Functionalization of waste-derived artificial aggregates: A state-of-the-art review

In modern civil engineering, advanced concrete materials are expected to not only possess excellent mechanical and durability properties but also exhibit additional functions. Waste-derived artificial aggregate (AA) is an innovative designable aggregate type with high sustainability and value-added properties. This study provided a comprehensive literature review on the functionalization of designable AA for the first time. The intrinsic characteristics of AA that are potential for realizing its functionalization were first introduced, where the AA's porous structure and chemical reactivity were ideal for internal curing, self-healing, purification, or foamed concrete application. Then, the functionalities of AA through encapsulating modification materials were discussed, where encapsulating AA with polymers or bacteria could enhance self-healing, combining AA with phase change materials allowed for energy efficiency, and adding additives like carbon fiber or magnetite could offer AA with conductivity and electromagnetic shielding characteristics. Additionally, the structural designs of AA for improved functions were summarized, where core-shell and hollow designs in AA could improve heavy metal immobilization and create cavities for specialized applications. Finally, the future perspectives of the AA functionalization technology were proposed. The contributions of this review could provide helpful guidelines for the future development, promotion, and practical applications of sustainable AA with additional functions.