IMPROVEMENT OF THE METHOD OF CONCRETE PHYSICAL AND MECHANICAL PROPERTIES DETERMINATION BY NON-DESTRUCTIVE METHODS

Abstract

Abstract. To ensure the reliability of existing buildings, facilities and building structures, objective information is required, the receipt of which is mainly associated with the use of non-destructive methods of control. Current normative documents regulate the strength and deformability characteristics of the material, which are used mainly in the design of structures. The normalized value is obtained on the basis of probabilistic and statistical processing and is characterized by some conditional value. Improvement of methods of calculation of constructions connected with the account of elastic-plastic properties of concrete is based on application of the standardized diagrams of work of concrete received on the basis of laboratory experiments. In the real structure due to differences in the composition of laboratory and real concrete, technologies of its manufacture and laying, there may be significant differences from the acquired value "Concrete strength" and "Modulus of elasticity", which was taken to calculate the structure. The above-mentioned influence of the stress level on the readings of the device in determining the strength of concrete by non-destructive testing methods was investigated on concrete samples of six different compositions. Concrete cubes measuring 150×150×150 mm were used to study the stated assumptions. The determination of the strength of concrete samples by the non-destructive method was performed. A sclerometer (Schmidt's Hammer MSH-225) was used to determine, which implements the method of elastic rebound. The determination was performed at different load levels, which was added to the test sample, followed by determination of the strength of concrete on a hydraulic press with a load up to 1250 kN. The analysis of the obtained results shows that the attempt to obtain a generalized calibration curve, which would take into account the change in the stress level in the structure, leads to a decrease in the accuracy of determining the physical and mechanical characteristics of concrete. The presented dependences demonstrate the significance of the influence of the stress level in the structural element on the results of determining the physical and mechanical characteristics of concrete by non-destructive methods. The analysis of these dependences shows the need to modernize non-destructive methods for determining the physical and mechanical characteristics of concrete.