An important but often overlooked consequence of overlaying a concrete surface is an increase in pavement surface temperature and the resulting effect on the surrounding facilities. As temperatures rise, cooling demands and electrical consumption increase. This is a direct consequence of the urban heat island effect. Prior to embarking on a long term strategy for noise reduction, agencies should consider the long term consequences on the other environmental issues.
The urban heat island effect is no exception…
The image on the top left, below, is an infrared photograph of an asphalt roadway leading into a concrete parking lot in Rio Verde, Arizona; the photo below it presents the same scene. Note the immediate transition from asphalt (red) to the concrete overlayed parking lot (yellow green) at the driveway. There was a 17ºC difference in temperatures between the asphalt and the concrete surfaces. The photo on the top right was taken of an asphalt parking lot adjacent to a golf course. Note the 29 - 32ºC temperature of the grass and the 57ºC temperature of the asphalt; the photo below it represents the same scene.
The figure at right shows a preliminary model by Arizona State University to predict pavement surface temperature as a function of the time of day. The three surfaces included are dense graded asphalt (AC), asphalt rubber friction course (ARFC), and concrete (PCCP). These are simulations modeled after real data from the Arizona freeway system and show concrete is by far the coolest surface.
- Exposure of 1 second to pavement at 70 ºC can burn human skin.
- At 70 ºC you can cook an egg on asphalt in five minutes.
- Asphalt pavement temperatures in Phoenix have reached as high as 77 ºC.
The photo at left is an infrared image of an Arizona ARFC overlay next to a concrete pavement. The ARFC overlay (red area) is near 65 ºC, while the concrete pavement is under 57 ºC.
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