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<p>Ultrahigh-performance concrete (UHPC) has great potential for use in extreme-load structures because of its ultrahigh compressive strength and excellent durability; however, its inherent brittleness restricts its seismic and blast resistances. This study investigates the mechanism by which the steel fiber content influences the dynamic mechanical behavior of steam-cured UHPC through split Hopkinson pressure bar (SHPB) experiments and mercury intrusion porosimetry (MIP). Results indicate that the dynamic compressive strength of UHPC increases exponentially with increasing strain rate and that the steel fiber content significantly regulates its dynamic performance. When the steel fiber content increases from 1% to 2.5%, the rate of improvement of the dynamic compressive strength increases from 12.3% to 13.8%. The effect of steel fibers presents a nonlinear threshold characteristic: 1% of the fibers form an incomplete network, 2% of the fibers induce large-pore defects because of weak interfacial zones, and 2.5% of the fibers cause the fiber network density to exceed the percolation threshold. At a 2.5% fiber content, the total porosity is reduced to 2.98% through physical blocking and chemical optimization, achieving a peak dynamic compressive strength of 215.1&#xa0;MPa. Steam curing refines matrix pores but embrittles the fiber–matrix interface, and a 2.5% fiber content mitigates such interfacial weakening by optimizing the pore distribution. This study confirms that 2.5% is the optimal steel fiber content for steam-cured UHPC, providing key parameters for its applications in impact-resistant structures and a theoretical basis for the development of high-toughness UHPC.</p>

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Role of steel fiber in the dynamic behavior of steam-cured UHPC

  • 期刊论文

  • 出版模式：

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  • 发表日期：

    2026年4月19日

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  • Zhu Yongsheng

摘要

Ultrahigh-performance concrete (UHPC) has great potential for use in extreme-load structures because of its ultrahigh compressive strength and excellent durability; however, its inherent brittleness restricts its seismic and blast resistances. This study investigates the mechanism by which the steel fiber content influences the dynamic mechanical behavior of steam-cured UHPC through split Hopkinson pressure bar (SHPB) experiments and mercury intrusion porosimetry (MIP). Results indicate that the dynamic compressive strength of UHPC increases exponentially with increasing strain rate and that the steel fiber content significantly regulates its dynamic performance. When the steel fiber content increases from 1% to 2.5%, the rate of improvement of the dynamic compressive strength increases from 12.3% to 13.8%. The effect of steel fibers presents a nonlinear threshold characteristic: 1% of the fibers form an incomplete network, 2% of the fibers induce large-pore defects because of weak interfacial zones, and 2.5% of the fibers cause the fiber network density to exceed the percolation threshold. At a 2.5% fiber content, the total porosity is reduced to 2.98% through physical blocking and chemical optimization, achieving a peak dynamic compressive strength of 215.1 MPa. Steam curing refines matrix pores but embrittles the fiber–matrix interface, and a 2.5% fiber content mitigates such interfacial weakening by optimizing the pore distribution. This study confirms that 2.5% is the optimal steel fiber content for steam-cured UHPC, providing key parameters for its applications in impact-resistant structures and a theoretical basis for the development of high-toughness UHPC.