Analysis of permeability reduction in drainage asphalt mixtures due to decrease in void volume

Pavements with a wearing course of drainage asphalt mixtures have been used in regions with high rainfall due to their ability to remove stormwater from the surface and increase the tire-pavement adhesion. However, over time, due to traffic flow together with dirt carried by surface runoff, the voids are reduced and become clogged. This work presents a laboratory study for the evaluation of the reduction in the void volume and permeability of drainage asphalt mixtures through the action of traffic and clogging. The reduction in the void volume was simulated in two different ways. Firstly, cylindrical specimens produced in a SUPERPAVE gyratory compactor were compacted using 50 gyrations as a reference and to simulate the action of traffic other specimens were compacted considering 75, 100, 150 and 200 gyrations. In order to evaluate permeability and voids content reduction due to permanent deformation along the time, slabs were conditioned applying 1,000, 3,000, 5,000, 10,000, 20,000 and 30,000 cycles in the traffic simulator. After that, the plates were core drilled to cylindrical specimens to perform tests. Specimens without conditioning were used as a reference. The permeability was then measured using clean water and surface runoff. From different levels of traffic simulation, the permeability from 1.84 mm/s (0 cycles) to 1.55 mm/s (30,000 cycles) while the void volume decreased from 23.50% (0 cycles) to 22.24% (30,000 cycles). Intervention was considered to be required when the reduction in the connected void volume reached 12%. In this case, intervention should be conducted annually for an average of void volume of 24.5% and within seven months for an average of void volume of 20.6%. Thus, in order to maintain the draining properties of the pavement surface, intervention such as cleaning and suction of pores should be carried out in the first year after the opening of the roadway to traffic. (C) 2019 Elsevier Ltd. All rights reserved.