Comprehensive Investigation of Aggregate Gradation, Mechanical Performance, Durability, and Life Cycle Assessment of Multi-Recycled Aggregate Concrete for Sustainable Infrastructure Applications

• Successive recycling generations increase aggregate water absorption and alter density and specific gravity because of accumulated adhered mortar. • Particle-packing methods improve aggregate packing efficiency; the reported increases over IS 383:2016 were 23.07% for MTM, 26.83% for JDD and 14.28% for CPM. • CPM-based proportioning reduces binder intensity compared with IS 10262:2019 while maintaining the required strength levels. • Workability decreases with recycling generation, making moisture conditioning and controlled admixture dosage important for production. • For 30 MPa concrete, 28-day CPM compressive strengths were 37.01, 34.53, 35.65 and 33.28 MPa for NCR, CR1, CR2 and CR3. • For 50 MPa concrete, the corresponding 28-day CPM compressive strengths were 56.14, 54.76, 55.27 and 53.23 MPa. • Split tensile and flexural strengths followed the general compressive-strength trend, with reported relationships of approximately 8–10% and 5–7% of compressive strength, respectively. • The reported mechanical-property relationships produced R² values of approximately 0.91–0.96, indicating strong correlation. • Life-cycle assessment indicates reductions in carbon footprint and energy demand through recycling and CPM-based proportioning; cement and transportation remain the major environmental contributors. • The combined use of multi-recycled aggregate and particle-packing-based proportioning provides a technically viable pathway for resource-efficient concrete when fresh-state and mechanical requirements are satisfied.

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