Combining different fiber types may improve the mechanical properties of fiber reinforced concrete. The present study is focused on investigating hybrid fiber reinforced concrete (HFRC) with steel and basalt fiber. Mechanical properties of fiber reinforced fine-grained concrete are investigated. The results demonstrate that using optimal steel and basalt fiber reinforcement ratios avoids concrete mixtures’ segregation and improves their homogeneity. Concrete with hybrid steel and basalt fiber reinforcement has higher strength. Effective methodology for proper design of HFRC compositions was proposed. It is based on the mathematical experiments planning method. The proposed method enables optimal mix proportioning of high-strength fine-grained concrete with hybrid steel and basalt fiber reinforcement.

Adding different fiber types may yield improvement of steel fiber reinforced concrete (SFRC) features. Therefore, the investigation of hybrid fiber reinforced concrete (HFRC) mechanical properties is relevant. The effect of adding hybrid steel and basalt fiber on the mechanical properties of fine-grained concrete is studied. It is shown that hybrid fiber reinforcement using optimal steel and basalt fiber ratio allows preventing concrete mixtures' segregation and improving their structure homogeneity. This, in turn, allows achieving higher concrete strength values. In most cases, the design of such concrete compositions is based on engineering experience that limits the designers' capabilities. Therefore, an effective methodology for proper HFRC composition design should be developed. The present study is focused on developing such a methodology. The developed methodology includes using the mathematical experiments planning method to design optimal composition of high-strength fine-grained fiber reinforced concrete with hybrid steel and basalt fiber reinforcement. It is demonstrated that the proposed method can be effectively used for the design of optimal compositions of HFRC.

Design of optimal concrete compositions with specified quality indicators at minimal cost still remains one of the most actual problems. The paper deals with methodology for designing optimal fiber reinforced concrete composition using experimental-statistical models of concrete properties. The obtained mathematical models for compressive and flexural strength of steel fiber reinforced concrete and a model of superplasticizer consumption are used. The proposed method of fiber reinforced concrete composition design takes into account the specific characteristics of the studied materials. It allows relatively easy composition optimization by applying a specific minimum cost criterion. Experimental results obtained in the frame of the study confirm efficiency of the proposed concrete mix design methodology for producing steel fiber reinforced concrete with necessary properties.

The impermeability of self-compacting fly-ash-containing concrete at different ash contents and specific surface areas of ash is studied. The experimental and statistical dependences of the water separation of concrete mixtures, as well as the water impermeability and compressive strength of self-compacting concrete, depending on the composition factors, were obtained. A correlation between concrete strength and its water impermeability has been determined, which allows predicting the latter with sufficient accuracy.

This study examines the utilization of granite stone-crushing waste in the production of porous concrete, with a particular emphasis on the influence of aggregate composition and cement paste layer thickness on the material’s strength and density. Two types of aggregates were employed in this study: granite crushing screenings and granite crushed stone. The impact of aggregate grain size on the properties of porous concrete properties was investigated, and it was found that the use of granite screenings (2.5–5 mm) resulted in superior concrete characteristics compared to granite crushed stone (5–10 mm). This study puts forward a method for optimizing the composition of porous concrete to achieve an optimal balance of compressive strength and density. A method for the design of porous concrete was proposed, incorporating experimental results and the dependencies of strength on the water/cement ratio (W/C). Equations were developed to predict concrete strength based on W/C and cement paste layer thicknesses (CPLTs). The method provides preliminary mix proportions, which should be validated and adjusted for the final design. The findings demonstrate the potential for utilizing stone-crushing waste to produce environmentally sustainable and high-quality porous concrete.

The possibility of contact hardening of dispersed rocks after their acid activation by phosphoric acid is shown. The parameters of pressing, content and concentration of phosphoric acid, as well as the values of temperatures during thermal treatment are given. It is established that the obtained pressed phosphate materials (analogs of geopolymers) have high acid resistance, alkali resistance and heat resistance.