Abstract
Pervious pavements have been advocated as a potential countermeasure to the urban heat island effect. To understand if pervious pavements stay cooler than conventional pavements, the albedo of the pervious concrete must be understood. This study measured the albedo of pervious concrete with different porosity. Four Portland cement concrete mixes were casted, using designed amounts of sand to vary the porosity of the pervious concrete samples. The samples were sliced and the spectral reflectance and albedo of the sliced samples were measured and analyzed. It is found that the albedo of pervious concrete decreases linearly with the increase of the porosity. The albedo of a pervious Portland concrete varies from 0.25 to 0.35, which is 0.05~0.15 lower than the albedo of conventional cement concrete. Due to this lower albedo, it should be cautious to develop pervious concrete to battle with urban heat island unless the evaporation of pervious concrete is promoted to compensate the additional solar absorption caused by the low albedo.
Highlights
Pervious concrete is mixed by eliminated most or all fine aggregates from the mixture
Pervious concrete is advocated as a potential countermeasure to mitigate the urban heat island effect (UHI) [1,2,3]
The reflectivity, or the albedo, of pervious pavements, is the most important factor because the solar absorption is the product of the albedo and the solar irradiance, which is the driven force to the variation of the pavement temperature
Summary
Pervious concrete is mixed by eliminated most or all fine aggregates from the mixture. When percolating through a pervious pavement, some amount of water may be retained in the cavity. To use the pervious pavements as an UHI mitigation effort, the designers must know if the thermal properties of pervious concrete are favorable to help the pervious pavements stay cooler than conventional pavements. Among these properties, the reflectivity, or the albedo, of pervious pavements, is the most important factor because the solar absorption is the product of the albedo and the solar irradiance, which is the driven force to the variation of the pavement temperature. It is necessary to characterize the albedo of pervious concrete and to estimate the albedo varying with the porosity
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