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Pavement temperature effects on overall urban heat island

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In recent years, an increase of environmental temperature in urban areas has raised many concerns. These areas are subjected to higher temperature compared to the rural surrounding areas. Modification of land surface and the use of materials such as concrete and/or asphalt are the main factors influencing the surface energy…

In recent years, an increase of environmental temperature in urban areas has raised many concerns. These areas are subjected to higher temperature compared to the rural surrounding areas. Modification of land surface and the use of materials such as concrete and/or asphalt are the main factors influencing the surface energy balance and therefore the environmental temperature in the urban areas. Engineered materials have relatively higher solar energy absorption and tend to trap a relatively higher incoming solar radiation. They also possess a higher heat storage capacity that allows them to retain heat during the day and then slowly release it back into the atmosphere as the sun goes down. This phenomenon is known as the Urban Heat Island (UHI) effect and causes an increase in the urban air temperature. Many researchers believe that albedo is the key pavement affecting the urban heat island. However, this research has shown that the problem is more complex and that solar reflectivity may not be the only important factor to evaluate the ability of a pavement to mitigate UHI. The main objective of this study was to analyze and research the influence of pavement materials on the near surface air temperature. In order to accomplish this effort, test sections consisting of Hot Mix Asphalt (HMA), Porous Hot Mix asphalt (PHMA), Portland Cement Concrete (PCC), Pervious Portland Cement Concrete (PPCC), artificial turf, and landscape gravels were constructed in the Phoenix, Arizona area. Air temperature, albedo, wind speed, solar radiation, and wind direction were recorded, analyzed and compared above each pavement material type. The results showed that there was no significant difference in the air temperature at 3-feet and above, regardless of the type of the pavement. Near surface pavement temperatures were also measured and modeled. The results indicated that for the UHI analysis, it is important to consider the interaction between pavement structure, material properties, and environmental factors. Overall, this study demonstrated the complexity of evaluating pavement structures for UHI mitigation; it provided great insight on the effects of material types and properties on surface temperatures and near surface air temperature.
ContributorsPourshams-Manzouri, Tina (Author) / Kaloush, Kamil (Thesis advisor) / Wang, Zhihua (Thesis advisor) / Zapata, Claudia E. (Committee member) / Mamlouk, Michael (Committee member) / Arizona State University (Publisher)
Created2013
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Mechanical and Thermal Properties of Copper Slag Concrete

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In this investigation, copper slag was used as a coarse aggregate in four different mixes of concrete, consisting of 0%, 25%, 50%, and 100% copper slag by volume. Locally available Salt river aggregate was used as a control, and mixes were tested for density, strength, thermal conductivity, specific heat capacity,…

In this investigation, copper slag was used as a coarse aggregate in four different mixes of concrete, consisting of 0%, 25%, 50%, and 100% copper slag by volume. Locally available Salt river aggregate was used as a control, and mixes were tested for density, strength, thermal conductivity, specific heat capacity, and thermal diffusivity. Density was shown to increase with increasing copper slag content, increasing an average of 2298 kg/m^3, 2522 kg/m^3, and 2652 kg/m^3 in the 25%, 50%, and 100% mixes. This represents a 15% increase in density from 0% to 100%. Compressive strength testing indicated that the presence of copper slag in concrete provides no definitive strength benefit over Salt River aggregate. This result was expected, as concrete's strength is primarily derived from the cement matrix and not the aggregate. Thermal conductivity showed a decreasing trend with increasing copper slag content. Th control mix had an average conductivity of 0.660 W/m*K, and the 25%, 50%, and 100% mixes had conductivities of 0.649 W/m*K, 0.647 W/m*K, and 0.519 W/m*K, respectively. This represents 21% drop in thermal conductivity over the control. This result was also expected, as materials formed at higher temperatures, like copper slag, tend to have lower thermal conductivities. Specific heat capacity testing yielded results that were statistically indeterminate, though unlike strength testing this arose from inaccurate assumptions made during testing. This also prevented accurate thermal diffusivity results, as diffusivity is a function of density, thermal conductivity, and specific heat capacity. However, given the trends of the first two parameters, it is plausible to say that diffusivity in copper slag concrete would be lower than that of the control ix. All of these results were plugged into ASU's Pavement Temperature Model to see what effect they had in mitigating the UHI effect.
ContributorsLaughlin, Colin (Author) / Kaloush, Kamil (Thesis director) / Phelan, Patrick (Committee member) / Witczak, Kenneth (Committee member) / Barrett, The Honors College (Contributor)
Created2012-05