Characterizing Thermal Impacts of Pavement Materials on Urban Heat Island (UHI) Effect

Pavements are one of the major contributors to the urban heat island (UHI) effect of cities because they cover a considerably large fraction of urban ground surfaces. Permeable pavements are considered an effective solution for mitigating the heat island effect in hot climates. In this study, the effect of pavement types on mitigating the UHI was investigated through a series of laboratory simulation experiments. Three commonly used pavement materials, asphalt concrete (AC), traditional Portland cement concrete (PCC), and Portland cement porous concrete (PCPC), were considered for the study. The thermal performances of those materials under simulated conditions were examined with specially designed testing methods. The testing results showed that under the same thermal radiation conditions, the surface temperature of PCPC was equivalent to that of PCC, whereas the AC showed much higher surface temperature. This indicates that AC pavements usually absorb more heats than PCC and PCPC pavements under solar radiations. Compared to the PCC, the AC and PCPC usually reflected less heat to the surrounding environments due to their relatively lower albedo values, which could mitigate the thermal discomfort for the nearby human and buildings to some extent. In addition, the PCC could store more thermal energy in day time and release them back to the atmosphere at night due to its relatively high density, thermal conductance and specific heat capacity. This indicates that PCC could produce negatively effects on the UHI at night.