Performance of ternary gypsum-based mortars in wet environment

Gypsum is one of the most environmentally friendly materials, but it could be used only in the dry environment. When gypsum is wet, its mechanical properties worsen substantially and namely its strength decreases significantly. Ternary gypsum-based binders, composed from gypsum, lime and pozzolan evince better resistance against the moisture, because water-resistant phases are created as products of pozzolanic reaction. The behaviour and properties of several gypsum composites with different types of pozzolans, exposed to the moisture, were investigated. Samples of ternary composites were stored in the water for 360 days and their properties were tested during the period and compared with the properties of gypsum mortar. While gypsum mortar degraded significantly, the ternary mortars retained its properties and the strength of some of them even increased.