###### Abstract  
High-early strength fiber-reinforced concrete 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/m\({}^{3}\) 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/m\({}^{3}\). 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/cm\({}^{2}\). These properties ensure the high durability of the repair material. fiber-reinforced concrete; road pavement; hardening accelerator; repair; shrinkage; abrasion +
Footnote †: journal: Applied Sciences  
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workability, and concrete mixtures can also be moreover modified with hardening accelerators [8; 9]. As a result, fast-hardening concretes are characterized by low \(W/C\) (0.3 and less) due to early and grade compressive strengths of more than 70-90 MPa and flexural strengths of more than 9 MPa being achieved [10]. As is known [11], high-strength concretes are characterized by increased brittleness, which is particularly important in conditions of dynamic loads from transport. In addition, due to the large amount of cement in the mixture, shrinkage deformations increase, especially in the early ages of hardening [12]. To solve the above-described issues, concretes with fiber reinforcement have been widely used in highway engineering, in which different fiber types are used: steel, basalt, polypropylene and glass [12; 13; 14; 15]. The usage of fiber permits increases in crack resistance and the most important parameters for rigid pavements--flexural strength and reduced abrasion [16]. At the same time, steel fiber is the most effectual for many types of structures. Steel fiber concrete was first used as a repair material for rigid road pavement in the USA [17]. The flexural strength of steel-fiber-reinforced concrete reaches high values > 12 MPa. The above-described benefits of this material make it possible to use it as a repair material for rigid road pavements. Quite a lot of research in recent years has been devoted to fiber-reinforced concrete for rigid pavement repair, including high-early strength concretes. In [18], concrete with a hardening accelerator and steel fiber in the amount of 37 kg/m\({}^{3}\) at the age of 1 month reached a flexural strength of 7.4 MPa with a cement content of 465-490 kg/m\({}^{3}\), but the early strength was not analyzed. In [19], using an accelerator and steel fiber in the amount of 72 kg/m\({}^{3}\), a fiber-reinforced concrete was developed with a compressive strength of more than 40 MPa and a flexural strength of more than 4 MPa already after 6 h of hardening. However, it required the use of a large number of expensive binders: type III fast-setting cement--320 kg/m\({}^{3}\) + aluminate cement--280 kg/m\({}^{3}\). In [20], by using fiber with a length of 55 mm in the amount of 78.5 kg/m\({}^{3}\), the flexural strength after 28 days was 8.81 MPa. At the same time, a large amount of Type I cement was used--462 kg/m\({}^{3}\)--as well as a silica fum modifier--66 kg/m\({}^{3}\).