An investigation on the suitability of coarse recycled concrete aggregate for structural concrete

Abstract

In view of the fast-depleting natural rock resources and shrinking land space for waste newlinedisposal, using coarse recycled concrete aggregate (RCA) in place of natural coarse newlineaggregate (NCA) to manufacture structural grade concrete is a highly sustainable newlineoption. Since coarse aggregate constitutes the bulk of any concrete, preferential use of newlineRCA-concrete (RAC) over NCA-concrete (NAC) has four distinct advantages: newlinereduction of waste, best reuse of waste, savings in construction cost and savings in newlinenatural rock resources. However, the practice is tardy mainly due to concerns over the newlineworkability, strength and durability of RAC which are sought to be addressed in this newlineresearch. newlineRAC produced in the early literature by mere percentage replacement of NCA with newlineRCA, without accounting for the residual mortar attached to the RCA particles, newlinecontained considerably high volume of mortar and low volume of virgin coarse newlineaggregate leading to significantly inferior all-round performance. In later studies, this newlinehas been addressed by suitably proportioning the concrete mix based on the newlineequivalent mortar volume (EMV) method. In the present study, through the fusion of newlinethe EMV method with the IS 10262 mix-proportioning steps and the novel two-stage newlineadministration of the normal 0.2% dosage of super-plasticizer, the issue of newlineworkability of RCA-concrete (RAC) has been largely resolved, and the need for newlineadmixing air-entraining agent suggested in the literature has been obviated. With newlinethese two innovations, RAC in this study is overall found to exhibit better newlineperformance than its companion NAC in terms of both fresh and hardened properties newlinelike workability, flowability, filling ability, cube compressive strength, modulus of newlinerupture and splitting tensile strength. newline