Permeability Loss of Open-Graded Friction Course Mixtures due to Deformation-Related and Particle-Related Clogging: Understanding from a Laboratory Investigation

Open graded friction course (OGFC) is effective in improving the surface function of asphalt pavements. However, it is prone to clogging including deformation-related and particle-related clogging. The aim of the research reported in this paper is to investigate the permeability loss or reduction due to deformation-related clogging and explore the critical size of solid particles attributed to OGFC particle-related clogging. A special falling head permeameter was developed with consideration of both rainwater flowing procedure and the pavement transversal slope. Eight types of OGFC mixtures with different air void contents, gradations, and nominal maximum aggregate sizes were prepared for deformation-related clogging evaluation. Wheel rutting tests were conducted on the OGFC samples with different loading times under two load levels [(1) 700 kPa, and (2) 900 kPa] at 45 and 60 degrees C, and next were permeability tests using the developed permeameter. Permeability loss after different wheel loading times were calculated to explore the effects of the initial air void content, nominal maximum aggregate size, temperature, and loading pressure on deformation-related clogging. Furthermore, seven types of suspension liquids were prepared for particle-related clogging evaluation. For each suspension liquid, the proportions of solids trapped in OGFC air void, passing OGFC sample, and retained on the sample surface were calculated after permeability tests to determine the critical sizes of particle attributed to particle-related clogging. Results show that with the increase in wheel loading times, the permeability of OGFC mixture shows a steady decrease after a sharp initial decline. Permeability loss due to deformation-related clogging can be reduced effectively by using larger nominal maximum aggregate size and larger air voids. Values of 0.15-0.3 and 1.18-2.36 mm are the critical sizes of trapped particles in OGFC mixtures. (C) 2015 American Society of Civil Engineers.