Unilateral heat-transfer asphalt pavement for permafrost protection

Much radiation absorption and accumulation by asphalt pavement result in serious deteriorations of embankment and permafrost along the Qinghai–Tibet Highway (QTH). In order to reduce these adverse effects, a unilateral heat-transfer (UHT) asphalt pavement is proposed in this paper. It is a tri-layered asphalt pavement with a decreasing conductivity from top to bottom. The pavement with such a conductivity gradient has a capability of UHT. Comparative laboratory experiments under lamplight were carried out to validate the UHT capability. The simulation result of summer pavement heat-absorbing showed that, comparing with the contrast group (CG), the temperature under the experimental group (EG) could be reduced by 2.5 °C. The simulation result of winter embankment heat-releasing showed that the temperature on the surface of the EG was 1.0 °C higher than that on the surface of the CG. The calculation of heat absorption and heat conduction in specimens demonstrated that the EG had a better cooling potential than the CG. These results demonstrate that the CG can not only aid in buffering the radiation heat into the embankment, but also help the accumulated heat to be released outward. If the technology can be applied in permafrost areas, it may provide a positive method to protect the embankment and permafrost.