Addressing Safety Through Evaluation and Optimization of Permeable Friction Course Mixtures

摘要

Permeable friction course (PFC) mixtures are a special type of hot mix asphalt characterized by a high total air voids content to guarantee proper functionality and stone-on-stone contact of the coarse aggregate fraction to ensure adequate mixture stability. Thus, PFC mixtures constructed in a thin layer at the surface of a pavement structure produce several benefits in terms of economy, safety, and the environment. This project focused on the analysis of functionality (i.e., drainability), stone-on-stone contact, and mixture internal structure to propose improvements in these three aspects for PFC mix design and evaluation. The analysis was based on both a macroscopic assessment of mixture properties and a study of internal structure using X-ray Computed Tomography (X-ray CT) and image analysis techniques. The assessment of drainability led to a recommendation to use the expected value of permeability (based on a modified Kozeny-Carman equation) for analytical prediction of permeability. The wateraccessible AV content was also proposed as a surrogate of the total AV content for indirect assessment of permeability.