A laboratory investigation on thermal properties of virgin and aged asphalt mixture

In this paper, the thermal properties of three dense graded asphalt mixtures, 20 mm DBM, AC 14, and AC 6, are presented. Density and air voids of the compacted specimens are also shown. Thermal conductivity was measured in the laboratory for non-aged, short-term aged and long-term aged asphalt mixtures at three different temperatures 19 (±1) oC, 65 (±5) oC, and 80 (±5) oC. Specific heat capacity and thermal diffusivity were calculated from equations derived from the literature. Heat penetration depth was also calculated and shows the heat from the thermal conductivity instrument heat source that dissipates into the asphalt specimens. The results were analysed to determine the effect of air voids content, transient line source (TLS) method, temperature and aggregate size in thermal conductivity and the effect of aging on the thermal properties of the asphalt mixtures studied. It was concluded that there is a minimal effect in thermal conductivity for 4% to 6.5% air voids. The method of measurement and temperature affect considerably thermal conductivity. However, the results were inconclusive in the effect of aggregate size on thermal conductivity. The effect of asphalt aging in thermal conductivity and thermal diffusivity varied between the asphalt mixtures studied and was relative to the temperature. Asphalt aging did not affect specific heat capacity.