Effects of recycled aggregates on mechanical and fractural properties of concrete: Insights from DEM modelling

Limited understanding of how recycled aggregate (RA) affects the mechanical behaviour of recycled aggregate concrete (RAC) hinders its widespread adoption for sustainable construction. This study addresses the knowledge gap by employing discrete element method to investigate the impact of RA components on RAC mechanics. Results reveal that old aggregates, constituting the dominant volume within RA, determine the overall quality of RA. The mechanical properties of attached mortar and old ITZ can influence the formation of localised microcracks, their influence on the overall mechanical behaviour of RAC becomes negligible when the attached mortar content falls below 30%. Conversely, the strength of ITZ formed between the attached old mortar and the new mortar exhibits a significant influence. In essence, the findings suggest that the influence of RA components on RAC’s mechanical performance resembles the well-known “bucket effect” concept. Strategically improving the weakest component within RA could achieve a stiffer and stronger RAC.