Impact of treatment methods on recycled concrete aggregate performance: a comprehensive review

The disposal of construction and demolition waste (CDW) poses a critical global environmental challenge, driven by the low recyclability of concrete due to the limitations of recycled aggregates (RA). These aggregates suffer from the high porosity of attached mortar, resulting in elevated water absorption, reduced density, and diminished mechanical performance, restricting their application in structural concrete. This comprehensive review examines innovative treatment methodologies—either removing or strengthening the attached mortar layer—aimed at mitigating these issues. The paper synthesizes findings from over 150 studies, offering a critical analysis of treatment effects on physical, mechanical, and durability properties of RAs and their corresponding concretes. The review highlights the most effective removal treatment methods, including ball milling and autogenous cleaning, and strengthening methods such as carbonation, polymer impregnation, and nano-silica treatments, demonstrating significant improvements in density, strength, and chloride resistance. Recommendations are provided for scaling these treatments, integrating durability testing, and exploring life-cycle assessment to ensure the environmental and economic feasibility of RA applications. This work underscores the transformative potential of RA treatments in advancing circular economy principles, making recycled concrete a sustainable solution for structural and non-structural applications.