Eco-efficient self-compacting concrete with high-volume reclaimed asphalt pavement: multi-criteria optimization of structural and sustainability performance

This study addresses the challenge of ensuring structural integrity while maximising resource efficiency by proposing an integrated optimisation framework for self-compacting concrete (SCC) with high-volume reclaimed asphalt pavement (RAP). The framework combines a comprehensive multi-scale experimental investigation with multi-criteria decision-making (MCDM) to identify the optimal trade-off between mechanical performance and sustainability. Microstructural and physical analyses revealed that RAP inclusion leads to a weakened interfacial transition zone (ITZ), which was quantitatively linked to increased porosity and explained the observed quasi-linear reduction in mechanical properties. Crucially, despite this reduction, the 100% RAP mixture maintained a stable long-term compressive strength exceeding 44 MPa after 2 years, thereby satisfying C30/37 structural class requirements. From a sustainability perspective, full substitution yielded significant environmental and economic benefits, reducing raw material consumption by over 35% and costs by 9%. To resolve decision-making complexity, the MCDM analysis, tested under dual weighting scenarios, consistently identified mixtures with 60–100% RAP as the most balanced and eco-efficient solutions. This study confirms that high-volume RAP-based SCC is not only a technically viable but also a highly eco-efficient solution and provides a robust decision-support framework for engineers to promote circularity in the building sector.