Ke-Fan Weng

Strain-hardening/engineered cementitious composites (SHCC/ECC) are fiber-reinforced concrete with outstanding tensile performance, but its widespread application is constrained by the high initial material cost primarily comes from high-performance polymer fibers like polyvinyl alcohol (PVA). This study explores partial replacement of PVA fibers with recycled polyethylene terephthalate (PET) fibers (with and without surface treatment) to reduce the cost and environmental impacts of ECC without compromising its flexural performance. Nine ECC mixes with a constant total fiber content of 2.0 vol% were tested under four-point bending. With 50% PET replacement, ultimate tensile strain decreased from 4.63% (control) to 1.83%–2.16%, whereas flexural strength only decreased from 11.40 MPa (control) to 10.10–10.19 MPa, and curvature capacity remained 79%–82% of the control. At 100% PET replacement, surface treatment improved the flexural ductility by about 70%. Finite element analysis confirmed the test results in terms of both flexural strength and deformation with good alignments. Additionally, overall performance evaluation of the developed ECC was assessed through a five-dimensional mechanical performance assessment framework and breakdown analysis of embodied energy, CO 2 emission, and material cost. The results support the hybrid PVA/PET fiber system as a feasible means of creating sustainable ECC for structural applications.

Ultra-high-performance fiber-reinforced concrete offers high strength, ductility, and durability, making it attractive for lightweight modular and marine structures. However, the optimal reinforcement strategy for advanced concrete remains unclear, particularly when considering thin-section applications and corrosion-resistant alternatives to steel. This study investigates the flexural behavior of thin structural panels made with ultra-high-performance concrete (UHPC), ultra-high-strength engineered cementitious composites (ECC), or lightweight ECC. The longitudinal reinforcements include steel, carbon fiber-reinforced polymer (CFRP), and hybrid steel-FRP composite (SFC) bars, while a stiffness-equivalent design was adopted to ensure comparable axial stiffness. Four-point bending tests were conducted to evaluate cracking performance, deflection capacity, failure mode, and energy absorption. Results showed that concrete ductility and bar type strongly influence the flexural performance. Steel-reinforced panels yielded in a ductile manner but had relatively low peak loads. CFRP-reinforced panels showed significantly higher peak loads (up to ~30 kN, nearly double that of steel case) but failed in a brittle manner. SFC-reinforced panels achieved high strength while maintaining ductility via a bi-linear response. Notably, ECC panels exhibited multiple fine cracks (<0.2 mm even near peak load) and large deformability, and showed significantly higher toughness and deformation capacity than UHPC panels. These findings highlight that combining lightweight, ductile ECC with corrosion-resistant bars yields thin structural panels with excellent flexural capacity, ductility, crack control, and weight efficiency, suited for modular construction and marine environments.