Mechanical, piezoelectric properties and microstructure of a novel 0-3 lead-free γ–C2S–BT composite

γ-dicalcium silicate (γ-C 2 S) forms a dense microstructure after carbonation, serving as a novel matrix material for barium titanate (BT)-based piezoelectric composites. Yet interfacial bonding mechanisms between carbonated matrix and BT ceramics lack investigation, and synergistic effects of key parameters on piezoelectric network and mechanical properties remain unclear. To address this gap, this study develops a novel 0-3 lead-free γ-C 2 S-BT composite via a room-temperature carbonation curing process. The effects of the w/s, BT particle size, BT volume, forming pressure, and polarization regime on the mechanical, piezoelectric properties and microstructure were systematically evaluated. Results demonstrate that an optimal w/s of 0.08 yields a peak compressive strength of 117.9 MPa and a d 33 of 11.8 pC/N. The d 33 scales positively with BT particle size and volume, reaching 18.2 pC/N for 0.56–1.0 mm particles and 34.7 pC/N at a 90 vol%. When the forming pressure was elevated from 25 to 100 MPa, d 33 exhibited minimal sensitivity. Optimal polarization regime (50 °C, 2.0 kV/mm, 20 min) maximize d 33 at 14.1 pC/N. Overall, the γ-C 2 S-BT composite containing an 80 vol% BT exhibited excellent comprehensive properties: d 33 of 21.6 pC/N, of 76.5, g 33 of 31.9×10 -3 V·m/N, and compressive strength of 58.7 MPa. Microstructural analyses confirm that dense interfacial cohesion between the calcium carbonate matrix and BT particles, alongside a high degree of carbonation, drives these excellent electromechanical properties. Coupled with rapid curing, superior properties and active CO 2 sequestration, this work presents a sustainable pathway for high-performance piezoelectric composites in structural health monitoring.