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• Binary mixtures with pyroclastic deposits (Mt. Etna volcano) and metakaolin. • Alkaline activating solutions based on Na or K cation. • Polycondensation reaction monitoring on fresh pastes through In situ FTIR analysis. • Performance in terms of structure, compressive strengths and porosity. The huge availability of volcanic deposits in Mt. Etna volcano and the wide use of volcanic materials as aggregates in local architecture encouraged us to apply them in alkaline environment to produce geopolymeric binders to restore historical buildings of Mt. Etna area. Two clusters of samples for each volcanic precursor (volcanic ash and ghiara paleo-soil) were produced, using 10 and 20% wt. of metakaolin and two different alkaline solutions based on sodium and potassium respectively. A comparative study was made in relation to activators used, focusing on evaluation of polycondensation step (in ATR); chemical and structural characterization (FT-IR); TGA analysis, qualitative XRD analysis and mechanical compressive test after 7 and 21 curing days. ATR results confirmed the occurrence of geopolymerization for all samples; FT-IR analysis showed a higher content of carbonates in potassium-samples, decreasing at increasing of metakaolin content. A low weight lost was recorded in consolidated samples, as well as a partial dissolution of volcanic phases. Higher mechanical compressive strengths for K-samples, reaching 89 MPa as highest value after 21 days, differently to sodium-samples (51 MPa) were recorded, reflecting the porosity of the different specimens. [ABSTRACT FROM AUTHOR]