Define Concrete Surface Finish - Limitations of Ultrasonic System?

The smoothness of the surface under test is important to ensure proper acoustical contact between the transducer and the concrete surface. A coupling agent, such as silicon grease, must be placed between the transducer and concrete surface to ensure transmission of maximum energy. If a coupling agent is not used, the transmitted signal will be severely attenuated which results in large errors in the measurement of transit time.