Comprehensive Study of Field Permeability Using the Vacuum Permeameter: Fid-Bau Portal

Comprehensive Study of Field Permeability Using the Vacuum Permeameter

S. G. Williams

The permeability of coarse-graded asphalt mixtures has been a great concern in recent years. Asphalt mixes that are permeable are susceptible to a number of distresses such as moisture damage, raveling, cracking, and binder oxidation. This project examined three field devices for the determination of permeability. These methods were the NCAT falling-head field permeameter (NCAT), the Kuss constant-head field permeameter (KSFP), and the Kuss vacuum permeameter (VACP). Seven sites were mapped according to the VACP method in order to determine the location and distribution of permeable voids. These results were compared to the permeability measurements obtained by the NCAT and KSFP methods. Mixes having three different nominal maximum aggregate sizes were tested, and field cores were cut in order to provide a relationship of permeability and density. Also, the variability of the pavement sites was evaluated as a means to determine the minimum required sample size for field permeability testing. Overall, the various methods for determining field permeability do not yield similar results. In most cases, the falling head test (NCAT method) yielded the largest values. Pavement sections that clearly failed the density specification had high permeability, and sections that clearly passed the minimum density specification were relatively impermeable. Pavements with marginal density were somewhat permeable, and contained variable levels of permeability. In general, high permeability was exhibited near the longitudinal joints. The variability of the sites was evaluated in order to determine an appropriate sample size. Relatively impermeable pavements were consistent, and pavements with moderate or high permeability were more variable. Relationships between sample size, reliability, and testing discrimination were presented.