Phase-change pavement structures with gradient low-thermal conductivity for permafrost protection

Abstract

Currently available permafrost protection techniques do not pay enough attention to the properties of asphalt pavement, and the problem of strong heat-absorbing asphalt pavement and permafrost constraining each other is a global challenge that needs to be urgently addressed. Phase change materials (PCMs) can regulate the operating temperature of pavement structures by storing and releasing large amounts of heat during phase changes. In this paper, composite shaped phase change material (CSPCM) was applied to the permafrost region of Qinghai-Tibetan Plateau, and a new method of phase-change pavement structures with gradient low-thermal conductivity was proposed to reduce the heat absorption of the pavement and realize the active protection of permafrost. The structures were designed based on finite element software, and the heat flux and temperature distribution within the structure were analyzed and verified with indoor and outdoor thermal regulation tests. Results showed that the preferred gradient low-thermal conductivity structure reduced the annual net heat absorption at the top of the pavement by 8.18 %, the heat absorption in summer by 7.65 %, and the heat release in winter by 6.75 % compared with the control group. The heat flux and the temperature distribution within the pavement structures were significantly altered by the phase-change asphalt pavement structures with gradient low-thermal conductivity, and the simulation results of the finite element model agreed well with the results of the indoor and outdoor thermal regulation tests. The temperature regulation factor (RT) was proposed as an evaluation index to quantitatively analyze the temperature regulation performance of CSPCM on the pavement structure, and the results showed that the flexible base layer had the greatest influence on the temperature regulation performance of the pavement structure. The phase-change asphalt pavement structures with gradient low-thermal conductivity proposed in this paper is a structure that has an efficient cooling effect on the interior of the pavement, and provides a new idea for improving the stability of permafrost subgrade and the integrated design of materials and structures in permafrost regions.