Effect of calcite on the brick body closing

Autores: Sokolar, R.
Fuente: Interceram
59 (2), 123-127
2010

The impermeability to water is an important property of clay roof tiles. The decrease of the permeability of the brick body to water with the time is a typical feature of the brick body closing process. Thus, test samples from two different types of mixtures of raw materials for the production of clay roof tiles in the Czech Republic fired in a laboratory kiln at temperatures of 800, 900 and 1,000°C were tested with respect to their permeability to water and porosity. The brick body closing process especially is influenced by the content of free CaO. After firing at lower temperatures, the body based on brick clay with a high content of calcite shows a considerable closing. The body closing is caused by the hydration of free calcium oxide CaO originating from the calcite decomposition and from the formation of calcium hydrate Ca(OH)2 that closes the capillary pores in the body after increasing its volume compared to CaO.