Evaluation of HMA laboratory permeability using the Karol-Warner Flexible Wall Permeameter

This document presents the results of a study initiated to evaluate the laboratory permeability of Hot Mix Asphalt (HMA) mixes placed on Tennessee roadways. The study consisted of using a Karol-Wamer Flexible Wall Permeameter to evaluate the permeability of eight Superpave™-designed mixes and nine Marshall designed mixes produced in 1999 and 2000.

The focus of this study was to evaluate the correlation between field and laboratory measurements of permeability using linear regression analysis. Linear regression analysis was also used to evaluate the relationship between roadway core density (%Gmm) and laboratory permeability. Appropriate statistical methods were used to evaluate the difference between Marshall and Superpave^'^ designed mixes and the effect saw cutting has on laboratory permeability measurements.

This study shows that in genera, laboratory permeability falls below 100x10^-5 (cm/sec) when 94% compaction is achieved. The results presented herein further demonstrate that a fair to poor relationship exists between field and laboratory measurements of permeability. It is also documented that there are significant problems achieving density requirements. This is evident by the fact that only 14 of 51 cores achieved 92% compaction as specified by the contract document. It was also observed that a difference exists between the laboratory permeability of Marshall and Superpave™ mixes as designed in Tennessee, while statistically speaking no difference exists. Finally, no definite trend was observed when evaluating the effects of saw cutting.