This report details the forensic investigations conducted to identify the causes of pavement failures shortly after a rehabilitation activity on five interstate highway projects in Oregon, and the research efforts conducted to develop guidelines to minimize the risk of premature failures on future projects. One of the principal objectives of this research effort was to identify sources of moisture and other conditions that led to the early rutting problems observed along the five projects. Overall, improper tack coat or failure, permeable dense-graded layers, inadequate drainage, and, possibly, inadequate compaction of dense-graded material, were all identified as the likely root causes of the observed moisture damage and consequential rutting problems. The other principal objective was to evaluate design, construction, and materials requirements that will minimize the risk of such failures for future rehabilitation projects so that guidelines could be developed for these processes. In this respect, this report contains guidelines for the following:
- Pre-construction site investigations to identify the potential for moisture-related problems.
- Pavement structural design techniques that have been effective in reducing the risk of failures related to moisture damage.
- Construction techniques that can reduce the risk of failure due to moisture damage.
- Materials selection and testing to assist in reducing the risk of failure due to moisture damage.