Utilization of construction and demolition waste and synthetic aggregates

Construction and demolition (C&D) waste are generated during the creation of structure or building or when renewing or demolishing a current structure. C&D waste exhibits many environmental problems including diminishing landfill, increasing wastage areas, landfill contamination, and increasing energy required for waste disposal and transportation. The re-using C&D waste as an aggregate in concrete making have reduced extraction demanding and landfill pressure. The utilization of C&D as recycled concrete aggregate (RCA) alternative to natural one not only decreases environmental problems but also leads to the conservation of naturally occurring resources. On the other hand, the synthesis of an aggregate from powdered industrial solid waste was also found to have a good alternative to natural aggregate with lower specific gravity and high thermal insulation. This work have reviewed the application of C&D and synthetic aggregates for making structural and non-structural concrete. Owing to the contaminants attached on the surface of RCA, the replacement of natural aggregate with this aggregate has resulted in a significant reduction in the performance of cement concrete. Therefore, many approaches have been done to enhance the quality of RCA. Among these different methods, the carbonation and pozzolan slurry are regarded as the best methods for enhancing the properties of RCA. Synthetic aggregate could be prepared by different methods including sintering, cold bonding, and autoclaving. Lightweight aggregate synthesized by the cold-bonding method could be successfully applied to fabricate a moderate strength lightweight concrete. More research is required to evaluate the resistivity of lightweight concrete containing autoclaved lightweight aggregate.