Effect of air voids content on thermal properties of asphalt mixtures: Fid-Bau Portal

Effect of air voids content on thermal properties of asphalt mixtures

Hassn, Abdushafi / Aboufoul, M. / Wu, Y. / Dawson, A. / Garcia, A.

Highlights•Asphalt mixture with high air voids content has lower thermal conductivity and specific heat capacity than asphalt mixture with lower air voids content. In addition, the emissivity of dense asphalt mixture is higher than the emissivity of porous asphalt mixture by a value of 0.02. This value is very small when compared to the emissivity of asphalt concrete; for this reason, the air voids content does not affect the emissivity of asphalt mixtures.•Asphalt mixtures with high thermal conductivity and specific heat capacity, dense asphalt mixture, have lower heating and cooling rates than asphalt mixtures with lower thermal conductivity and specific heat capacity, porous asphalt mixture.•The surface of asphalt slabs with high air voids content reaches higher steady state temperature than the surface of asphalt slabs with lower air voids content. The average temperature of asphalt mixture during heating and cooling is almost independent of the air voids content in the mixture.•The total amount of energy accumulated in asphalt mixtures with different air voids content, but with the same constituting materials, during heating and cooling depends only on the density of the mixtures. Convective and radiative heat losses can be considered constant for mixtures with different air voids contents.•In general, asphalt mixture with high air voids content accumulates less energy than asphalt mixture with lower air voids content. For this reason, mixtures with high air voids content are recommended to alleviate heat urban island effect while mixtures with low air voids content are recommended for harvesting solar energy from the pavement.

AbstractAir voids content is considered as one of the factors that may affect heat transfer through asphalt mixture, although their specific role on the asphalt mixture temperature is still unclear. The objective of this research is to have a deep insight of the effect of air voids content on the temperature evolution, transport and storage of heat in asphalt mixture under dry conditions. With this objective, asphalt mixture slabs with different air voids content have been built and their thermal conductivity, specific heat capacity, light absorptivity and thermal diffusivity related to their temperature evolution have been measured when they are exposed to infrared light and during the cooling process. It was observed that asphalt mixture with high air voids content exhibited slightly higher steady state temperatures than denser asphalt mixture and that the heating and cooling rates are higher in porous asphalt mixture than in denser materials. The reason for the faster increase and decrease in temperature of porous mixture and for the higher temperature reached by porous asphalt is its lower specific heat capacity and thermal conductivity. Finally, it could be observed that the connectivity of air voids in asphalt mixture did not play an important role on the temperature reached by asphalt mixture.