不同钢纤维掺量的UHPC断裂性能试验研究

Experimental research on the fracture property of ultra high performance concrete with various steel fibre contents

采用楔入劈拉试验方法,开展不同钢纤维掺量UHPC和普通混凝土(NC)、高强混凝土(HSC)断裂性能的试验研究。结果表明:与NC和HSC相似,UHPC断裂过程也可分为起裂、裂缝扩展和失稳破坏阶段;不掺钢纤维的UHPC0相比于NC、HSC呈无征兆的脆性断裂,掺入钢纤维后UHPC由多条微裂纹汇聚为一条曲折的主裂缝并因钢纤维的拔出而破坏;与NC相比,UHPC0的起裂韧度提高了31%,失稳韧度和断裂能反而降低(分别为72%和45%),而掺入1%钢纤维的UHPC1的起裂韧度、失稳韧度和断裂能分别提高到3.60倍、10.96倍和49.16倍;随着钢纤维掺量的增加,UHPC起裂韧度大致呈线性增长,失稳韧度与断裂能也随之增长,但其提高幅度逐渐趋缓,表明钢纤维的掺入可改善UHPC强度高而脆性强的特性,提高UHPC抗断裂性能。

Wedge splitting tests were used to investigate the fracture property of ultra high performance concrete(UHPC) with different steel fiber contents,as well as normal concrete(NC) and high strength concrete(HSC).Experiment results indicated that similar to NC and HSC,the fracture process of UHPC can also be divided into initiation,fracture propagation and instability failure stages;compared with NC and HSC,UHPC0 without steel fiber was brittle fracture without warning,the UHPC specimen mixed with steel fiber was gathered into a tortuous main crack by multiple microcracks and was destroyed by steel fiber pulling out,compared with NC specimens,UHPC0 specimens have 31 percent times higher initiation toughness,but showed a reduction in instability fracture toughness and fracture energy(only 72 percent and 45 percent respectively).UHPC1 specimens with 1% steel fiber volume were 3.60 times(initiation toughness),10.96 times(instability fracture toughness) and 49.16 times(fracture energy) higher than that of NC specimens.The fracture initiation toughness of UHPC increased linearly with the increasing of steel fiber content,and the instability toughness and fracture energy also increased,but the increase gradually slows down,indicating that the incorporation of steel fiber can improve the characteristics of high strength and brittleness of UHPC and improve the fracture resistance of UHPC.