Comparing Flexible Pavement Performance Using Emerging Analysis Tools

In recent years, a variety of tools have been developed to assist in the analysis of flexible pavement service life in the United States. Although the output from many of the approaches is similar, each tool varies in the amount of testing effort, materials, and equipment necessary to arrive at the resulting predictions. Building upon the findings from research conducted in the National Cooperative Highway Research Program (NCHRP) Project 9-22B, this study focused on comparing flexible pavement performance predictions using three emerging analysis tools. One of the pavement analysis software packages, which considered the standard of, predicts performance in terms of incremental distresses and damage accumulation during a pavement’s service life. The other two programs are performance-related specification (PRS) tools that predict pavement performance in terms of service life factors. Three different asphalt mixtures were evaluated including a conventional mixture and two unconventional mixtures modified with emerging material technologies. The conventional mixture was used in a full-depth reconstruction project that featured low-level truck traffic. The two unconventional mixtures were placed as overlays on two structures featuring heavy truck traffic and the same substructure. Results from all three programs indicated that rutting predictions were similar among different analysis tools. However, the fatigue cracking predictions showed the greatest differences due to how the different analysis tools model climatic conditions. A comparison of the different analysis tools also suggested that for the mixes evaluated, one of them could be used effectively with Level 2 hot mix asphalt (HMA) inputs, in lieu of requiring the more time-intensive Level 1 HMA inputs, to predict the service life of flexible pavements. By performing a parametric analysis, it was established that this tool was sensitive to traffic variations and changes in structural support in combination with higher traffic. Certain modifications to the volumetric properties of the HMA layers produced significantly different performance predictions using this particular tool. The results of this study showed that the three analysis tools are comparable and produce equivalent performance predictions. Thus, the decision of which analysis tool to use should be based on a transportation agency’s assessment of its testing capabilities, budget level, and project complexity. In addition, the approach developed in this study can be enhanced in the future to form the basis of a decision-making procedure to help direct the amount of effort and funding necessary in the pavement and mixture design phase.