Effect of incorporation of high volume of recycled concrete aggregates and fly ash on the strength and global warming potential of concrete

Abstract

This study presents the effects of using supplementary cementing materials and recycled concrete aggregates (RCA) in concrete, with emphasis on the ability of using high volumes of fly ash (FA) and RCA to reduce the environmental impacts of the concrete's production process without jeopardizing most of its long-term durability characteristics. Three mix families (0% fine RCA, 50% fine RCA and 100% fine RCA) were produced and, for each of these three families, two incorporation levels (0% and 100%) of coarse RCA were used with 0%, 30% and 60% of FA without SP. In addition, in order to see the effect of w/b ratio and admixture, more than half of the mentioned concrete mixes were repeated using superplasticizer (SP). In order to optimize the concrete mixes, the hardened properties, namely compressive strength, and environmental impacts of production, namely global warming potential (GWP), were obtained for each concrete mix. The results of this investigation show that using FA in RCA concrete is advisable from the strength and environmental impact points of view. The optimum mixes in terms of strength and environmental impacts are the ones made with incorporation of both RCA and FA rather than individual incorporation. It was also found that the strength to GWP ratio of concrete mixes depends on the FA-RCA incorporation ratio rather than the content of the individual materials.