Durability issues of one-part alkali-activated mortars in aggressive environments

This paper presents an experimental study carried out to investigate the durability of one-part alkali-activated slag (AAS) mortars in different aggressive environments, such as chloride- and sulphate-rich solutions or in presence of freezing-thawing cycles. The mixtures were manufactured at equal water content and were activated by using sodium silicate, potassium hydroxide and sodium carbonate in powder form. In particular, the behavior of AAS mortars with different alkali content was compared with that of mixtures based on Portland cement and blast-furnace cement. Results show that the alkali content is a key-parameter for the durability of these innovative binders. In fact, in mortars manufactured with an alkali content higher than 0.06 by binder mass, the strength loss is similar to those of mixtures based on blast furnace cement after 150 freeze/thaw cycles. On the contrary, the sulphate-rich solution promotes a stronger degradation of the slag-based mortars respect to that shown by cement-based mixtures, regardless of the alkali content. Finally, the strong deterioration of cement matrix promoted by the formation of oxychloride in CaCl 2 -rich environment is negligible in AAS mortars due to the lack of calcium hydroxide in the slag matrix.