Investigation of Permeability on Indiana SR-38

Abstract

In 1999, a 9.5 mm nominal maximum size hot-mix asphalt mixture, designed according to the Superpave mixture design method, was placed as an overlay on Indiana State Road 38. Within one year of construction, the pavement showed signs of significant distress, including aggregate pop-outs and degradation, the presence of free water (weeping) on the driving surface, and longitudinal and fatigue cracking. At the request of the District, an investigation was undertaken to determine the cause of the pavement distress. As part of the investigation, core samples were taken from the roadway surface and tested for compliance with material properties and volumetrics, and to determine the mixture permeability. The mixture met all applicable materials and volumetric specifications, but had a low in-place density and was permeable. The results indicate that the mixture was too coarsely graded to achieve compaction in the relatively thin lift specified by the Department of Transportation. The resulting recommendations were that the mixture be removed and replaced, and that the mixture specifications be revised to more closely control gradation and increase mixture lift thickness.