Characterization of Asphalt Mixtures with Addition of Drill-Well Gravel

Abstract

One of the by-products of the oil industry that is disposed of in nature as waste is oil well gravel. When improperly disposed of, it pollutes the soil, deteriorates the urban landscape, and constitutes an environmental liability if it is destined for landfills without prior treatment. As a way of reusing gravel from oil wells, this research proposed using gravel as a filler in hot asphalt mixtures. This study evaluated hot asphalt mixtures dosed with 2% filler by the Superpave methodology. The 2% filler was partially replaced by the oil well gravel (1% gravel and 1% lime) and totally (2% gravel), compared to the use of 2% lime as a commonly used filler in traditional blends. Rheological tests such as rotational viscosity, performance grade (PG), creep and recovery under multiple stresses (MSCR), and linear sweep amplitude of strain (LAS) were carried out in order to investigate the effects on asphalt mastic when incorporating oil well gravel in the contents proposed. The asphalt mixtures were evaluated through mechanical tests: tensile strength, modulus of resilience, dynamic modulus, flow number, and modified Lottman. The rheological evaluation could prove the gain in viscosity and stiffness of the asphalt binder, showing less susceptibility to thermal variation and, consequently, an increase in the resistance to permanent deformation. It was also found that the incorporation of the gravel residue caused a reduction in the resistance to damage and shorter fatigue life to the binder at the highest deformation amplitudes. The use of gravel from oil wells did not cause a significant change in the mechanical performance of the asphalt mixtures at the tested contents, presenting itself as a sustainable option for use mainly in regions with low rainfall, such as the Northeast region of Brazil.