Evaluation of Dynamic Modulus in Asphalt Paving Mixtures Utilizing Small-Scale Specimen Geometries

摘要

The results of dynamic modulus testing have become one of the primarily used performance criteria to evaluate the laboratory properties of asphalt mixtures. This test is commonly conducted to characterize asphalt mixtures mechanistically using an asphalt mixture performance tester (AMPT) as developed in NCHRP Project 9-29. The test specimen geometry consists of a cylinder with a 100 mm diameter and a 150 mm height. This geometry is practical for laboratory-prepared specimens produced using a gyratory compactor. However, the specimen scale is problematic when the test specimen is prepared from field cores and the investigator wants to isolate the testing to a single asphalt mixture material/layer. This is because most asphalt mixture layers, especially surface and intermediate layers, are placed with a thickness less than 150 mm. This study investigated the use of small-scale specimens as an alternative means to conduct dynamic modulus testing of asphalt mixture materials. To validate the small-scale approach, the dynamic modulus measured on small-scale cylindrical specimens was compared to the dynamic modulus measured on full-size cylindrical specimens (100 × 150 mm) using asphalt mixtures with a nominal maximum aggregate size (NMAS) of 9.5, 12.5, 19.0, and 25.0 mm. Small-scale specimens with a diameter and height of 38 × 135 mm, 50 × 135 mm, 38 × 110 mm, and 50 × 110 mm were evaluated. From the findings of this study, for 9.5 and 12.5 mm NMAS mixtures, any of the four small-scale geometry dimensions tested appears to be suitable alternatives to the full-size specimen. For 19.0 and 25.0 mm NMAS mixtures, the two small-scale geometries with a diameter of 50 mm appear to be suitable alternatives to the full-size specimen.