Experimental Study on Critical Characteristics of Self-Organized Behavior of Concrete under Uniaxial Compression Based on AE Characteristic Parameters Information Entropy

The purpose of this study is to clearly understand the self-organized critical phenomenon of concrete in the process of uniaxial compression. During the compression tests, acoustic emission (AE) waveform and its characteristic parameters were collected synchronously. The AE characteristic parameters information entropy was defined by combining information entropy theory with AE characteristic parameters in the time domain and frequency domain. Moreover, the evolution law of the AE characteristic parameters weighted information entropy composed of typical characteristic parameters in the time domain and the AE peak frequency information entropy in the frequency domain are obtained during the loading process. The results reveal that, as the stress grows, the AE characteristic parameters weighted information entropy of concrete shows an evolution characteristic of “descending, stabilizing and rising,” while the AE peak frequency information entropy shows the evolution characteristic of “ascending and declining.” Meanwhile, as the AE characteristic parameters weighted information entropy reaches the minimum value (e≈0.9 peak stress), the critical state of concrete ends. After that, the information entropy value increases rapidly, and the penetrating cracks initiate. When the specimen is destroyed, the information entropy value reaches the maximum. The evolution process of cracks in concrete, switching between a chaotic state that develops in random and an organized state that develops in order, follows certain laws (disordered–ordered–disordered), which corresponds well to the AE characteristic parameters weighted information entropy. The research results provide a new method for concrete damage monitoring based on AE.