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CHAPTER 4 CONCLUSIONS AND SUGGESTED RESEARCH The durability performance of precast segmental bridges has been excellent in the United States (U.S.) to date. While it is true that current inspection strategies that rely almost exclusively on visual inspection may not detect on-going corrosion of internal tendons, current research indicates that a properly grouted tendon surrounded by matchcast epoxy joints provides a corrosion resistant detail for construction utilizing internal tendons. Thus, it is highly probable that properly designed and constructed precast segmental bridges are durable. Durability problems in the United Kingdom (U.K.) and Europe which led to the current moratorium on precast segmental construction in the U.K. are due to poor design and construction choices and execution rather than intrinsic durability problems with precast segmental construction. In order to insure good durability performance of precast segmental bridges in the future, especially those with internal tendons, the following measures should be considered by the AASHTO Subcommittee on Bridges and Structures: I. The AASHTO Segmental Guide Specification should be adopted as a full specification or be incorporated into the Standard Specifications for Highway Bridges to insure that the guidelines are followed in future design and construction. 2. AASHTO Specifications should clearly and specifically preclude the use of mortar segment joints. Additionally, the specifications should not allow match-cast dry joints ~ -- a, ~ r~~-~ . · - in a marine or any other corro. save environment. 3. AASHTO should adopt more stringent and comprehensive grouting specifications to insure that post-tensioning tendons are completely encapsulated in a high quality grout. 29
4. AASHTO Specifications should require that the end cover for the maid reinforcement of segment joints be consistent with the clear cover specified for the top deck slab. in. Additional research and field teals should be perfonned with current and evolving non- destructive testing (NDT) and evaluation techniques to further develop NDT capabilities so as to provide bndge owners with better inspection of grouted post- tensioned structures. 6. A reasonably comprehensive field testing and evaluation program should be conducted on a few of the older segmental bridges in the U.S. that are exposed to a corrosive environment. The purpose of this comprehensive evaluation would be to gain additional insight into the performance and long-term durability of precast segmental bndges that heretofore has mostly been garnered by visual inspection. Moreover, data from this program could then be compared with the favorable performance data from the University of Texas at Austin laboratory study. This would permit a connection of long-te~m field results to the results of accelerated laboratory testing. . 30
