纤维对混凝土的损伤、裂缝曲折度及裂缝恢复的影响

来源：中国复合材料学会

《复合材料学报》优先在线发表论文。

摘  要：通过混凝土圆饼劈裂试验预制准确宽度的裂缝，本文研究了钢纤维、聚丙烯长纤维对荷载作用下混凝土的损伤、裂缝曲折度及裂缝恢复率的影响。使用数码显微镜（Supereyes）和Image Pro Plus图像处理软件对不同位置裂缝实际宽度进行测量。通过测量劈拉作用下穿过圆饼试件的超声波速，分析、对比了各组试件超声波速与裂缝宽度、损伤变量因子之间的关系。研究表明：纤维的桥接作用使裂缝扩展得以控制，同时提高了卸载时的裂缝恢复程度和裂缝曲折度。钢纤维掺量55kg/m3混凝土试件比钢纤维掺量25kg/m3混凝土试件，曲折度增加26.9%，混杂使用聚丙烯长纤维和钢纤维对提高混凝土裂缝表面曲折度有显著的正混杂效应。桥接于裂缝处的钢纤维有利于超声波的传播，减缓超声波速损失。超声波速随着裂缝宽度的增加而逐渐降低、且与裂缝之间存在较好的指数关系，可用于表征混凝土内部裂缝的发展。

关键词：纤维；超声波；劈裂试验；曲折度；裂缝恢复

Abstract: Through the disc splitting testing, the exact crack width of concrete has been prefabricated. In this work, the effect of steel fiber and macro polypropylene fiber on tortuosity, recovery rate and damage of concrete cracks were studied. The crack widths at different locations were measured using the digital microscope (Supereyes) and Image Pro Plus (an image processing software). In order to analyze the relationship between ultrasonic velocity and crack width as well as damage variable factors of different specimens, the ultrasonic velocity passing through the concrete disc under splitting load was also measured. The experimental results show that the crack widening could be controlled by the fiber bridging effect, and the crack recovery and tortuosity of crack can be increased simultaneously. Compared with concrete sample with a steel fiber content of 25kg/m3, the crack tortuosity of sample with a steel fiber content of 55kg/m3 increased by 26.9%; the hybrid use of macro polypropylene fibers and steel fibers indicates significant positive hybrid effect on the increasing of crack surface tortuosity. The steel fibers acrossing the cracks may improve the propagation of ultrasonic wave and decline the loss of the ultrasonic velocity. The ultrasonic velocity may decrease with the increasing of the crack width, and there is an exponential relationship between the crack width and ultrasonic velocity, which can be used to illustrate the crack development of concrete matrix.

Keywords: fiber; ultrasonic; splitting testing; tortuosity; crack recovery

作者：丁一宁等，大连理工大学 海岸与近海工程国家重点实验室，大连

通讯作者：丁一宁，大连理工大学 海岸与近海工程国家重点实验室，大连

全文详见中国知网学术期刊优先数字出版。