An east coast government agency raised concern about the structural integrity of a viaduct located on a main north-south highway that dealt with roughly 75,000 vehicles per day. The viaduct, comprised a 42-foot wide concrete deck of 40 piers and spans, was constructed in 1953 and was showing signs of general degradation.
The agency had appointed a civil engineering construction company to handle repairs. As part of the process, the agency had approached RJ Lee Group to provide data on the current state of the concrete, an estimation of service life, and failure analysis. It was a difficult task to deal with such a large structure in multiple environments. Nevertheless, RJ Lee Group’s experts successfully completed the challenging project, creating a comprehensive report within two months.
Sample Collection
RJ Lee Group is an industrial forensics laboratory and consulting firm with a capability to approach external partner firms to provide a complete solution. In this project, the company together with the support of a joint venture partner performed on-site visual inspection of the viaduct including concrete piers, the deck and expansion joints. During the analysis, they collected 38 core samples from three different sites, of which 20 from the deck’s lateral face and 18 from the concrete deck. The RJ Lee Group laboratory’s expert analysts examined and characterized these concrete and steel samples. Mechanical tests conducted on these samples determined variability in compressive strengths, which implied internal defects in the concrete.
Sample Characterization
RJ Lee Group’s petrographers inspected the concrete cores and identified that air-void spacing was more than the recommended value for frost durability under saturated conditions. They also determined that alkali-silica reaction (ASR) affected the concrete. ASR had been initiated several years ago and was not likely to continue due to its mature state. Moreover, ASR did not affect samples taken from the viaduct parts that had been safeguarded by the pavement from water penetration and chloride contamination was different from one pier to another.
Service Life Simulation
RJ Lee Group’s experts noticed very little signs of rebar corrosion in the sound concrete samples. Hence, the company teamed up with its partnering firm to perform service life simulations to assess the potential for future corrosion.
The service life simulation modeling engaged different mechanisms including moisture transport and time-dependent boundary conditions. The time of corrosion initiation based on the types of concrete covers was estimated from the results obtained for each pier. With these mechanisms, RJ Lee Group was able to predict the long-term service life, which was helpful to engineers in selecting solutions for effective maintenance and repair of concrete structures and providing support for the application of surface protection systems like sealers as a cost-effective solution.
Conclusions
The concrete core analysis determined the damage caused by the ASR on the viaduct deck and pier concrete. However, that deterioration was confined to the damp areas in the vicinity of the joints. Freeze-thaw cycles further increased deterioration in those areas not effectively protected from frost damage. Cracks found at the pier-deck junction were limited to a small area on each side of the deck and most probably caused by restrained movement. Results signified the benefits of protection systems and covers for concrete exposed to adverse conditions and provided the much needed data to the engineering company overseeing repairs.
About RJ Lee Group
For nearly 30 years, RJ Lee Group, Inc. has excelled at providing analytical services, technical consulting, information management, and expert testimony in materials characterization and forensic engineering. Our services are sought by leading organizations in academia, industry, and government. Clients choose RJLG because of our reputation as an innovative solutions firm that is reliable, ethical, and committed to quality. The end result is outstanding customer satisfaction.
RJ Lee Group applies the most appropriate and efficient testing methods to deliver scientific resolution for a wide range of industries.Using state-of-the-art analytics, our multidisciplinary staff addresses diverse needs — including regulatory compliance, quality control, materials R&D, industrial hygiene and environmental health and safety.
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RJ Lee Group defines our expertise as the capabilities of those who day in and day out verify the established, expose the concealed, investigate the problem, provide the solution and confront the unknown.
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This information has been sourced, reviewed and adapted from materials provided by RJ Lee Group.
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