Currently hot-mix asphalt (HMA) mixture design and pavement structural design are not fully integrated though Superpave asphalt mixture design is somewhat project specific. The objective of this study was to compare elastic moduli assumed during structural design of pavements with the back-calculated moduli of HMA layers obtained from the Falling Weight Deflectometer(FWD) tests and the dynamic modulus values measured in the laboratory. Five newly built Superpave pavements, designed using the 1993 AASHTO DesignGuide were selected as study sites in this research. Deflection data was collected with a Dynatest 8000 FWD on a 1000-ft test section on each site. The HMA layer moduli were then back-calculated using an elastic layer analysis program. Full depth cores were taken from each section and tested in the laboratory for dynamic moduli. The results show that back-calculated and laboratory moduli are somewhat comparable for all practical purposes. The laboratory dynamic moduli increase with loading frequency indicating the need for considering the vehicle speed in the HMA pavement structural design. HMA design moduli, assumed by the Kansas Department of Transportation (KDOT) during pavement structural design, are lower than both back-calculated and laboratory dynamic moduli. Thus current HMA design moduli are achievable in the field through Superpave mixture design despite the fact that the pavement structural design and mix design processes are not integrated.
Abstract