Damage of porous stones by salt crystallization

Abstract

Porous sedimentary rocks have been popular construction, decorative and artistic materials for many centuries. Their durability has been an important issue due to their porosity and relatively low mechanical properties. One of the crucial mechanisms of porous rocks deterioration is crystallization of salts in their pores. This crystallization is accompanied by generation of crystallization pressure which can be higher than the strength of the rock and thus cause failure of stone. The paper deals with experimental testing of crystallization damage caused by sodium sulfate. Four kinds of sandstones quarried in Czech Republic are studied; the stones were selected with respect to their different pore size distribution and total porosity. The damage of stones is expressed as their weight loss after cyclic crystallization. The results are correlated with the stone properties (pore size distribution and strength) and crystallization pressure exerted by crystals on the stone. Various methods of crystallization pressure estimation are discussed.