm sieve—could achieve the adequate compressive and tensile strength of concrete. This study confirmed that the particle fineness of cement replacement materials has a significant influence on strength performance of concrete.