The durability of one-part alkali-activated slag-based mortars in different environments

Abstract

The paper assesses the durability of one-part alkali-activated slag-based mortars (AAS) in different aggressive environments, such as calcium chloride-and magnesium sulphate-rich solutions, in comparison with traditional cementitious mortars at equal water to binder ratio. Moreover, the freezing and thawing resistance was evaluated on mortars manufactured with and without air entraining admixture (AEA). Experimental results indicate that the alkali content is a key parameter for durability of AAS: the higher the alkali content, the higher the resistance in severe conditions. In particular, high-alkali content AAS mortars are characterized by freeze-thaw resistances similar to that of blast furnace cement-based mixtures, but lower than that of Portland cement-mortars while AAS with low activators dosages evidence a very limited resistance in cold environment. The effectiveness of AEA in enhancement of freeze-thaw resistance is confirmed also for AAS mortars. Moreover, AAS mixtures are quasi-immune to expansive calcium oxychloride formation in presence of CaCl2-based deicing salts, but they are very vulnerable to magnesium sulphate attack due to decalcification of C-S-H gel and gypsum formation.