Experimental investigation on the rutting resistance of permeable friction courses

Abstract

This paper presents an experimental investigation on the rutting resistance of permeable friction courses (PFC). In practice, PFC are prone to permanent deformation due to heavy traffic loads and a weak mineral skeleton caused by their high air void contents. Consequently, the draining capacity of the PFC is diminished making the roads unsafe in wet conditions. Hence, the rutting mechanism of PFC is evaluated through three laboratory tests: dynamic modulus (DM), flow number (FN), and Hamburg wheel tracking test (HWTT). The samples were prepared and compacted considering four air voids (AV) contents: 18%, 20%, 22% and 25%. From the HWTT, a comparative analysis was conducted using X-ray computer tomography (X-ray CT) images obtained before and after the tests in order to investigate AV distribution due to rutting. The results show that the dynamic modulus, the flow number and the rutting response are severely affected by increasing the AV content in the PFC mixes. After increasing the AV content, the dynamic modulus and the flow number decreases significantly, while the rutting depth increases. From the analysis of the X-ray CT images, a larger AV densification was observed in the upper part of the samples beneath the developed rut, whereas in the bottom part the AV content increased further weakening the mineral skeleton.