Effect of different aggregate treatment techniques on the freeze-thaw and sulfate resistance of recycled aggregate concrete

The inferior durability of recycled aggregate concrete (RAC) is causing hindrance in the application of recycled concrete aggregates (RCA) in structural concrete. This research focuses on the influence of different treatment methods of RCA on the freeze-thaw and sulfate resistance of resulting concrete. For this reason, freeze-thaw and sulfate resistance tests were conducted on carbonated RAC (C-RAC), lime carbonated RAC (LC-RAC), acetic acid immersed RAC (A-RAC), acetic acid immersed and rubbed RAC (AR-RAC) and acetic acid immersed and carbonated RAC (AC-RAC). Furthermore, mechanical properties and porosity of all the specimens were also explored. The results of this study showed improved mechanical performance and porosity of treated RAC. Enhanced frost and sulfate resistance was also observed for the treated RAC specimens. For example, 23, 17, and 21% reduction in the weight loss was noticed for LC-RAC, AR-RAC, and C-RAC after the freeze-thaw test than RAC specimens, respectively. Similarly, 24 and 19% less reduction in compressive strength was observed after sulfate exposure for LC-RAC and AR-RAC than RAC specimens, respectively. Scanning electron microscopic images of specimens after freeze-thaw test also showed lesser microcracks and denser interfacial transition zone for AR-RAC and LC-RAC than RAC supporting the improved frost resistance due to RCA treatment. Based on the results obtained in this study, LC-RAC and AR-RAC may be used in colder and sulfate-rich environments leading towards sustainable construction. Furthermore, regression models developed in this study show that the durability performance of concrete can be estimated through the physical properties of aggregates leading towards the durable and eco-friendly design of concrete structures.