Upcycling high-volume phosphogypsum into low-carbon ECC: Synergistic hydration, mechanical performance, and eco-efficiency

In this study, high-volume phosphogypsum (PG) was successfully utilized in synergy with fly ash and ground granulated blast-furnace slag to produce green Engineered Cementitious Composites (PG-ECC) reinforced with polyethylene (PE) fibers. Under a high PG content of 40%, the optimized PG-ECC achieved an excellent maximum compressive strength of 70 MPa and an ultimate tensile strain capacity of up to 6.75%. The effects of mixture proportion on the mechanical properties, hydration mechanisms, and environmental impacts of PG-ECC were comprehensively investigated. Results revealed that a balanced FA to GGBS ratio could maximize the consumption of PG and facilitate the synergistic formation of a dense C-(A)-S-H and ettringite (AFt) cross-linked network, thereby optimizing the matrix fracture toughness and fiber-matrix interfacial friction. Furthermore, by establishing normalized environmental-mechanical evaluation indices and benchmarking against existing literature, the exceptional low-carbon advantages of the developed PG-ECC were demonstrated. The ternary solid waste matrix achieved exceptionally low carbon intensities, with values down to 1.83 kg CO₂/m³ /MPa for strength and 19.92 kg CO₂/m³ /% for ductility. These findings could help promote the upcycling of industrial PG and facilitate the engineering applications of this novel low-carbon composite in resilient and sustainable infrastructure.