Relationship between backcalculated dynamic modulus, estimated dynamic modulus, and fatigue damage in asphalt concrete

Abstract

ABSTRACT There are several methods for determining the stiffness of asphalt concrete in an existing pavement. The three primary methods are dynamic modulus testing in the laboratory, predictive equations, and falling weight deflectometer (FWD) testing. The Pavement ME asphalt over asphalt (AC/AC) overlay design procedure uses multiple methods to characterise fatigue damage in the existing asphalt concrete. This paper examines the relationship between backcalculated dynamic modulus, estimated dynamic modulus, and fatigue damage in in-situ asphalt concrete. FWD load magnitude and asphalt temperature, both of which have been shown to affect the relationship between backcalculated and estimated dynamic modulus, are also considered. A statistical analysis is performed using data from the Long-Term Pavement Performance Programme (LTPP). Analyses are performed within individual LTPP sections and using pooled data from multiple pavement sections. It is determined that the relationship between backcalculated dynamic modulus and estimated dynamic modulus is significantly related to the amount of fatigue damage in the in-situ asphalt concrete. However, there is also a threshold of fatigue damage above which the relationship between backcalculated modulus, estimated modulus, and fatigue damage is no longer significant.