Comparison of Frost Damages of Ceramics under One Dimensional- and Three Dimensional-Cooling

Abstract

The resistivity against frost action in ceramics has usually been examined by freezing and thawing under three dimensional-cooling. But, it seems to be reasonable to examine under one dimensional-cooling, because structural materials are generally exposed under such a condition of one dimensional-cooling. Standing on this point of view, it was aimed to compare the appearances of frost damages caused under three dimensional- and one dimensional-cooling.
As the results of investigation on an insulator brick, a roofing tile body, a wall tile and an earthenware body, several differences in the nature of frost damages between the two cooling methods have been elucidated as follows:
(1) Provided that there is no directional difference in strength resulting from lamination and/or preferred orientation of particles in ceramic bodies, stratified cracks perpendicular to the cooling direction are developed under one directional-cooling, while under three dimensional-cooling non-stratified, random cracks are formed.
(2) The stratified cracks stem plausibly from the preferred growth of ice along the cooling direction. This thought is strongly supported by the preferred expansion along the cooling direction observed on a model system in which thin glass plates are stacked together holding water films between them.
(3) Under one dimensional-cooling the lower the rate of cooling the more severe damages occurs, while under three dimensional-cooling the higher rate of cooling causes the more severe damages.
(4) Regardless of the two cooling methods, cracks develop along the direction of lower bonding strength in ceramic materials resulting from, if any, lamination and/or particle orientation.