The NCAT Asphalt Field Permeameter Vessel is a 4-tiered, graduated standpipe supplied in two sections and constructed of rugged plastic. A sealing material is placed on the base plate. The unit is then positioned on the test site and seated against the pavement using gentle foot pressure and included base weights. After filling with water, outflow is observed against the clearly marked graduations and timed. The smallest, uppermost tier allows rapid determinations in low-porosity pavements. The larger diameter tiers permit enough time to accurately read flow on more porous pavements.
The NCAT Field Permeameter is a falling-head permeameter using Darcy’s Law to determine rate of water flow through asphalt pavement. This design was selected by the National Center for Asphalt Technology (NCAT) for its close correlation with laboratory test results. Studies show that some Superpave mixes can be permeable to water even when compacted to an acceptable air void ratio. Field testing permits on the spot, accurate estimation of permeability, eliminating the need for coring, patching and laboratory testing. Corrections to mix and placement procedures can be implemented right away. Testing and subsequent calculations can usually be completed in 10-15 minutes by one technician. The simple procedure means no extensive training is required.