Utilizing original and activated coal gangue wastes as alternative mineral fillers in asphalt binder: Perspectives of rheological properties and asphalt-filler interaction ability

Abstract

Seriously environmental pollution has been induced by discarding of coal gangue (CG) that produced during coal mining and washing processes. Using CG as an alternative of traditional mineral filler in asphalt mastic has significant benefits on saving resources and protecting environments. In order to improve the compatibility of CG particles with asphalt binder, the thermal and chemical activations were conducted in this study. Meanwhile, the morphology, mineralogy and chemical information were characterized to analyze the activation mechanisms of thermal and chemical treatments. Taking limestone asphalt mastic as control sample, the rheological characteristics of asphalt mastic prepared by CG were analyzed, including master curves, rutting resistance and fatigue resistance properties. Furthermore, the K-B-G and L-A-δ parameters were applied to measure the differences on asphalt-filler interaction ability. As the result of replacing limestone with CG, the rutting resistance of asphalt mastic was improved, while the fatigue resistance at intermediate temperature was deteriorated. The microstructure of CG transformed from plate structure and porous structure due to the crystal phase change and chemical graft after thermal and chemical treatments, respectively. Therefore, the activations on CG particles can enhance the interaction ability with asphalt binder and then improve the rutting resistance under 3.2 kPa and fatigue resistance properties. Considering the low cost and satisfied service performances, it is feasible to utilize CG as substitute of limestone to prepare asphalt mastic.