The Interrelationship between Indirect Resilient Modulus and Dynamic Modulus for Dense Graded Hot Mix Asphalt

Abstract

Permanent deformation is one of the most important types of distress in flexible pavement. Currently and based on the Australian Mechanistic-Empirical Pavement Design Procedure, the indirect tensile test (IDT) is conducted in New Zealand in order to determine the asphalt modulus. This test is carried out on a 100 mm diameter by 50 mm height specimen. However, the current Simple Performance Test (SPT) procedure requires the dynamic modulus to be obtained from the axial compression test performed on 100 mm diameter by 150 mm height specimen. One issue related to the axial compression test is that it is often impossible to obtain this size specimen from actual pavement since a typical asphalt layer thickness is less than 150 mm in New Zealand. Therefore, IDT becomes more appropriate for existing pavement evaluation due to its privilege of testing on cored size specimens. The objective of this research is to perform an experimental and analytical study on the dynamic modulus parameters derived from the aforementioned test methods to improve design accuracy. In this research, two common types of asphalt cement are tested at three different air void percentages. Graphical and statistical comparisons of results from the axial compression and IDT test methods are presented in order to assess their interrelationships. The findings show that, the dynamic modulus determined form IDT test is in good agreement with that form axial compression tests. Based on the statistical analysis, more than 90% of data showed complete similarity for the dynamic modulus calculated from these two tests.