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This article presents the latest improvements in a recently developed nondestructive testing (NDT) approach for early detection of various flaws (corrosion, delamination, and concrete cracking) in reinforced concrete (RC) bridge decks. The proposed method involves the use of internal steel reinforcement as a wave guide for transmitting ultrasonic waves through the system and the measurement of leaked energy from the surface of the concrete. This paper builds upon the progress made in the previously published phases of the project and aims to further explore the capabilities and practicality of the proposed NDT method. Specifically, the limits of propagation distance, effect of bidirectional reinforcement, methods of attachment and coupling of the sensors to the reinforcement and concrete, and suggestions for optimal sensor arrays are discussed in this paper based on the findings from the most recent laboratory tests and pilot field tests. The results show that with careful placement of sensors and data interpretation, early stages of localized corrosion and delamination can be detected, even when bidirectional and multiple layers of reinforcement are present. For field applications, an angled seat made of fast-setting Hydrocal gypsum cement is recommended, and it is projected that the optimal angle of attachment is 33 degrees or less from the vertical axis.

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Pan-girder (PG) bridges became popular in Texas, USA, in the 1950s and 1960s as a viable alternative for short-span bridges due to their speed of construction, low-labour requirements and cost–effectiveness. However, these bridges were designed for lighter live loads than the current AASHTO HL-93 loading, resulting in gradual decline in their usage. Existing PG bridges may have various structural and non-structural deteriorations because they are nearing or have crossed their service lives. In this study, the existing condition of four selected PG bridges in the Dallas–Fort Worth metroplex were visually inspected to assess their current condition. The bridges exhibited significant concrete spalling, cracking and crushing, resulting in exposed and corroded steel rebars. The newest bridge, built in 1992, experienced less severe damage than the other three bridges built in 1955–1971. The bridges’ safety could be compromised due to deteriorations and lighter design live loads. Therefore, the following recommendations were made: (a) glue a polyvinyl chloride pipe on the form-lowering holes extending beyond the concrete surface of the arch to minimise water infiltration and related damage; (b) conduct load testing and ratings to verify the structural safety and load-carrying capacity of the deteriorated bridges; and (c) retrofit to upgrade the existing bridge condition and safety and mitigate against further damage.

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