Nondestructive Condition Assessment of Concrete Slabs with Artificial Defects Using Wireless Impact Echo

Abstract

The use of nondestructive testing (NDT) methods for the condition assessment of reinforced concrete structures is increasing due to the various advantages of NDT compared to traditional approaches, such as qualitative visual inspections and destructive testing protocols. Nevertheless, there remains some uncertainty over how to develop appropriate and cost-effective assessment procedures that account for the inherent advantages and disadvantages of various available NDT tools and technologies. In this study, a new wireless impact echo (IE) prototype system is presented. The system consists of a handheld device that connects via Bluetooth to a user-friendly software interface optimized for tablet computers. The wireless IE system was validated using a series of three reinforced concrete slabs containing artificial defects intended to simulate geometric discontinuities, delamination, internal voids, cracks, and a hollow conduit. The IE prototype was compared with other common NDT devices used for similar purposes, namely ground-penetrating radar (GPR) and ultrasonic pulse echo (UPE). GPR was the quickest method by far, although the results gathered were significantly influenced by the presence of steel reinforcement and failed to locate certain defects. UPE was slower than GPR but was generally able to identify the locations of the artificial defects more accurately; UPE readings were also affected by the presence of steel reinforcement. The IE method was not as rapid as the other two approaches but was able to locate most of the artificial defects and was less significantly affected by the presence of steel reinforcing bars than the other two methods. Based on these results, a general framework for the condition assessment of reinforced concrete slabs is presented.