**Aspasia Karozou 1,\*, Stavroula Konopisi 1, Eleni Pavlidou <sup>2</sup> and Maria Stefanidou <sup>1</sup>**


Received: 22 July 2020; Accepted: 25 August 2020; Published: 27 August 2020

**Abstract:** The need to increase the durability of clay-based materials, due to their inherent low strength and vulnerability in contact with water, led researchers to examine different options. In this paper, clay mortars were produced using four different activating solutions. Alkali hydroxides, alkali carbonates, and alkali silicates activating solutions were used. Interest is given to long term properties while their behavior to wetting–drying and freeze–thaw cycles is recorded. In total, the results of the experiments indicated the positive effect of the potassium metasilicate on mechanical characteristics presenting, however, low performance at wetting–drying. The combination of sodium metasilicate with sodium hydroxide solution has also presented a positive effect on both mechanical and physical properties. In contrast, sodium carbonate acted better in enhancing physical properties and granting water-resistant abilities. Moreover, the performance of the specimens mixed with water–glass addition presented excellent volume stability and low mass loss in durability tests.

**Keywords:** clay mortars; activating solutions; wetting–drying; freeze–thaw cycles; microstructure
