United States Department of Transportation
i
Determining the Equivalent Thermal Gradient for Rigid Pavements at the National Airport Pavement Test Facility
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2024-07-01
[PDF-1.68 MB]
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Abstract:In recent years, the Federal Aviation Administration (FAA) has focused on identifying and quantifying corner breaking in rigid airport pavements. Prior research studies at the FAA National Airport Pavement Test Facility (NAPTF) have shown premature corner breaks that were not anticipated during design. The FAA has since attributed the corner breaks to Portland Cement Concrete (PCC) curling occurring in the NAPTF; however, little research effort has been aimed at quantifying the severity of PCC curling. Thus, the purpose of this research study was to quantify the severity of PCC curling occurring at the NAPTF using information and data Construction Cycle 1, Construction Cycle 2, and Construction Cycle 6. The research study quantified PCC curling through an Equivalent Thermal Gradient (ETG), which included temperature, shrinkage, and permanent (built-in) gradients. The ETG was calculated using literature, environmental, and thermocouple data collected from within the PCC slabs. In parallel, ETGs were backcalculated using finite element analysis and instrumentation data collected during each NAPTF construction cycle. The finite element analysis included thermal and aircraft loading similar to the conditions of the respective experiment. Finally, the calculated and backcalculated ETGs were then compared to determine an appropriate ETG for the NAPTF. Based on the findings from this research study, the rigid pavements at the NAPTF experience an ETG range of approximately -3.0 to -6.0 °F/inch. Further, the primary cause of curling at the NAPTF was found to be associated with permanent curling experienced during construction.
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