Experimental investigation on performance degradation of insulation materials induced by freeze–thaw cycles and its applications

Abstract

• The degradation of XPS board induced by FTCs is analyzed and discussed in details. • The quantitative relationships between the numbers of FTCs and the performance degradation of XPS board are established. • The optimal thickness of XPS board by different laying methods is proposed by numerical simulation. XPS board as a good insulator is extensively used in construction and engineering to reduce heat loss. Unfortunately, the performance degradation of XPS board caused by freeze- thaw cycles (FTCs) was poorly studied. In view of this, a series of experiments were carried out in the laboratory. The compressive strength, thermal conductivity and volumetric water absorption of XPS board subjected to hundreds of FTCs are measured. Afterward, the optimal laying method of XPS board is proposed using numerical simulation method by taking a high-speed railway tunnel as a background. The results show that the compressive strength of XPS board is significantly affected by the thickness and numbers of FTCs. The maximum reduction rate of compressive strength caused by FTCs can reach 33 %. Additionally, the thermal conductivity and volumetric water absorption increase linearly with the number of FTCs. The thermal conductivity is always changed between 0.0329 W/(m·°C) to 0.0481 W/(m·°C). Based on that, the XPS board still has a good adiabatic performance after hundreds of FTCs. Besides, when the XPS board is laid in tunnel structural layer by surface method (SM) and interlayer method (IM) with the thickness of 6.5 cm, it can effectively prevent the surrounding rocks from freezing. In order to avoid frost heave of the secondary lining, the thickness of XPS board should be greater than 8.5 cm when the IM is selected. This study can provide some guidelines for the application of XPS board in constructions and engineering, especially for the cold regional tunnels.