Portland cement is the most widely used type of binder in construction materials. World cement production has reached 3780 million tons in 2012. By producing 1 ton of Portland cement 222 kg of CO2 are emitted in the atmosphere that creates serious environmental pollution problems. The possibility to replace Portland cement with alternative binders is a topical issue in the world. According to the results of research made in the last 25 years, alkali activated binder is considered as Portland cement substitute. By using kaolin clay, waste glass, alkali activator and sand it is possible to obtain materials, which are similar to the cement based materials. Properties of the low-calcium alkali – activated mortars (AAMs) were tested in this research with the regard to concentration of activator - alkali solution.