The paper describes influence of content of dispersed polymer fiber on mechanical properties of mortar on basis of geopolymer binder. The studies were carried out on a geopolymer binder based on crushed granite and ground-granulated blast-furnace slag . Polypropylene fiber with length of 6 mm at a dosage of 0.22, 0.44 and 0.66% by volume was used as a reinforcing fiber. Dependencies were established for the compressive strength, flexural strength, fracture energy, and density from the dosage of the fiber at various times of hardening. It was established that fiber increases flexural strength and tensile strength of geopolymer mortar. It was shown that investigated fiber is characterized by high resistance to alkaline environment of the geopolymeric stone

Keywords: geopolymer, polypropylene fiber, dispersed reinforcement, compressive strength, flexural strength, tensile strength, resistance in alkaline environment