Influence of coal bottom ash as fine aggregate on fresh properties of concrete

This paper investigates the influence of the use of coal bottom ash as a replacement for natural fine aggregates on the properties of concrete in the fresh state. Tests for water loss through bleeding, and the determination of the setting times and plastic shrinkage, were carried out in order to evaluate the material in the presence of bottom ash. The influence of the porosity of bottom ash on the potential water absorption and water loss of the material, as well as on the water consumption of concretes produced with bottom ash, is also discussed. The results showed that in the fresh state the concretes produced with the bottom ash are susceptible to water loss by bleeding and the higher the percentage of bottom ash used as a natural sand replacement the lower the deformation through plastic shrinkage. The results also showed that the setting time is affected by the presence of bottom ash in the concrete. In conclusion, different forms of bottom ash mix result in concretes with different properties in the fresh state, but the behavioral tendencies are maintained when bottom ash is employed as a replacement for natural aggregates. (C) 2008 Elsevier Ltd. All rights reserved.