Impacts as a Source of Acoustic Pulse-Echo Energy for Nondestructive Testing of Concrete Structures

The construction industry lags behind the aerospace, automotive, and other industries in the development of nondestructive testing systems for assessing the condition of one of their primary building materials, concrete. A research investigation was made to determine the feasibility of using impacts to create high-energy, high-resolution stress waves for making sonic and ultrasonic pulse echo UPE measurements in concrete. No method presently exists to probe the deep interior of large concrete structures such as locks and dams. Impacts from air guns that shoot steel balls, the Schmidt rebound hammer, and small explosives demonstrate the potential for generating the appropriate kind of energy for UPE measurements. Measurements were made to demonstrate that the frequencies generated by these types of impacts are in the proper range for making UPE measurements in concrete, i.e. less than 200 kHz. Also, it was demonstrated that the energy level from these impact sources was high, suitable for penetrating large distances. Various criteria are discussed in this study that have a bearing on the development of a practical impact UPE system for concrete structures.... Concrete, Nondestructive testing, Sonics, Construction, Pulse-echo, Ultrasonics, Impact-echo, Resonant frequency.