Modification of recycled aggregate and conservation and application of recycled aggregate concrete: A review

Accumulated construction and demolition waste (CDW) can occupy much land and cause environmental pollution. To dispose of CDW and slow down the depletion of natural resources, the use of recycled aggregates (RA) prepared from CDW as a substitute for natural aggregates (NA) in preparing concrete materials has become an essential trend in the construction materials industry. RA has high porosity, which affects concrete's mechanical strength and durability. In this paper, it is concluded that chemical modification-removal of adhered mortar (AM), physical modification to enhance AM, biological modification, and composite modification can improve the performance of RA to varying degrees. Then, the performance of recycled aggregate concrete (RAC) can be further enhanced by various forms of curing. Meanwhile, combining factors such as economic efficiency and carbon emissions, it is also found that the replacement rate of RA and the transport distance are the main factors limiting the large-scale application of RAC. This paper addresses three aspects of RA modification, RAC maintenance, and RAC application. The study results help RAC to be applied accurately and on a large scale in practical projects, reducing environmental damage and lowering carbon emissions.