Evaluation of the Mechanical Performance of Warm Bio-Recycled Asphalt Mixtures
Roads are the most crucial infrastructure in every nation, and they must be constructed to provide an adequately strong and durable surface for the smooth movement of traffic during their design life to ensure the safety of their users. Regarding this, the asphalt mixtures used to build road pavements are designed to be able to endure climatic fluctuations and traffic loads. Aggregates and bitumen are the main components of an asphalt mixture. Bitumen is a viscoelastic component that provides tensile resistance and cohesion. Aggregates are mineral particles that provide the mixture with resistance to compression due to friction between them. Aggregates and binders need to work together to ensure the combination performs as intended.
Within this framework, and to go a step further towards more sustainable asphalt mixtures, the main purpose of this investigation is to use biobinders as total bitumen replacement in new asphalt mixtures with high RA content manufactured at decreased temperatures. The combination of these three points leads to the production and evaluation of warm bio-recycled asphalt mixtures. The laboratory campaign was focused on characterizing both the binders and the warm bio-recycled asphalt mixtures. Bearing capacity, cohesion, resistance to moisture damage, and resistance to permanent deformations were studied as the main distresses affecting such asphalt mixtures.
This study analyzed the performance of asphalt mixtures produced using biobinders as the only virgin binders, high reclaimed asphalt rates, and reduced manufacturing temperatures, i.e., warm bio-recycled asphalt mixtures. Based on the results, the following conclusions can be drawn:
At the binder level, the rheological characterization of the binders showed that the combination of the stiff RA binder and the soft biobinder might be suitable to achieve a compromise for the rutting and fatigue resistance of the warm bio-recycled asphalt mixtures.
At the mixture level, the warm bio-recycled asphalt mixtures exhibited adequate mechanical properties, including enhanced bearing capacity and resistance to permanent deformations, shedding light on the possible issues regarding these distresses and the use of soft biobinders. The improvement in cohesion and water sensitivity reduced the concern about moisture damage in these types of asphalt mixtures.
The soft consistency of the biobinder combined with the high stiffness of the RA provided favorable results and allowed the positive reduction in manufacturing temperatures. This temperature reduction implies energy consumption savings and decreased greenhouse gas emissions, which must be specifically measured in future research.
These findings reveal that warm bio-recycled asphalt mixtures might be viable solutions for flexible road pavements. The innovative approach of manufacturing warm bio-recycled asphalt mixtures may represent a pivotal advancement in sustainable pavement engineering. The utilization of biobinders and the strategic integration of reused materials, coupled with reduced manufacturing temperatures, not only aligns with sustainable goals but also demonstrates promising performance characteristics. Future research will be focused on incorporating further low-temperature manufacturing technologies for bio-recycled asphalt mixtures, studying their aging and evaluating their reduced environmental impact.
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