钢纤维类型对超高性能混凝土高温爆裂性能的影响

为了探寻可以有效改善超高性能混凝土（Ultra-high-performance concrete，UHPC）抗火性能的钢纤维类型，本文试验测定了不同类型钢纤维（3种普通钢纤维和2种来自于废旧轮胎的再生钢纤维）增韧UHPC及空白组混凝土的从常温至800℃高温爆裂行为和断裂能。结果显示，未掺入任何钢纤维的空白组UHPC试件全都发生了严重高温爆裂，钢纤维可以显著减轻其高温爆裂但却不能避免爆裂的发生，而掺入端钩型普通工业钢纤维（长度为35 mm，直径为0.55 mm）的UHPC呈现出最优的抗高温爆裂性能，其次是掺入未附着橡胶颗粒（RSF）的再生钢纤维（RSFR）增韧UHPC。可见，钢纤维自身性能特征显著影响了钢纤维增韧UHPC的高温爆裂，相同掺量情况下混凝土单位体积内分布密度较大的钢纤维或者分布密度较小但可以显著增加混凝土断裂韧性（断裂能）的钢纤维比较适合应用于具有较高抗火要求的UHPC结构中。

Influence of different types of steel fiber on explosive spalling behavior of ultra-high-performance concrete exposed to high temperature

To explore the steel fiber which can improve the fire resistance of ultra-high-performance concrete (UHPC), explosive spalling behavior of different types of steel fiber (three types of normal steel fiber and two types of recycled steel fiber from waste tire) reinforced UHPC and plain UHPC exposed to high temperature up to 800℃ were experimentally investigated in this paper, and fracture energies of these concretes were also tested. All of plain UHPC specimens encounter severe explosive spalling. Steel fiber significantly alleviates the explosive spalling of UHPC but cannot avoid the occurrence of explosive spalling. UHPC incorporating normally available commercial steel fiber with hooked-end (35 mm long and 0.55 mm in diameter) exhibits the best resistance to explosive spalling, and the second is the UHPC incorporating recycled steel fiber without attached rubber. This suggests that the characteristics of steel fiber affect the explosive spalling of steel fiber reinforced UHPC significantly. The steel fiber which has a large distribution density or that without a large distribution density but can make concrete have high toughness (fracture energy), is more appropriate to be utilized in UHPC structures with high fire resistance requirements.