纤维对超高性能混凝土残余强度及高温爆裂性能的影响
Effect of fiber on residual strength and explosive spalling behavior of ultra-high-performance concrete exposed to high temperature

采用普通原材料制备56 d龄期抗压强度为140~160 MPa的空白组超高性能混凝土、钢纤维超高性能混凝土及混杂纤维超高性能混凝土，测定其遭受高温作用后的残余抗压强度和劈裂抗拉强度，并对100%含湿量的混凝土试块进行高温爆裂试验。此外，测定大小2种加热速率对超高性能混凝土高温爆裂行为的影响。结果表明：所配制混凝土的残余抗压强度均随着目标温度的升高呈现先增大再降低的趋势，800℃高温后的残余抗压强度约为常温强度的30%。钢纤维与混杂纤维混凝土的残余劈裂抗拉强度亦呈现先升高再降低的趋势，800℃高温后的残余劈裂抗拉强度分别为常温强度的15.1%和35.4%。空白组混凝土的残余劈裂抗拉强度随着目标温度的升高而单调下降，800℃高温后的强度值约为常温强度的20.3%。7.5℃/min加热速率下，100%含湿量的3种混凝土试块均发生了严重高温爆裂，单掺钢纤维可以改善超高性能混凝土的高温爆裂，但不能避免爆裂的发生，而混杂纤维对超高性能混凝土高温爆裂的改善效果并未显著优于钢纤维。2.5℃/min加热速率下，混杂纤维可避免部分超高性能混凝土试块发生爆裂。 Plain concrete, steel fiber and hybrid fiber reinforced ultra-high-performance concretes, with 140-160 MPa compressive strength at 56 d, were prepared using common raw materials. The residual compressive strength and tensile splitting strength of these concretes after exposure to high temperature were determined experimentally. Explosive spalling test was carried out on the specimens with 100% moisture content and two heating rates were employed to study the effect of heating rate on spalling behavior of ultra-high-performance concrete. The results indicate that residual compressive strength of each type of concrete increases firstly, and then decreases with increasing temperature. After exposure to 800℃, residual compressive strength is approximately 30% of that at normal temperature. Residual tensile splitting strength of both steel fiber reinforced concrete and hybrid fiber reinforced concrete also increase firstly and then decrease, which are 15.1% and 35.4% of the original strength, respectively. Residual tensile splitting strength of plain concrete decreases with increasing temperature, which is 20.3% of its original strength after exposure to 800℃. At 7.5℃/min heating rate, explosive spalling of each type of concrete specimens with 100% moisture content is quite severe. Nevertheless, steel fiber can alleviate explosive spalling but does not avoid the occurrence of explosive spalling, and the effect of hybrid fiber on improving spalling resistance behavior of ultra-high-performance concrete is not significantly superior to that of steel fiber. At 2.5℃/min heating rate, incorporating hybrid fiber inhibits the occurrence of explosive spalling in some specimens. 国家自然科学基金（51278048，50978026）；北京交通大学基本科研业务费（C11JB00720）