Use of recycled coarse and fine aggregates in structural eco-concretes. Physical and mechanical properties and CO2 emissions

Abstract

This study analysed the effect of simultaneously replacing 0% to 100% natural with recycled concrete coarse aggregate and natural fines with 50% recycled concrete or mixed CDW fines. Characterisation of these new secondary raw materials is followed by an analysis of the effect of their use on the fresh and hardened state properties of the resulting eco-concretes. The implications for the mechanical requirements laid down in the existing legislation are determined and proposals put forward for new expressions for calculating splitting tensile and flexural strength. The CO2 emitted (global warming potential, GWP) by the new formulations is also explored and eco-efficiency, defined as the ratio between strength and CO2 emissions, is assessed. The findings show declines of no >17% in compressive and tensile strength with these new aggregates and in flexural strength of <15%. Emissions analysis reveals that ecoefficiency is enhanced with the separate or joint use of recycled coarse and fine aggregates, due to the CO2 emissions abatement ensuing.