Institute for Transportation

About the research

The objective of this research was to improve the construction, economic analysis, material selection, in situ testing, and inspection of pavement foundation layers and to develop a performance-based framework to improve the evaluation and performance of pavement foundations. The outcome of this study is a set of conclusive findings that can help make pavement foundations more durable, uniform, constructible, and economical.

Detailed and comprehensive field studies were conducted in multiple states at various sites that featured either existing pavement sections with different levels of performance or new pavement foundation construction. To maximize the range of field conditions evaluated, field study sites were selected to reflect a variety of soil and climatic conditions. All aspects of pavement foundation layers were investigated, including thickness, material properties, permeability, modulus/stiffness, strength, volumetric stability, and durability.

For each field study site, forensic and in situ testing plans were developed that incorporated measurements taken using existing and emerging technologies (e.g., intelligent compaction) to evaluate performance-related parameters rather than simply index or indirectly related parameters. In situ testing was extensive and reflected both the current state of the practice and emerging testing technologies, including non-destructive methods and intelligent compaction. Further, an interactive open house was conducted at each site to facilitate discussion and review of the field measurements.

The results of the study are compatible with the Mechanistic-Empirical Pavement Design Guide (MEPDG). The evaluation of pavement foundation design input parameters at each site provided a link between what is actually constructed and what is assumed during design. Many design inputs are relevant to pavement foundation layers, and this project resulted in recommendations for establishing and verifying the values of these inputs.

Comprehensive project reports for each field testing site summarize the findings from the field investigations. The final report generated as part of this project compiles current knowledge and summarizes the new knowledge gained during the course of this study. The report includes best construction practices for providing stable and uniform pavement foundations, recommendations on quality control/quality assurance (QC/QA) testing, design aids, and suggested improvements to specifications using a performance-based framework.