Swelling and breaking characteristics of limestone under high temperatures

The elemental composition, heat expansibility and breaking characteristics of limestone have been investigated with the use of an energy spectrum analyzer, a SEM, an optical microscope and an experimental heat swelling power system. The results show that 1) the heat expansibility of limestone has anisotropic properties, and 2) the heat expansion rate in the direction perpendicular to stratification is eight times greater than the rate parallel to stratification. The changes in heat expansibility as a function of heating temperature is essentially coincident with that of swelling and breaking of mineral particles and the appearance of cracks, indicating that the reason for causing the heat expansion of rock are the structural changes of limestone caused by thermal stress, crystal transformation and mineral decomposition. The apparent destruction of limestone under high temperatures is largely characterized by rock stratification breaks. When the limestone is heated beyond a certain limit, the rock destroys into crazed cracks.