Towards Carbon Negative Built Environment: The Use of Critical Aging Point
April 1, 2022
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Presented by: Dr. Ellie Fini, Ph.D., P.E., F. ASCE
Abstract: Effective upcycling and recycling is critical to reduce carbon footprint of construction industry. In case of pavements, recycling can be limited by the type and extent of aging that occurs during pavements’ service life. This talk will discuss aging mechanisms of asphalt as well as critical aging point (CAP) beyond which recycling of aged asphalt may not be effective. We will discuss the effect of aging on the restoration capacity of asphalt binder via both computational modeling and laboratory experiments. Our molecular-level analysis shows that as aging progresses, the binding energy of asphaltene monomers increases, leading to an increase in the size of asphaltene nanoaggregates. The latter increase in intermolecular interactions is supported by our laboratory experiments showing an increase in shear thinning as aging progresses. It is also found that aging continuously increases the crossover modulus, Glover-Rowe parameter, stiffness, and critical cracking temperature; aging continuously decreases the stress relaxation capacity, healing index, and thermal conductivity. The rejuvenator effectively restores aged asphalt; however, the rejuvenator's efficacy diminishes as aging progresses, to a point that it had only a marginal effect on asphalt binder aged beyond 80 h (equivalent to 2nd or 3rd generation RAP depending on pavement location and sun intensity). This is especially critical since with the increasing use of RAP in new pavements, road authorities soon will be dealing with second, third, fourth, and older generations of RAP. This talk will further highlight the importance of accounting for the age of as received RAP; for instance, RAP in states with high temperature and high sun intensity are aged more than RAP in milder climates. The results emphasize that adjusting the age of the RAP using a rejuvenator before each recycling stage is critical to avoid reaching and passing the CAP beyond which rejuvenation is not effective.
Speaker bio: Dr. Ellie Fini is an Associate Professor at Arizona State University, an Invention Ambassador at the American Association for the Advancement of Science, a Fulbright Scholar of Aalborg University of Denmark, a Senior Sustainability Scientist at the Global Institute of Sustainability and Innovation and Director of the Innovation Network for Materials, Methods and Management. Her research focuses on the production, characterization and atomistic modelling of sustainable novel materials for use in construction. In addition to more than 200 scholarly publications and numerous invited talks, her research has been featured by BBC Women in STEM, Science Nation, Wired Magazine, and CNBC. She is editor of the ASCE Journal of Materials and Journal of Resources, Conservation & Recycling. She has served as the president of ASCE’s North Carolina Northern Branch and a program director of the National Science Foundation.
