Validation of Nondestructive Testing Equipment for Concrete

摘要

The Florida Department of Transportation (FDOT) would like to implement nondestructive test and evaluation (NDT/NDE) technologies to assess quality of concrete constructed in the field as means to reduce flaws introduced by faulty construction. Toward this aim, the primary objective of the project was to design, construct, and implement a facility for calibrating and validating methodologies for the NDT/NDE of structural concrete materials and members. Four concrete test blocks have been designed and built in which specific testing problems (e.g., concrete cover, concrete thickness, and tendon ducts) were implemented to investigate them under defined conditions in the laboratory. The specimens were designed to challenge NDT techniques, and serve to demonstrate their capabilities as well as their limitations. An automated test frame has been designed, built, and implemented, and a software platform for scanner control, data acquisition with different sensors, real-time imaging and data analysis has been developed and successfully applied in the project. Automated measurements were taken with impact-echo, ultrasonic echo, and covemeter on the four concrete test specimens. GPR equipment has been procured but will require extra effort to be operated on the scanner. Covermeter measurements on the specimen with reinforcement steel clearly demonstrated the potential of this method, but also showed some limitations. Complementary ultrasonic-echo measurements in combination with the synthetic aperture focusing technique (SAFT) analysis showed the potential of this method to resolve reinforcement in cases where it cannot be resolved by the covermeter. Measurements conducted on the specimen with varying thicknesses demonstrated the capabilities of especially ultrasonic-echo. The tendon ducts in the tendon duct specimen were located in 2D by impact-echo and in 3D by ultrasonic echo. Overall, a first stage NDT validation facility has been established, and the system has been demonstrated to work precisely and reliably.