Calibration of Asphalt Concrete Cracking Models for California Mechanistic-Empirical Design (CalME)

Abstract

Cracking is one of the major distress mechanisms for pavements with asphalt concrete surfaces. Given the composite nature of asphalt concrete, simulation methods such as the Discrete Element Method (DEM) that can incorporate material microstructure are required for properly describing the formation and progression of cracking in flexible pavements. These methods are however typically too time-consuming for use in routine design. As a trade off, a simplified approach based on continuum damage mechanics is taken in the California Mechanistic-Empirical method, called CalME, for practical considerations. The effect of cracking (broken contacts) is described as decreases in overall stiffness, which is indicated by damage. The rate of damage increase is in turn empirically related to peak strain energy endured by the material. The format and constants of this relationship are determined from laboratory fatigue testing of the asphalt concrete. Except for the first few loads, where temperature effects may be pronounced, all of the stiffness versus number of load applications curve are used. Once damage history is calculated, visual surface cracking history can be derived as an empirical function of damage and asphalt layer thickness. This paper presents the CalME fatigue and reflective cracking model and its calibration process using deflection data collected from various Heavy Vehicle Simulator (HVS) tests and the WesTrack accelerated pavement testing experiment.