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.

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.

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.

The influence of the hardening accelerator and steel fiber on the concrete adhesion strength for the repair of rigid highway and airfield pavements has been investigated. The concretes were mixed based on the CEM II/A-S 42.5 and included MasterGlenium SKY 608 superplasticizer. Experiment with two variable concrete composition factors was carried out. The amount of steel fiber varied from 0 to 100 kg/m3, the amount of Sika Rapid 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. Fiber-reinforcement increases the adhesion strength of repair concrete by 7-15% due to reducing 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 fiber-reinforced concrete to the base reaches 3 MPa. Due to the high early and design strength, modified steel fiber-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.

In this study, a comparison of the strength and durability of concrete with sulfate-resistant cement and cement with pozzolana additive was performed. In assessing the concrete durability, three indicators were compared: sulfate resistance, water permeability, and frost resistance. All concrete mixtures were used without admixtures. The absence of chemical admixtures in the concrete mixtures was because of the need to compare properly the properties of concretes with different cements without the influence of modifiers, which may result in different efficiencies for different types of binders. The concrete compositions of grades C20/25 and C30/35 were presented. The use of Portland cement with pozzolana additive in concrete mixtures provided the necessary level of corrosion resistance and frost resistance of concrete, as well as higher water permeability and lower cement content in comparison with using sulfate-resistant Portland cement.