Optimizing hybrid ratio of steel and polyethylene fibers on the compressive and tensile properties of ultra-high-strength lightweight concrete

초록

This study aims to optimize the hybrid ratio of steel and polyethylene (PE) fiber in ultra-high-strength lightweight concrete (UHSLC) through mechanical and sustainability performance. UHSLC offers exceptional compressive properties while maintaining a reduced self-weight, yet its tensile resistance remains insufficient due to weak aggregate interlock and brittle fracture. To address this limitation, the synergistic effect of hybrid fiber reinforcement was investigated by combining steel and PE fibers. A total of nine mixtures were designed with varying total fiber volumes and hybrid fiber ratios. Experimental results revealed that steel fibers predominantly enhanced compressive properties and tensile strength, while PE fibers contributed significantly to tensile strain capacity and tensile toughness. The 50:50 hybrid mixture achieved the highest tensile toughness and synergy index, confirming the multiscale crack bridging mechanism of hybrid reinforcement. Notably, most hybrid mixtures exhibited positive synergy, validating the benefit of combining steel and PE fibers. Furthermore, sustainability indicators demonstrated that fiber-reinforced UHSLC exhibited competitive normalized cost and CO2 emission compared to conventional fiber-reinforced cementitious composites and concrete, with the added advantage of self-weight reduction. A multi-criteria decision-making (MCDM) approach using the weighted sum method (WSM) and technique for order preference by similarity to ideal solution (TOPSIS) was employed to identify the optimal hybrid fiber ratio. Both analyses confirmed that a 50:50 hybrid fiber ratio resulted the best balance between mechanical performance and sustainability. This research provides a strategic foundation for the development of environmentally efficient UHSLC for future structural applications.

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