Studying the Impact of Imposed Actual Loads on the Non-Destructive Test Results for Evaluating the Compressive Strength and Other Properties of Concrete

Abstract

Among all the concrete characteristics, the compressive strength is known as the most important feature and therefore, it is often utilized to quantify the quality of concretes. The assessment of concretes strength in existing constructions is important during their service life. Thus, in addition to destructive evaluation of strength, many non-destructive techniques have been adopted to assess the concretes strength. Ultrasonic Pulse Velocity (UPV) is one of the nondestructive techniques that involve measuring the speed of ultrasonic wave through concretes to predict concretes strength. According to the Griffith's theory, the strength of the material is greatly affected by the defects' existence (for example, small cracks). These cracks can be current prior to the application of any loading or could create throughout the load application. The presence of micro-cracks in concretes that generate due to the applied load may affect the UPV test results in comparison with unloaded concretes. An experimental investigation is conducted in order to assess the impact of the applied of load (ultimate load) on the measured ultrasonic wave velocity and compared with the results of compressive strength from destructive test. A total of thirty (150 mmx150mm) cube specimens have been utilized with water to cement ratios (0.45). These cubes have been examined in ultrasound without any loads and then they have been tested in the same way with applied ultimate load which is approximately equal to half of the required design load (failure load) and then inspected or tested in the normal way (destructive test). In order to assess the compressive strength of concretes using (UPV), loading condition is considered in order to study the impact of the applying load. In addition, the water absorption has been examined for thirty concretes samples under the impact of the applied loads (20%, 40% and 60%). The results of nondestructive tests of concretes samples under the influence of imposed loads (60%) have showed to be less by compressive strength 5 MPa than the results obtained from testing of unloaded concretes samples through the resulting equation and comparing them to the equation from previous research. This is consistent with the water absorption test of the specimens under the imposed loads (60%) where Absorption values have been greater than concretes models without applied loads. Copyright