Abstract:

Dynamic modulus is a fundamental property of viscoelastic materials and is typically used as an indicator of mix performance and input for the structural design of flexible pavements. Dynamic modulus can be measured in the laboratory using the Asphalt Mixture Performance Tester (AMPT) using the standard-size test specimen geometry (100-mm diameter by 150-mm length). However, determining dynamic modulus from specimens representing field conditions (field cores) is challenging because the lift thickness of pavement layers is usually less than 150 mm. Therefore, this study compared dynamic modulus test results measured from three airfield asphalt mixes using the standard-size and two small-scale test specimen geometries. The comparative study used several approaches, including evaluating dynamic modulus magnitudes, master curves, statistical variability, and modeled pavement responses from pavement analysis software. Overall, dynamic modulus values from small-scale test specimens show uniformity and good agreement compared to the standard geometry and present less than a 10% difference. Therefore, it is recommended to implement small geometries in dynamic modulus testing to determine performance properties in the laboratory. However, results from small-scale test specimens conducted at high temperatures may need a careful review before implementation since they show more variability and less consistency than the standard-size test specimen’s results.