Justification of the methods for operational research of the operational reliability of acid-resistant concrete under the influence of climate cycles “freezing – thawing” by the ultrasonic pulse method

An important task of the construction industry is to establish the operational reliability of construction objects under the influence of cyclic climatic loads from freezing and thawing on the concrete. This is especially relevant if such loads are accompanied by moistening followed by the concrete freezing. Such loads cause a violation of the structure of concrete and lead to a decrease in its strength. It is especially important to solve this problem for acid-resistant concrete, which is used in the construction of platforms for unloading or using material and liquids characterized by their aggressive action – acids, alkalis, etc. According to regulatory documents and official methods, the class of concrete in terms of its frost resistance is determined at the stage of its design using destructive methods. For this purpose, a series of concrete samples are prepared, the strength of which is determined by compressive load during a series of “moistening – freezing – thawing” cycles. Samples are frozen in a special freezer. The peculiarity of the operation with acid-resistant concrete is that its saturation in real conditions occurs not only with water, but also with a solution of an aggressive environment. This can intensify the decrease in the concrete strength, and therefore the decrease in its operational reliability. Published research results aimed at improving the determination of frost resistance of the concrete involve the use of, for example, strain gauges embedded in concrete, the acoustic emission method, etc. The main disadvantage of such methods is the significant complexity of implementation, or the impossibility to test the concrete in production conditions. The results of the experiments presented in the paper indicate a real possibility of determining the strength of acid-resistant concrete during operation using the improved ultrasonic pulse method.