Effect of frost damage on the pore interconnectivity of porous rocks by spontaneous imbibition method

Frost damage due to freeze-thaw activity in hard rocks is a process that influences the appearance of the geo-relief of the landscape. Methods of frost damage assessment in rocks are based on parameters obtained mainly by destructive testing of samples. In this paper, nondestructive methods for the determination of pore connectivity as an important topological parameter affecting the migration of the fluid in rock material, as well as its variability due to freeze-thaw cycling, were employed. Tuff, andesite, and travertine, as well as two types of sandstones, were subjected to spontaneous imbibition testing. Based on the variation of the diffusion front with time, the slope of imbibition curve- C(I) was estimated and compared before and after 100 freeze-thaw thermal cycles. The samples were tested within a temperature range from - 10 to 10 degrees C in a fully saturated state in a controlled thermal chamber. Imbibition slopes were analyzed for fast (0.1-1 min) and medium (1-10 min) time intervals due to the variable petrophysical properties of the tested rocks. A considerable increase in imbibition slopes was detected, making the C(I) value a promising parameter that characterizes the interconnectivity of pores inside porous rocks. This parameter, in combination with the length of ice crystallization t(c) obtained from a thermistor probe located in the center of saturated dummy samples prepared from the same rock type subjected to freeze-thaw cycling, is capable of giving important indications of the degradability of rocks due to frost damage.