Temporal-spatial evolution characteristics of acoustic emission in asphalt concrete cracking process under low temperature

Abstract

In this study, the acoustic emission test has been performed on a three-point bending beam so as to simulate the initiation, propagation and penetration process of tensile cracks on an asphalt pavement under −10 °C. The characteristic parameters, such as the acoustic emission ringing count, signal energy, amplitude, average frequency under continuous load, have been obtained. In addition, the spatial evolution process of the internal micro-cracks have been tracked with the acoustic emission location. The results of the test show that the acoustic emission signal originates from the damage deformation in the area where the asphalt concrete specimen is weak. Its activity reflects the development level of the micro-cracks. The change curve of the acoustic emission (AE) parameters with the change in loading can be divided into three stages: calm period, slow-rapid growth period and step growth period. In the signal stepped growth period, the macro-crack “cracking point” of the specimen occurred. During this period, the sound emission ringing count and energy increased suddenly before falling back, and the signal amplitude and the dominant frequency range increased. These changes can be regarded as the forewarning generated by the acoustic emission before the occurrence of the macroscopic fracture damage of the specimen, and have certain predictability of the appearance of macro-cracks. The three-dimensional positioning of the acoustic emission technique can be utilized effectively to track the position of the main crack surface of the specimen, and reflect the dynamic evolution process of low temperature cracking of asphalt concrete. The acoustic emission has the potential for the detection of cracks in asphalt pavement in cold regions.