## 3 Results and Discussion
### Reinforcement of Geopolymers with Basalt Grid  
Figure 16 shows the average compressive strength values for fly ash and sand-based geopolymers and metakaolin and sand-based geopolymers reinforced with basalt grids (Table 6) using different molar concentrations of alkali activator. The lowest average compressive strength values were obtained for samples based on metakaolin (5 M NaOH solution), using a single basalt grid (5.1 MPa), and a geopolymer based on metakaolin (5 M NaOH), using two layers of basalt grid reinforcement (4.7 MPa). The highest compressive strength values were obtained for fly ash-based geopolymer materials reinforced with two layers of basalt grid. For the geopolymer based on 5 M NaOH solution, the value was 60.6 MPa, and for the geopolymer based on 10 M NaOH, the value was 66.2 MPa. The highest value of compressive strength for the sample based on metakaolin was achieved with the use of double reinforcement of basalt grid and 10 M alkaline solution (45.1 MPa). Figure 17 shows the average flexural strength values for fly ash and sand-based geopolymers and metakaolin and sand-based geopolymers reinforced with basalt grids (Table 6) using different molar concentrations of alkali activator. As in the case of compressive strength, the lowest flexural strength value was obtained for the sample based on metakaolin and sand (5 M NaOH) reinforced with a single layer of basalt grid (2.0 MPa) and reinforced with two layers of basalt grid (1.4 MPa). A similar average flexural strength value was obtained for the fly ash and sand (5 M NaOH)--based sample, which was reinforced with a single layer of basalt grid (1.3 MPa). The same average values of flexural strength (and at the same time the highest) were obtained for geopolymers based on fly ash and sand (10 M NaOH), which were reinforced with one and two layers of basalt grid 12 MPa. The highest value for the group of geopolymers based on metakaolin and sand was obtained for the sample activated with 10 M NaOH solution and reinforced with two layers of basalt grid (9.2 MPa). Figure 16: Compressive strength for metakaolin and fly ash-based geopolymers reinforced with a basalt grid. Figures 18 and 19 show the specimens after the flexural strength test was completed. It can be seen that only the geopolymer matrix fractured and not the applied reinforcement. As a result of the conducted tests, it was observed that the best compressive strength results for samples reinforced with basalt grids were obtained for fly ash-based geopolymers. The highest results were registered for geopolymers reinforced with two layers of basalt grids. When using a 5 mol alkali solution, this value was 60.6 MPa, while for the geopolymer based on a 10 mol alkali solution, this value reached 66.1 MPa. Figure 19: Geopolymer samples after the flexural test (10 M NaOH solution): (**a**) metakaolin + sand + 1 layer of basalt grid; (**b**) fly ash + sand + a layer of basalt grid. Figure 17: Flexural strength for metakaolin and fly ash-based geopolymers reinforced with a basalt grid. Figure 18: Geopolymer samples after the flexural test (5 M NaOH solution): (**a**) metakaolin + sand + 1 layer of basalt grid; (**b**) fly ash + sand + 1 layer of basalt grid. The best flexural strength results were obtained for fly ash-based geopolymer samples (10 mol solution) reinforced with one and two layers of basalt grid. The flexural strength results in these cases oscillated around 12 MPa. In the case of using 5 mol alkali solution, grid reinforcement did not influence the high results for the fly ash-based geopolymer samples (results below 2 MPa). For samples based on metakaolin, the best values were obtained for samples reinforced with two layers of basalt mesh (10 mol alkaline solution). In a metakaolin-based geopolymer with a 5 mol alkaline solution, the amount of reinforcement layers did not have a positive effect on the compressive strength results (values below 5 MPa). [PERSON] and his team researched the use of basalt fibers as a potential reinforcement for geopolymer composites.