The Moisture Effect on Ultrasonic, Rebound Hardness and Drilling Resistance Data in Non-Destructive Testing of Concrete

As the volume of reinforced concrete structures continues to grow, it is important to determine the quality of concrete in the shortest time possible. Therefore, the development and validation of methods for non-destructive testing (NDT) of concrete structures are becoming increasingly important. However, some factors may affect the accuracy of the measurement results obtained as concrete is often exposed to a moist environment, e.g., in marine structures. Ignoring these factors may lead to an inaccurate interpretation of measurements. Therefore, in this research, the water saturation factor of concrete was investigated in response to various NDT methods. C25/30 and C40/50 MPa concrete were evaluated using ultrasonic pulse velocity and rebound hardness devices, and for the first time, a drilling resistance (DR) method was systematically adapted and validated for moisture-affected concrete testing. Unlike conventional approaches that only consider surface effects, the DR method introduced here provides in-depth profiling of concrete, revealing variations in resistance with depth and identifying zones influenced by internal moisture distribution. This study demonstrates that the DR method can complement traditional NDT techniques, providing a more reliable evaluation of moisture-induced variations in concrete properties. Moreover, with the novel DR method, changes in the mechanical response with depth have been quantified, offering new insight into internal moisture effects that are not accessible by conventional NDT methods.