Measurement of G* in Fine Asphalt Mixes

This study characterized the mechanical properties in fine asphalt mixtures by means of a microscale test. The method involved the design of the fine asphalt matrix, the specimen preparation, the performance of shear tests, and the construction of complex shear modulus master curves based on the obtained results. The tests were performed with a device called a dynamic mechanical analyzer (DMA). The test configuration consisted of a temperature and frequency sweep for a given strain level, within the linear viscoelastic range of the material. The test implementation experimental design involved the use of two aggregate sources and three asphalt types (neat, styrene–butadiene rubber modified, and ethylene copolymer modified). On the basis of the results for the mixes, master curves were calibrated by sigmoidal, Christensen–Anderson, and Christensen–Anderson–Marasteanu general models and using Arrhenius and William–Landel–Ferry shift factors. As part of the study, the DMA test based on shear loading mode was successfully implemented and allowed for measurement of a fundamental material property: complex shear modulus ( G*). The G* estimation involved measurement of shear stress, strain, and phase angles. Complex shear moduli in the range of 40 to 170 MPa were obtained; the fine asphalt mixtures modified with ethylene block copolymer developed higher stiffness, and the ones with neat binder had lower stiffness. From the G* results, master curves were developed. A higher fit was obtained when the general sigmoidal formula was used; this result indicated the high degree of similitude in behavior between the fine asphalt matrix and the complete hot-mix asphalt mixtures.