Методика експериментального дослідження зчеплення арматури з фібробетоном

Abstract

The article describes the method of experimental research on the determination of the peculiarities of the adhesion of sickle-shaped profile rebar with dispersion-reinforced concretes - steel fiber reinforced concrete (SFRC) and fiber concrete on the basis of basalt fiber.

The purpose of the research is to determine the peculiarities of the adhesion of the sickle-shaped profile rebar with SFRC and fiber concrete on the basis of basalt fiber, the construction of mathematical models to determine the limiting stresses of the adhesion and the analysis of the influence of determining factors on the adhesion stress of the surface contact of the rebar reinforcement with the fiber concrete.

The adhesion of rebar with concrete and its anchoring - fixing the ends of the rods in the concrete - significantly affects the reliability of reinforced concrete structures. The adhesion of rebar with plain concrete is studied and there are mathematical models for determining the ultimate stresses, but adhesion of rebar with fiber concrete have not yet been conducted in Ukraine.

Although the fiber concrete itself is increasingly used in reinforced concrete structures, in which it is necessary to ensure reliable anchoring of rebar.

Fiber concretes, as well as concretes, belong to the number of poorly organized or so-called diffuse systems, the characteristic features of which are the impossibility to clear selection of separate phenomena and the need to take into account many mixed factors. With regard to the adhesion of rebar to concrete, the system "concrete - reinforcement" can be considered as a diffuse system. The regression equation is obtained on the basis of mathematical modeling, as a result of which it is possible to obtain the surface of feedback factors. The most convenient is the representation of the unknown response function in the form of polynomials.

The main factors that significantly affect the anchoring stress of reinforcement with fiber concrete can be taken as the percentage of fiber content, diameter of rebars, length of anchoring rebars in the concrete. These factors are not correlated with each other. As it is known that concrete is an elastic-plastic material, which has curvilinear diagrams of the mechanical state, let's choose the Box–Behnken design for obtaining the quadratic dependences (quadratic mathematical model).

The experimental samples will be made of C25/30 fine-grained concrete. Based on the results of the experiments, the following will be performed: their statistical processing; mathematical models will be constructed; the influence of the accepted factors will be analyzed; the table of calculated values of the rebar and fiber concrete anchoring strengths will be presented.