Influence of Rest Period on the Fatigue Response of Bituminous Mixture at Low Temperature

Abstract

Laboratory fatigue characterization of bituminous mixtures is carried out typically by conducting a beam bending test at a given frequency and temperature for various strain/stress levels. In the current fatigue test methods, the material is tested at 20°C with continuous loading, and the fatigue life is estimated based on the stiffness modulus and energy dissipation. Very little data exist on the influence of low temperature (0°C), and tests with a rest period. In this study, the fatigue life of the bituminous mixture is estimated at 20 and 0°C, and the influence of the rest period is quantified. For this purpose, a typical bituminous mixture used in Indian highways was fabricated. Experiments were conducted at 0 and 20°C with and without a rest period in strain-controlled mode (600 and 800 microstrains) in a four-point beam bending test setup. For tests with a rest period, a 0.9 s rest period was provided after 0.1 s loading. The evolution of stiffness modulus as per AASHTO T321 [1] and normalized modulus by ASTM D7460 [2] was used in fatigue life estimation. Also, the evolution of energy dissipation during testing was analyzed to characterize the response of material (elastic/viscoelastic) and the beneficial effect of the rest period, if any. The influence of the rest period was more pronounced when tested at 20°C in comparison to testing at 0°C.