A review on the properties of natural and recycled coarse aggregates concrete made with different coal ashes

This article emphasis the effective use of coals ashes in concrete which were generally dumped or used for low profile applications in early times. In meantime with profound studies, researchers started using coal ashes such as Fly Ash (FA), Coal Bottom Ash (CBA) and Pond Ash (PA) in concrete to reduce the dumped land sites to attain sustainable environment. Moreover, utilization of coal ashes in concrete overcome the risk of depletion of natural resources and also helps in to reduce the carbon emissions. Therefore, the current article presents a systematic review of 209 studies related to utilization of coal ashes which were carried out over a period of 70 years ranging from 1950 to present time. The performance of coal ashes (i.e., FA, CBA and PA) in concrete in terms of fresh properties such as water requirements and consistency of cement paste, workability of different concretes i.e., Normally Vibrated Concrete (NVC), Self Compacting Concrete (SCC) containing natural and recycled aggregates is critically evaluated and summarized. Further, the mechanical properties such as compressive strength and tensile strength and durability properties dealing from permeability consideration of concrete to chemical attack are also reviewed in this article. The different studies revealed that incorporation of FA in concrete as supplementary cementing material enhances the workability properties, mechanical strength and durable properties due to their fineness and pozzolanic effect. Similarly, CBA also gave positive results when used as fine aggregates in appropriate content in concrete.