Methods and instrumentation for studying the strength of concrete joints in adhesive structures under the influence of operational and technological factors by the ultrasonic pulse method

The use of concrete adhesive joints in repair and restoration works is an effective technological solution from technical and economical point of view. To make such joints, polymer glues are used, for example, epoxy, siloxane, acrylic, etc. The use of such technology reduces material consumption, labour costs, and time of construction works. The analysis of published research results showed that the use of acrylic adhesives is effective. When performing an adhesive concrete joint, the main task is to ensure the required strength of the adhesive structure during its operation. The analysis of publications revealed that the strength of the structure is influenced by the following main factors: external load, strength of concrete to be glued, gluing area, and the thickness of the glue layer. Currently, the influence of the specified factors is being studied on samples of adhesive structures using mechanical, press equipment. During the experiments, external loads are applied to the manufactured sample of the adhesive structure, for example, tensile, bending or shear forces. The measured parameter is the strength of the adhesive structure. With such studies, it is difficult to determine the value of the maximum external load that leads to the formation of microcracks, which makes the strength of the structure reduce. As a result, this approach can cause an error in research conclusions, which will lead to a decrease in the reliability of operation of a real construction object. In addition, this approach makes it impossible to control the condition of those adhesive concrete structures that are used on real construction sites. The developed methods to study adhesive concrete structures using the ultrasonic pulse method are based on the dependence of the speed of propagation and attenuation coefficient of ultrasonic vibrations on the relative change in the structure of the material under consideration. The application of the developed methods and instrumentation for their implementation allows determining the value of the maximum permissible external load and ensuring the control of the state of adhesive structures in terms of crack formation on real construction sites.