Thermal fracturing (spallation) is a method of breaking rocks and concrete. It is based on heating the surface (usually with open flame), utilizing thermal stresses to develop small chips (spalls) at the surface. The method is inexpensive and easy to use, however, its practical applications are restricted by the relatively low pace of the breakage and by sensitivity to the material properties and micro structure. Thermal spallation only occurs when the temperature is kept just below the melting point of the particular material. The process is also very sensitive to the presence of water in materials such as rock and concrete. It has been found that thermal fracturing is controlled by the internal permeability of the material in materials with low permeability, water in the pores and pre-existing cracks cannot escape during heating, evaporates and drives the crack in an uncontrollable manner. In this case, the sample fails in splitting without any spallation. The difference between these two failure modes is also controlled by the material's tensile strength.Notes: Includes photo.
|Journal||Australian Journal of Mechanical Engineering|
|Publication status||Published - 2003|