Application of non-destructive geophysical methods for testing concrete structures

Abstract

Non-destructive testing of reinforced concrete structures is of utmost importance in construction and civil engineering, where many factors can cause internal and external deterioration of reinforced concrete structures: the environment, nuclear radiation, and structural defects, among others. Geophysical non-destructive testing methods such as ultrasonic and radar have been increasingly used in civil engineering in recent years. Improvements in the ultrasonic testing of concrete have produced detailed images of the interiors of even the most complex structures and allowed for the earliest possible detection of deterioration. In this study, three geophysical methods were applied to inspect concrete structures: parallel seismic, sonic echo, and ultra-seismic. These three testing methods are applied to concrete foundations of two depths, namely 5, and 7 m; the deep foundation has a fracture at a depth of 4.5 m. The collected data are processed using a low-pass filter to remove the higher frequencies. These results of parallel seismic tests accurately predict foundation depths of 5.0 and 6.6 m and P-wave velocities of 2551 and 1097 m/s, respectively. Sonic echo tests yield depth predictions of 5.07 and 7.01 m for the tested foundations and 4.44 m for the depth of the crack. Meanwhile, ultra-seismic tests give depth predictions of 7.1 and 4.6 m for the foundation and fracture, respectively, while clarifying the P-wave velocities of the corresponding reflections: 3447 m/s exiting the 7-m foundation and 2668 m/s exiting the embedded fracture. Depth estimates based on each method show strong agreement with true depths. In conclusion, these three geophysical methods have great potential to provide quantitative data to drive quality assurance and remediation for concrete structures.