Compressive strength, drying shrinkage and chemical resistance of concrete incorporating coal bottom ash as partial or total replacement of sand

Coal bottom ash produced in large volumes by the coal fired thermal power plants is being dumped on land adjoining their sites over the years. Stockpiling of coal bottom ash on land is causing air pollution as well as posing a danger to living beings. The present research was aimed to evaluate the potential of coal bottom ash as fine aggregate in concrete. Utilization of coal bottom ash in the manufacturing of concrete will present economical as well as ecological way of their disposal and conserving the natural resources. The results of mechanical properties of concrete incorporating coal bottom ash were encouraging. Evaluation of durability aspects of concrete incorporating coal bottom ash as a sand replacement is as important as the mechanical properties. In this study compressive strength and durability aspects of concrete such as drying shrinkage, chloride ion penetrability, resistance to external attack of sulphate and sulphuric acid were examined by performing laboratory test. The test results indicate that bottom ash concrete exhibit better dimensional stability, slightly better resistance to sulphuric acid attack as compared to conventional concrete. Performance of bottom ash concrete under sulphate attack was almost identical to that by control concrete. No weight loss and reduction in compressive strength of bottom ash concrete specimens were observed after 180 days of immersion in 10% magnesium sulphate solution. No sign of sulphate attack was observed during examination of SEM image and XRD spectrum of concrete samples immersed in sulphate solution up to 180 days. Bottom ash concrete showed better resistance to chloride ion penetration.