A rapid field test is proposed to evaluate the permeability of open-graded road bases and other drainage-layers. The same test also should be adaptable to evaluate permeabilities of other exposed pavement layers including those composed of bituminous or Portland cement concretes, as an index to permeation and possibly to deterioration. It is proposed that the permeability be evaluated through use of air as a permeant rather than a liquid. Advantages of measuring air instead of liquid permeability includes (1) flow rates increased by the reduced viscosity, greatly reducing testing time, (2) no need to transport the permeant to the test site, (3) no requirement for saturating the test area, (4) avoiding capillary suction and wetting effects, (5) removing gravitational drive, and (6) a possibility for utilizing the compressibility of air to drive the system for one-shot determinations. Determination of air permeability by both steady state and dynamic flow conditions is proposed. The dynamic or one-shot procedure would provide greater testing speed and could allow definition of permeability as a function of air pressure which can be extrapolated to give a measure of permeability of an incompressible fluid.Anticipated Results/Potential Commercial Applications Of Results:The Phase I Study will involve the development of a prototype apparatus to test whether the use of air as a permeant is a viable method to measure permeability of a drainage layer in-situ. The goal is a rapid, inexpensive procedure that will be made available to the highway industry for on-site control tests of new and existing drainage layers and potentially for other-pavement layers.
