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Repair and Maintenance of Post-Tensioned Concrete Bridges (2021)

Chapter: Chapter 4 - Summary and Conclusions

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Page 62
Suggested Citation:"Chapter 4 - Summary and Conclusions." National Academies of Sciences, Engineering, and Medicine. 2021. Repair and Maintenance of Post-Tensioned Concrete Bridges. Washington, DC: The National Academies Press. doi: 10.17226/26172.
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Page 62

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62 Concerted efforts to improve the durability of post-tensioned bridges have been made since the technology made it into the concrete bridge industry, yet opportunities for further improve- ment remain. For some states, existing PT structures continue to require repair and maintenance actions. Often, these are the solutions that bridge owners have formulated after consultation with industry consultants and one key agency—the Florida Department of Transportation. Some states on the other hand, such as Texas and California, have many PT structures in their inventories, but they did not report in their survey response that they had instigated repairs. Lessons of the current state-of-the-practice can be gathered from the results of a survey of state departments of transportation on their construction, inspection, and repair practices specific to PT structures. Several findings of the survey and case examples are salient: • A majority of states have PT structures (44). • The number of PT structures in different states is widely varied, with some states having no or few structures, and others having hundreds. • Many states (23) have experience with PT repair. • While many state DOTs are referencing key guidance documents (such as PTI/ASBI M50 and PTI M55) or other states’ specifications when developing or updating their own PT speci- fications, nonuniformity is significant from state to state. • Consideration of durability during the design phase, through the designation of a protection level, for example, is not widely practiced among state DOTs. • Issues related to methods of construction remain. Most often, they are related to the process of grout/filler injection and duct pressure testing prior to injection. • State DOTs continue to have issues with particular materials specific to PT construction, most notably grout filler materials and pour-back materials. • Several state DOTs have made it a standard practice to make provisions for the installation of tendons in the future to provide redundancy when addressing issues with a PT structure. • Routine inspections are not sufficient in identifying issues in PT structures before they become severe. As found in several of the case examples, evidence of PT system damage was not identified before the situation became critical. Inspection by persons with PT-specific experience is recommended. • Recently, states have begun to use materials in novel applications in an effort to improve the corrosion protection of existing structures, including the use of injectable, proprietary corrosion inhibitors and flexible filler materials (such as microcrystalline waxes). Several states have injected proprietary corrosion inhibitors into compromised tendons. C H A P T E R 4 Summary and Conclusions

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The use of post-tensioning in concrete structures has allowed for the construction of economical long-span bridges. However, very limited information is available to guide bridge owners on how to maintain existing structures or, more specifically, to repair degraded post-tensioned structures.

The TRB National Cooperative Highway Research Program's NCHRP Synthesis 562: Repair and Maintenance of Post-Tensioned Concrete Bridges gathers information on the practices used by bridge owners to repair and maintain post-tensioned bridges and facilitates knowledge transfer across state departments of transportation (DOTs), aiding bridge owners in the identification of repair practices that are working and that will extend the useful life of the bridges.

Supplemental materials to the report include appendices containing the survey and the survey responses.

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