The application of geopolymer concrete in buildings and structures is becoming widespread because of its low cost and high strength characteristics. At the same time, the capabilities of geopolymer concrete are not fully used, especially to strengthen flexural properties. The article examines the problems of developing an effective composition of geopolymer concrete based on ground granulated blast furnace slag (GGBS) by selecting the optimal composition of the alkaline activator and the amount of basalt fiber (BF). To determine the degree of effectiveness of the proposed formulation solutions, the characteristics of geopolymer fiber-reinforced concrete (FRC) were determined. It has been investigated the most effective composition of an alkaline activator is an activator containing a NaOH solution with a molarity of 12 M. The most optimal dosage of BF is 1.5% by weight of GGBS. The increase in compressive and flexural strength for the most effective composition of geopolymer FRC 12 M/BF1.5, which combines the most effective parameters of formulation solutions, compared to the least effective composition 8 M/BF0 was 40.54% and 93.75%, respectively, and the decrease of water absorption was 45.75%. The obtained scientific result represents a significant empirical basis for future research in the field of geopolymer FRC. The developed effective composition of geopolymer FRC is ready for use in practical construction.
