Effects of Binder and Mix Properties on the Mechanistic Responses of Fatigue Cracking APT Sections

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One of the major benefits of Accelerated Pavement Testing (APT) as a research tool is that the performance of pavement materials and structures can be evaluated at a reduced cost and in a short period of time. The Civil Infrastructure Systems Laboratory (CISL) for APT at Kansas State University was established in 1997. Six fatigue pavement sections that had 100 mm thick hot mix asphalt layer were constructed for APT in CISL. The sections had the same base and subgrade materials. The sections were instrumented using strain gauges and pressure cells to measure pavement responses under APT loading. They were loaded with a 100 kN single axle load at 20 °C. The main objective of this paper is to investigate the effects of binder content, binder grade, and mixture nominal maximum aggregate size (NMAS) on the mechanistic responses from the experimental sections. Stress, strains, deflections, and profile data were collected periodically. Normalized falling weight deflectometer (FWD) deflection data were used to back-calculate moduli using the EVERCALC software. Measured pavement temperatures were used to adjust back-calculated moduli to a temperature of 20 °C. The stiffer the binder, the lower the longitudinal strain, permanent deformation, and roughness, but the higher the transverse strain, stress on the top of subgrade in general, and back-calculated moduli. Higher binder content results in a higher longitudinal strain, transverse strain, stress on top of subgrade, permanent deformation, rut depth, and roughness. The larger the NMAS, the higher the transverse strain, back-calculated moduli, permanent deformation, and roughness, but the lower the longitudinal strain, stress on the top of subgrade, and rut depth.