Ways to increase the reliability and accuracy of determining the geometric parameters of cracks in the concrete of buildings using the ultrasonic pulse method

Abstract

During the exploitation of buildings, cracks appear in the concrete of structural elements, which can reduce the physical and mechanical characteristics of their structures. With a certain exposure width and depth, cracks are subject to filling with special materials. In case of error in determining the crack depth, the repair material may not fill it sufficiently. This might lead to accidents. Nowadays, the most common method is to measure the parameters of cracks with a microscope and a measuring probe. Its disadvantage underlies in insufficient reliability of the crack depth measurement. This is because if there is an internal lintel of concrete residues in the crack, there may be an error in measuring its depth. The ultrasonic pulse method is also used, when the depth of the crack is determined by the time of travel of ultrasonic vibrations on the section of high-quality concrete and on the section with a crack. This method is not very reliable because the ultrasonic vibrations can also propagate through the internal lintel of the concrete residues in the crack. In this case, the measurement result will be false. An improved ultrasonic pulse method is used when the combined amplitude of the information signal is also measured. The use of this parameter is insufficient because solving the problem requires taking into account spectral characteristics of the parameter. At the stage of development, there is a method that uses surface ultrasonic waves. Its disadvantages are relative complexity of research in concrete and high cost of equipment. To increase the reliability and accuracy of determining the geometric parameters of cracks in concrete, studies were carried out using a complex ultrasonic pulse method. During the research, the value of the normalized propagation time of ultrasonic vibrations, the amplitude, and duration of the first half-period of the information signal were measured. The results of the research allow us to recommend the developed method for solving the problem.