A comprehensive study on sustainable development of pavement quality concrete utilising fly-ash and copper slag

Huge requirement of aggregates and cement for the construction of a large network of concrete pavements, scarcity of natural resources, degradation of river beds due to unabated extraction of river sand (RS), and increasing generation of industrial wastes, motivate researchers to explore the utilisation of industrial wastes like fly ash (FA) and copper slag (CS) as replacement of OPC and RS respectively in the production of pavement quality concrete (PQC). Earlier studies have reported on the utilisation of these wastes independently for cheap and sustainable concrete. Though all such studies have been found to result in positive and improved results of PQC mixes, it is important to study the strength and durability aspects of PQC mixes containing these two waste materials together, along with cost and environmental impacts in view of ensuring sustainability. To fulfill this objective, forty-eight samples of M40 and M50 grade PQC mixes were prepared by using FA and CS in varying proportions. Compressive and flexural strength tests were conducted to satisfy the strength criteria of PQC mixes. Various durability tests conducted on PQC mixes included accelerated carbonation resistance, chloride resistance, sorptivity, slake durability and abrasion resistance. It is concluded from this study that all PQC mixes with 20% FA and 100% CS replacements have higher compressive and flexural strength as compared with the control mix. The durability characteristics such as resistance to chloride ion penetration, sorptivity value, slake durability and abrasion resistance, of PQC mixes improved. The cost of PQC slab of a a typical design thickness, made with CS and FA was found to decrease by 21%. The environmental factors like global warming potential (GWP) and embodied energy (EE) decreased by 27% and 25.8%, respectively. Considering the strength and durability aspects, cost and environmental impact, replacements OPC and RS by 20% FA and 100% CS respectively, contribute to development of the best satisfying and sustainable PQC mix for paving applications. This study may lead to a sustainable solution for concrete pavement applications which may preserve natural resources, reduce the waste disposal concerns, maintain ecology, and reduce the carbon footprint for future generations.