Sustainable Permeable Asphalt System on Road Infrastructures

Permeable Asphalt Systems (PAS) ensure, as well as road safety, environmental benefits by promoting the infiltration and filtration of stormwater and thus restoring the hydrological cycle. This work focuses on the evaluation of the filtration efficiency of a sustainable permeable asphalt system actually implemented on the Adriatic Bridge (Bari, Italy). In order to reach this goal, firstly, several laboratory studies for in-deep analyzed every aspect of permeable asphalt and of materials involved in the filtration processes were carried out. Hence, the first part of this work is intended to present the results obtained from these preliminary study: dry roads particulate matter (PM) samples from Apulia roads were collected and granulometrically characterized by means of mathematical model; then the clogging process within the PM loaded-permeable pavement specimens and the hydraulic conductivity reduction connected to it were observed; afterwards the pore structure of permeable pavement specimens was re- constructed by means of x-ray tomography; thereon a numerical model for determining the hydraulic conductivity of a 3D reconstructed permeable pavement specimens was developed by means of the Computational Fluid Dynamics (CFD). The findings of these studies have made a critical contribution to the development of the practical part of this work. The second part of the work is devoted to analyzing and modeling the experimental sustainable permeable asphalt system of the bridge. The system, composed of an open-graded friction-course (OGFC) and an infiltration trench, was reproduced in laboratory. The filtration efficiency was evaluated both for the individual system components and for the whole integrated system simulating various rainfall conditions. Meanwhile, quality analyses of the inflow and outflow stormwater collected directly in-situ from the system were also performed. The integrated system showed both in laboratory and in-situ good filtration properties and a high power of depletion of PM materials. In conclusion, the system, with some shrewdness, can be implemented on road infrastructures as a diffuse treatment system. Further researches are aimed at developing a numerical model able of predicting the particulate separation processes within the PAS for investigating the applicability in any context as geographical and environmental conditions change.