Considerações mecânicas e ambientais sobre misturas asfálticas recicladas a quente para o suporte à tomada de decisão

Abstract

The road pavement industry has been striving to mitigate environmental impacts through the adoption of sustainable measures. One widely adopted alternative is the use of reclaimed asphalt pavement, known as RAP. The overall objective of this thesis was to contribute to the understanding of environmental impacts and performance prediction in pavement by replacing part of the virgin aggregates and asphalt binder with RAP in hot asphalt mixtures. The addition of the milled material was based on the RAP Binder Ratio (RBR) parameter, i.e., the proportion of binder derived from RAP in relation to the total asphalt binder in the mixture. Various recycled mixtures containing up to 30% RBR were analyzed, including Stress Sweep Rutting (SSR) and Tensile/Compression Fatigue tests, which provided data for an analysis and design program for asphalt pavements. Finally, a Life Cycle Assessment (LCA) was conducted, an environmental management technique to assess the potential environmental impacts of producing these mixtures in asphalt plants. The dissertation was organized in the form of a compilation of academic publications. In the first document, the environmental impacts of recycled asphalt mixtures were related to the Sustainable Development Goals (SDGs). It was concluded that recycling significantly contributes to Brazil's international commitments towards sustainable development. The second document addressed the effects of the fine fraction of RAP on stiffness and Tensile Strength (TS) in hot asphalt mixtures. It was observed that the use of the fine fraction of RAP increased TS with an increase in RBR, but this relationship for stiffness only manifested in mixtures with higher RBR proportions. The third document presented a structured questionnaire designed to assist in the life cycle inventory of asphalt pavements. This tool can be applied by producers of asphalt mixtures, companies, and organizations responsible for the construction and maintenance of pavements. In the fourth document, an LCA of asphalt mixture production was conducted. It was highlighted that the extraction of virgin raw materials represented the largest negative environmental impacts. Therefore, the higher the proportion of RAP in the mixture, the greater the environmental benefits. The fifth document analyzed the influence of RAP on resistance to permanent deformation and the prediction of performance in terms of Wheel Track Rutting (WTR) in the asphalt layer. It was observed that recycled mixtures had a predicted WTR of less than 11mm at the end of a simulated 10-year period. The sixth document evaluated the environmental and structural responses of recycled asphalt mixtures. It was concluded that RAP is viable, especially in scenarios of medium traffic, and that its substitution contributes to reducing negative environmental impacts, particularly in the phase of raw material extraction. In general, the research pointed out that the use of modeling programs allows for more sustainable decision-making, even in the design phase. Thus, based on these programs, recycled mixtures demonstrated both environmental and structural viability for use in pavement wearing courses.