Sustainable development of basalt fiber-reinforced high-strength eco-friendly concrete with a modified composite binder

The aim of the paper is to development of basalt fiber-reinforced high-strength eco-friendly concrete with modified composite binder for sustainable construction. Cement composites based on a modified polymineral binder with the use of enriched aluminosilicates obtained from coal ash have been developed. A technology has been developed for extracting aluminosilicates from coal ash, which includes five stages. The choice of grinding technology of modified composite binder in a vario-planetary mill up to 550 m²/kg has been made, where the combined action of high impact energy, strong friction and centrifugal forces achieves the maximum mechanical activation of the binder. The developed fresh mixes are characterized by good flowability (slump 20 cm and slump flow 47–49 cm). The resulting composites are characterized by high 28-day compressive and flexural strengths of 59.1 and 13.3 MPa, respectively, which is 44% and 66% higher than that of the control sample. At the same time, the high ratio of 28-day flexural and compressive strengths, reaching 0.31 (for the control sample 0.19), proves the high potential of this material to work under shock and dynamic complex loading. These trends are also preserved for the ages of 1 and 7 days, which allows us to speak about the high early strength of the materials. Microstructural analysis using scanning electron microscopy, X-ray diffraction and energy dispersive spectroscopy showed that the modified cement matrix has a denser microstructure with a large amount of low-basic calcium silicate hydrates (C-S-H), while the reference cement paste contains more high-basic C-S-H and hexagonal portlandite plates. The formed materials are able to withstand up to 15 thermal cycles at a temperature of 700 °С (4 times higher than that of the control sample), 13 thermal cycles at a temperature of 900 °С (4.3 times higher), 8 thermal cycles at a temperature of 1100 °С (exceeding eight times the characteristics of the unmodified sample, which is destroyed without enduring a single thermal change).