Investigation of different fracture modes in cement-based materials by acoustic emission

Characterization of the cracking mode in cementitious materials allows evaluations concerning the remaining life of the structure since in general, shear-like phenomena occur after tensile cracking. Individual modes of cracking cause different motion of the crack tip dictating the waveforms emitted after cracking events. In this study fracture experiments on cementitious specimens are conducted. The fracture mode is controlled by modifying the experiment geometry and the process is monitored by acoustic emission. The distinct signature of the cracking modes is reflected on acoustic waveform parameters like the amplitude, RA-value and frequency. Signals emitted by the shear testing exhibit longer waveforms and lower frequency than those by the tensile testing. The influence of inhomogeneity is also evident as signals acquired at different distances exhibit distinct characteristics. Results show that AE study leads to characterization of the dominant fracture mode using only two AE descriptors and offers the potential for in-situ application.