Using construction and demolition waste materials to alleviate the negative effect of pavements on the urban heat island: A laboratory, field, and numerical study

In this study, construction and demolition waste (CDW) materials, including waste clay bricks, concrete, and glass, were used as aggregates of chip seal layers to enhance the reflectivity and reduce the temperature of asphalt pavements as an urban heat island (UHI) mitigation policy. UHI is an urban area that has a higher temperature in comparison to its suburbs. As considerable parts of cities are covered with asphalt pavements, their heat absorption and heat release can directly affect the UHI. Four types of chip seal layers, containing CDW aggregates were prepared in this study. The reflectivity and cooling effects of asphalt pavement coated with the developed chip seals were then evaluated with laboratory, field experiments, and computational fluid dynamics (CFD) simulation. Regarding the laboratory methods, UV-Visible-NIR spectrometer reflectance, a trident thermal properties measurement, and solar simulation cooling effect were used. Besides, the albedo and cooling effects of the developed chip seals were evaluated with a pyranometer and thermocouples through a field experiment. The indoor reflectance test showed yellow and red brick chip seals reflected almost 136 % higher than the aged asphalt pavement, followed by concrete chip seals with 80 % higher solar reflectance. Besides, the surface temperatures of yellow brick, red brick, and concrete chip seals were 23 %, 18 %, and 15 % cooler than the hot mix asphalt (HMA) specimens. More importantly, clay brick chip seals had the lowest nighttime heat release, followed by the concrete chip seal. The field test indicated that the albedo of yellow brick was 2 and 6 times higher than the aged and new HMA, causing 17 % and 27 % lower surface temperatures. The numerical models also revealed that using the yellow brick and concrete chip seals decreased the surrounding air temperature at least by 18 % and 14 % respectively. Overall, the numerical modeling, laboratory, and field tests showed similar results, indicating the benefits of using clay bricks and concrete aggregates for chip seal development, which can mitigate the UHI effectively.