AbstractsEngineering

Damage can be limited to the top layer in perpetual pavements through the use of a very thick surface layer or a binder-rich intermediate layer. To achieve this goal, tensile strains at the bottom of the top hot-mix asphalt (HMA) layer must be limited to below a certain value known as the fatigue endurance limit (FEL). In this thesis, a method for estimating the allowable strain in the asphalt layers of flexible airfield pavements is proposed based on the concept that HMA fatigue failure is associated with a significant reduction in HMA layer modulus, usually taken as 50 percent. Falling Weight Deflectometer (FWD) testing results collected from flexible pavements at the FAA’s National Airport Pavement Test Facility (NAPTF) were analyzed to determine the loading pass for each section that the HMA layer modulus was reduced by 50%. NAPTF tensile strain data was then used to determine the strain at the critical pass for each pavement section by averaging the two or three peaks in the strain profile at the critical loading pass. The proposed approach was validated by comparing the results to those obtained from Shen and Carpenter’s Rate of Dissipated Energy Change (RDEC) model to estimate the theoretical Nf50 tensile strain. In addition, it was also observed that the variability of peak tensile strain values increased at pass corresponding to a 50% reduction in HMA modulus, confirming that the proposed criterion in fact relates to observable damage. Federal Aviation Administration