Análise da modificação de ligante asfáltico pela adição de polímero estireno-butadieno-estireno (SBS) na caracterização física e reológica

Abstract

The intense process of degradation of asphalt coatings in recent years, due to the increasing action of traffic and more severe climatic conditions, has led to the development of research in the search for new technologies in order to improve the performance and useful life of pavements. In this sense, the modification of asphalt binders by polymers has been shown to be a promising technological option in improving physical, chemical and rheological properties. This work aims to evaluate the influence of the addition of different levels of SBS polymer (2.5%, 5.0% and 7.5%) in pellet format in the conventional 50/70 binder, characterized in virgin and short-term aged conditions in RTFOT (Rolling Thin Film Oven Test). Conventional softening point, penetration and elastic recovery tests were performed. For rheological characterization, the Brookfield viscosity, the high temperature PG and the master curves of Dynamic Modulus and Phase Angle were obtained by means of the Dynamic Shear Rheometer (DSR). For the data analysis, 2S2P1D modeling was used. Damage assessment was performed by Multiple Stress Creep (MSCR) tests for permanent deformation and Linear Amplitude Sweep (LAS) for fatigue. Finally, the storage stability of the modified binders was verified by the Phase Separation test. The mixing protocol performed at high and low shear, with crosslinking by the addition of sulfur, caused excessive stiffening in the binder, while the addition of SBS increased the stiffness by action of the polymer, while generating protective behavior against aging. The joint occurrence of these effects prevented obtaining clear trends regarding the percentage of SBS added in the analysis of physical and rheological properties. The high viscosity values obtained suggest the need for higher than usual temperatures to obtain adequate workability for compaction and mixing. The analysis of the master curves indicated higher values of dynamic shear modulus and lower values of phase angle. A significant increase in high temperature PG was also observed, which extended the range of use of the modified binder. The addition of SBS reduced the permanent deformation gain as well as improved the behavior of these binders against fatigue phenomena at low shear strain values.The phase separation test indicated the need for constant agitation in the asphalt tanks for the highest polymer concentrations. Finally, it is concluded that the mixing protocol was the most responsible for the changes in the behavior of the asphalt binders, indicating the need for its optimization. Likewise, further studies on the asphalt-polymer interaction are necessary in order to expand its use in paving.