Acoustic Emission Behavior and Damage Evaluation of Cement Emulsified Asphalt Mortar under Compression

Cement emulsified asphalt (CA) mortar is a commonly used material in the construction of ballastless slab track on high-speed railways, which can reduce the vibration of the track. Therefore, studying the properties and health monitoring technology of CA mortar is very useful. This study applied acoustic emission (AE) technology to investigate the damage process of CA mortar under compression. The variables include asphalt–cement ratios (A/C), loading rates, and initial static loads. Meanwhile, an innovative method called phase cumulative proportion (PCP) analysis of AE parameter was proposed. Then, based on the rate process theory, the damage of CA mortar during compression was assessed. The results showed that void compaction and original crack propagation occurred first in the test, then elastic strain energy accumulation and stable microcracking in mortar, and finally macrocrack propagation. The rise of A/C leads to the increase of AE counts and energy of CA mortar upon macroscopic cracking. The increase in loading rate resulted in the contribution of macrocrack cracking to the failure process of CA mortar was reduced. With the growth of the initial static load, the cumulative value of AE parameters increases, and the contribution of stable microcracks increases. A polynomial model of the relation between strain level and AE parameters was developed. Finally, a damage assessment criteria of CA mortar and an evaluation method were put forward.