Rutting Performance of Airport Hot-Mix Asphalt Characterized by Laboratory Performance Testing, Full-Scale Accelerated Pavement Testing, and Finite Element Modeling
Rushing, John Ford
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Hot Mix Asphalt (HMA) laboratory mixture design is intended to provide a durable, rut-resistant mixture for a given traffic type. Current mixture design procedures using the Superpave Gyratory Compactor (SGC) rely on volumetric properties of the compacted mixture to assure reliable performance; however, a definitive performance test does not exist. This study provides guidance for selecting a laboratory performance test for airport HMA mixture designs based on; (a) data analyses of results from four potential laboratory tests, (b) comparisons of laboratory tests results to full-scale accelerated pavement test results, and (c) analyses of results from finite element simulations. The laboratory study evaluated of the repeated load test, the static creep test, the dynamic modulus test, and the Asphalt Pavement Analyzer (APA) test as potential performance tests to accompany airport HMA mixture design with a goal of providing acceptable threshold test results that predict rutting performance under aircraft traffic. Over 340 specimens were tested from 34 asphalt mixtures. Specific criteria for each test method were developed. Next, the test methods and criteria were applied to an HMA mixture design selected for accelerated pavement testing. The full-scale tests applied wheel loads that simulated both military fighter aircraft and heavy cargo aircraft traffic to a pavement constructed to meet typical airport design standards. In the first test, simulating fighter jet aircraft, the tire inflation pressure was 2241 kPa, and the pavement temperature was maintained at 43?C. The second test, simulating cargo aircraft, used a tire inflation pressure of 980 kPa and a pavement temperature of 25?C. As expected, rutting was much more severe in the first test. The full-scale tests were then simulated computationally using finite element modeling. The asphalt layer was modeled using the nonlinear viscoelastic, viscoplastic components of the Pavement Analysis Using Nonlinear Damage Approach (PANDA) model. The pavement sections and wheel loads from the field-tests were recreated using two-dimensional simulations within ABAQUS. The simulations resulted in very high rates of viscoplastic strain for the conditions of the first test, but almost no permanent deformation in the second test. Finally, recommendations for implementing APA criteria into airfield HMA mixture design are presented.