Hybrid-fiber-reinforced strain-hardening ultra-high-performance concrete (SH-UHPC) with recycled fine aggregates

Abstract

In order to increase environmental sustainability and to address the issue of construction and demolition (C&D) wastes accumulation, this study investigates the feasibility of using recycled fine aggregates (RFA) as a substitute to fully replace fine silica sand (FSS) in the production strain-hardening ultra-high-performance concrete (SH-UHPC). Results showed that RFA-based SH-UHPC with hybrid fiber reinforcement achieved comparable compressive strength (over 100 MPa), and an impressive enhancement on tensile ductility by 68.3 %. Microstructural analyses via SEM, X-CT and microhardness test revealed that due to the lower intrinsic hardness of RFA more internal cracks were observed RFA-based SH-UHPC, indicating the role of RFA as active flaws in high strength matrix of SH-UHPC resulting in more saturated multiple cracking and enhanced strain-hardening behavior. In the end, the strategic utilization of RFA not only improves mechanical performance but also lowers overall environmental impacts, which highlights the sustainable and effective use of C&D wastes for developing greener high-performance construction materials.