Corrosion of Porous Building Ceramics Caused by Double Sulphate Salt

Porous materials are subjected to the corrosive effects of soluble salts. This corrosion, typically known as efflorescence, is primarily superficial. However, internal corrosion within the material is also frequently observed. This article presents a simulation of volumetric damage in sintered porous ceramic materials (made of clay (75 vol.%), quartz sand (10 vol.%), and sawdust (15 vol.%), fired at 950 °C), caused by the crystallization of double salts, specifically ploweite (6Na₂SO₄·7MgSO₄·15H₂O) and/or glauberite (CaSO₄·Na₂SO₄). The exact mechanism responsible for the formation and interaction of these salts has yet to be fully comprehended. It is established that this mechanism occurs in ceramic materials containing calcium compounds and in mixtures of Na₂SO₄ and MgSO₄ salts. Dissolved Na₂SO₄ acts as a substrate for the formation of glauberite, while dissolved MgSO₄ participates in intermediate reactions (which are necessary for the creation of glauberite).