‘Cold pavement’ reduced asphalt temperature by up to -11ºC in a city in the United States
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The first results of the ‘cold pavement’ project carried out in Phoenix, in the United States, showed that the new asphalt can reduce surface temperatures by up to -11º C during the summer. The result presented by the Department of Street Transport of City of Phoenix It is part of the second stage of the research, which began in 2022.
According to the department, cold pavement can reduce the temperature by reflecting sunlight, rather than absorbing it. Because of this reflection, new asphalt also reduces the need for long-term road maintenance. According to the researchers, reflection makes it difficult for heat to enter deeper layers, preventing internal wear of the asphalt.
Cold floor
CoolSeal 2.0, as the project is called, is a partnership between the City of Phoenix and Arizona State University (ASU). The research took place through the Rob and Melani Walton Sustainability Solutions Service program, in free translation. The pavement was applied in residential neighborhoods, such as in West Phoenix, and temperature collection took place throughout the summer and autumn days of 2022. The project began the first phase in 2020, covering approximately 57 km with the product.
According to the report, ATU researchers evaluated the thermal performance of the reflective coating, in conjunction with residents’ shared perceptions. Phase II began in the summer of 2022, with testing of the new CoolSeal 2.0 pavement. Compared to the first product used, CoolSeal 2.0 has a darker color and different formulations. The color change was a contribution from the residents.
Results from the first stage of the research also showed that the night air temperature at approximately 1.80 meters above the asphalt was -17º C lower than on untreated surfaces. But, because of reflectivity, the daytime temperature can increase or remain the same. According to the researchers, the experience of midday and afternoon heat exposure on the cold pavement was similar to walking on a conventional concrete sidewalk.
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