Deformation and permeability of recycled aggregate concrete : a comprehensive review

Properties of recycled aggregate concrete (RAC) were found to be dependent on the source, its composition and consistent quality of demolished concrete waste. Many studies have shown that using recycled aggregate (RA) in concrete suffers from strength and durability problems caused mainly due to relatively porous residual mortar adhered on the surface of aggregate grains resulting in high water absorption and increase in permeability and shrinkage. Also, the weaker interfacial transition zone (ITZ) of about 20–50 μm thickness in-between mortar and aggregate particles plays important role in reducing the bond strength between RA and fresh concrete, hence the physical and mechanical properties of RAC are usually inferior than virgin aggregate concrete (VAC). This review paper focuses on two main characteristics of RAC: (a) deformation (shrinkage and creep); and (b) permeability (carbonation, chloride ingress and air and water penetration) which have a direct effect on the durability of RAC and recommends methods for the mitigation of their adverse effects. The effects of mineral admixtures, water to cement (w/c) ratio, and high-range (HR) superplasticisers on the durability properties of RAC have been reviewed. This research showed that a very meager number of authors (only 12 publications) have focused on both the essential durability characteristics i.e., deformation and permeability together; therefore, we feel a need to present a review focusing on both of these essential properties