Effect of Permeameter Size and Anisotropy on Measurements of Field Pavement Permeability

The permeability of hot-mix asphalt is important to a pavement's durability. Measuring permeability along with density will give a better indication of a pavement's durability than will density alone. The presence of water in the pavement for extended periods is directly linked to early deterioration. A modified field permeameter was developed for study of the water–pavement contact area (permeameter size) and anisotropy effect on field permeability measurements. A reliable sealing system was created to be consistent but not detrimental to the pavement surface. The results of the study showed that larger water–pavement contact areas yielded increasing influence on vertical flow, which better represented the one-dimensional flow conditions prescribed by the falling head method using Darcy's law. Equations to calculate both vertical and horizontal permeability coefficients were developed with finite element (FE) simulations of the field tests as an axis-symmetric flow. Two permeability tests with two plate sizes were conducted with this approach to obtain both vertical and horizontal permeability coefficients. The FE simulations indicated that the nominal permeability calculation with one-dimensional assumptions was valid when the water–pavement contact area was large.