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초록

Given the application constraints of ultra-high performance concrete (UHPC) due to high cost and raw material scarcity, along with adverse environmental effects from iron tailings accumulation, this paper presents economically feasible and eco-friendly UHPC (e-UHPC) by completely replacing quartz sand with iron tailings. This study aims at boosting the efficient utilization of iron tailings and improving the applicability of UHPC materials in practices. The effects of mono steel fibers and hybrid steel and polyoxymethylene (POM) fibers on the tensile properties of e-UHPC were investigated through direct tension tests with various fiber type and content. The results showed that both steel and hybrid fiber-reinforced e-UHPC can exhibit high post-cracking load-bearing capacity and obvious strain hardening behavior with sensitive cracking patterns depending on fiber contents. Steel fibers significantly improved the strength of e-UHPC but barely impacted on its deformability, whereas higher POM fiber content in hybrid specimens apparently enhanced the strain capacity of e-UHPC without improving its strength. Based on tensile stress-strain responses of test specimens, a multi-parameter tensile constitutive model for e-UHPC with varying fiber contents was established, enabling the accurate estimation of e-UHPC under direct tension.

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