Selection of Laboratory Test Specimen Dimension for Permanent Deformation of Asphalt Concrete Pavements

Permanent deformation of asphalt concrete pavements is a critical distress mechanism. Efforts are currently being made to understand, analyze, and predict permanent deformation response. To characterize asphalt concrete, laboratory testing is routinely performed. The concept of the representative volume element for determining the minimum specimen dimensions to obtain reliable and repeatable laboratory test data is discussed here. Two conceptual laboratory tests that are currently used to characterize asphalt concrete—the restricted triaxial test and the simple shear test at constant height—are also discussed. The imperfections of both tests are investigated and recommendations for specimen size and the aspect ratio for each of the tests are made.