Comprehensive Laboratory Testing and Evaluation of the Evaporative Cooling Effect of Pavement Materials

This paper presents a methodology to quantify the evaporative cooling effect (ECE) of eight paving mixtures, including asphalt and cement concrete types with varying material properties in the laboratory. Further, quantification of the ECE of the different mixtures entailed recommendation of those materials that could be appropriate to mitigate urban heat island (UHI) effects. In dry and wet conditions, asphalt-rubber open-graded and dense asphalt mixtures had nonlinear temperature gradients and higher temperatures at surface, 25- and 50-mm depths, whereas asphalt-rubber gap-graded mixture had insignificant gradients and lower temperatures. Open and dense-graded asphalt mixtures had higher temperature differentials between dry and wet conditions than gap-graded mixture illustrating that they will have higher ECE. However, based on temperature gradients and profiles, gap-graded mix showed an unvarying thermal behavior under dry and wet conditions demonstrating that thermophysical properties also play prominent roles in heat energy transport and storage through the system. Pervious concrete mixtures with 20 % and 25 % air voids depicted nonlinear temperature gradients and higher temperature differentials compared to pervious concrete with 30 % air voids and conventional concrete mixtures that provided superior ECE and could indeed act as suitable UHI mitigation strategies.