Flow regime analysis of fluid in permeable asphalt mixture

•Developed a multidirectional water-filled void content test apparatus.•Experimental investigated Non-Darcy permeability of permeable asphalt mixture.•Analyzed the effect of structure characteristics of asphalt mixture on flow regime.•Clarified the effect of asphalt mixture permeability on fluid flow. The flow regime of the fluid refers to all kinds of motion forms of fluid, and the fluid flow regime in permeable asphalt mixture impacts the permeability of the structure. Accordingly, as the flow regime of fluid in permeable asphalt mixture is clarified, the permeability can be delved into. This study aimed to explore the flow regime of fluid in permeable asphalt mixture. Five types of permeable asphalt mixtures were synthesized. By developing a multidirectional water-filled void content test apparatus and computed tomography, the differences in void content and void diameter in vertical and horizontal directions of asphalt mixture were analyzed. Subsequently, the permeability test of permeable asphalt mixture was performed using self-developed multidirectional permeability test apparatus. The results suggest that Darcy permeability changes to non-Darcy permeability in the process of fluid flow in the asphalt mixture. On that basis, the transition of flow regime in permeable asphalt mixture was analyzed. The results suggest that the variation of flow regime is consistent with the variation of fluid from Darcy to non-Darcy permeability. The flow regime is affected by the anisotropy, gradation type of asphalt mixture and flow space. The permeability of permeable asphalt mixture is associated with the transition point of fluid flow regime. The higher the permeability, the higher the critical Reynolds number will be.