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• A new transversal heat transfer channel structure was first proposed here. • The structure can quickly transfer heat accumulated in asphalt pavement to road shoulders. • Transverse thermal conductivity of asphalt mixtures is significantly improved. • The structure provides a new method for active cooling of asphalt pavement. On the Qinghai-Tibet Plateau, intense solar irradiation will cause serious heat accumulation in asphalt pavement. Downward heat transfer will disturb the permafrost under subgrade, thus leading to a series of subgrade and pavement diseases. This makes construction of asphalt pavement in the permafrost regions of the Qinghai-Tibet Plateau a world-class challenge. This paper proposes for the first time a transversal heat transfer channel in asphalt pavement, which can quickly transfer heat accumulated in pavement to road shoulders. Finite element software ABAQUS was used to simulate the rutting plate with high axial thermal conductivity carbon fibers inserted transversely. Under the constant heat load of 500 W / m 2 , the heat flux near the carbon fibers showed the characteristic of convergence. The maximum transverse heat flux in the carbon fibers reached 4.97 × 10 7 W / m 2 , which was 14 times that in the asphalt mixture. Meanwhile, the maximum vertical heat flux in the carbon fibers reduced to 2.62 × 10 6 W / m 2 , which was 12 % less than the asphalt mixture. The effective thermal conductivity of composite specimens with different carbon fiber parameters was studied through control experiments. When the axial thermal conductivity, volume fraction and number of carbon fiber bundles increased to 100 W / m · ° C , 10.72 % and 4 bundles respectively, the transverse ETC of composite specimens increased to 4.05 W / m · ° C , 7.09 W / m · ° C and 16.18 W / m · ° C respectively. They were 3.12 times, 5.45 times and 12.45 times of the control group. The radial thermal conductivity of carbon fibers has a significant effect on the vertical ETC. When it decreased to 0.2 W / m · ° C , the vertical ETC decreased by 6.15 % compared with the control group. The temperature variation trend of specimens were measured by a laboratory irradiation experiment. The maximum temperature difference between the control group and the experimental group at 0 mm was 5.81 °C, and the average temperature difference within 2 h was 5.14 °C. The maximum temperature difference at 50 mm was 3.84 °C and the average temperature difference within 2 h was 3.24 °C. The results showed that the transverse heat transfer channel can reduce downward heat transfer. The application of the channels will enhance transverse heat release and relieve heat accumulation of asphalt pavement. This can create a low temperature state for pavement structure and has a positive effect on maintaining the stability of the permafrost regions on the Qinghai-Tibet Plateau. [ABSTRACT FROM AUTHOR]

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 of heat was introduced into the soil and less than 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. [ABSTRACT FROM AUTHOR]

• A new grouting compound directional heat induced structure was first proposed. • The structure can significantly adjust the heat budget of the pavement. • Internal heat transfer is induced and driven rapidly in a directional way. • It provides a new grouting compound method for actively cooling pavement. In order to control directional heat induced efficiency and reduce pavement temperature, a grouting compound directional heat induced structure (GC-DHIS) was proposed and analyzed in this paper. The structure was formed by pouring grout with different thermal conductivity successively into the same matrix asphalt mixture framework. According to the structural characteristics of grouting compound pavement and the principle of gradient thermal conductivity, the heat in the pavement could be quickly transferred down to the subgrade. The heat transfer performance and cooling effect of GC-DHIS were studied by finite element simulation, and the simulation results were verified by laboratory irradiation experiment. The results showed that the heat exchange between the designed structure and the atmosphere in the endothermic and exothermic periods was 7.10% and 7.98% less than that of the control structure, respectively. Moreover, the effective downward heat transfer rate of pavement throughout the day could be improved, and the maximum temperatures inside the pavement were reduced by 0.9 °C(2 cm), 1.9 °C(5 cm) and 0.8 °C(10 cm). The GC-DHIS with gradient high thermal conductivity grout increased the total downward heat transfer at the depth of 2 cm, 5 cm and 10 cm by 7.0%, 11.9% and 17.4% during the endothermic period. Meanwhile, the surface temperature of this structure in this period showed a slower rising trend. Therefore, it could be concluded that GC-DHIS is a promising pavement structure with the function of actively enhancing heat directional transfer and cooling pavement. [ABSTRACT FROM AUTHOR]

• Carbon fibers are used to build directional heat-induced channels. • Channels induced heat convergence and fast heat conduction in asphalt mixtures. • Directional thermal conductivity of asphalt mixtures is significantly improved. • Channels will help improve the efficiency of asphalt solar collectors. Low thermal conductivity makes heat conduction in asphalt pavements quite slow, restricting asphalt solar collectors. To enhance the directional thermal conductivity of asphalt mixtures and induce directional heat transfer, directional heat-induced channels are built in asphalt mixtures by using carbon fibers with high axial thermal conductivity. A finite element method is used to simulate and study the temperature field and heat flow distribution of asphalt mixtures. A parametric analysis of the carbon fiber parameters is performed to evaluate the variation in the performance of the effective thermal conductivity of asphalt mixtures. The temperature trend of asphalt mixtures is measured by an indoor irradiation experiment and compared with the simulation results. The results show that heat-induced channels have obvious heat convergence effects and can induce heat to be efficiently conducted along its axial direction. These channels can significantly improve the directional thermal conductivity of asphalt mixtures and are expected to play a heat transfer bridge between the pavement surface and the energy collection system when using them in asphalt solar collectors in the future. [ABSTRACT FROM AUTHOR]

Efficiently and actively dissipating accumulated heat within asphalt pavement is crucial for reducing pavement distress and improving subgrade stability. This paper proposed a novel inverted "T" shaped heat induced structure (IT-HIS) that facilitates the rapid transfer of heat from the pavement to the subgrade and shoulders. The IT-HIS consists of two components: a vertical gradient thermal conductivity structure utilizing steel slag, and a horizontal oriented carbon fiber heat induced structure. The heat transfer behavior of the IT-HIS was analyzed using a finite element heat transfer model created in ABAQUS, and the results were validated through indoor irradiation experiments. The findings demonstrated that the IT-HIS enhanced heat flow and promoted secondary aggregation in the vertical direction, while facilitated lateral heat dissipation. Compared to the ordinary group (OG), the heat flux of IT-HIS at depths of 5 cm and 6.5 cm increased by 19.8 % and 64.6 %, respectively. The indoor irradiation experiment results indicated that during the heat absorption period, the IT-HIS reduced temperatures at depths of 0 cm, 2 cm, and 5 cm by 1.5 ℃, 1.7 ℃, and 1.1 ℃, respectively. During the heat dissipation period, the IT-HIS reduced temperatures at depths of 0 cm, 5 cm, and 10 cm by 0.9 ℃, 0.7 ℃, and 1.8 ℃, respectively. The IT-HIS enhanced the cooling effect during daytime and inhibited heat upward during nighttime based on the gradient thermal conductivity structure. The proposal and validation of this structure provide a fundamental approach to forming large-scale high-speed microchannel heat dissipation within asphalt pavements, and is expected to provide experimental and theoretical foundations for the development of directional active cooling technologies. • In order to reduce heat accumulation within asphalt pavement, this paper proposed a novel inverted "T" shaped heat induced structure (IT-HIS). • IT-HIS enhanced heat flow and promoted secondary aggregation in the vertical direction, while facilitated lateral heat dissipation. • IT-HIS enhanced the cooling effect during daytime and inhibited heat upward during nighttime. [ABSTRACT FROM AUTHOR]