Monitor Field Performance of Full-Depth Asphalt Pavements to Validate Design Procedures

As a means to validate the Texas perpetual pavement (PP) design procedure, this study monitored the construction and performance of various Texas PP sections. The research methodology and scope of work included data collection, extensive laboratory and field testing, computational modeling, performance evaluations, and database development. Based on the study findings, the researchers recommend the following:

• transitioning to a PP structural design with about 14 inches total hot-mix asphalt (HMA) thickness (use the FPS 21W and MEPDG software for PP structural thickness design and performance predictions, respectively),
• using constructable dense-graded mixes such as the Type B mix for the main structural load-bearing layers,
• revising the design moduli value to a range of 700 to 1200 ksi for the load-bearing layers and a minimum strength of 35 ksi for the foundation,
• improving and enforcing construction quality specifications, and
• monitoring the pavement sections over the long term.

A structural thickness reduction from the current 22 to about 14 inches total HMA thickness translates into 8 inches of HMA cost savings. This difference saves millions of dollars while yielding satisfactory performance with minimal rehabilitation activities. Additionally, use of dense-graded mixes such as the Type B (as opposed to coarse-graded Stone-Filled HMA mixes) will lead to better construction quality with minimal subsurface defects. The rich bottom layer is generally not necessary to meet structural requirements but may be necessary to ensure density of lower HMA layers or to serve as a moisture barrier in certain environments. Overall, the developed Texas PP database will serve as an ongoing reference data source for Texas Department of Transportation engineers as well as other transportation professionals.