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11 1.3.2 Batching Materials and Sealants dinal web cracking in precast/prestressed concrete girders. In addition to the literature review, a national survey was Batching materials typically are used to fill the cracks but not developed to collect information on the experience regard- to restore the concrete tensile strength at the cracks; sealants ing longitudinal end zone cracking. The national survey was are used to create impermeable concrete surfaces that prevent sent to all state DOTs, other owner agencies, selected bridge moisture from getting into the girders and causing corrosion consultants, and precast concrete producers. It was also sent of the reinforcement. A wide range of commercial batching to about 150 PCI bridge product producers, the PCI Com- materials and sealants are available in the market. Precast pro- mittee on Bridges, the PCI Bridge Producers Committee, ducers make their choice based on experience and performance and selected Canadian agencies. The questionnaire included of the selected material. Appendix A of this report provides questions on reinforcement details, strand release process, some examples of batching materials and sealants used by criteria for repair and rejection of cracked members, and precast producers in Nebraska and Washington State. repair methods. Task 2. Using information assembled in Task 1, the factors 1.4 Objective and Scope that alone or in combination may initiate or propagate lon- of the Research gitudinal web cracking were identified and documented. Task 3. Using the findings from Tasks 1 and 2, the research The NCHRP objective of this project is stated as follows: team proposed evaluation criteria for assessing the strength and durability consequences of longitudinal web cracking. To establish procedures for the acceptance, repair, or rejec- tion of precast/prestressed concrete girders with longitudinal The evaluation included consideration of when repairs are web cracking. A user's manual for the application of these pro- required and what repair methods are appropriate. cedures will be prepared based on the research findings. Task 4. The research team prepared a future work plan to develop and validate the evaluation criteria and repair The research team also attempted to include as many of the methods proposed in Task 3. following related objectives as practicable, without interfering Task 5. Tasks 1 through 5 were conducted within four with the accomplishments stated in the primary objective: months of the contract start and an interim report, doc- umenting the results of Tasks 1 through 4, was developed 1. Develop limits for cracking that can not be tolerated, result- and submitted to NCHRP for review. The report in- ing in product rejection. cluded the future work plan envisioned by the research 2. Develop repair methods for cracking that is tolerable but team to reach the project objectives (Tasks 6 through 8). must be repaired before the girder is used. Two months were given to the members of the project panel 3. Develop guidelines for cracks that are not required to be to review the interim report. Then, the research team had repaired. These guidelines must be based on both initial a meeting with the panel to discuss their comments on the and long-term performance and on the potential for re- interim report and future work plan. Based on this meet- inforcement corrosion or further crack propagation. This ing, a modified version of the future work plan was devel- objective must focus on how the girders are used and in oped by the research team and submitted to NCHRP for what environmental conditions. final approval. 4. Develop a user's manual for acceptance criteria and repair Task 6. Based on the results collected from Task 6, the re- materials and methods at the precast plant. Repair materi- search team prepared a manual for the acceptance, repair, als and methods must be validated before they are included or rejection of precast/prestressed concrete girders with in the manual. longitudinal web cracking. The manual went through sev- 5. Develop improved crack control reinforcement details for eral revisions based on the comments received from the use in new girders. project panel. 6. Propose revisions to the AASHTO LRFD Bridge Design Task 7. The research team developed a final report describ- Specifications as warranted. ing the entire research effort. To accomplish these objectives, the following tasks were 1.5 Applicability of Results performed: to Highway Practice Task 1. The research team reviewed and interpreted U.S. The project was structured to provide a manual of pro- and international practices, performance data, research cedures for the acceptance, repair, or rejection of precast/ findings, and other information related to the types, causes, prestressed concrete girders with longitudinal web cracking. mitigation, evaluation, and acceptance or repair of longitu- The manual, which is provided in Chapter 3 of this report, can