Avaliação reológica de ligante asfáltico modificado com óleo de pequi

Abstract

In recent years, there has been an effort to develop more sustainable asphalt mixes, using alternative materials and technologies that reduce application temperatures, such as Warm Asphalt Mixes (WAM). These mixes, prepared between 100°C and 150°C, consume less energy and emit fewer greenhouse gases. In Brazil, the use of organic additives, such as vegetable oils, has been studied to improve the performance of these mixes, especially in the production of warm mixes. One example is pequi oil, extracted from the fruit of the pequi tree, a tree typical of the Brazilian Cerrado. Pequi oil is rich in unsaturated fatty acids and antioxidants, showing potential for use in asphalt binders. This study analyzed the use of pequi oil as a modifier of the CAP 50/70 asphalt binder. Three additional levels (1%, 2%, and 3%) were investigated, and the modified binders were compared to the CAP 50/70 reference binder. The study was conducted in two main stages: (i) empirical characterization, with penetration, softening point, thermal susceptibility index (TSI), and short-term aging (RTFO) tests; and (ii) rheological characterization, including grade of performance (PG), multiple stress creep and recovery (MSCR), linear amplitude scanning (LAS), and master curve tests. Far-infrared spectroscopy (FTIR) confirmed the presence of characteristic functional groups of the oil, such as esters and fatty acids. It indicated that these compounds remain in the asphalt matrix even after short-term aging (RTFO). The rheological results show that pequi oil reduces the rotational viscosity, complex modulus (G*), and elasticity of the binder, while increasing the phase angle (δ). This change makes the binder more susceptible to flow and less resistant to permanent deformation. Therefore, modification with pequi oil requires limiting the incorporated content to ensure the binder maintains properties compatible with road paving requirements. The incorporation of 2% content presented the best balance between flexibility, aging resistance, and rheological performance.