Micro-cracking monitoring and fracture evaluation for crumb rubber concrete based on acoustic emission techniques

A micro-cracking monitoring and fracture evaluation method for crumb rubber concrete based on the acoustic emission technique was developed. The precursory micro-cracking activity and fracture behavior of crumb rubber concrete with different rubber contents, 0%, 10%, and 15%, were analyzed. The various acoustic emission statistical parameters including cumulative event, frequency distribution, amplitude distribution, and b-value were used for the analysis. The general fracture process is similar for all normal and crumb rubber concretes and can be divided into three distinct stages of micro-crack activity, namely, early stage, main collapse stage, and post-fracture stage. The following conclusions were drawn from the analysis: (1) more micro-cracks initiated and grew at early stage in the normal concrete, while less micro-cracks in the crumb rubber concrete but with longer stage duration; (2) the duration and crack number are both increasing with the increase in the rubber contents in main collapse and post-fracture stages; (3) new crack types associated with the rubber particles were recorded due to the change of the peak frequencies; and (4) the amplitude of the cracks decrease with the increase in the rubber content due to the damping ratio and interface improvement by the mixed rubbers. The results obtained in this article demonstrate that the acoustic emission technique can provide valuable information for a better understanding of micro-cracking and fracture monitoring of crumb rubber concrete.