The Formation of Microcracks in Water-Saturated Porous Ceramics During Freeze-Thaw Cycles Followed by Acoustic Emission
Abstrakt
The acoustic emission (AE) technique was employed to monitor crack formation in the water-saturated ceramic material subjected to freeze-thaw cycles. The samples with water accessible porosity ranging from 6 to 50 vol% were prepared from the illite-rich clay by the sacrificing template method.
The experimental samples were fired to 1100 degrees C in the static air atmosphere. Afterward, they were saturated with distilled water and subjected to the freeze-thaw cycles in the temperature range from - 22 to 20 degrees C.
The AE signals occurred repeatedly during freeze-thaw cycling and they were attributed to the formation of microcracks in the ceramic body. The intensity of microcracking increased with increasing porosity.
The microcracks were created primarily during the freezing stages of the experiment. Nevertheless, a considerable number of microcracks also appeared during thawing, especially in the ceramic body with pores below 1 mu m.
The microcracking during thawing was attributed to the reabsorption of water by tiny pores.