Unidirectional Heat-Transfer Asphalt Pavement for Mitigating the Urban Heat Island Effect

Abstract

The absorption of solar radiant heat is the primary reason for the high temperature of asphalt pavement and the exacerbation of the urban heat island effect. In this paper, a novel unidirectional heat-transfer (UHT) asphalt pavement structure was proposed, which allows heat transfer along a fixed direction. The UHT effect was demonstrated under lamp lit indoor and sunlit outdoor environments. Compared with the control specimens, the UHT specimens were able to reduce the surface temperatures of 6.2°C (day) and 1.3°C (night), after one day’s cycle of simulating indoor heat absorption and release. The outdoor measurements showed that reductions of 3.4 and 1.2°C in the surface temperature of the UHT specimens were achieved during the day and night, respectively, when compared with the temperature of the control specimens. The calculation results also indicated that more than 466 W/m2 of heat was introduced into the soil and less than 462 W/m2 of heat was transferred out of the UHT specimens, which validated the self-cooling effect of the designed UHT structures. The proposed gradient thermal conductivity structure is a promising new technology to mitigate the urban heat island effect.