Investigation of surface micro-crack growth behavior of asphalt mortar based on the designed innovative mesoscopic test

The objective of this study is to design an innovative mesoscopic test for characterizing the damage evolutions and fracture performances of the asphalt mortar. Based on the SEM-Servopulser devices and improved specimens, the pure mode I cracking tests were conducted successfully under scanning electron microscope (SEM). It can have a real-time online observations and records of the surface micro-crack behaviors and evolutions under different loads. And it is the first time in road engineering to capture the dynamic micro-behavior and micro-structure of the bituminous materials in such high accuracy (Am level), especially the synchronous recording when applying loads without stopping on-going tests. This proposed method will have significant meaning in revealing the fracture mechanism of the bituminous materials since the traditional specimen sizes and the self-healing property of the asphalt hinder the further micro-scale investigations in this field. With the help of the pioneering designed tests, the damage variable based on the micro-crack density was proposed and was verified by the experimental results. It is found that the interface failure dominated during the overall process in pure mode I cracking tests, which should be paid more attention on in the future material design. (C) 2019 The Authors. Published by Elsevier Ltd.