A comparison of the effect of steel and polypropylene fibers on the strength, frost resistance, abrasion, and corrosion resistance in an acidic environment of fiber-reinforced concrete for industrial floors and road pavements was carried out. Steel fibers with a length of 50 mm and a diameter of 1 mm and polypropylene fibers with a length of 36 mm and a diameter of 0.68 mm were used. The amount of steel fiber varied from 15 to 25 kg/m³, and the amount of polypropylene fiber varied from 2 to 3 kg/m³. It has been established that steel fiber more significantly increases the concrete compressive strength, and both types of dispersed reinforcement increase the flexural strength equally by 27–34%. Also, dispersed reinforcement reduces the concrete abrasion resistance by 15–35% and increases its frost resistance by 50 cycles, which helps to improve the durability of industrial floors and road pavements. The use of steel fiber in an amount of 20 kg/m³ and polypropylene fiber in an amount of 2.5 kg/m³ also increases the concrete corrosion resistance in an acidic environment. In general, dispersed reinforcement with both fiber types has approximately the same technological effect concerning the mentioned applications. However, the use of polypropylene fibers is economically more profitable since an increase in the cost of 1 m³ of concrete with steel fiber reinforcement is from $22.5 to $37.5, and an increase in cost with polypropylene fiber is from $10 to $15.

High-early strength fiber-reinforced concretes are effective materials for the full depth repair of rigid highway and airfield pavements. A comprehensive study was carried out on the influence of the amount of steel anchor fiber and hardening accelerator on properties that are important for repairing concrete. A two-factor experiment was carried out, in which the influence of the hardening accelerator and fiber dosages on the strength, frost resistance, wear resistance and shrinkage of repaired steel-fiber-reinforced concrete for rigid pavements was studied. The investigated concretes contained 400 kg/m³ of cement and polycarboxylate plasticizer in the amount of 1.2% of the cement content. It has been established that the optimal concrete compositions are with the amount of Sika Rapid 3 hardening accelerator from 1 to 2% of the cement content and the steel fiber amount from 60 to 90 kg/m³. Optimal fiber-reinforced concrete compositions have a reduced shrinkage during hardening, and at the age of 2 days they have a compressive strength of at least 55 MPa and a flexural strength of at least 8.5 MPa. At the design age, the fiber-reinforced concrete compressive strength is 85–90 MPa, its flexural strength ranges from 15.5 to 17.5 MPa, it has a frost resistance of F200 and abrasion not higher than 0.24 g/cm². These properties ensure the high durability of the repair material.

The article is devoted to ranking of quality criteria for multiparameter, multicriteria production technology of lightweight concrete depending on their significancy using fractal formalism. The proposed approach allows to determine the operation area of stability of the physicomechanical properties of expanded clay concrete with preset technology parameters depending on the size of their self-similarity area and to control the technological process relative to the determine parameter - watertightness. For concrete thin-walled hydraulic structures watertightness is one of the main indicators of quality, ensuring the durability of structures. In the experiment conducted on 15 points optimal plan, 3 factors of the composition varied: sulfate-resistant portland cement, silica fume, water reducing admixture. Possibility of ranking the indicators of W/C and physicomechanical properties of expanded clay concrete depending on the variation of concrete mixture components is shown. Stability of physical and mechanical properties of expanded clay concrete is necessary to ensure its durability and accordance with design requirements. Expanded clay concrete similar to those described in this article can be used in reinforced concrete shipbuilding to reduce weight of structures.

This paper discusses the state of the art in research on the use of textile-reinforced concretes in structural maintenance. Textile-reinforced concretes can be used in structural maintenance for various purposes, including the sealing and protection of the existing building structures, as well as for the strengthening of structures. The first-mentioned aspects are explained in this paper on the basis of example applications. A special focus is placed on the maintenance of heritage-protected structures. The development, characterization, and testing of a textile-reinforced concrete system for a heritage-protected structure are presented. Examples of the application of textile-reinforced concrete for strengthening highway pavements and masonry are also given. In particular, the possibility of adapting the textile-reinforced concrete repair material to the needs of the individual building is one advantage of this composite material.

Rigid road pavements and industrial floors are not only subjected to moving traffic loads, but can also be exposed to environmental influences such as acid attack. The strength and corrosion resistance of fiber-reinforced concrete with steel fibers (15–25 kg/m³) and polypropylene fibers (2–3 kg/m³) in an acidic environment were compared. The influence of the amount and type of dispersed reinforcement on water absorption and the volume of permeable voids, which in turn characterizes the durability of fiber-reinforced concrete under the action of acids, was determined. The change in the compressive strength of the studied fiber-reinforced concrete after 12 months of exposure in an acidic environment was studied. At low dosages of fibers (15 kg/m³ for steel and 2 kg/m³ for polypropylene fibers), dispersed reinforcement has little effect on the corrosion resistance of concrete. In turn, the decrease in the compressive strength of concrete without fibers after 12 months of aging in acid medium led to a reduction in the design class of the concrete from C25/30 to C20/25. At a higher consumption of dispersed reinforcement (25–30 kg/m³ of steel fiber and 2.5–3.0 kg/m³ of polypropylene fiber), fiber-reinforced concrete had a higher corrosion resistance while maintaining the design compressive strength class C25/30. Structural changes in fiber-reinforced concrete after aging in an acidic environment were determined by X-ray diffraction analysis and compared with samples aged in water. It has been experimentally confirmed that the efficiency of polypropylene fibers in an acidic environment is not lower than that of steel fibers. However, the use of polypropylene fibers is economically advantageous.

This paper investigates the influence of hardening accelerator and steel fibre on concrete adhesion strength for the repair of rigid highway and airfield pavements. The concretes were mixed based on CEM II/A-S 42.5 and included MasterGlenium SKY 608 superplasticiser. Experiments with two variable concrete composition factors were carried out. The amount of steel fibre varied from 0 to 100 kg/m³ and the amount of SikaRapid hardening accelerator varied from 0 to 9.6 kg/m³. It was found that modified repair concretes have a sufficiently high adhesion strength to ‘old’ concrete, from 2.30 MPa when tested by the pull-off method and from 2.05 MPa when tested by the flexural strength test method. Fibre-reinforcement increases the adhesion strength of repaired concrete by 7–15% due to the reduction of shrinkage during hardening. Treating the contact surface of ‘old’ concrete with a primer additionally increases adhesion strength by 6–10%. The maximum adhesion strength of fibre-reinforced concrete to the base reaches 3 MPa. Due to the high early and design strength, modified steel fibre-reinforced concrete provides the possibility of quick resumption of traffic while ensuring the integrity of the road structure due to the joint work of the repair material with the old concrete repair area.