Assessment and Rehabilitation of a 50-Year Old Concrete Bridge Deck in Nackawic NB

Abstract

With infrastructure across Canada continuing to age, Engineers are now more than ever seeing the need to perform comprehensive evaluations of existing structures. Such evaluations are crucial to accurately assess the condition of aging infrastructure and to design and implement the appropriate rehabilitation measures. The subject of this case study is a 50-year-old cable-stay bridge located in Nackawic NB; the structure is owned and operated by the New Brunswick Department of Transportation and Infrastructure (NBDTI) and has recently been selected to undergo a detailed structural evaluation. The bridge structure is two-lanes in width and spans approximately 85 m; the structure consists of an asphalt surfaced continuous concrete deck supported by steel girders and a single-tower cable-stay system. The focus of this article is on assessment and rehabilitation of the concrete bridge deck. A nondestructive testing program was developed and deployed, which involved: (1) a deterioration/delamination survey by use of ground penetrating radar (GPR), and (2) a half-cell potential survey to identify areas of probable corrosion. Nondestructive field inspections were complemented by laboratory testing of extracted core samples for determination of chloride ion content and compressive strength. Good correlation is observed between the two independent nondestructive field inspection techniques (GPR and half-cell potential), and problematic areas identified during nondestructive field inspections also yielded core samples having high chloride contents during laboratory testing. Based on the results of this detailed deck evaluation, recommendations for deck rehabilitation are developed and are scheduled for implementation during the summer of 2021.