Study on the influence mechanism of polypropylene fiber on crack propagation of concrete with existing cracks under uniaxial compression

Abstract

In the process of long-term service of concrete, cracks are inevitable, especially in the state of tension and compression, the crack expansion speed is accelerating, which seriously affects the service performance of concrete, and even causes major disasters. While polypropylene fiber has remarkable cracking resistance, there is a lack of theoretical analysis on crack initiation and path expansion of concrete cracks with existing cracks during the compression process. In order to analyze the inhibitory effect of fiber on the propagation of pre-existing cracks, we performed uniaxial compression tests on concrete prisms containing pre-existing cracks. Acoustic emission technology was used to monitor each test group and obtain relevant data on the cracking process of the specimens. GDEM software was used to simulate typical test conditions, and the results were compared with the test results to further explain the mechanism of crack propagation and fiber suppression. The results show that: (1) fiber can inhibit the initiation and propagation of tension wing cracks at the existing crack tip. The higher the fiber content, the shorter the symmetrical wing cracks become. (2) With the increase of fiber content (0 ∼ 4 kg/m3), the failure mode of polypropylene fiber-reinforced concrete prismatic specimens changes from tensile failure to tensile-shear failure, and finally shear failure. (3) The crack initiation stress and peak strength of prismatic specimens first increase and then decrease with the increase of fiber content. (4) The increase of fiber content delays the crack initiation time, prolongs the time to the disappearance of the peak of the acoustic emission signal, and prolongs the total time of the failure process.