Acoustic emission characteristics of semi-rigid bases with three moisture conditions during bending tests

The water absorbed in a semi-rigid base is a major cause of road damage. Thus, moisture condition detection in the road base layer is essential for assessing the degree of road diseases. The main method used for such detection is oven drying, in which core samples are extracted from the road by drilling, which aggravates road damage. Acoustic emission (AE) detection is a typical non-destructive method. In this study, AE testing was performed on semi-rigid base specimens with three different moisture conditions. A mechanical testing machine and an AE system were used to determine the AE characteristics corresponding to three different moisture conditions in semi-rigid bases. Results indicated that the saturated condition corresponded to the highest amplitude attenuation of the AE signal, and the natural condition corresponded to the highest velocity of the AE signal. With an increase in moisture content, the AE counts and cumulative AE energy of the semi-rigid base specimens decreased during the bending test. The peak frequency of the semi-rigid base was mainly in the ranges of 8–40 kHz and 80–120 kHz, and the signal of the saturated specimen is almost the component of 8–40 kHz.