Bipartisan Infrastructure Law Series

Aligning your Department’s Priorities with BIL Funding Priorities

This installment is part of the IGGA’s multi-part series aimed at helping your organization design and specify projects that meet the intent of BIL funding.

August Spotlight: Albedo

Diamond-ground concrete pavements have high albedo and help meet the intent of the PROTECT Formula Program established by the BIL.

BIL Funding

The Promoting Resilient Operations for Transformative, Efficient, and Cost-Saving Transportation (PROTECT) Formula Program, which includes a focus on how to make surface transportation more resistant to natural hazards, including climate change. (Read more guidance from the FHWA here.)

Light-Colored Pavement Surfaces Lead to Cooler Temperatures and Lower UHI

Heat is the number one weather-related killer in the United States, and city planners and other decision-makers are beginning to consider ways to enhance urban heat resilience.

The urban heat island (UHI) effect is caused when features of the built environment absorb and re-emit the sun’s heat more than would a natural landscape. A surface's degree of reflectance is known as its albedo, which is expressed as a numerical value between 0 and 1. A light-colored object has a high albedo—near 1, or 100 percent reflectance. A dark-colored object has a low albedo—closer to 0.

The albedo of a new asphalt pavement is about 0.05. Aged asphalt, which has faded to a lighter color, generally has an albedo between 0.10 and 0.18. New, cured gray cement concrete pavement, however, has an albedo in the range of 0.35 - 0.40. As concrete ages, it tends to darken because of dirt and tire wear, so older concrete may have an albedo in the range of 0.20 - 0.30. The use of light-colored aggregates, white cements and slag cements can improve albedo; white cement concrete pavements have albedos in the range of 0.70 - 0.80 when new and 0.40 - 0.60 after aging. Diamond-grinding as part of concrete pavement preservation also lightens the pavement surface by removing the weather-worn and soiled surface.

Study Shows High Albedo Lowers Temperatures

Phoenix is one of the nation’s fastest-warming big cities, and in August 2021, IGGA partnered with the American Concrete Pavement Association (ACPA) to conduct infrared testing of diamond-ground concrete and asphalt-rubber-surfaced pavements in the Phoenix area. Data was collected for three pavement structures on eastbound SR202 between 40th Street and Dobson Road:

A concrete pavement with a diamond-ground surface.
A concrete pavement overlaid with a one-inch-thick asphalt rubber surface.
An asphalt concrete pavement overlaid with a ½-inch-thick asphalt rubber surface.

Test results showed higher temperatures on the asphalt rubber compared to diamond-ground concrete over a 24-hour period.

Pavement shoulder temperatures for three pavement structures from a drone infrared test. The roadway’s shoulder best represents the heat disparity among surface types because it is a non-trafficked area with minimal convection cooling from traffic.

Diamond-ground concrete surfaces consistently remained cooler. Just before sunrise, diamond-ground concrete measured 1 degree to 10 degrees Fahrenheit cooler than asphalt rubber surfaces. At peak temperature, diamond-ground concrete was 27 degrees Fahrenheit cooler than asphalt pavement overlaid with asphalt rubber.

An added benefit is diamond-ground portland cement concrete pavement has an expected life span exceeding 30 years with minimal maintenance compared to the 15 years of service expected with rubberized asphalt, which needs to be sealed five times and crack sealed two times during its lifespan.

As cities respond to rising temperatures, diamond-ground concrete surfaces offer a solution to increase albedo, reduce the UHI effect and overall greenhouse gas emissions, improve the health of local residents, and decrease roadway maintenance costs.

Stay tuned for the next installment of the IGGA series Aligning your Department’s Priorities with BIL Funding Priorities: Reduced Maintenance and Traffic, coming in September.

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