Study on Main Fracture Precursor Characteristics of Polypropylene Fiber Recycled Concrete

In order to study the cracking scale and main fracture precursor characteristics of polypropylene fiber recycled concrete, 20 groups of specimens with coarse aggregate replacement rates of 25% and 50% were designed and manufactured. Through the uniaxial compression acoustic emission test, the acoustic emission energy and main frequency of polypropylene fiber recycled concrete fracture process were extracted. Using energy as a medium, the correspondence between cracking scale and acoustic emission characteristics is discussed. In this paper, K-means clustering method is used to perform a two-dimensional cluster analysis of large scale cracking and small scale cracking, and then a support vector machine is used to obtain the boundary between large scale cracking and small scale cracking. The evolution law of acoustic emission signal in the fracture process of polypropylene fiber recycled concrete was analyzed. It was found that the acoustic emission event rate decreased, the large scale cracking signal increased, and the low-energy small scale cracking signal disappeared. The concept of main fracture precursor response coefficient is introduced. The calculation results show that the precursor response coefficient of the disappearance characteristics of low energy small scale cracking signal is the largest, whose precursor response time is the earliest.