This report documents an investigation of water-related distress on portions of I 65 in Hardin County, Kentucky, on Muldraugh Hill. An open-graded surface placed on a full-depth asphaltic concrete pavement had shown areas of flushing and shallow shear failures in the outer lanes after one year of service. Cores were obtained from the outer lanes in areas exhibiting no problems to shear and flow failures. Core sites also were chosen across the lane to represent edge, wheel track, and between wheel track conditions. Visual inspection of the cores was made under normal lighting and an ultraviolet light and photographs were taken. Construction data and records indicated no abnormal construction problems. Results of laboratory density, extraction, and gradation tests coupled with nuclear density tests and visual inspection of the cores indicate water had caused the asphalt to be stripped from the aggregate. Soft particles in the dense-graded surface course below the open-graded course had deteriorated. The stripped asphalt and deteriorated soft particles had migrated toward the surface causing the pores to be filled in most locations. Where the asphalt/matrix was particularly weak, heavy truck tireloads had caused the material to move laterally over the adjacent stiffer material. Water is being held in the pores of the open-graded course and allowing the dense-graded surface course below to become saturated causing the asphalt to be stripped from the aggregate and softer particles to become deteriorated.

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The contents of this report reflect the views of the authors who are responsible for the facts and accuracy of the data presented herein. The contents do not necessarily reflect the official views or policies of the Kentucky Transportation Cabinet, the University of Kentucky nor, of the Federal Highway Administration. This report does not constitute a standard, specification, or regulation.