Albedo Estimation of Finite-Sized Concrete Specimens

Albedo in the context of the Urban Heat Island contributes to the environmental impact of a pavement. Measuring the pavement albedo is difficult as it depends on the size of the specimen, background interference, and variations in the incoming solar spectrum. For this study, the albedo was determined for a 1-m(2) concrete slab cast with white cement containing titanium dioxide nanoparticles. The size of the exposed surface of the slab was varied using black paper. To calculate the albedo of these nonstandard specimen sizes, a new testing technique was proposed that uses an albedometer and various geometric conditions, including the exposed slab surface and measurement height. The albedo of the finite-sized concrete specimen was found to range from 0.50 to 0.55, depending on the number of unknowns assumed, with the most reasonable estimate of 0.54. The measured slab albedo from the new method was also verified using a laboratory spectrophotometer. With this proposed methodology to account for background surfaces, the albedo of laboratory-sized concrete specimens of any shape can now be easily measured at various test site locations.