Deformation and sorptivity of recycled aggregate concrete produced by two state mixing approach
The amount of construction and demolition (C&D) waste has grown to such an extent that it has aroused much public concerns. Among them, concrete occupies more than seventy percent of the total C&D waste. As a result, landfill areas will soon be exhausted in the coming few years. However, owing to the uncertainty in using Recycled Aggregate (RA), practitioners are skeptical in using these as a natural aggregate substitute. Poor performance of RA is well acknowledged to be resulted from its higher porosity due to cement mortar remains attaching to the RA surface. Deformation and water sorptivity are of particular concern, which will affect the long term durability of building structures. To improve the quality of Recycled Aggregate Concrete (RAC), Two-Stage Mixing Approach (TSMA) is proposed, attempting to form a layer of cement slurry to fill the cracks and voids in the RA, leading to improvement at the interfacial zone of aggregate. In this study, the drying shrinkage, creeping, and water sorptivity of concrete made from the normal mixing approach and TSMA are compared. The results show that concrete from TSMA performs better than that from Normal Mixing Approach (NMA), which can be explained by the improved Interfacial Transition Zone (ITZ) around the RA. Moreover, the concrete mix that contains 20% RA substitution has performed the best.
Surveying and Built Environment