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Studies on urban heat island (UHI) have been more than a century after the phenomenon was first discovered in the early 1800s. UHI emerges as the source of many urban environmental problems and exacerbates the living environment in cities. Under the challenges of increasing urbanization and future climate changes, there is a pressing need for sustainable adaptation/mitigation strategies for UHI effects, one popular option being the use of reflective materials. While it is introduced as one effective method to reduce temperature and energy consumption in cities, its impacts on multi-dimensional environmental sustainability and large-scale non-local effect are inadequately explored. This paper provides a synthetic overview of potential environmental impacts of reflective materials at a variety of scales, ranging from energy load on a single building to regional hydroclimate. The review shows that mitigation potential of reflective materials depends on a portfolio of factors, including building characteristics, urban environment, meteorological and geographical conditions, to name a few. Precaution needs to be exercised by city planners and policy makers for large-scale deployment of reflective materials before their environmental impacts, especially on regional hydroclimates, are better understood. In general, it is recommended that optimal strategy for UHI needs to be determined on a city-by-city basis, rather than adopting a “one-solution-fits-all” strategy.
ContributorsYang, Jiachuan (Contributor) / Wang, Zhi-Hua (Correspondent) / Kaloush, Kamil (Contributor)
Created2015-06-11
Description
Waste plastic is considered an environmental pollutant because it is not biodegradable. Therefore, there is increased interest in the use of recycled plastic in pavement construction. Polyethylene terephthalate (PET) is a thermoplastic polymer that is commonly used in the manufacturing of containers and bottles. Waste PET is a durable material that has shown enhancement in performance when introduced into asphalt binder and asphalt mixtures. However, PET particles tend to separate from asphalt because of differences in density, molecular structure, molecular weight, and viscosity, leading to inadequate dispersion of PET particles in the asphalt. This incompatibility between PET and asphalt causes segregation, where storage stability becomes an issue. To solve this problem, applying a surface activation on the PET using another abundant urban waste (waste vegetable oil) was examined in this study, showing this method can be effective to enhance PET-asphalt interactions and consequently the storage stability of PET-modified asphalt. To ensure proper surface activation, it is important to thoroughly understand the chemo-mechanics of asphalt containing PET particles as well as the underlying interaction mechanism at the molecular level. Therefore, this study integrates a multi-scale approach using computational modeling based on density functional theory along with laboratory experiments to provide an in-depth understanding of the mechanisms of interaction between surface-activated PET and asphalt. To do so, the efficacy of bio-oil treatment was examined in terms of both the surface-activation capability and the durability of the resulting PET-modified asphalt. It was found that the grafted bio-oil on the PET particles can make a strong interaction with bituminous composites, leading to enhancing the durability and extending the service life of asphalt pavement by reducing the diffusion of free radicals and moisture into the bulk. The study was further extended to study the effect of coating the PET with biochar, showing the latter coating can improve the mechanical properties of the PET-modified asphalt and the adsorption behavior of the PET for volatile organic compounds. The performance of the waste PET was compared with another widely used modifier, crumb rubber.
ContributorsAldagari, Sand (Author) / Fini, Elham (Thesis advisor) / Kaloush, Kamil (Committee member) / Ozer, Hasan (Committee member) / Arizona State University (Publisher)
Created2024