Thermal Properties of Compost Biocover Subjected to Freeze-Thaw Cycles

In this paper, the key heat-transfer parameters, thermal conductivity, and thermal diffusivity of biocover material made of compost subjected to freeze-thaw cycles (FTCs) for a wide range of water contents is investigated by means of the transient method. The samples were kept at -12 degrees C to freeze and at room temperature (23 degrees C) to thaw. The results obtained show that FTCs have an impact on the thermal properties of compost biocovers. However, more than approximately 70% of the total thermal conductivity changes occurred in the first two FTCs. Moreover, it was found that a linear relation between thermal conductivity and degree of saturation is valid even under FTCs. Furthermore, variations in the thermal properties are due to the combined effect of three factors: volume change, grain-size distribution, and crack formation. Finally, an empirical equation has been developed to predict thermal conductivity changes versus FTCs.