Variability of Portable Nondestructive Test Methods for Airfield Pavement Evaluations

Abstract: The evaluation of airfield pavement structural conditions is undergoing a gradual transition from traditional destructive and semi-intrusive testing methods, such as the dynamic cone penetrometer, coring, and test pits, towards non-destructive testing (NDT) evaluation techniques. Currently, airfield pavement evaluation (APE) teams use the heavy-weight deflectometer (HWD) and vehicle-mounted ground penetrating radar (GPR) as standard NDT methods with established testing procedures to estimate pavement layer thickness and structural condition. In military airfield evaluations, there is a growing interest in portable, lightweight, and rapidly deployable NDT equipment. The gradual shift to portable NDT surges from the need to minimize pavement disturbance that could accelerate deterioration and compromise the integrity of the infrastructure. This paper discusses the effectiveness and variability of various portable NDT tools that can be readily implemented as routine testing techniques for airfield pavement inspections. The present study introduces a lightweight deflectometer, an impulse-response test, a handheld GPR, and an ultrasonic pulse-echo. A large-scale test section was utilized to conduct NDT tests, including both standard and portable methods, and to generate field data for this study. A total of four test items were selected from the test section: two asphalt pavements, with surface thicknesses of 3 and 7 in.; and two concrete pavements, with surface thicknesses of 8 and 15 in. The effectiveness of the portable LWD and impulse-response test was evaluated by collecting stiffness data on nine different test locations per test item to develop linear relationships between the results from the portable devices and the HWD. Similarly, the effectiveness of the portable GPR and ultrasonic pulse-echo was assessed by comparing the measurements obtained from the devices to field core samples. In addition, the portable NDT tests were evaluated by two independent operators, each performing ten measurement trials at two different locations within each test item to systematically determine the variability of the test results. From this study, the impulse-response and lightweight deflectometer test results matched the impulse stiffness modulus calculated from HWD test data. The ultrasound pulse echo measurements matched the as-built pavement surface layer thickness and field cores. Variability statements were generated from this study for APE teams to ensure that field data is consistent and reliable when evaluating airfield pavement structures.