Inflence of different recycled concrete aggregate treatment methods on the performance of concrete: a comparative assessment

Rapid urbanization and infrastructure development around the globe is causing surge in the construction and demolition (C&D) waste generation resulting into exhaustion of natural resources and waste disposal problems. Recycling of C&D waste in the concrete is considered a sustainable way. However, recycled concrete aggregates (RCA) with inferior properties are produced as compared to virgin natural aggregates. This study aims to improve the RCA performance utilizing different treatment methods and to evaluate the properties of the resulting recycled aggregate concrete (RAC). For this reason, modifid carbonation treatment along with four other treatment methods (i.e. carbonation, acetic acid immersion, acetic acid immersion with rubbing and acetic acid immersion with carbonation) were adopted to improve the quality of RCA. Variety of physical properties of RCA were evaluated to understand the effect of treatment methods. Compressive, split tensile and flxural strength tests were performed on all the concrete mixes incorporating treated RCA. Moreover, stress-strain behavior of RAC with treated and un-treated RCA was also studied. 20% and 17% drop in the water absorption was observed for the RCA treated by the modifid carbonation and carbonation techniques, respectively. Decrease in the crushing value was also observed for the all the treated RCA. Mechanical properties of RAC incorporating treated RCA were also enhanced, with the maximum improvement observed for mixes having RCA treated by the modifid carbonation and acid immersion with rubbing methods. For instance, 24% and 28% rise in compressive strength was noticed in the modifid carbonation and acid immersion with rubbing treated RCA mixes, respectively. Scanning electron microscopy of RAC incorporating treated RCA also showed a dense microstructure as compared to un-treated RCA mix.