Indian Journal of Science and Technology

Abstract

Background/Objectives: This paper presents development of non destructive testing methods for calculating the compressive strength of concrete. Methods/Statistical Analysis: The compression tests along with impact echo tests and Ultrasonic Pulse Velocity (UPV) tests are carried out at different load which was the increased compressive loadat certain interval on concrete cubes of various mixes. The frequency spectrum and the ultrasonic pulse time are recorded. A MATLAB based code is used to calculate the maximum frequency of the sound signals corresponding to each impact echotest under a certain compressive load. The graphs for frequency and compressive load are plotted. The graph for ultrasonic pulse velocity on the various compressive load are also plotted for different samples of concrete. Findings: Important observations are found from the graphs of frequency and ultrasonic pulse velocity. The frequency and ultrasonic pulse velocity peak values were continuously found decreasing under the increase in the compressive load. After initial crack formation with the further increase in load the frequency was found increasing trend but with showing a small increased value. Whereas the ultrasonic pulse velocity was found reducing trend in nature. These plots give the clear indication of crack formation. Application/Improvements: These graphs are used for comparison of variation of frequency and ultrasonic pulse velocity to predict the undamaged and damaged state of concrete under compression. A mathematical expression is developed between compressive strength, frequency and ultrasonic pulse velocity.
Keywords: Compressive Load, Frequency Spectrum, Impact Echo Test, MATLAB, Non Destructive Testing, Ultrasonic Pulse Velocity