Toxicity characteristics and durability of concrete containing coal ash as substitute for cement and river sand

Abstract

The main aim of this study was to investigate the toxicity characteristics and durability of concrete containing bottom ash (BA) and fly ash (FA), as partial or total replacement of fine aggregate and Ordinary Portland cement (OPC), respectively. Concrete mixtures were prepared containing 0, 20, 50, 75 and 100% of BA as a substitute for river sand and 20% of FA as a replacement for OPC. Tests carried out were Toxicity Characteristics Leaching Procedure (TCLP), sulfate and acid attack (change in compressive strength, microstructure and weight) and elevated temperature effects (loss in compressive strength and mass as well as change in pulse velocity). Results showed that submerging coal ash concrete (CAC) mixtures in 5% sulfuric acid solution resulted in less reduction of compressive strength and mass loss compare to that of the control concrete. Moreover, sulfate resistance tests on concrete mixtures indicated that there were no mass loss and no reduction in compressive strength of all the mixtures after submersion in 5% magnesium sulfate solution. CAC showed higher weight loss and greater compressive strength reduction at elevated temperatures. From TCLP results, it is concluded that none of the elements leached higher than the maximum concentration of contaminants for toxicity characteristics. It indicates that transportation, disposal and utilization of BA and FA as clean construction material's replacement could be utilized to reduce their environmental problems, increase efficiency and reduced unit cost production of concrete.