Deformability and strength of fine grain steel fibro concrete under axial tensile

Abstract

The purpose of these studies is to study the influence of the coefficient of fiber reinforcement with bent ends of the HE1050 type by volume   and the strength of the concrete-matrix   on the deformability and strength of steel-reinforced concrete under axial tension.

  Taking into account the requirements of the standards for the design of steel fiber concrete constructions, fine-grained concrete of classes C20/25 and C30/35 was used in the experiment, since concrete classes in this range are used most often in real structures without pre-tensioning of rods. Coefficients of fiber reinforcement by volume are taken as  = 0.007; 0.0125 and 0.018, since at lower reinforcement coefficients the strength effect is practically absent, and at higher ones, structures cease to be competitive. Ukrainian-made steel fiber with bent ends 50 mm long and 1 mm in diameter (type НЕ1050) was used. The strength and deformability of steel-reinforced concrete under the action of short-term tension was studied by testing samples of 400 x 120 x 30 mm, since in the future the test results will be used to evaluate the stress-strain state of beam elements of a П-shaped section with a shelf to the bottom, the cross section of which is 120 x 30 mm.

The following composition was adopted for the production of samples from concrete class C20/25: M400 cement of "Ivano-Frankivskcement" with an activity of 41.2 MPa - 445 kg, sand with a coarseness modulus of 2.1 from the Yasinetsky quarry - 1645 kg, water - 240 l. To obtain concrete class C30/35, the following composition was adopted: cement grade M500 of "Ivano-Frankivskcement" with an activity of 52.3 MPa - 431 kg, sand with a coarseness modulus of 2.1 from the Yasinetsky quarry - 1724 kg, water - 216 liters. Fiber consumption per 1 m3 was equal to 54.95; 98.13 and 141.3 kg for reinforcement percentages of 0.7; 1.25 and 1.8, respectively.

Based on the results of the experiments, a regression equation was obtained to determine the relative deformations corresponding to the peak point of the deformation diagram of the stretched steel-reinforced concrete reinforced with fiber with bent ends of the HE1050 type. The proposed formula for determining the tensile strength of fiber concrete reinforced with steel fiber with bent ends of type HE1050 under short-term load action.