Behaviour of sustainable slag enriched concrete: Effect of fully replacement of natural coarse aggregate with construction waste

Abstract

In construction domain and especially making concrete, the wise exploitation of natural resources along with the incorporation of recycled construction waste are solutions for making concrete an environmentally friendly construction material. This investigational study examines the performance of recycled aggregate concrete (RAC) made fully from recycled coarse (RC) aggregate. Only one mix made with natural coarse (NC) aggregate was prepared as a control for comparison purposes. The fresh concrete workability, the hardened concrete mechanical properties and the dynamic modulus of elasticity (Ed) were investigated. The impact of utilizing ground granulated blast furnace slag (GGBFS) as a replacement of cement at contents of 5%, 10%, 15%, and 20% on RAC performance was evaluated as well. Six mixes (two with no GGBFS and four with GGBFS) were prepared for measuring RAC behaviour. The findings of this study disclose that the workability (slump test values) decreases when GGBFS partially replaced cement in the mixes made fully with RC aggregate. A reduction of 26% in slump was observed when NC aggregate fully replaced with RC aggregate keeping cement without replacement and also in case of replacing only 5% of cement by GGBFS. Further reduction in slump was noticed when cement replacement by GGBFS increases in which the reduction reaches 43% for 20% replacement. Nevertheless, GGBFS can make a significant enhancement in concrete compressive strength as it almost reached 97% of NC aggregate concrete strength when 20% of cement replaced with GGBFS in the mix. The same positive effect of replacing cement with GGBFS was noticed in Ed results of concrete as well as resulted in slight enhancement in the density of the RAC.