As previously reported, Phoenix, Az had a successful trial project of its “cool pavement” project ending in late 2021. Unfortunately, the city’s Street Transportation Department recently reported that some roads with the treatment are crumbling. Since the Cool Pavement Program began in 2020, 73 miles (~117 km) in 17 neighborhoods have been treated, but none of those other locations have had issues.
Cool pavement is a sealant made up of asphalt, water, an emulsifying agent (soap), mineral fillers, polymers, and recycled materials that is applied on top of the existing asphalt pavement. As the treatment reflects back the sunlight that hits it – rather than retaining the heat – it has the potential to offset rising nighttime temperatures. The cool pavement technology was installed in hopes of reducing the heat island effect and reducing temperatures in the city. A 2021 study conducted by ASU’s Global Institute of Sustainability and Innovation, Healthy Urban Environments and the Urban Climate Research Center for the City of Phoenix found that “cool pavement” had an average surface temperature of 10.5 to 12 degrees Fahrenheit lower than traditional asphalt at noon and during the afternoon hours.
According to the Street Transportation Department, the current problems arose when the first application failed to adhere to the existing asphalt correctly. A different treatment was later applied, but recent heavy rains have exacerbated the problems.
“The mixture of those two products, and a rain event during the weekend of December 3-4, unfortunately caused the coating to peel off the roadway,” the city’s official statement said. “City staff has an initial cleanup underway using street sweepers and is working to find a permanent solution. Communication with the affected residents is underway.”