1665549 - Can Cool pavement Coating be Recycled in Future RAP Asphalt Mixture?

Abstract: Many cities around the world are experiencing higher temperatures due to the urban heat island (UHI) effect, which is caused by the heat absorption and retention of the built environment. The materials used for buildings and roads, such as concrete and asphalt, have low reflectivity and high thermal mass, meaning that they capture a lot of solar radiation during the day and release it slowly at night. This increases the surface and air temperatures in urban areas compared to rural areas. One way to reduce the UHI effect is to use cool pavement coatings, which can reflect more solar radiation and lower the heat absorption by the pavement, thus cooling down its surface temperature.
According to a recent study by researchers affiliated with the MIT Concrete Sustainability Hub, paving material selection could mitigate extreme heat and greenhouse gas emissions. The study focused on “cool pavements”, which reflect more solar radiation and emit less heat than conventional paving surfaces. The study found that cool pavements could lower air temperatures in Boston and Phoenix by up to 1.7 C (3 F) and 2.1 C (3.7 F), respectively. They would also reduce greenhouse gas emissions by up to 3 percent in Boston and 6 percent in Phoenix.
As part of the Cool Pavement Pilot Program, which involved researchers from Arizona State University (ASU) and the City of Phoenix evaluating the performance of reflective Cool Pavement, this study examines the recyclability of cool pavement products in a laboratory setting. To assess the effect, three performance tests were conducted: the dynamic modulus test, which measures the stiffness of asphalt; the indirect tension test (IDT), which measures its resistance to cracking; and Hamburg wheel track test, which measures its resistance to rutting. The results showed that cool pavement products have no major effects on the recyclability of asphalt . In fact, they improve its stiffness, cracking resistance, and rutting resistance.