11. Features of High-Speed Deformation and Fracture of Fine-Grained Concrete Under Tensile Stress

This paper analyzes an experimental study of high-rate deformation and fracture of fine-grained concrete under tensile stresses. A number of sources of foreign and domestic authors are analyzed. Based on the analysis, it was concluded that some properties of concrete have not been fully investigated. In connection with the above, an experimental study of the dynamic properties of concrete materials is relevant today. Experimental studies were carried out on the basis of modifications of the Kolsky method. These modifications make it possible to determine the strength and time characteristics of concrete deformation under high-speed loading. To analyze the nature and time of the destruction, experiments were carried out using high-speed photography. Splitting (Brazilian test) and straight tensile experiments have two speed modes. On the basis of the performed experimental work, tensile strain diagrams and stress versus time diagrams during splitting were obtained. The experimental data indicate the effect of the strain rate on the ultimate tensile strength characteristics. The dynamic tensile strength of fine-grained concrete was about 8 MPa. The value of the coefficient of dynamic tensile hardening is in the range from 4 to 6 MPa. This factor depends on the strain rate. The opposite effect of the influence of the loading rate was obtained both during splitting and stretching. This means that with an increase in the strain rate, the maximum breaking stresses decrease. On the basis of high-speed photography, the features of high-speed destruction of fine-grained concrete under tensile stresses are revealed. The found characteristics can be used to create mathematical models necessary to determine the strength of concrete structures subjected to dynamic effects.