Fundamental behavior of recycled aggregate concrete - Overview II: Durability and enhancement

Although recycled aggregate concrete (RAC) has been extensively studied, several critical problems with its fundamental behaviors still urgently need to be figured out. Therefore, this series of two reviews re-thinks fundamental behaviors of RAC based on the latest literature. In the last review (part I), the mechanical and deformation behaviors of RAC were intensively discussed. Here in part II, the relationships between the replacement ratio of recycled aggregates (RA) and the durability of RAC are further presented. It is found that, owing to the increase of total porosity, the resistance of RAC to freeze-thaw cycles, carbonation, and chloride ion penetration is usually decreased with the increasing replacement ratio of RA. As a result, the steel corrosion and corrosion-induced cracking in RAC are more serious than those in natural aggregate concrete (NAC). The prediction models for carbonation and chloride ion penetration of RAC and the corrosion-induced crack patterns are also presented. To address the degradation on the performance of RAC, several enhancement technologies such as the combined/optimisation pre-treatment on RA and fiber reinforcement are put forward. Finally, the prospects of the high-performance/efficiency methodologies and applications of RAC are also shown.