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采用普通原材料制备56d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。
The blank raw materials were used to prepare the blank group of ultra-high performance concrete, steel fiber ultra high performance concrete and hybrid fiber ultrahigh performance concrete with 56d age compressive strength of 140 ~ 160 MPa. The residual compressive strength Crack tensile strength, and 100% moisture content of the concrete block burst test at high temperature. In addition, the size of the two kinds of heating rate of the ultrahigh-performance concrete burst at high temperature impact. The results show that the residual compressive strength of the concrete increases first and then decreases with the increase of the target temperature. The residual compressive strength after 800 ℃ high temperature is about 30% of the strength at room temperature. Residual splitting tensile strength of steel fiber and hybrid fiber concrete also showed the trend of first increasing and then decreasing. The residual splitting tensile strength after 800 ℃ high temperature were 15.1% and 35.4% of the room temperature respectively. The residual splitting tensile strength of concrete in the blank group decreases monotonously with the increase of the target temperature. The tensile strength at 800 ℃ is about 20.3% of that at room temperature. Severe high temperature burst occurred in three kinds of concrete specimens with 100% moisture content at 7.5 ℃ / min heating rate. Single steel fiber could improve the high temperature burst of ultrahigh performance concrete but could not avoid the occurrence of burst, while hybrid fibers The improvement effect of ultrahigh performance concrete at high temperature burst is not significantly better than that of steel fiber. 2.5 ℃ / min heating rate, the hybrid fiber can avoid some ultra-high performance concrete block burst.