Influence of aging, RAP content, and recycling agent on the performance of asphalt mixtures

A great complexity limits its use as the degree of aging of the asphalt binder of the RAP is a determinant for the interaction with the new binder and recycling agents to design asphalt mixtures with reclaimed asphalt pavement (RAP). One of the ways to analyze the level of interaction between the aged binder and the recycling agent is through the analysis of the performance of the mixtures after the accelerated aging of the samples in the laboratory. Thus, this paper evaluated the mechanical performance of asphalt mixtures with high contents of RAP (50%, 75%, and 100%) and organic type recycling agents (residual engine oil) and surfactant (ADCAP WM), submitted to aging protocols short and long term. The data obtained verified the feasibility of adding up to 75% of RAP in the recycled mixtures. However, detailed monitoring of its execution and performance throughout its useful life is necessary. Fatigue and flexural fracture data were highly altered by aging conditioning, evidencing the reduction in the performance of the compositions of the recycled mixtures. The statistical test showed significance for the parameters RAP content and type/content of the recycling agent used. In addition, there was an increase in the deformation capacity and better resistance to aging and cracking with the incorporation of the surfactant recycling agent.

Effects of the addition of fatty acid from soybean oil sludge in recycled asphalt mixtures

Recycling agents provide better additions of reclaimed asphalt pavement (RAP) in the production of new asphalt mixtures. Alternative and residual materials that have the potential as asphalt binder viscosity reducers have gained visibility in the field of paving due to the perspective of circular economy in recycled mixtures. Soybean oil sludge fatty acid is a material produced from soybean oil sludge, a waste generated in the soybean oil refining step. Thus, this paper investigated the physical, chemical, and rheological effects of the asphalt binder PG 64-XX modified by the fatty acid of soybean oil sludge in the contents of 6% and 7% by weight of the binder. The modified binder samples were submitted to penetration tests, softening point, rotational viscosity, performance grade (PG), before and after short-term aging (RTFO), and multiple stress creep and recovery (MSCR). A control asphalt mixture and recycled asphalt mixtures produced with 40% RAP and fatty acid-modified binders were subjected to tensile strength, induced moisture damage, resilient modulus, and fatigue life. A Student's t statistical test verified the significance of the data, as well as the estimation of production costs of these asphalt mixtures. The use of the fatty acid significantly reduced the stiffness and viscosity of the control asphalt binder, decreasing the mixing temperatures at 14 °C and 17 °C to 6% and 7%, respectively. Using higher fatty acid contents from soybean oil sludge significantly improved the performance of recycled mixtures in tensile strength, moisture damage, and fatigue life. The production cost of recycled asphalt mixtures was lower than that of the control mixture.