Viscoelastic characterization and comparison of Norwegian asphalt mixtures using dynamic modulus and IDT tests

Abstract

This paper presents the comparison of stiffnesses of two types of asphalt concrete mixes (Ab11 and Agb11) fabricated in the laboratory using two commonly used stiffness tests. (1) uniaxial compression dynamic modulus (E*) and (2) Indirect tensile resilient modulus (Mr) tests are conducted at various temperatures, frequencies, and loading times. As expected, both E* and Mr values decrease as temperature increases and frequency decreases. It is observed that the Mr is generally less than the E*. However, this phenomenon is dependent on frequency, temperature, and material type. The viscoelastic property of the two mixes is characterized using the time-temperature superposition principle. Master curves are developed using the mathematical sigmoid and the rheological 2S2P1D models. It has been observed that the rheological model has shown difficulty to converge optimization error to fit Mr master curve while sigmoid function accurately fitted the measured data. Mr is compared with E* both in frequency and time domains using master curves. A closer comparison is observed with the storage modulus((E')and time-domain relaxation modulus E(t) master curves. Considering the inherent time-domain property of Mr, it is recommended to compare with E' or E(t). From the master curves and data analysis and by considering inputs such as energy loss, modular ratio, frequency, temperature, and other volumetric properties, a rigorous Mr vertical shifting function can be developed. Finally, a material database is obtained for Norwegian asphalt mixes.