The high value utilization characteristics of coal gangue powder with emulsified asphalt mastic through rheological and viscoelastic damage theory

In order to solve the problems of rutting and early fatigue cracks in emulsified asphalt cold recycled pavement, and the shortage of natural stone resources and new environmental hazards caused by the use of traditional limestone powder filler. In this study, coal gangue powder was added to prepare Emulsified Asphalt Mastic (EAM) to improve the rheological properties and fatigue performance. A series of tests, including frequency scanning, temperature scanning, Multiple Stress Creep Recovery (MSCR), Linear Amplitude Scanning (LAS), and Fourier Transform Infrared spectroscopy (FTIR) were conducted. Through rheology theory, viscoelastic damage theory, the impact of three fillers: Coal Gangue Powder (CGP), Limestone Powder (LP) and Portland Cement (PC), as well as four kinds of Powder-Binder ratios (P/B) (0.6, 0.9, 1.2, 1.5) on the high temperature rheology and medium temperature fatigue performance of EAM was analyzed. The findings reveal that the filler content has a great influence on the proportion of viscoelastic components of EAM in the low frequency domain. The complex shear modulus (G*) and phase angle (δ) of EAM were suitable for Christensen-Anderson-Marasteanu model (CAM) model in the wide frequency domain. Increasing the filler content and Rotating Thin Film Oven Test (RTFOT) aging can improve the high-temperature stability and stress sensitivity of EAM, but it reduced its fatigue resistance. The high temperature performance of EAM containing PC and CGP exhibit superior high-temperature performance compared to LP fillers. Conversely, LP mastic demonstrate superior anti-fatigue performance under actual strain levels in both thin and thick asphalt pavement layers, surpassing the performance of PC mastic and CGP mastic. Therefore, coal gangue powder can be used as a new type of green filler to replace limestone powder. An appropriate amount of incorporation can improve the high temperature stability of the mortar and does not have a huge impact on the fatigue performance. The most suitable range of P/B is identified as 0.6-1.0 when utilizing LP as the filler, 1.2-1.5 when utilizing PC or CGP as the filler.