Microstructural investigation of recycled aggregate concrete produced by adopting equal mortar volume method along with two stage mixing approach

Abstract

This article discusses about equal mortar volume (EMV) mix design method and two stage mixing approach for preparing recycled aggregate concrete (RAC) by considering the residual mortar content (RMC) on the surface of the recycled concrete aggregate (RCA). In this method of mix design, the suitable percentage of RCA component depends on the RMC value of respective RCA. For the present source of RCA, the suitable percentage of RCA component for the proposed method of mix design is found to be 61.01%. Eleven different concrete mixes are prepared with proposed mix design method in conjunction with ten different mixing approaches suggested in published research articles and one proposed two stage mixing approach (TSMAsic). The mechanical properties of the concrete prepared from the above mixes are compared among all and with the control concrete mix which is produced by following conventional mix design method from natural coarse aggregate (NCA). The best mechanical properties are found to be for the concrete prepared with proposed EMV mix design method and two stage mixing approach, and the properties are nearly similar to that of control mix. The microstructural analysis reveals the reason for the improvement of interfacial transition zone (ITZ) and the properties due to the adoption of the EMV mix design method and the mixing approach. Quantitative analysis and elemental mapping are also carried out to know the presence of strength contributing elements.