The Albedo of Pervious Cement Concrete Linearly Decreases with Porosity

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.

Temperature Characteristics of Porous Portland Cement Concrete during the Hot Summer Session

“…Albedo is the ratio of the reflected radiant flux to the incident solar radiant flux, which characterizes the ability of the pavement to absorb and reflect solar radiation [8]. Albedo and coefficient of thermal storage were calculated according to the references [9,11,18].…”

“…Because PPCC have more air void content than traditional PCC, there are obvious differences between them. Studies 2 Advances in Materials Science and Engineering by Haselbach et al and Zhang et al have shown that PPCC has rougher surface and lower albedo than traditional PCC pavement, so that PPCC can absorb more solar radiation [10,11]. Kevern et al collected temperature data of pervious pavement and traditional pavement at different depths, respectively, and found that the temperature at middlelevel (8 cm below the surface) in both concrete types was always higher than the air temperature.…”

A review on the development of cool pavements to mitigate urban heat island effect

“…First, there are limited reported on the reflectance of pervious concrete [18,74]. The rough of pervious surface makes its albedo less than normal concrete and thus absorbs more solar irradiation [18,74].…”

“…First, there are limited reported on the reflectance of pervious concrete [18,74]. The rough of pervious surface makes its albedo less than normal concrete and thus absorbs more solar irradiation [18,74]. Haselbach and Boyer [18] found the solar reflectance index of pervious concrete pavement is 14 but that of traditional concrete pavement is 37.…”

Urban Heat Island: Causes, Consequences, and Mitigation Measures with Emphasis on Reflective and Permeable Pavements

“…Compared to conventional concrete pavements, pervious concrete pavements have lower reflectivity, heat volumetric capacity, thermal conductivity, and absorb additional heat. The reflectivity of pervious concrete determines the reflectivity of aggregates, binders, and voids [12,67]. The higher porosity pavements have a larger surface temperature than lower porosity pavements as they have higher thermal diffusivity, which decreases by porosity increase [62].…”