Light Coloured Cool Asphalt Pavements

Abstract

The black colour of an asphalt pavement causes it to reach very high temperatures throughout the summer months. Asphalt binder is a temperature dependent material, so these high temperatures can result in damage to the road surface. This report explores the use of light coloured surface coatings to decrease the temperature of an asphalt pavement. A field testing method was developed to compare the effect of several surface materials on temperature. To support this field test, a method was developed to characterize the surface colour (albedo) through the use of a simple light meter. As well, the durability of the surface coatings applied to asphalt pavement surfaces was examined using the Wet Track Abrasion Test, and methods for further testing were suggested. A numerical model was developed in Abaqus to predict the temperature effects based on the surface colour and climate conditions. This model can be used to predict the temperature in an asphalt concrete pavement at the surface and throughout the depth of the pavement. Two versions of this model were created: A complete model, which is used when all climate data is available, and a simplified model, which uses estimated values to replace any data that is not available The temperature difference between white and black painted asphalt concrete surfaces was found to be as much as 17C. Using light coloured surfaces with albedo values in the range of 0.2 to 0.3 yielded a temperature decrease of approximately 7 to 10C as compared to a black painted surface. Microclimate effects were found to be significant; wind speed can drastically affect the temperature of a pavement. The use of hydrated lime in conjunction with a polymer modified asphalt surface course yielded good results for both temperature reduction and durability. It should be considered for future work.