Abstract Alkali-activated systems are a more sustainable alternative to Portland cement concrete. The activation of latently hydraulic and pozzolanic raw materials in these composites is one of the many investigated factors, where the price ratio and the ability to optimally activate the mentioned precursors with the given activator play a major role. The subject of the presented work is a comparison of the influence of NaOH and KOH on the development of the strength-mechanical properties of alkali-activated materials based on granulated blast furnace slag - the secondary raw material of metallurgical processes.