Design of gussasphalt mixtures based on performance of gussasphalt binders, mastics and mixtures

Gussasphalt has been widely used as a surfacing material for long-span steel bridge decks. While most existing studies focus on the engineering properties of gussasphalt mixtures, this study aims to design gussasphalt mixtures using Trinidad Lake Asphalt (TLA) based on the mechanical performance of gussasphalt binders, mastics and mixtures. Three base asphalts (the styrene-butadienestyrene modified asphalt, the Pen 20/40 and Pen 60/80) and four dosages of TLA (20%, 30%, 40% and 50%) were used to prepare gussasphalt binders. The performance of Pen 20/40 with 30% TLA was found to be a qualified design according to the penetration, softening point and ductility of the gussasphalt binder and the dynamic shear properties of gussasphalt mortar. Afterward, optimum binder-aggregate ratio of 8.75% was obtained based on workability, high temperature performance, and low temperature performance. Lastly, the mechanical response of the gussasphalt mixture to dynamic loading was analysed using the dynamic frequency sweep test and triaxial repeated load permanent deformation test. The findings also indicated that the SBS modified asphalt binder may be not suitable as the base asphalt of gussasphalt. The cumulative strain level of gussasphalt mixture in triaxial loading linearly increased with respect to load stress, but exponentially increased with respect to testing temperature.