Abstract
Many studies were conducted to find possible strategies for reducing the urban heat island (UHI) effect during the hot summer months. One of the largest contributors to UHI is the role that paved surfaces play in the warming of urban areas. Solar-reflective cool pavements stay cooler in the sun than traditional pavements. Pavement reflectance can be enhanced by using a reflective surface coating. The use of heat-reflective coatings to combat the effects of pavements on UHI was pre-viously studied but no consistent conclusions were drawn. To find a conclusive solution, this work focuses on the abilities of heat-reflective pavement coatings to reduce UHI in varying weather conditions. Within this context, both concrete and asphalt samples were subject to a series of per-formance tests when applied to a heat-reflective coating, under the influence of normal, windy, and humid conditions. During these tests, the samples were heated with a halogen lamp and the surface temperature profile was measured using an infrared thermal camera. The air temperature was recorded with a thermometer, and the body temperature at multiple depths of the samples was measured using thermocouples. The results from these tests show that the effectiveness of the heat-reflective coating varies under different weather conditions. For instance, the coated samples were about 1 °C cooler for concrete and nearly 5 °C cooler for asphalt, on average. However, this temperature difference was reduced significantly under windy conditions. As such, the findings from this work conclude that the heat-reflective coatings can effectively cool down the pavement by increasing the surface albedo, and thus might be a viable solution to mitigate UHI impacts in the city/urban areas.
Highlights
The rapid urbanization of populations occurring around the globe has led to drastic changes in the natural environment, from species displacement and water contamination to air or light pollution
Man-made construction materials, such as concrete and asphalt, which have a high specific heat capacity, are part of this process. These infrastructures lead to the urban heat island (UHI) effect, which is found to create a 1 to 3 ◦ C annual air temperature increase in cities [1]
The term UHI can be used to refer to any area that is relatively hotter than its surroundings, but, in general, it refers to human-disturbed areas [2]
Summary
The rapid urbanization of populations occurring around the globe has led to drastic changes in the natural environment, from species displacement and water contamination to air or light pollution. As cities become larger and more populated, the infrastructure needs to be maintained as soon as the influx of people quickly takes the place of natural forests and other ecosystems These natural land surfaces are, being replaced by man-made infrastructures that contribute heat release through human activities [1]. Man-made construction materials, such as concrete and asphalt, which have a high specific heat capacity, are part of this process These infrastructures lead to the urban heat island (UHI) effect, which is found to create a 1 to 3 ◦ C annual air temperature increase in cities [1]. Climate model projections found that heat stress increases twice as much as a result of climate change in cities compared to rural areas, leading to longer and more extreme heat waves [5] Existing studies linked this UHI effect to human well-being and health problems. Mitigation strategies such as cool pavements or cool roofs have the potential to limit these consumer costs [11,12]
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