Mechanical properties and acoustic emission data analyses of crumb rubber concrete under biaxial compression stress states

Crumb rubber concrete (CRC) is increasingly becoming one of the environmental protection ways to solve the problem of waste rubber tires. This paper mainly analyzes the mechanical properties and acoustic emission (AE) parameters under biaxial compression stress states of CRC with different rubber contents (0%, 5% and 10%). Two biaxial loading modes, constant lateral pressure loading mode (LPM) and propor-tional loading mode (PM), were used to determine the failure modes, strength characteristics and peak strain of the concrete under different stress ratio conditions. The experiment results show that the com-pressive strength and peak strain of CRC are improved under biaxial stress like plain concrete (PC), but due to the weak bond between rubber and cement-based materials, the strength growth rate of CRC is not as much as PC. Therefore, the modified Kupfer failure criterions are proposed to describe its strength growth laws. Meanwhile, under the uniaxial loading mode and LPM, the initiation and growth of concrete cracks were monitored based on AE technology. The analysis used various AE statistical parameters, including the AE ringing counts, cumulative energy, amplitude distribution, b-value and RA-AF value analyses. Based on the above AE parameters can be related to the mechanical characteristics of the con-crete, and the similarities and differences between CRC and PC are analyzed in the whole failure stage. The results show that CRC has better integrity in main collapse stage with mainly microcracks, which means the plastic failure characteristics. This paper provides experimental and theoretical foundations for the strength analyses and failure characteristics of CRC structures under complex stress states. (c) 2021 Elsevier Ltd. All rights reserved.