Materials Characterization and Testing of Heat-Reflective Coatings to Mitigate the Urban Heat Island

The Urban Heat Island (UHI) effect—urban areas higher in temperature than rural counterparts—is exacerbated by pavement surfaces. Heat-Reflective Coatings (HRC) are being developed to cool pavements for UHI mitigation. Six HRCs were tested via engineering performance tests, spectroscopy, and microscopy to determine changes in surface temperature and to understand optimal cooling mechanisms of each coating based on microstructure-property-performance architecture. Integrated multimodal characterization approaches were used to: 1. Determine the micro/nano scale heat reflection mechanisms that in each coating material; 2. Compare the heat reflection performance of each coating and rank them by cost effectiveness; 3. Inspire the design and optimization of new cool pavement with specifications and recommendations. During engineering performance tests, coated concrete samples underwent heating and cooling cycles in which the surface, atmospheric, and subsurface temperatures were recorded using an infrared thermal camera, a thermometer and thermocouples, respectively. Results from performance testing clearly demonstrated an overall decrease in surface temperature for coated samples compared to uncoated concrete. Ultraviolet-Near-Infrared and Fourier Transform Infrared spectrometers were used to quantify solar and thermal reflectance and HRCs were found to have significantly higher reflectance in the visible and near-infrared range compared to uncoated concrete. Scanning Electron Microscopy imaging of HRCs revealed the presence of silicon dioxide and titanium dioxide nanoparticles of varying size and morphology. Results of engineering performance testing and multimodal characterization indicate the potential of using HRCs to mitigate the UHI effect by cooling pavement surfaces