Investigation on fracture and fatigue performance of cold recycling emulsified asphalt mixture based on acoustic emission parameters

Cold recycling technique of asphalt reduces the demand for building materials, saves resources and costs, and meets the requirements of low-carbon and high-quality development. The purpose of this study is to improve the fracture and fatigue performance of cold recycling emulsified asphalt mixture. In this paper, cold recycling ordinary, basalt fiber (BF) emulsified asphalt mixture and cold recycling styrene butadiene rubber (SBR) modified emulsified asphalt mixture were taken as the research objects. Four-point bending strength and fatigue tests of specimens with and without prefabricated cracks were carried out respectively, and acoustic emission (AE) was used for real-time monitoring during these tests. The fracture mechanics method was used to study the fracture strength of cold recycling ordinary, BF and SBR modified emulsified asphalt mixtures. The phenomenological theory and energy analysis method were adopted to research their fatigue performance. The characterization parameter analysis method was employed to analyze the AE parameters. Furthermore, the effect of BF and SBR on the performance of the mixture was compared and analyzed. The test results show a significant improvement in the fracture energy and stress intensity factor of cold recycling BF and SBR modified emulsified asphalt mixtures, indicating that both BF and SBR can reduce the cracking risk of cold recycling emulsified asphalt mixture, of which BF is more effective compared with SBR. The dynamic modulus and cumulative dissipation energy attenuation law of cold recycling emulsified asphalt mixture during the fatigue process were revealed. Based on AE technique, a nondestructive test method for the fatigue damage of cold recycling emulsified asphalt mixture was established. This study expands the application scope of cold recycling emulsified asphalt mixture, which has good energy-saving, economic and environmentally friendly benefits.