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50 Table 3.14. Sealers used in this study and their chemical composition. Product Chemical Compound Pipewipe Cementitious product: silicon dioxide + Portland cement DuralPrep A.C. Water-based, epoxy-modified Portland cement bonding agent and anti-corrosion coating Part A: water + bisphenol A polyglycidyl ether resin + phenol + glycidyl ether + octylphenoxypolyethoxy ethanol + benzyl alcohol Part B: water + polyamine polymer+ polyamine + tetraethylene pentamine Part C: Portland cement + Portland cement + amorphous silica + vinyl acetate copolymer Transpo Sealate T-70 A specially formulated, high molecular weight methacrylate resin system Xypex Concentrate A crystalline waterproofing system DegaDeck Crack Sealer A reactive methacrylate resin Plus SilACT A clear penetrating silane with ethylsilicate treatment specially formulated to treat limestone; the treatment causes concrete, masonry and many natural stones to become repellent to water, chloride, and other waterborne contaminants and weathering elements REM 800 Fast-setting concrete patching material; self-bonding patching compound with special cement and additives production and examination for signs of reinforcement these possible cracks; therefore, they would not be a threat to corrosion and concrete delamination. the girder. The research team was not able to get the records of end zone cracking from the precast producer. The complete inspection reports for all bridges inspected in this project are presented in Appendix F. 3.5.2.2 Platte River Bridge Members of the research team visited a bridge on Inter- 3.5.2 Nebraska Department of Roads (NDOR) state I-80 over the Platte River in Cass County, Nebraska. The With help from NDOR, the research team selected two bridge was in the process of being replaced with new spans bridges for inspection. The first bridge was located on High- of precast prestressed concrete girders. It consists of 10 spans way 6, near the 168th Street exit, over a branch of Papillion total; two 156-ft spans and eight 166.5-ft spans. The bridge Creek, in Omaha, Nebraska. The second bridge is located on deck is 206 ft wide and the girders are prestressed with fifty- I-80 over the Platte River in Cass County, Nebraska. eight 0.6-in.-diameter strands. See Figure 3.60. The research team compiled and reviewed the girder produc- tion records and post-pour product inspection reports from 3.5.2.1 Papillion Creek Bridge the precast producer, Coreslab Structures, Inc., of Omaha, This bridge is located on Highway 6, near the 168th Street Nebraska. The team was able to inspect both interior and exit, over a branch of Papillion Creek, in Omaha, Nebraska. exterior girders on the Platte River Bridge. A self-propelled The bridge consists of three spans (95 ft, 122 ft, and 95 ft, re- scissor boom lift was used to get right up next to the girder spectively), with a bridge deck 117 ft wide on the east end and ends on the eastbound section. The team also walked along 124 ft wide on the west end, as shown in Figure 3.58. the eastern side of the river and was able to inspect each of the The bridge was constructed in 2002 to 2003 and girder girder ends resting on that bank on both the westbound and ends were consistently encased from the top flange to the top eastbound sections. of the bottom flange. The team members were able to get All of the girders that were inspected are NU2000s (79-in.- close access to all of the girder ends in order to look for end deep section), and they all experienced end zone cracking. zone cracks. No visible cracking was noted at the ends of any The crack patterns, as well as the crack widths and lengths, of the girders, as shown in Figure 3.59. The concrete encasing were fairly consistent from one girder to another. Generally, the ends of each girder extended about a foot from the end. It the cracks in the end zones were reported to be 0.004-in. to is possible, although unlikely, that very small end zone cracks 0.008-in. wide and ranged from 2 ft to 6 ft long. may have existed within a foot from the end of the girder, but Although evidence of end zone cracking was prevalent, these would have been covered by the end block. The end there were no signs of further damage to the girders (such block would prevent any water or chlorides from penetrating as reinforcement corrosion or delamination). Most cracks

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51 (a) Longitudinal Profile (b) Cross Section of the Westbound Side (c) Cross Section of the Eastbound Side Figure 3.58. Papillion Creek Bridge, Omaha, Nebraska. had a white-colored efflorescence surrounding them. There The cracks shown on the girders in Figure 3.61 are traveling appeared to be neither structural nor durability problems in two distinct directions. Near the top portion of the web, the occurring. The girders have only been in place for a few years, cracks are traveling diagonally downward. Near the bottom but so far no durability issues have been observed at the girder portion of the web, the cracks are traveling diagonally upward. ends. Examples of the girder ends with end zone cracks are The top section of cracks was caused by the prestressing force shown in Figure 3.61 where the cracks are highlighted for of strands in the bottom flange. Likewise, the collection of clarity. cracks on the bottom was caused by the prestressing strands

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52 one girder in the project, and there are no repetitions. How- ever, this number is not carried over once the girder leaves the precast plant. Once the girder is in the field and placed on a bridge, there is no way to identify its piece mark number and there is no way to get previous information on any specific girder. Therefore, it was impossible to follow a specific girder from the precast yard to storage and then to the construction site. If a girder was repaired, one would not be able to locate this girder on the bridge to see if the original damage was causing any problems. If a girder on a bridge started to show signs of deteri- oration after years of use, there would be no way to look up that girder's specific history to see what kind of cracking, damage, or repair it was subjected to earlier on in its service life. For this reason, the research team recommends giving each individual girder an identification number for the entire life of the girder. Figure 3.59. Girder showing end block. Although every single girder that was observed experienced end zone cracking, there is no record of these cracks drawn on the inspection sheets. There are records of vertical cracks and near the top of the girder. This arrangement of prestressing shrinkage cracks, but nothing is mentioned about end zone strands in both the top and bottom portions of a girder creates cracks. In their response to the research team, the precast pro- increased stress on the girder end, amplifying the likelihood of ducer made the following statement: increased end zone cracking. . . . the inspectors do not record end zone cracks unless they The team received inspection documents from Coreslab exceed acceptable limits. The presence of these cracks is expected, Structures, Inc. The inspector was looking for any imperfections and it would be redundant to mark down the same cracks for every or damage to the girders. Each individual girder design has its girder, especially if they are inconsequential. The only way these own unique piece mark number. This number identifies each cracks would be reported would be if the inspector felt they were girder in the prestressing plant. Each number belongs to only severe enough to be repaired. (a) Longitudinal Profile (b) Cross Section of the Westbound Side Figure 3.60. I-80 Platte River Bridge, Nebraska.