SARCOS Project: Mechanical Performance, Durability and Sustainability of Composite Slabs with Recycled Concrete Aggregates

This study presents the results of the PRIN 2022 SARCOS Project, which investigates the mechanical performance, durability, and sustainability of Recycled Aggregate Concrete Composite Slabs (RACCS) for structural applications. The research aims to assess the feasibility of using high replacement ratios of coarse and fine recycled concrete aggregates (RCA) from construction and demolition waste in composite steel–concrete systems while maintaining acceptable structural performance under service and ultimate loads. An extensive experimental campaign was carried out on six concrete mixes with 0%, 20%, 30%, 50%, 70%, and 100% RCA content, identified as M0, M20, M30, M50, M70, and M100, respectively. Each mix was tested across three span configurations (2.40 m, 2.80 m, and 3.20 m), totalling 48 full-scale slab specimens. The experimental setup included cyclic preloading and monotonic loading until failure, with comprehensive monitoring through eight LVDTs capturing both flexural and longitudinal slip behavior. The results reveal that slabs with up to 70% RCA exhibit comparable peak load and ductility to those with natural aggregates. Horizontal slip measurements highlighted earlier and more sustained debonding phenomena in higher RCA mixes, yet without compromising global stability. These findings demonstrate the structural viability of using RCA in composite systems and suggest optimal performance at intermediate replacement ratios. The results contribute to the broader goal of promoting circular construction practices and reducing the carbon footprint of reinforced concrete structures. The study also provides a robust experimental database for validating numerical models and informing design code development for recycled aggregate concrete in composite applications.