Selection of Structural Overlays Using Asphalt Mixture Performance

Abstract

Rehabilitating and preserving the current pavement networks have become top priorities for many highway agencies. The structural overlay is one type of rehabilitation solution widely used to improve the structural capacity of pavements. Selecting the proper overlay mixture with the desired performance plays a significant role in extending the service life of an existing pavement. This study focuses on evaluating the performance of overlay mixtures commonly used in rehabilitation projects in Oklahoma. The overlay performance was assessed by integrating laboratory tests with field distress surveys. Five mixtures varying in binder content, nominal maximum aggregate size, and reclaimed asphalt pavement content were identified. Laboratory performance of these mixtures was determined through conducting dynamic modulus tests, direct tension cyclic fatigue tests, Hamburg wheel tracking tests, and indirect tension creep and strength tests. The effect of mixture variables on stiffness and performance was investigated, and resistance of mixtures to fatigue cracking, thermal cracking, and rutting was evaluated. Also, the correlation between five different types of performance test results was investigated. It is recognized that Hamburg and direct tension cyclic fatigue test results are highly correlated, and the mixtures with less permanent deformation under cyclic loading are less susceptible to fatigue cracking. Also, a strong correlation between dynamic modulus and direct tension fatigue test results was found. The laboratory-estimated performance of the selected mixtures was then compared with observations from field distress over a period of time after placement of overlays. A few representative flexible pavement sections in the Oklahoma highway network rehabilitated with these overlay mixtures were identified, and their distress data were monitored. It was observed that field performance data are in a good agreement with laboratory evaluations, and the ranking of mixtures for cracking and rutting susceptibility captured in the laboratory correlates well with observations from the field. At the end of this study, a decision table is suggested for the use of laboratory tests in the selection of appropriate overlay mixtures. The decision tree is developed to prioritize the use of performance tests based on the condition of existing pavements and correlation between the performance test results.