Investigation on applicability of ultrasonic pulse velocity measurements to estimate thickness of reinforced concrete wall panel

Abstract

In Sri Lanka, Concrete has been widely used as a construction material for more than hundred years and it is necessary to analyse some of these existing old structures to check their structural adequacy, for retrofitting works, repair works and rehabilitation works, etc. For these purposes it is necessary to know the sectional dimensions of structural elements and reinforcement details to evaluate the structural adequacy with the existing strength of concrete. In most of the cases it may not be possible to find the structural drawings to obtain these required structural details and also it may not be possible to measure the required thicknesses of structural elements due to accessibility problems. The objective of this research study is to establish a suitable non destructive method to estimate the thicknesses of various types of concrete members with accessibility problems. Hence, from a thorough literature study, it was found that using ultrasonic pulse velocity methods it could be possible to determine the uniform thicknesses of concrete walls. It is reported that this ultrasonic pulse velocity is affected by the concrete properties as well as the other factors such as temperature, stress history/ level of stress, path length, moisture and curing condition of concrete, presence of reinforcement and size and shape of the specimen. Accordingly, testing was conducted to study the influence of reinforcement percentages and to observe the influence of some other parameters such as age of concrete, moisture condition and temperature on the accuracy of the thickness predictions using ultrasonic pulse velocity method. Further to verify the results, some existing structures were also investigated. From this experimental study and the field investigations, it is found that the UPV test method could be used to estimate the thickness of concrete walls with a reasonable accuracy.