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Guidelines for Adjacent Precast Concrete Box Beam Bridge Systems (2023)

Chapter: Appendix C - Experimental Program

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Suggested Citation:"Appendix C - Experimental Program." National Academies of Sciences, Engineering, and Medicine. 2023. Guidelines for Adjacent Precast Concrete Box Beam Bridge Systems. Washington, DC: The National Academies Press. doi: 10.17226/27029.
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Suggested Citation:"Appendix C - Experimental Program." National Academies of Sciences, Engineering, and Medicine. 2023. Guidelines for Adjacent Precast Concrete Box Beam Bridge Systems. Washington, DC: The National Academies Press. doi: 10.17226/27029.
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Suggested Citation:"Appendix C - Experimental Program." National Academies of Sciences, Engineering, and Medicine. 2023. Guidelines for Adjacent Precast Concrete Box Beam Bridge Systems. Washington, DC: The National Academies Press. doi: 10.17226/27029.
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Suggested Citation:"Appendix C - Experimental Program." National Academies of Sciences, Engineering, and Medicine. 2023. Guidelines for Adjacent Precast Concrete Box Beam Bridge Systems. Washington, DC: The National Academies Press. doi: 10.17226/27029.
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Suggested Citation:"Appendix C - Experimental Program." National Academies of Sciences, Engineering, and Medicine. 2023. Guidelines for Adjacent Precast Concrete Box Beam Bridge Systems. Washington, DC: The National Academies Press. doi: 10.17226/27029.
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Suggested Citation:"Appendix C - Experimental Program." National Academies of Sciences, Engineering, and Medicine. 2023. Guidelines for Adjacent Precast Concrete Box Beam Bridge Systems. Washington, DC: The National Academies Press. doi: 10.17226/27029.
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Suggested Citation:"Appendix C - Experimental Program." National Academies of Sciences, Engineering, and Medicine. 2023. Guidelines for Adjacent Precast Concrete Box Beam Bridge Systems. Washington, DC: The National Academies Press. doi: 10.17226/27029.
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Suggested Citation:"Appendix C - Experimental Program." National Academies of Sciences, Engineering, and Medicine. 2023. Guidelines for Adjacent Precast Concrete Box Beam Bridge Systems. Washington, DC: The National Academies Press. doi: 10.17226/27029.
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Suggested Citation:"Appendix C - Experimental Program." National Academies of Sciences, Engineering, and Medicine. 2023. Guidelines for Adjacent Precast Concrete Box Beam Bridge Systems. Washington, DC: The National Academies Press. doi: 10.17226/27029.
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Suggested Citation:"Appendix C - Experimental Program." National Academies of Sciences, Engineering, and Medicine. 2023. Guidelines for Adjacent Precast Concrete Box Beam Bridge Systems. Washington, DC: The National Academies Press. doi: 10.17226/27029.
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Suggested Citation:"Appendix C - Experimental Program." National Academies of Sciences, Engineering, and Medicine. 2023. Guidelines for Adjacent Precast Concrete Box Beam Bridge Systems. Washington, DC: The National Academies Press. doi: 10.17226/27029.
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Suggested Citation:"Appendix C - Experimental Program." National Academies of Sciences, Engineering, and Medicine. 2023. Guidelines for Adjacent Precast Concrete Box Beam Bridge Systems. Washington, DC: The National Academies Press. doi: 10.17226/27029.
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Suggested Citation:"Appendix C - Experimental Program." National Academies of Sciences, Engineering, and Medicine. 2023. Guidelines for Adjacent Precast Concrete Box Beam Bridge Systems. Washington, DC: The National Academies Press. doi: 10.17226/27029.
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Suggested Citation:"Appendix C - Experimental Program." National Academies of Sciences, Engineering, and Medicine. 2023. Guidelines for Adjacent Precast Concrete Box Beam Bridge Systems. Washington, DC: The National Academies Press. doi: 10.17226/27029.
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Suggested Citation:"Appendix C - Experimental Program." National Academies of Sciences, Engineering, and Medicine. 2023. Guidelines for Adjacent Precast Concrete Box Beam Bridge Systems. Washington, DC: The National Academies Press. doi: 10.17226/27029.
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Suggested Citation:"Appendix C - Experimental Program." National Academies of Sciences, Engineering, and Medicine. 2023. Guidelines for Adjacent Precast Concrete Box Beam Bridge Systems. Washington, DC: The National Academies Press. doi: 10.17226/27029.
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Suggested Citation:"Appendix C - Experimental Program." National Academies of Sciences, Engineering, and Medicine. 2023. Guidelines for Adjacent Precast Concrete Box Beam Bridge Systems. Washington, DC: The National Academies Press. doi: 10.17226/27029.
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Suggested Citation:"Appendix C - Experimental Program." National Academies of Sciences, Engineering, and Medicine. 2023. Guidelines for Adjacent Precast Concrete Box Beam Bridge Systems. Washington, DC: The National Academies Press. doi: 10.17226/27029.
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Suggested Citation:"Appendix C - Experimental Program." National Academies of Sciences, Engineering, and Medicine. 2023. Guidelines for Adjacent Precast Concrete Box Beam Bridge Systems. Washington, DC: The National Academies Press. doi: 10.17226/27029.
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Suggested Citation:"Appendix C - Experimental Program." National Academies of Sciences, Engineering, and Medicine. 2023. Guidelines for Adjacent Precast Concrete Box Beam Bridge Systems. Washington, DC: The National Academies Press. doi: 10.17226/27029.
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Suggested Citation:"Appendix C - Experimental Program." National Academies of Sciences, Engineering, and Medicine. 2023. Guidelines for Adjacent Precast Concrete Box Beam Bridge Systems. Washington, DC: The National Academies Press. doi: 10.17226/27029.
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Suggested Citation:"Appendix C - Experimental Program." National Academies of Sciences, Engineering, and Medicine. 2023. Guidelines for Adjacent Precast Concrete Box Beam Bridge Systems. Washington, DC: The National Academies Press. doi: 10.17226/27029.
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Suggested Citation:"Appendix C - Experimental Program." National Academies of Sciences, Engineering, and Medicine. 2023. Guidelines for Adjacent Precast Concrete Box Beam Bridge Systems. Washington, DC: The National Academies Press. doi: 10.17226/27029.
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Suggested Citation:"Appendix C - Experimental Program." National Academies of Sciences, Engineering, and Medicine. 2023. Guidelines for Adjacent Precast Concrete Box Beam Bridge Systems. Washington, DC: The National Academies Press. doi: 10.17226/27029.
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Suggested Citation:"Appendix C - Experimental Program." National Academies of Sciences, Engineering, and Medicine. 2023. Guidelines for Adjacent Precast Concrete Box Beam Bridge Systems. Washington, DC: The National Academies Press. doi: 10.17226/27029.
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Suggested Citation:"Appendix C - Experimental Program." National Academies of Sciences, Engineering, and Medicine. 2023. Guidelines for Adjacent Precast Concrete Box Beam Bridge Systems. Washington, DC: The National Academies Press. doi: 10.17226/27029.
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Suggested Citation:"Appendix C - Experimental Program." National Academies of Sciences, Engineering, and Medicine. 2023. Guidelines for Adjacent Precast Concrete Box Beam Bridge Systems. Washington, DC: The National Academies Press. doi: 10.17226/27029.
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Suggested Citation:"Appendix C - Experimental Program." National Academies of Sciences, Engineering, and Medicine. 2023. Guidelines for Adjacent Precast Concrete Box Beam Bridge Systems. Washington, DC: The National Academies Press. doi: 10.17226/27029.
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Suggested Citation:"Appendix C - Experimental Program." National Academies of Sciences, Engineering, and Medicine. 2023. Guidelines for Adjacent Precast Concrete Box Beam Bridge Systems. Washington, DC: The National Academies Press. doi: 10.17226/27029.
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Suggested Citation:"Appendix C - Experimental Program." National Academies of Sciences, Engineering, and Medicine. 2023. Guidelines for Adjacent Precast Concrete Box Beam Bridge Systems. Washington, DC: The National Academies Press. doi: 10.17226/27029.
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Suggested Citation:"Appendix C - Experimental Program." National Academies of Sciences, Engineering, and Medicine. 2023. Guidelines for Adjacent Precast Concrete Box Beam Bridge Systems. Washington, DC: The National Academies Press. doi: 10.17226/27029.
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Suggested Citation:"Appendix C - Experimental Program." National Academies of Sciences, Engineering, and Medicine. 2023. Guidelines for Adjacent Precast Concrete Box Beam Bridge Systems. Washington, DC: The National Academies Press. doi: 10.17226/27029.
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Suggested Citation:"Appendix C - Experimental Program." National Academies of Sciences, Engineering, and Medicine. 2023. Guidelines for Adjacent Precast Concrete Box Beam Bridge Systems. Washington, DC: The National Academies Press. doi: 10.17226/27029.
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Suggested Citation:"Appendix C - Experimental Program." National Academies of Sciences, Engineering, and Medicine. 2023. Guidelines for Adjacent Precast Concrete Box Beam Bridge Systems. Washington, DC: The National Academies Press. doi: 10.17226/27029.
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Suggested Citation:"Appendix C - Experimental Program." National Academies of Sciences, Engineering, and Medicine. 2023. Guidelines for Adjacent Precast Concrete Box Beam Bridge Systems. Washington, DC: The National Academies Press. doi: 10.17226/27029.
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Suggested Citation:"Appendix C - Experimental Program." National Academies of Sciences, Engineering, and Medicine. 2023. Guidelines for Adjacent Precast Concrete Box Beam Bridge Systems. Washington, DC: The National Academies Press. doi: 10.17226/27029.
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Suggested Citation:"Appendix C - Experimental Program." National Academies of Sciences, Engineering, and Medicine. 2023. Guidelines for Adjacent Precast Concrete Box Beam Bridge Systems. Washington, DC: The National Academies Press. doi: 10.17226/27029.
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Suggested Citation:"Appendix C - Experimental Program." National Academies of Sciences, Engineering, and Medicine. 2023. Guidelines for Adjacent Precast Concrete Box Beam Bridge Systems. Washington, DC: The National Academies Press. doi: 10.17226/27029.
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Suggested Citation:"Appendix C - Experimental Program." National Academies of Sciences, Engineering, and Medicine. 2023. Guidelines for Adjacent Precast Concrete Box Beam Bridge Systems. Washington, DC: The National Academies Press. doi: 10.17226/27029.
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Suggested Citation:"Appendix C - Experimental Program." National Academies of Sciences, Engineering, and Medicine. 2023. Guidelines for Adjacent Precast Concrete Box Beam Bridge Systems. Washington, DC: The National Academies Press. doi: 10.17226/27029.
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Suggested Citation:"Appendix C - Experimental Program." National Academies of Sciences, Engineering, and Medicine. 2023. Guidelines for Adjacent Precast Concrete Box Beam Bridge Systems. Washington, DC: The National Academies Press. doi: 10.17226/27029.
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Suggested Citation:"Appendix C - Experimental Program." National Academies of Sciences, Engineering, and Medicine. 2023. Guidelines for Adjacent Precast Concrete Box Beam Bridge Systems. Washington, DC: The National Academies Press. doi: 10.17226/27029.
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Suggested Citation:"Appendix C - Experimental Program." National Academies of Sciences, Engineering, and Medicine. 2023. Guidelines for Adjacent Precast Concrete Box Beam Bridge Systems. Washington, DC: The National Academies Press. doi: 10.17226/27029.
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Suggested Citation:"Appendix C - Experimental Program." National Academies of Sciences, Engineering, and Medicine. 2023. Guidelines for Adjacent Precast Concrete Box Beam Bridge Systems. Washington, DC: The National Academies Press. doi: 10.17226/27029.
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Suggested Citation:"Appendix C - Experimental Program." National Academies of Sciences, Engineering, and Medicine. 2023. Guidelines for Adjacent Precast Concrete Box Beam Bridge Systems. Washington, DC: The National Academies Press. doi: 10.17226/27029.
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Suggested Citation:"Appendix C - Experimental Program." National Academies of Sciences, Engineering, and Medicine. 2023. Guidelines for Adjacent Precast Concrete Box Beam Bridge Systems. Washington, DC: The National Academies Press. doi: 10.17226/27029.
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Suggested Citation:"Appendix C - Experimental Program." National Academies of Sciences, Engineering, and Medicine. 2023. Guidelines for Adjacent Precast Concrete Box Beam Bridge Systems. Washington, DC: The National Academies Press. doi: 10.17226/27029.
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Suggested Citation:"Appendix C - Experimental Program." National Academies of Sciences, Engineering, and Medicine. 2023. Guidelines for Adjacent Precast Concrete Box Beam Bridge Systems. Washington, DC: The National Academies Press. doi: 10.17226/27029.
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Suggested Citation:"Appendix C - Experimental Program." National Academies of Sciences, Engineering, and Medicine. 2023. Guidelines for Adjacent Precast Concrete Box Beam Bridge Systems. Washington, DC: The National Academies Press. doi: 10.17226/27029.
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Suggested Citation:"Appendix C - Experimental Program." National Academies of Sciences, Engineering, and Medicine. 2023. Guidelines for Adjacent Precast Concrete Box Beam Bridge Systems. Washington, DC: The National Academies Press. doi: 10.17226/27029.
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Suggested Citation:"Appendix C - Experimental Program." National Academies of Sciences, Engineering, and Medicine. 2023. Guidelines for Adjacent Precast Concrete Box Beam Bridge Systems. Washington, DC: The National Academies Press. doi: 10.17226/27029.
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Suggested Citation:"Appendix C - Experimental Program." National Academies of Sciences, Engineering, and Medicine. 2023. Guidelines for Adjacent Precast Concrete Box Beam Bridge Systems. Washington, DC: The National Academies Press. doi: 10.17226/27029.
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Suggested Citation:"Appendix C - Experimental Program." National Academies of Sciences, Engineering, and Medicine. 2023. Guidelines for Adjacent Precast Concrete Box Beam Bridge Systems. Washington, DC: The National Academies Press. doi: 10.17226/27029.
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Suggested Citation:"Appendix C - Experimental Program." National Academies of Sciences, Engineering, and Medicine. 2023. Guidelines for Adjacent Precast Concrete Box Beam Bridge Systems. Washington, DC: The National Academies Press. doi: 10.17226/27029.
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Suggested Citation:"Appendix C - Experimental Program." National Academies of Sciences, Engineering, and Medicine. 2023. Guidelines for Adjacent Precast Concrete Box Beam Bridge Systems. Washington, DC: The National Academies Press. doi: 10.17226/27029.
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Suggested Citation:"Appendix C - Experimental Program." National Academies of Sciences, Engineering, and Medicine. 2023. Guidelines for Adjacent Precast Concrete Box Beam Bridge Systems. Washington, DC: The National Academies Press. doi: 10.17226/27029.
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Suggested Citation:"Appendix C - Experimental Program." National Academies of Sciences, Engineering, and Medicine. 2023. Guidelines for Adjacent Precast Concrete Box Beam Bridge Systems. Washington, DC: The National Academies Press. doi: 10.17226/27029.
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Suggested Citation:"Appendix C - Experimental Program." National Academies of Sciences, Engineering, and Medicine. 2023. Guidelines for Adjacent Precast Concrete Box Beam Bridge Systems. Washington, DC: The National Academies Press. doi: 10.17226/27029.
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Suggested Citation:"Appendix C - Experimental Program." National Academies of Sciences, Engineering, and Medicine. 2023. Guidelines for Adjacent Precast Concrete Box Beam Bridge Systems. Washington, DC: The National Academies Press. doi: 10.17226/27029.
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Suggested Citation:"Appendix C - Experimental Program." National Academies of Sciences, Engineering, and Medicine. 2023. Guidelines for Adjacent Precast Concrete Box Beam Bridge Systems. Washington, DC: The National Academies Press. doi: 10.17226/27029.
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Suggested Citation:"Appendix C - Experimental Program." National Academies of Sciences, Engineering, and Medicine. 2023. Guidelines for Adjacent Precast Concrete Box Beam Bridge Systems. Washington, DC: The National Academies Press. doi: 10.17226/27029.
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Suggested Citation:"Appendix C - Experimental Program." National Academies of Sciences, Engineering, and Medicine. 2023. Guidelines for Adjacent Precast Concrete Box Beam Bridge Systems. Washington, DC: The National Academies Press. doi: 10.17226/27029.
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Suggested Citation:"Appendix C - Experimental Program." National Academies of Sciences, Engineering, and Medicine. 2023. Guidelines for Adjacent Precast Concrete Box Beam Bridge Systems. Washington, DC: The National Academies Press. doi: 10.17226/27029.
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Suggested Citation:"Appendix C - Experimental Program." National Academies of Sciences, Engineering, and Medicine. 2023. Guidelines for Adjacent Precast Concrete Box Beam Bridge Systems. Washington, DC: The National Academies Press. doi: 10.17226/27029.
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Suggested Citation:"Appendix C - Experimental Program." National Academies of Sciences, Engineering, and Medicine. 2023. Guidelines for Adjacent Precast Concrete Box Beam Bridge Systems. Washington, DC: The National Academies Press. doi: 10.17226/27029.
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Suggested Citation:"Appendix C - Experimental Program." National Academies of Sciences, Engineering, and Medicine. 2023. Guidelines for Adjacent Precast Concrete Box Beam Bridge Systems. Washington, DC: The National Academies Press. doi: 10.17226/27029.
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Suggested Citation:"Appendix C - Experimental Program." National Academies of Sciences, Engineering, and Medicine. 2023. Guidelines for Adjacent Precast Concrete Box Beam Bridge Systems. Washington, DC: The National Academies Press. doi: 10.17226/27029.
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59   A P P E N D I X C Experimental Program C.1 Introduction Experimental testing was performed to verify the findings of the analytical program and to determine the practical variables that cannot be addressed analytically. The experimental testing consisted of two phases: 1. Determination of the tensile strength and bond strength of keyway material as a function of the surface preparation. 2. Full-scale system testing of two different shear key configurations. C.2 Full-Scale Testing The full-scale experimental testing consisted of the following: 1. Plant monitoring of individual girders to establish thermal stresses experienced by the girders at the plant and to simulate field conditions. 2. A system tests on three girders forming two Type IV shear key joints cast with two different grouts and subjected to thermal and fatigue loading. 3. A system tests on three girders forming two Type V shear key joints cast with small aggregate concrete and subjected to thermal and fatigue loading. C.2.1 Shear Keys for the Full-Scale Tests For the full-scale tests, it was decided to test two shear key configurations, the narrow, full-depth Type IV, and the wide, full-depth Type V (Figure C-1). The Type IV shear key was to be filled with grout and two different grouts were used: a standard non-shrink grout (Sika 212) and a high bond non-shrink grout (Masterflow 4316). The Type V shear key was modified as shown in Figure C-1. The Type V shear key shown in literature has a gap at the bottom. This would have required forming the bottom, so the gap was eliminated. The volume of the Type V shear key is such that using a bagged grout was impractical as it would have required mixing too many bags in a short time. For this reason, the Type V shear key used a concrete fill. Table C-1 shows the mix proportions. Table C-1. Concrete mix proportions. Material Pounds/cubic yard Cement Type I 1,100 River Sand 1,450 Coarse Aggregate (#8) 1,596 Water 385 High-Range Water Reducer (MasterGlenium 7920 or 7925) 100 ml/100# cement

60 Guidelines for Adjacent Precast Concrete Box Beam Bridge Systems Figure C-1. Shear Keys used in the full-scale tests. C.2.2 Girder Design Four girders were fabricated. One girder was fabricated with a Type V shear key on both faces and another with a Type IV shear key on both faces. The other two girders had a Type IV shear key on one face and a Type V shear key on the other face. These last two girders were the outside girders and could be reused by simply swapping their position from one test to the next test. This saved fabrication time and cost, disposal costs and was much easier to deal with in the lab. The test girders were designed based on a standard box girder meeting the requirements of the AASHTO LRFD specifications. Ohio Department of Transportation (ODOT)standard drawings for box girders were used for basic details. The ODOT design data tables were used to determine the strand pattern and stirrup spacing. The finite element analyses showed that girder length, girder depth, and girder skew had no significant effect on the behavior of the shear keys. Therefore, to accommodate the girders on the laboratory floor, the length of the girders was limited to 36 feet and no skew was provided. The girders were 4 feet wide and 21 inches deep. The 21-inch girder was used because the temperature gradient shown in the AASHTO LRFD Specifications (Article 3.12.3) affects the top 16 inches of the girder. Using a shallow section places almost the entire shear key in the temperature gradient zone. Intermediate diaphragms, at the mid and quarter span points, and end diaphragms were provided according to the ODOT standard drawings. These were 18-inch-thick diaphragms. Each diaphragm had a 3-inch diameter sleeve to run the tie rods. Two lifting anchors were installed at each end to transport and erect the girders. Figure C-2 shows the typical cross section of the test girder with Type V shear key on left face and Type IV shear key on right face. The location of diaphragms and lifting hooks are shown in Figure C-3. Figure C-4 shows the strand location and stirrup detail for a typical girder. Four girders, as shown in Figure C-5, were designed. Girder 1 and Girder 3 were edge girders with Type IV shear key on one face and Type V shear key on the other face. Girder 2 and Girder 4 were the center girders with Type IV and Type V shear key on both faces, respectively.

Experimental Program 61 Figure C-2. Typical test girder section with Type IV shear key on one face and Type V shear key on other face. Figure C-3. Location of diaphragms and lifting hook for a typical girder.

62 Guidelines for Adjacent Precast Concrete Box Beam Bridge Systems Figure C-4. Strand location and stirrup detail for a typical test girder.

Experimental Program 63 Figure C-5. Test girders.

64 Guidelines for Adjacent Precast Concrete Box Beam Bridge Systems To test the Type IV shear key configuration, the edge girders (Girder 1 and Girder 3) were placed with Type IV shear key face on the inside. The center girder with Type IV shear key on both faces (Girder 2) was placed in the middle to form a system of three girders with two Type IV shear key joints. The arrangement is shown in Figure C-6. Figure C-6. Arrangement of girders for Type IV shear key test. After the testing for Type IV shear key was completed, the joints were cut, and the middle girder was removed. The edge girders (Girder 1 and Girder 3) were then swapped placing the Type V shear key face on the inside. The center girder with Type V shear key on both faces (Girder 4) was placed in the middle to form a system of three girders with two Type V shear key joints. The arrangement is shown in Figure C- 7. Figure C-7. Arrangement of girders for Type V shear key test. C.2.3 Girder Fabrication The girders were fabricated at the Prestress Services plant in Mount Vernon, Ohio. During fabrication, the girders were instrumented with vibrating wire strain gages (VW gages). These instruments have a vibrating wire to measure the strain coupled with a thermistor to measure temperature. The advantage of using these gages is that they are very stable and do not drift like bonded resistance strain gages. They can also be corrected for temperature. The disadvantage of using these gages is that it takes several seconds to read each gage and they can only be read one at a time. It takes approximately 2 minutes to read all of the gages, so they are only usable for static test situations. The VW gages were installed at midspan in both the lateral and longitudinal directions. This would allow measurement of both the lateral strain profile and the temperature profile during thermal loading, and the longitudinal strains during fatigue loading. The ends of the girder were also instrumented because the finite element analyses showed the ends of the girder are the most critical points for temperature movements. Lateral strain gages along with several thermistors were installed to measure the temperature profile at the end of the girders. Figure C-8 and Figure C-9 shows various stages during girder fabrication. Figure C-10 shows the schematics of the instruments installed in each girder during fabrication. 3 2 1 1 4 3

Experimental Program 65 Figure C-8. Stages during girder fabrication: (a) prestressing bed with the side forms coated with retarder to provide an exposed aggregate finish, (b) VW gages installed at midspan, (c) thermistors installed at the girder end, (d) bottom flange placement.

66 Guidelines for Adjacent Precast Concrete Box Beam Bridge Systems Figure C-9. Stages during girder fabrication: (a) setting the voids, (b) top flange placement, (c) finished girders inside the prestressing bed, (d) girders taken out from the bed and placed in the yard.

Experimental Program 67 Figure C-10. Girder instrumentation layout.

68 Guidelines for Adjacent Precast Concrete Box Beam Bridge Systems The specification for the girders called for the contractor to provide an exposed aggregate finish. The sides of the form were coated with a set retarding admixture and the surface cement was to be removed after the girder concrete had set. Unfortunately, the contractor was unable to get the required surface. Instead, the surface was sandblasted. Figure C-11 shows the keyway surface finish prepared by the contractor. Figure C-11. Girder side surface finish after aggressive sandblasting. The research team (RT) contacted Greg Wirthlin, a local consultant whose firm specializes in concrete repair and uses grouts frequently. He is a member of the International Concrete Repair Institute (ICRI) and did some previous work on shear key grout material (Gulyas, Wirthlin, and Champa, 1995). Mr. Wirthlin stated that the sides of the girders had been prepared to at least a CSP-3 (concrete surface profile) and should be sufficient to provide good bonding with grout. The concrete surfaces profiles are defined by ICRI. They range from CSP-1 which has a surface like a medium sandpaper to CSP-10 which has roughness of about 0.2 inches. CSP is determined by comparison with chips available from ICRI as shown in Figure C- 12. After making a number of comparisons of the girder sides with the ICRI chips, the RT judged that the surface was more consistent with CSP 4 as shown in Figure C-12. The girders had been sandblasted and there was no way to change that. Since the RT had good reason to believe that this would provide a sufficient bonding surface, they elected to continue with the tests. This was discussed and approved by the NCHRP project director. The RT also believes that sandblasting is likely to be a preferred method of surface preparation among bridge contractors. To verify the bond performance, a separate panel was made of girder concrete as detailed in Chapter 2. This panel was then sandblasted to the same surface profile as the girders and pull-off testing was performed on this panel. The results of these pull-off tests can be found in the following section.

Experimental Program 69 Figure C-12. Finished girder surface alongside CSP-3 and CSP-4 chip. C.2.4 Field Monitoring of the Girders After the test girders were cast, they were moved out of the prestressing bed and placed in the yard outside. During this time one of the girders was monitored to record the temperature profile experienced by the girders in the field. This was not part of the original testing plan, but the RT saw this as a way to verify the temperature gradients for the full-scale tests. A remote data acquisition (DAQ) system was taken to the prestressing yard and the embedded VW gages in the girder were connected. Additionally, a thermistor was duct taped to the surface of the girder to measure the surface temperature. Due to the limitation of the channels on the remote DAQ, only the midspan and one of the ends of one of the girders were monitored. Figure C-13 shows the girder that was monitored in the field. Note that for most of the day, one face of the shear key was shaded while the other was directly exposed to sunlight. The shaded face is representative of the shear key surface, whereas the exposed surface is representative of the exterior faces of the facia girders.

70 Guidelines for Adjacent Precast Concrete Box Beam Bridge Systems Figure C-13. Field monitoring of the girder. The instruments were monitored from 11:35 a.m. on July 22, 2021, to 1:19 p.m. on July 23, 2021. Readings were taken every 2 minutes. The maximum recorded air temperature on both the days was 88°F. Figure C-14 and Figure C-15 show the variation in temperature at various depths of the girder at midspan and end of the girder respectively. From these figures it is evident that: 1. For the face exposed to sunlight, the temperature variation inside the girder follows the surface temperature variation. For the face shadowed from direct sunlight, the peak temperature inside the girder occurs several hours later than the peak temperature on the surface. 2. The temperatures inside the girder are higher and closer to surface temperature for the face exposed directly to sunlight than the face shadowed from sunlight. This would result in more severe temperature gradient on the face shadowed from sunlight. 3. The peak temperatures inside the girder are higher at the end of the girder than at midspan. This is probably because the girder end was directly exposed to sunlight.

Experimental Program 71 Figure C-14. Temperature variation at various depths at midspan of the girder during field monitoring: (a) face shadowed from sunlight, (b) face exposed to sunlight.

72 Guidelines for Adjacent Precast Concrete Box Beam Bridge Systems Figure C-15. Temperature variation at various depths at end of the girder during field monitoring: (a) face shadowed from sunlight, (b) face exposed to sunlight. Figure C-16 and Figure C-17 show the temperature gradient across girder depth at various times during the day at midspan and end of the girder, respectively. The AASHTO gradient band from Zone 1 and Zone 4 are also plotted for comparison. From these figures it is evident that: 1. The temperature gradient observed in the field is comparable to the gradient suggested by AASHTO. The location where the girder was monitored lies in Zone 3 of the AASHTO zoning map for which the suggested temperature gradient at the surface and at 4-inch depth is 41°F and 11°F respectively. The maximum temperature gradient observed at midspan of the girder was 30°F on the surface and 10.5°F at 4-inch depth. Although these values are short of the suggested values, the field monitoring was performed for a very short duration and the girder can experience days with more severe temperature variations.

Experimental Program 73 2. As expected, the gradients are more severe on the face shadowed from sunlight compared to the face exposed to sunlight because the shaded sides have only the top surface exposed to sunlight while the other sides are more uniformly heated. This suggests that while performing the system testing, the inside faces of the girders, where the shear keys are, would be more critical. 3. The gradients are more severe at the midspan than the end of the girder. This is likely due to the presence of the large end block which requires more heat to change temperature. 4. The peak gradient occurs at around 3 p.m. This is important as it provides valuable data on when shear keys should be cast. Casting keys on a sunny, summer afternoon will subject the keys to the worst possible thermal movements. Figure C-16. Temperature profile across girder section at midspan during various times of the day compared to AASHTO gradient: (a) face shadowed from sunlight, (b) face exposed to sunlight.

74 Guidelines for Adjacent Precast Concrete Box Beam Bridge Systems Figure C-17. Temperature profile across girder section at end of the girder during various times of the day compared to AASHTO gradient: (a) face shadowed from sunlight, (b) face exposed to sunlight.

Experimental Program 75 C.2.5 Type IV Shear Key Testing This test assessed the effects of temperature and fatigue loading on a Type IV shear key cast with a non- shrink grout and a high bond grout. A system of three girders with two Type IV shear key joints was tested. C.2.5.1 Test Setup and Instrumentation Girder 1, Girder 2, and Girder 3 were assembled adjacent to each other on the lab floor such that they formed two Type IV shear key joints as shown in Figure C-18. At each end, the girders were simply supported on two 6-inch square elastomeric bearing pads. Load cells were placed under the bearing pads to measure the end reactions of the girders. The pad size and placement were recommended by Timothy Keller, Administrator, Office of Structural Engineering, Ohio Department of Transportation. The lateral tie rods were placed in PVC pipes to prevent the grout from bonding the tie rods to the girders. This allowed the tie rods to be removed so that the girders could be reused. Figure C-18. Test assembly for Type IV shear key test. Typ. = typical. To apply the temperature load, a temperature gradient along the girder depth as suggested by the AASHTO zoning map was developed. For this a closed environmental chamber or “insulated box” was built on top of the girder deck. This methodology was adapted from a paper by Shi et al. (2019). A wooden framing was constructed on top of the girders which was then covered with 2-inch-thick Styrofoam sheets. The top view of the insulated box in shown in Figure C-19. Sixteen 250-watt heat lamps, four high-capacity heaters, and six circulation fans were installed inside the insulated box. The heat lamps, heaters and fans were uniformly distributed inside the insulated box and were regulated to generate the thermal gradient in the girder. The inside view of the insulated box in shown in Figure C-20.

76 Guidelines for Adjacent Precast Concrete Box Beam Bridge Systems Figure C-19. Insulated box over the girders to apply thermal loads. Figure C-20. Heat lamps, heaters, and circulation fans installed inside the heat box. (Insulation removed for clarity.)

Experimental Program 77 To monitor the performance of the shear key at various stages during the test, several instruments were installed. As previously detailed, thermistor and VW gages were installed inside the girder during fabrication. These gages were monitored to record temperature profiles and measure strains inside the girder. The layout of these gages is shown in Figure C-10. Since gages were placed at both the flanges on midspan and end spans of each girder, there were effectively six locations on each girder and a total of 18 locations in the system that would be monitored. Since many of these locations were identical to each other due to symmetry, it was not necessary to show results of these 18 locations individually Therefore, a total of four unique locations were identified as shown in Figure C-21. The result from each of these unique locations would be averaged and discussed as a single representative value for that location. Figure C-21. Locations for thermal monitoring. To measure the girder camber during heating/cooling cycles and during live load tests, wire potentiometers were installed at midspan and third spans of girders. The wire potentiometer was firmly placed on the floor using a weight and a wire was run from the instrument and attached to the underside of the girder using an eye screw drilled into the girder. Load cells were used at each support of the girders to measure the support reactions. To measure any differential movement of the joints, linear variable differential transformers (LVDTs) were installed. A rigid wooden frame was attached to the underside of a girder such that the arm of the frame spanned across the joint onto the second girder where an LVDT was attached to the arm of the frame such that it rested against the underside of the second girder. These instruments were installed at the midspan, third span, and end span of the joints. To measure the lateral movement of the joints because of applied temperature load, 12-inch-long vibrating wire strain gages were attached on the top surface of the girders such that they spanned across the joints. A total of five VW gages were installed on each joint. Since the VW gages have an inbuilt thermistor, these gages were also used to measure the surface temperature of the girders. To measure the strains in the joints, 6-inch-long VW gages were embedded approximately 1 inch deep into the joints during grouting at the positions of the tie rods. This position was chosen since there were block outs (handholds) at these locations to help workers thread the tie rods from girder to girder and it was sufficient width for a gage. Figure C-22 shows the instruments installed in the girder system. Figure C-23 shows the locations and labels for load cells, LVDTs and wire potentiometers. Figure C-24 shows the locations and labels for VW Midspan Interior End Span Interior Midspan Exterior End Span Exterior

78 Guidelines for Adjacent Precast Concrete Box Beam Bridge Systems gages across the joints. Figure C-25 shows the location and labels of the VW gages embedded into the joints. Figure C-22. Instruments installed on girders and across joints. Pot. = potentiometer.

Experimental Program 79 Figure C-23. Locations and labels for load cells at supports, LVDTs across joints, and wire potentiometers under girders for Type IV shear key test. Figure C-24. Location and labels of VW gages across joints for Type IV shear key test. Figure C-25. Locations and labels of VW gages embedded in the joints for Type IV shear key test. Girder 1 Girder 2 Girder 3

80 Guidelines for Adjacent Precast Concrete Box Beam Bridge Systems C.2.5.2 Thermal Loading Before Grouting Concrete does not have set thermal properties as the properties vary with the mix. Therefore, an initial establishment of thermal properties of the girders was required. The girders were heated and cooled several times prior to casting the shear keys. Strain, deformation, and thermal response of the individual girders were recorded. This served three purposes: 1. Establish an appropriate “heat cycle” protocol that develops a similar gradient through girder depth as suggested by AASHTO and that would be used for thermal loading of the girder system. Several trial heating and cooling cycles were performed by varying the intensity of the heaters and placement of the circulation fans until an appropriate gradient was developed in the girders. 2. Establish the thermal properties of the system, without shear keys, such as the camber of the individual girders, strain across the joints, and differential movement of the joints. This would serve as a reference for the measurements taken after the grouting. 3. Allow a comparison of the laboratory developed gradient in the girders to that recorded in the field during field monitoring of the girders. To apply the thermal gradient to the girders, the heat lamps and circulation fans were turned on initially. The heaters were ramped up gradually to heat the top of the surface. The placement of the heating equipment was such that to heat the entire top of the girder system as uniformly as possible. AASHTO stipulates a gradient of 39 F to 40°° F between the top of the girder and a position 4 inches deep and a gradient of 9°F to 14°F between the depths of 4 inches and 16 inches. In an artificially simulated heating environment, it was not possible to control both the temperatures simultaneously. Since the top 4 inches of the shear key is not intended to be grouted, the gradient between 4 inches and 16 inches is more critical and was therefore the key parameter that was monitored during a typical heat cycle. It was this value to temperature gradient that marked the peak of the heating and once this gradient was around 14°F at the ‘midspan interior,’ the heat was turned off. Figure C-26 shows the gradient at a depth of 4 inches for various locations identified in Figure C-21 during a typical heating cycle. As expected, the ‘midspan interior’ developed the highest gradient followed by ‘end span interior.’ The ‘midspan exterior’ and ‘end span exterior’ locations represent the outer faces of the facia girders and do not develop severe gradient. These results are consistent with the observations made during filed monitoring. Figure C-27 shows the temperature profiles through the depth of the girder at various locations during a typical heat cycle. The surface temperature is taken as the average of all the surface thermistors and is therefore same for all the locations. Again, the interior locations have higher temperatures at all the depths than the exterior locations as the exterior locations were exposed to ambient laboratory temperature. Figure C-28 compares the gradient at various locations with the AASHTO recommended gradient band. At first, it appears as if the gradient between the surface and 4 inches below (T1) is more severe for the exterior locations. However, this is not important as there is no grout at these locations. It is the interior locations that are important. The gradient between 4 inches and 16 inches below (T2) is accurately measured using thermistors at those exact depths. T2 is higher for interior locations than the exterior locations. This is consistent with the field observations.

Experimental Program 81 Figure C-26. Thermal gradient at a depth of 4 inches from the surface of the girder for various locations during a typical heat cycle of Type IV shear key. Figure C-27. Temperature profiles through girder depth at various locations during a typical heat cycle of Type IV shear key. 0 2 4 6 8 10 12 14 16 18 4:48 9:36 14:24 19:12 0:00 4:48 9:36 Te m pe ra tu re D iff er en tia l ( °F ) Time (24-hour format) Midspan Interior Midspan Exterior End Span Interior End Span Exterior 0 4 8 12 16 20 80 100 120 140 G ird er D ep th (in ) Temperature (°F) Midspan interior Midspan Exterior End Span Interior End Span Exterior

82 Guidelines for Adjacent Precast Concrete Box Beam Bridge Systems Figure C-28. Temperature gradient at various locations compared with AASHTO gradient band for a typical heat cycle of Type IV shear key. Figure C-29 shows the camber of the girders before grouting during a typical heating cycle. All the girders cambered up with increase in temperature and cambered down on cooling the girders. Girder 2 and Girder 3 had almost same camber of approximately 0.15 inch, whereas Girder 1 cambered up to about 0.13 inch. This slight difference in the camber of different girders is expected due to concrete variability. Figure C-29. Camber of the girders during a typical heating cycle before grouting for Type IV shear key. -0.02 0 0.02 0.04 0.06 0.08 0.1 0.12 0.14 0.16 0.18 4:48 9:36 14:24 19:12 0:00 4:48 9:36 C am be r ( in .) Time (24 hour) Girder 1 Girder 2 Girder 3 0 4 8 12 16 20 0 20 40 60 G ird er D ep th (in ) Temperature Gradient (°F) Midspan interior Midspan Exterior End Span Interior End Span Exterior AASHTO Zone 1 AASHTO Zone 4

Experimental Program 83 C.2.5.3 Grouting of the Joints The Type IV shear keys were cast with two different grouts. Jute was used to seal the small gaps between the bottoms of the girders. A non-shrink grout (Sika 212) was used in the north joint and a high-strength grout (Masterflow 4316) was used in the south joint. The following procedure was used: 1. The girders were heated to simulate field conditions. The shear keys were to be cast such that the grout did not fill the top 4 inches of the shear key. Thus, the important temperature was the temperature of the girders 4 inches from the top. Since the intent was to have the girders at the maximum temperature gradient, the target temperature for the girders between 4 inches and 16 inches from the top was a gradient of 12°F to 14°F after the keys were cast, with the intent of heating the assembly, if necessary, to restore the temperature gradient to 14°F as soon as possible after the shear keys were cast. To this end, the girders were slightly overheated to allow for cooling during the casting process. 2. The sides of the girder were prewet. Since the girders were hot, there was some evaporation of the water, so the sides were rewet as necessary. 3. The grout was mixed in a standard mortar mixer according to the manufacturer’s specification. Two mixers were used, and the keys were cast simultaneously. Grout was mixed using the amount of water specified by the manufacturer for a flowable condition. This was adequate for the Masterflow 4316, but the Sika 212 was too stiff to flow without need for consolidation. Given the narrowness of the Type IV shear key, this was difficult. Additional water was added to make the grout flow better. Unfortunately, the RT got several bags of bad Sika grout. The effect of this is discussed below this list of procedures. 4. At each diaphragm, there was a cut-out in the top of the girders, called a “hand hold.” This allowed workers to get their hand into the joint to either thread the tie rod from girder to girder or install a nut when only a few girders are tied together. Additional vibrating wire gages were installed in the lateral (perpendicular to the shear keys) at these locations just under the surfaces (approximately 5 inches from the tops of the girders). 5. After completing shear keys, the girders were heated to restore the 14°F gradient. This took about 1 hour. 6. The girders were then allowed to cool and thermal cycles were applied the next morning. As noted above, the RT got some bad Sika grout. The grout had been ordered just a few weeks before casting and the initial bags used for shear key were in good condition, so there was no reason to suspect a problem. After casting about half the shear key, RT found that some of the bags of grout were hard, as though they were old or had gotten wet. Since the key cast with the Masterflow 4316 was almost complete and half the key with the Sika 212 was cast, the RT had little choice but to use the grout and hope for the best. The RT broke up the “lumps” in the grout, mixed it and cast the keys. However, the delay in dealing with the bad grout likely caused a cold joint in the shear key. Table C-2 shows the strength of mortar cubes made from the grout. Unfortunately, the RT had not made mortar cubes for the good Sika 212, so the strengths reflect the bad grout.

84 Guidelines for Adjacent Precast Concrete Box Beam Bridge Systems Table C-2. Strength of the grouts used for Type IV shear key. Grout Strength (psi) One day Seven days 43 days Sika 212 1,436 4,221 4,664 Masterflow 4316 10,461 12,803 14,564 C.2.5.4 Thermal Loading and Flooding of Joints after Grouting From the day after grouting, thermal loading as described in the previous section was applied to the girder system. The girders were heated until the temperature gradient between 4 inches and 16 inches below the girder surface reached approximately 14°F, and then were allowed to cool until the gradient fell at least below 4°F. Ideally, the gradient should have been reduced to 0°F before the next cycle, but cooling the girders all the way back in the enclosed lab setup with the ‘heat box’ on top would have taken a very long time. Also, during field monitoring it was observed that girders hold some gradient overnight, so a decision was made to limit the lower gradient to 4°F or less. A total of 30 thermal cycles were applied to the system. Six cycles were done over the first seven days, with only one cycle per day to allow the grout to reach strength. However, after 7 days it was possible to run 3 cycles over a 2-day period to keep the project on schedule. Figure C-30 shows the girder camber during thermal cycles after grouting. Cambers during the first and last cycles are compared. Girders cambered up almost the same during both the cycles, with Girder 2 cambering the most, followed by Girder 3. Just like before grouting, the camber in Girder 1 is lagging. Also, compared to camber before grouting, the camber after grouting has slightly reduced. The maximum camber before grouting was 0.15 in Girder 2 whereas the maximum camber after grouting was 0.125 in Girder 2. This was expected as the joint would provide some resistance to the movement of the girders. Figure C-31 shows the relative joint displacement during thermal loading after grouting. Joint displacement is higher in the joint between Girder 1 and Girder 2 (Joint 1-2) compared to the joint between Girder 2 and Girder 3 (Joint 2-3). This may be explained by the difference in the camber of Girder 1 relative to Girder 2. The figure also compares the relative joint displacement during the first and the last cycle. While the displacements are identical for Joint 2-3, there is an increase in the displacement for Joint 1-2. While this may be an indication of cracks or delamination developing in Joint 1-2, the joint displacements were very small so no firm conclusion can be drawn. Figure C-32 shows the strains across the top of the joints during the last thermal cycle. As expected, the strains are compressive with increase in temperature. The maximum strain in Joint 1-2 is 250 micro strains whereas the maximum strain in Joint 2-3 is 300 micro strains. For both the joints, the girder ends develop a higher strain compared to the girder midspans. Figure C-33 shows strains in the VW gages that were embedded into the joints 1 inch deep. The strain in the joints is almost negligible with the highest strain being 20 micro strains. This also reflects the importance of shifting the shear key from the surface to 4 inches deep into the joints. The strains at the top of the joints were in the range of 200–300 micro strains, compared to the strain at a depth of 5 inches, which was less than one-tenth of that value.

Experimental Program 85 Figure C-30. Girder camber during thermal loading of Type IV shear keys after grouting: (a) during first thermal cycle, (b) during 30th thermal cycle.

86 Guidelines for Adjacent Precast Concrete Box Beam Bridge Systems Figure C-31. Differential joint movement during thermal loading of Type IV shear keys after grouting: (a) joint movement during first thermal cycle, (b) joint movement during 30th thermal cycle.

Experimental Program 87 Figure C-32. Strain across the top of the joint during a typical thermal loading of Type IV shear keys after grouting: (a) strains across Sika joint (joint 1-2), (b) strains across Masterflow joint (joint 2-3).

88 Guidelines for Adjacent Precast Concrete Box Beam Bridge Systems Figure C-33. Strains in VW gages embedded 1 inch into the joint. To further investigate the joints at various stages during thermal loading, ‘dye penetration’ tests were performed. For this test, the ends of the girder were sealed, and water dyed with a specific color was poured into the shear keys as shown in Figure C-34. Cracks in the joints, if any, would allow this water to seep through and be detected at the bottom of the girder. Each joint was filled with enough water to create a head of at least 1 inch and the water was allowed to sit into the joints for at least 2 hours before being vacuumed out. After 2 hours, the bottoms of the girders were inspected for any leaks. A dye test was performed after one heat cycle (black dye), after the 5th heat cycle (blue dye), after the 15th heat cycle (green dye), and after the 30th heat cycle (red dye). Since lighter dyes will not cover darker dyes, the progression of cracking could be seen as later cracks showed lighter dyes. Shear key cast with the Masterflow grout (Joint 2-3) showed no signs of leaking during any dye test. The shear key cast with Sika 212 grout (Joint 1-2) showed some leakage in one-half of the joint – west of midspan. Leakage was observed through the bottom of the joint in three places. One leak appeared at the first cycle. This was in the area where the RT suspects a cold joint formed between the “good” grout and the bad grout as there was a time delay while the RT was determining how to handle the bad grout. The second leak occurred after the 5th cycle and was in bad grout near the cold joint. Third leak appeared after the 15th cycle and was also in the region of bad grout. Figure C-35 shows the leaking joint. During the dye test after first cycle, some leakage was also observed in the tie rod hand holes on the exterior face of Girder 1. Each of the end tie rod locations showed some leakage. There was no leakage in the tie rod location at midspan. Since, a PVC shielding was provided to house the tie rods, water from cracks in either of the joints might have entered this shielding and traveled to the tie rod ends (Figure C-36). -100.0 -60.0 -20.0 20.0 60.0 100.0 7:12 8:24 9:36 10:48 12:00 13:12 M ic ro st ra in s Time (24-hour format) N-A N-B N-C S-A S-B S-C

Experimental Program 89 Figure C-34. Flooding Type IV shear keys with dyed water to investigate leakage. Figure C-35. Through joint leakage in the shear key with Sika grout: (a) leakage after first cycle, (b) leakage after 5th cycle, (c) leakage after 15th cycle.

90 Guidelines for Adjacent Precast Concrete Box Beam Bridge Systems Figure C-36. Leakage in the tie rod on the side face of Girder 1: (a) minor leak at the east end, (b) major leak at the west end. C.2.5.5 Live Loading After completing 30 cycles of thermal testing, the girder system was subjected to live loading. The live load consisted of a cyclic load between 0 kip and 66.5 kip applied at a frequency of 2 Hz for a total 100,000 cycles. This load represents a tandem load of two, 25 kip loads plus a 33% impact. The girders have a span of 35 feet, so the tandem load controls. The load was applied using a spreader beam so that the actual load was two, 33.25-kip loads, 4 feet apart, centered on the Girder 2 (middle girder) as shown in Figure C-37. The tandem load has wheels spaced 6 feet in the lateral direction. This was not duplicated. Figure C-38 shows the tandem loading with a 6-foot spread and the actual load used. The shear force in the shear keys is the same, 33.25 kips. However, the use of the load on the center beam allowed the RT to assess load distribution. To inspect the deterioration of the joint, if any, due to the live loading, static tests were performed prior to the start of live loading and then after 500,000, 10,000, 25,000, 50,000, and 100,000 cycles. During static loading, a load of 66.5 kip was applied statically at the midspan of Girder 2 (middle girder) and was held there for 10 to 15 minutes to allow for adequate instrumentation records. The load was then slowly ramped down to zero. Figure C-39 shows the support reactions during static load tests. The load applied at the center distributed almost equally to all six support points. This indicates that the girder system is acting as a unit and complete load transfer is achieved by the shear keys. A comparison of the load distribution before and after loading showed no change in the distribution, meaning that no degradation of the joints occurred due to live load test. Figure C-40 shows the camber of the girders during static load tests. Girder 2 and Girder 3 cambered down 0.25 inch whereas Girder 1 cambered down approximately 0.22 inch. Again, there is no difference in the girder camber before and after loading. (a) (b)

Experimental Program 91 Figure C-37. Live load setup. Figure C-38. Loading depiction: (a) Tandem load pattern with 6-foot spread, (b) actual load pattern used during the test.

92 Guidelines for Adjacent Precast Concrete Box Beam Bridge Systems Figure C-39. Support reactions during static tests of Type IV shear key: (a) before starting cyclic loading, (b) after completion of cyclic loading.

Experimental Program 93 Figure C-40. Girder camber during static tests of Type IV shear key: (a) before starting cyclic loading, (b) after completion of cyclic loading. After the load cycles were completed, a final dye test was performed to investigate any new leaks that developed due to loading. Joints were flooded with a yellow dye, and it was allowed to sit for two hours. The dyed water leaked from the previously existing leaks only and no new leaks were found.

94 Guidelines for Adjacent Precast Concrete Box Beam Bridge Systems C.2.5.6 Joint Cutting and Inspection After the load cycles were completed, the top deck of the girder system was cleared for joint cutting. The heat box, heating equipment, and instrumentations were all removed and stored for second series of tests. A professional cutting company was called to cut the joints and an in-depth inspection of the joint surfaces was performed. The only defect in the Joint 2-3—grouted with high bond strength Masterflow grout—was the cracking near the tie rod locations at each end of the girder as shown in Figure C-41. A possible cause for this cracking might be the stress concentration at the opening due to using the PVC pipe. The leakage through the tie rod hole at the east end of Girder 1 observed during the dye tests (Figure C-36a) may have come from this crack as there was no such cracking found on Joint 1-2 at the east end of the girders. Figure C-41. Cracking at tie rod locations in joint 2-3: (a) cracking at west end, (b) cracking at east end. Severe defects were found in the west half of Joint 1-2 in the region that had the bad grout, and a cold joint was suspected. As expected, and as shown in Figure C-42, a cold joint was found west of the midspan, where the grouting had to be stopped to break up the lumps in the bad grout. This is the same region that leaked during the dye test after first thermal cycle (Figure C-35a). Figure C-43 shows the cracking found in the region that leaked during the dye tests after the 5th thermal cycle and 15th thermal cycle (Figure C- 35, b and c). Figure C-44 shows severe cracking at the west end of the joint including cracking at the tie rod location. There was no through leakage observed at this location from the bottom of the joint, which is also consistent with the crack pattern. Cracks are horizontal and lead up to the tie rod opening. No vertical through cracking is found at this location. However, these cracks may have contributed to the leakage through the tie rod hole at the west end of girder 1 (Figure C-36b). To investigate any delamination of the shear key grout material from the girder surface, the cut keys were checked both by sounding with a hammer and by using a delamination sounding device. (Figure C-45a). No delamination was found in Joint 2-3 (grouted with high bond strength Masterflow grout). Joint 1-2 (grouted with non-shrink Sika grout) showed delamination at each end of the joint as shown in Figure C- 45b and Figure C-45c. Delamination was also found in the region of bad grout as shown in Figure C-45d.

Experimental Program 95 Figure C-42. Signs of poor consolidation due to a cold joint in the region that leaked after first thermal cycle: (a) cold joint on girder 1, (b) cold joint on girder 2. Figure C-43. Cracking in the region that leaked during dye tests after 5th thermal cycle and 15th thermal cycle.

96 Guidelines for Adjacent Precast Concrete Box Beam Bridge Systems Figure C-44. Cracking at the west end of joint 1-2. Figure C-45. (a) Joint inspection for delamination, (b) delamination at the west end of Joint 1- 2, (c) delamination at the east end of Joint 1-2, (d) delamination in the region of bad grout away from the end. To further investigate the joints, the grout was removed to reveal the girder surface using a chipping hammer (Figure C-46a). This would allow the RT to find defects in the joints that were missed during visual inspection or during the hammer sound test. Any defects between the grout and girder surface would have

Experimental Program 97 allowed the dye water to seep in and leave color patterns. Removing the grout and revealing the girder surface to examine these patterns would provide information about the time and the intensity of these defects. For the joint with Masterflow grout (Joint 2-3), it was not possible to break the bond between the grout and the girder to reveal the girder surface. Several locations were tried along the length of the joint with little success. The chipping hammer ended up damaging the surface of the girder before it could separate the grout from it. This was consistent with the results of the pull-off tests where the mode of failure for the Masterflow 4316 grout was in the substrate. This further enforces the initial findings that there were no leaks or delamination in this joint except for the stress concentration crack at the tie rod. For the joint with Sika grout (Joint 1-2), the grout was easy to remove, implying a weaker bond between the grout and girder surface. This was consistent with the pull-off test results where the Sika 212 usually failed in bond. The region that was identified as delaminated during sound hammer testing showed clear signs of dye patterns (Figure C-46b). Darker colors (black and blue) were present at the top of the joints whereas lighter colors (green and red) were visible at the bottom of the joint. This indicated that the delamination occurred at or before the first heating cycle (when the black dye test was performed). The delamination progressed with the further loading of the system. No dye patterns were observed on the surface where no delamination was found during sound testing (Figure C-46c and Figure C-46d). Figure C-46. (a) Chipping grout from joints using a chipping hammer, (b) dye patterns in the region where delamination was observed during sound testing, (c) no dye found at the end where no delamination was observed, (d) no dye found in the region of good grout. C.2.6 Type V Shear Key Testing This test assessed the effects of temperature and fatigue loading on a Type V shear key cast with small aggregate concrete. A system of three girders with two Type V shear key joints was tested. (a) (b) (c) (d)

98 Guidelines for Adjacent Precast Concrete Box Beam Bridge Systems C.2.6.1 Test Setup and Instrumentation Girder 2, the middle girder during Type IV shear key test, was removed from the laboratory floor. Girder 1 and Girder 3 were swapped such that Girder 1 was now at the south side and Girder 3 was on the north side. The fourth girder (Girder 4) was brought in and placed in the center to form two Type V shear key joints as shown in Figure C-47. While tightening the tie rod at the east end of the girder assembly, a piece of concrete from the bottom flange of the Girder 4 broke off and fell on the ground as shown in Figure C- 48. The RT also observed this in box girders in the field. If the edges of the girder are not completely flat and square, stress concentrations occur along the edges as the girders are pulled together by tightening the tie rods. This is what occurred during setup, and it does not affect the results of the test. In the field, this would be patched. Figure C-47. Girder assembly for Type V shear key test. Figure C-48. Concrete spalled from the bottom flange of Girder 4 during tightening of the tie rod at east end. Damage is cosmetic. The procedures for this test (the construction of heat box, application of thermal loading, instrumentations used for monitoring, fatigue, and static load setup) are like Type IV shear key. Since these procedures are already described in detail in the previous sections, they are not repeated here.

Experimental Program 99 However, because the girder assembly was changed to utilize the Type V shear key surface, a new scheme of instrumentation labels is used to be consistent with the changed girder labels and to avoid confusion with the previous scheme of instrumentation used in Type IV shear key. These are shown in Figure C-49, Figure C-50, and Figure C-51. Figure C-49. Locations and labels for load cells at supports, LVDTs across joints, and wire potentiometers under girders for Type V shear key test. Figure C-50. Location and labels of VW gages across joints for Type V shear key test.

100 Guidelines for Adjacent Precast Concrete Box Beam Bridge Systems Figure C-51. Locations and labels of VW gages embedded in the joints for Type V shear key test. C.2.6.2 Thermal Loading Before Grouting Once the girder assembly was complete, the girder system was loaded thermally prior to grouting to re- establish the heating protocol as previously described. Figure C-52 shows the gradient at a depth of 4 inches for various locations during a typical heating cycle. Again, the interior locations developed a higher gradient than the exterior locations. These results are consistent with the observations made during filed monitoring. Figure C-53 shows the temperature profiles through the depth of the girder at various locations during a typical heat cycle. The surface temperature is taken as the average of all the surface thermistors and is therefore same for all the locations. Again, the interior locations have higher temperatures than the exterior locations at all the depths since the exterior locations were exposed to ambient laboratory temperature. Figure C-54 compares the gradient at various locations with the AASHTO recommended gradient band. The results are nearly identical to those presented previously for the Type IV shear key. Figure C-52. Thermal gradient at a depth of 4 inches from the surface of the girder for various locations during a typical heat cycle of Type V shear key. 0 2 4 6 8 10 12 14 16 4:48 9:36 14:24 19:12 0:00 4:48 9:36 Te m pe ra tu re D iff er en tia l ( °F ) Time (24-hour format) Midspan Interior Midspan Exterior End Span Interior End Span Exterior

Experimental Program 101 Figure C-53. Temperature profiles through girder depth at various locations during a typical heat cycle of Type V shear key. Figure C-54. Temperature gradient at various locations compared with AASHTO gradient band for a typical heat cycle of Type V shear key. Figure C-55 shows the camber of the girders before grouting during a typical heating cycle. As in the Type IV shear key test, all girders cambered up with increase in temperature and cambered down on cooling the girders. However, the maximum girder camber was slightly reduced from 0.15 for Type IV shear keys to around 0.11 for Type V shear keys. This may be because the Type V shear key is wider and there may be more heat circulation around the top of the girder. 0 4 8 12 16 20 80 100 120 140 G ird er D ep th (i n. ) Temperature (°F) Midspan Interior Midspan Exterior End Span Interior End Span Exterior 0 4 8 12 16 20 0 20 40 60 G ird er D ep th (i n. ) Temperature Gradient (°F) Midspan Interior Midspan Exterior End Span Interior End Span Exterior AASHTO Zone 1 AASHTO Zone 4

102 Guidelines for Adjacent Precast Concrete Box Beam Bridge Systems Figure C-55. Camber of the girders during a typical heating cycle before grouting for Type V shear key. C.2.6.3 Grouting of the Joints Instead of using two different grouts (one for each joint as was used in the Type IV shear key) only small aggregate concrete was used in both the joints for the Type V shear key. The following procedure was used: 1. The girders were heated to simulate field conditions. The shear keys were to be cast such that the grout did not fill the top 4 inches of the shear key. Thus, the important temperature was the temperature of the girders 4 inches from the top. Since the intent was to have the girders at the maximum temperature gradient, the target temperature for the girders between 4 inches and 16 inches from the top was a gradient of 12°F to 14°F after the keys were cast, with the intent of heating the assembly, if necessary, to restore the temperature gradient to 14°F as soon as possible after the shear keys were cast. To this end, the girders were slightly overheated to allow for cooling during the casting process. 2. The sides of the girder were prewet. Since the girders were hot, there was some evaporation of the water, so the sides were rewet as necessary. 3. Ready-mix concrete was ordered from a commercial supplier. The mix design is shown in Table C-1. The ready-mix concrete from the truck was transferred into concrete bucket that was lifted using an overhead crane and placed on top of the joints. The bucket lever was released, and the concrete was allowed to flow directly into the joints. A mild vibration was used to compact the concrete. 4. The north joint (Joint 3-4) was poured first, followed by the south joint (Joint 4-1). Concrete placement went fine during first joint pour, however, when the RT reached the second joint, the mix began to lose slump. This is not uncommon with mixes using high doses of high-range water reducer. The RT likely took a longer time to pour the joint than a commercial contractor would be -0.02 0 0.02 0.04 0.06 0.08 0.1 0.12 4:48 9:36 14:24 19:12 0:00 4:48 9:36 C am be r ( in .) Time (24-hour format) Girder 3 Girder 4 Girder 1

Experimental Program 103 due to the need to work around the heat box. The concrete stopped flowing out from the bucket into the joint and an additional dose of high-range water reducer (HRWR) had to be used. Once the mix was re-dosed with the HRWR, it flowed better and was placed in the second joint as quickly as possible. However, by the time the RT finished placing the concrete, it started to become plastic. 5. After completing shear keys, the girders were heated to restore the lost gradient. 6. The girders were then allowed to cool and thermal cycles were applied from the next morning. C.2.6.4 Thermal Loading and Flooding of Joints after Grouting From the day after grouting, thermal loading was applied to the girder system. The girders were heated until the temperature gradient between 4 inch and 16 inches below the girder surface reached approximately 14°F, and then were allowed to cool until the gradient fell at least below 4°F. Ideally, the gradient should have been reduced to 0°F before the next cycle, but cooling the girders all the way back in the enclosed lab setup with the ‘heat box’ on would have taken a very long time. During field monitoring it was observed that girders hold some gradient overnight, so a decision was made to limit the lower gradient to 4°F or less. A total of 30 thermal cycles were applied to the system. Six cycles were done over the first seven days, with only one cycle per day to allow the grout to reach strength. However, after 7 days it was possible to run 3 cycles over a 2-day period to keep the project on schedule. Figure C-56 shows the girder camber during thermal cycles after grouting. Cambers during the first and last cycles are compared. Slight variation is the maximum girders between the first and last cycle is due to slight variations in heating from one cycle to another. Figure C-57 shows the relative joint displacement during thermal loading after grouting. Joint displacements from first and last cycles are compared and are extremely small. As is evident from the figure, the relative joint displacement of the joints is negligible during both the first cycle and the last cycle, suggesting no significant cracking in the joints due to thermal loads. To further investigate the joints at various stages during thermal loading, ‘dye penetration’ tests were performed. For these tests, the ends of the girder were sealed, and water dyed with a specific color was poured into the shear keys as shown in Figure C-58. Cracks in the joints, if any, would allow this water to seep through and be detected at the bottom of the girder. Each joint was filled with enough water to create a head of at least 1 inch and the water was allowed to sit in the joints for at least 2 hours before being vacuumed out. After 2 hours, the bottoms of the girders were inspected for any leaks. A dye test was performed after one heat cycle (black dye), after the 5th heat cycle (blue dye), after 15th heat cycle (green dye), and after 30th heat cycle (red dye). No leaks were discovered during dye tests at any stage. The temperature tests took about 3 weeks to complete. This is not enough time for any significant shrinkage to occur in the joint concrete thus no conclusions about shrinkage cracking can be drawn. It is recommended that shrinkage reducing or compensating admixtures be added in field applications.

104 Guidelines for Adjacent Precast Concrete Box Beam Bridge Systems Figure C-56. Girder camber during thermal loading of Type V shear keys after grouting: (a) during first thermal cycle, (b) during 30th thermal cycle.

Experimental Program 105 Figure C-57. Differential joint movement during thermal loading of Type V shear keys after grouting: (a) joint movement during first thermal cycle, (b) joint movement during 30th thermal cycle.

106 Guidelines for Adjacent Precast Concrete Box Beam Bridge Systems Figure C-58. Flooding Type V shear keys with dyed water to investigate leakage. C.2.6.5 Live Loading After completing 30 cycles of thermal testing, the girder system was subjected to 100,000 cycles of live loading as described earlier. To inspect the deterioration of the joint, if any, due to the cyclic loading, static tests were performed prior to the start of cyclic loading and then after 5,000; 10,000; 25,000; 50,000; and 100,000 cycles. During static loading, a load of 66.5 kip was applied statically at the midspan of Girder 2 (middle girder) and was held there for 10 to 15 minutes to allow for adequate instrumentation records. The load was then slowly ramped down to zero. Figure C-59 shows the support reactions during static load tests. The load applied at the center distributed almost equally to all six support points. This indicates that the girder system is acting as a unit and complete load transfer is achieved by the shear keys. A comparison of the load distribution before and after fatigue loading showed no significant change in the load distribution, meaning that no degradation of the joints occurred due to fatigue test. Figure C-60 shows the camber of the girders during static load tests. All girders cambered down to almost 0.25 inch when the load was applied and returned to zero on removing the load. Again, there is no significant difference in the girder camber before and after fatigue loading. After the load cycles were completed, a final dye test was performed to investigate any new leaks that developed due to fatigue loading. Joints were flooded with a yellow dye, and it was allowed to sit for two hours. No leaks were discovered.

Experimental Program 107 Figure C-59. Support reactions during static tests of Type V shear key: (a) before starting cyclic loading, (b) after completion of cyclic loading.

108 Guidelines for Adjacent Precast Concrete Box Beam Bridge Systems Figure C-60. Girder camber during static tests of Type V shear key: (a) before starting cyclic loading, (b) after completion of cyclic loading.

Experimental Program 109 C.2.6.6 Joint Cutting and Inspection As with the Type IV shear keys, after the completion of cyclic loading, the joints were cut and inspected visually for any cracks or defects. Hammer sound technique was used to find any delamination. Grout was removed from locations with suspected delamination to look for dye patterns. Joint 3-4 was poured first, had no problems during grouting, and showed no cracks or defects in the joint away from the ends. At the girder ends the hammer sound results revealed some delamination at two locations (Figure C-61a and Figure C-61c). However, when the grout was removed from these locations, no dye was found on the girder surface (Figure C-61b and Figure C-61d). This led the RT to conclude that this delamination was not due to the thermal or fatigue loading but would have occurred during the joint cutting operation. Figure C-61. (a) Suspected delamination at east end of joint 3-4, (b) no dye impressions at east end girder surface, (c) suspected delamination at west end of joint 3-4, (d) no dye impressions at west end girder surface. Joint 4-1, that was poured second when concrete started to set and was re-dosed with the superplasticizer, has some spots with bad compaction that had dye in them (Figure C-62c and Figure C-62d). The hammer sounding method indicated delamination at the east end of the joint. Removing the concrete from the joint revealed the dye on the girder surface (Figure C-62a). A large patch of black dye was found with green and red dye around its periphery (Figure C-62b). This again indicated that the delamination occurred at an early age and grew bigger with the application of heat cycles. (a) (b) (c) (d)

110 Guidelines for Adjacent Precast Concrete Box Beam Bridge Systems However, it was found that outside of this area, the concrete bonded very well to the surface. It was difficult to remove with the chipping hammer. In most cases, attempts to remove the concrete resulted in damage to the underlying substrate. Figure C-62. (a) Suspected delamination at east end of joint 4-1, (b) dye impressions at east end girder surface, (c) and (d) spots of bad compaction in Joint 4-1 with dye in them. C.2.7 SUMMARY AND CONCLUSIONS OF FULL-SCALE TESTING 1. Full-depth shear keys where the top 4 inches are not grouted appear to be very effective in preventing leakage in the joints. In the full-scale experiments, leakage was found only at places where problems with the shear key grout were identified. No leakage was found at other locations. 2. Not grouting the top 4 inches keeps the grout out of the area of severe thermal movement and reduces the lateral strain in the joints by a factor of 10 or more. This helps to prevent cracking. 3. The surfaces of the girder must be roughened and prewet prior to placing the grout. At the very least, the surface must be sanded or shot blasted to a Concrete Surface Profile (CSP) of 4 as defined by the International Concrete Repair Institute. Rougher surfaces, such as exposed aggregate or higher values of CSP, can improve bond even more. (a) (b) (d)(c)

Experimental Program 111 4. The bonding characteristics of the grout are one of the most important parameters. The best performance came from the Master Flow 4316 grout which showed the best performance in the ASTM C1583 bond test. However, the Sika 212, which had the lowest bond strength in the ASTM C1583 bond test still performed in an acceptable manner. (See Section C.3 for the ASTM C1583 Bond Test Data.) 5. Use of concrete as fill material in the wider Type V shear key provided an acceptable performance. However, the tests performed here were short in duration (about 30 days). The effect of shrinkage of the concrete was not assessed. Use of the shrinkage compensating or shrinkage reducing admixture is advisable. 6. The full-depth shear keys appeared to bind the boxes together and cause them to behave as a single slab in the 3-girder test. This would be beneficial in live load distribution. This should be verified with a larger test involving more girders or with a field test. 7. The AASHTO temperature gradients are consistent with field measurements for box girders and can be used to assess thermal movements in the joints. C.3 Tensile and Bond Strength Testing of Keyway Material A series of tests were performed to establish the standards for strength of keyway material, bond strength of keyway and girder material, and the surface preparation requirements for the keyways. ASTM C1583 Standard Test Method for Tensile Strength of Concrete Surfaces and the Bond Strength or Tensile Strength of Concrete Repair and Overlay Materials by Direct Tension (Pull-off Method) was used as the standard test for this phase of testing. This test is a relatively simple, standard technique that the RT has used in the past and it is recommended by Graybeal (2017a). The test is suitable for both field and laboratory use and provides information on: 1. Near-surface tensile strength of the substrate as an indicator of surface preparation (girder surface in this case). 2. Bond strength of the overlay material to substrate (this represents the bond between the keyway material and the girder surface). 3. The tensile strength of the overlay material (this represents the strength of the keyway material). The test is performed by initially preparing the substrate to a desired surface condition and then pouring the overlay material. Once the overlay material is cured, test specimens are formed by drilling cores through the overlay material and at least 0.5 inches into the substrate. The cores are left intact, and a steel disk is bonded to the top surface of the cores using an epoxy. A vertical tensile load is applied to the steel disk until failure occurs. The failure load and mode of failure are recorded. The possible failure modes are (a) failure in the substrate, (b) failure at the bond between overlay and substrate, (c) failure in the overlay, and (d) failure of bond between epoxy adhesive and overlay. A test is discarded if the failure is in the bond between the overlay and the epoxy (failure type d). The test is repeated until three samples with similar failure mode are obtained. Concrete panels simulating shear key surface conditions were constructed. A total of three panels with different surface finishes were used for the pull-off testing. The specifics of each panel, the surface preparation, the overlay materials used in each case, and the testing procedure used are described in subsections below.

112 Guidelines for Adjacent Precast Concrete Box Beam Bridge Systems C.3.1 Pull-off Test Panel I: Steel Formed and Round Aggregate Finish An 8-foot-long by 4-foot-wide panel was constructed. It consisted of a 4-foot-by-4-foot section of steel formed surface and a 4-foot by 4-foot section of exposed aggregate surface (see Figure C-63). The aggregate was 1-inch rounded river gravel. One-inch rounded river gravel was chosen as the “worst case” for bond. The steel formed surface provided a surface typical of box girders where there is no surface treatment. Prior to casting the shear key material, the surface was lightly sandblasted to remove laitance and some cosmetic rust stains from aggregate which had iron. Four different shear key materials were cast in 2-foot wide by 8-foot-long strips. Each strip included a 4-foot section of exposed aggregate and a 4-foot section of steel formed surface. In addition, prior to casting, a 2-foot by 2-foot section of each surface was prewet (see Figure C-64). In most cases, the grout manufacturers advise ponding the surface for 24 hours, but this would not be practical for the vertical surfaces of box girders. In the field, workers would likely spray the surfaces with water prior to placement so this was done for these specimens. Grouts were mixed according to manufacturers’ instructions to a fluid consistency. The grout materials used were: (a) Sika 212 non-shrink grout, (b) Masterflow 928 non-shrink grout, (c) Masterflow 4316 non-shrink grout with high bond, and (d) small aggregate concrete. Mix proportions for the concrete are provided in the section on full-scale testing. This resulted in a total of 16 regions with different surface finish, grout type, and surface condition (prewet or dry). The final specimen after grouting is shown Figure C-65. Table C-3 shows the complete test matrix for all the regions and the rationale behind them. Figure C-63. Substrate Panel I with round aggregate and steel finish. Round aggregate finish Steel formed finish Cosmetic rust strain due to iron in aggregate (removed after sandblasting)

Experimental Program 113 Figure C-64. Prewetting a 2-foot-by-2-foot section before grouting. After allowing the grout material to set and achieve strength, the following procedure was used to calculate the pull-off strengths in each region. This procedure was utilized or all the subsequent pull-off tests. 1. Nominal 2-inch diameter cores were cut into specimen. Wet coring was used to avoid damage to the specimen and to limit the dust. In accordance with ASTM C1583: a. The cores penetrated at least ½ inch into the substrate. b. The center-to-center distance between the cores was at least 4 inches. c. The distance from the center of a core to the edge of the region was at least 2 inches. d. The cores diameters were measured with a caliper in two perpendicular directions to an accuracy of 0.001 inch. The average diameter was used to find the area. 2. A 2-inch diameter by 1-inch-thick steel disk was epoxied to the core as required by ASTM 1583. 3. A tensile load was applied using the apparatus shown in Figure C-66. 4. The following was recorded: a. The failure loads. b. Type of failure as described in ASTM C1583: a = substrate; b = bond; c = “grout;” d = epoxy. c. If the failure was in two modes, the percentage of each mode was estimated (e.g., 80% bond and 20% grout). 5. Testing was done until at least three “good” tests were obtained for each region. This was defined as: a. Epoxy failures (mode d) were discarded. b. The failures were of the same or similar modes. c. The tensile strengths were reasonably similar and obvious outliers were eliminated. 6. 2-inch x 2-inch x 2-inch cubes of each material were tested for compressive strength.

114 Guidelines for Adjacent Precast Concrete Box Beam Bridge Systems Figure C-65. Final specimen (panel I) after grouting showing different surface finishes, grout types, and surface condition. Figure C-66. Pull-off test apparatus.

Experimental Program 115 Table C-3. Pull-off test matrix for panel I. Region Grout Material Surface type and condition Rationale 1 Masterflow 4316 – High bonding grout Round exposed aggregate, Prewet Effect of surface roughness, improved bond, and prewetting 2 Masterflow 4316 – High bonding grout Round exposed aggregate, Dry Effect of surface roughness and improved bond 3 Masterflow 4316 – High bonding grout Steel formed, Dry Effect of improved bond 4 Masterflow 4316 – High bonding grout Steel formed, Prewet Effect of improved bond and prewetting 5 Masterflow 928 – Non- shrink grout Round exposed aggregate, Prewet Effect of surface roughness and prewetting on current practice 6 Masterflow 928 – Non- shrink grout Round exposed aggregate, Dry Effect of surface roughness on current practice 7 Masterflow 928 – Non- shrink grout Steel formed, Dry A common current practice 8 Masterflow 928 – Non- shrink grout Steel formed, Prewet Effect of prewetting on current practice 9 Concrete with small aggregate Round exposed aggregate, Prewet Effect of surface roughness and prewetting on concrete bond 10 Concrete with small aggregate Round exposed aggregate, Dry Effect of surface roughness on concrete bond 11 Concrete with small aggregate Steel formed, Dry Used for wide, full-depth shear keys 12 Concrete with small aggregate Steel formed, Prewet Effect of prewetting on concrete bond 13 Sika 212 – Non-shrink grout Round exposed aggregate, Prewet Same as ‘Region 5’ with different brand of grout 14 Sika 212 – Non-shrink grout Round exposed aggregate, Dry Same as ‘Region 6’ with different brand of grout 15 Sika 212 – Non-shrink grout Steel formed, Dry Same as ‘Region 7’ with different brand of grout 16 Sika 212 – Non-shrink grout Steel formed, Prewet Same as ‘Region 8’ with different brand of grout Table C-4 shows the average strength, standard deviations, coefficient of variation, and the failure modes for each region. Table C-5 shows the results of the cube tests for compressive strength. The observations from these set of pull-off tests are summarized below: 1. The Masterflow 4316 performed the best with highest bond strength and a predominant mode of failure in the substrate. However, it had very high standard deviations. This was caused by the mode of failure being in the substrate. The cores were only 2 inches in diameter and the concrete had a 1- inch aggregate. If there was an aggregate close to the surface or some voids due to bleed water, the substrate may have had variable strength in different areas. It has also been found in field applications that if an exposed aggregate surface has aggregate with insufficient embedment, it can pull out (pluck).

116 Guidelines for Adjacent Precast Concrete Box Beam Bridge Systems 2. The remaining materials seemed to perform about the same. Specifically: a. The Sika 212 tended to fail mostly in bond. b. The Masterflow 928 failed in the grout. There was some concern about this grout. It was mixed according to manufacturer’s instructions but was still soft after one day. The specimen was cast outside, and the temperature was cool (50-60ºF) but not outside of the manufacturer’s specified temperature range. The grout cubes show proper strength was achieved. The RT wondered if this was just a bad bag of grout. c. The concrete mix tended to fail in bond. d. There were high standard deviations for steel formed dry surfaces. This is not unexpected. Bond in concrete is highly variable and smooth, dry surfaces are a worst case. 3. All the material had a bond/failure strength above 200 psi and most were above 300 psi. De la Varga et al. (2016) suggested that a strength of 150 psi was needed, and all the grouts and all the conditions met this minimum. Most met Lopez de Murphy’s (2010) suggested value of 300 psi. The results seem to agree with Graybeal (2017a): a. The grout with better bonding characteristics performed best, but none of the grouts performed poorly. b. The exposed aggregate surface performed better than the steel formed surface. The exposed aggregate was a rounded river gravel, and this would likely have the worst performance of any exposed aggregate surface. An angular aggregate would likely perform better. c. There was no clear effect of prewetting. In some cases, it improved performance but in others it did not seem to affect the results. One note is that the steel formed surface was very dense, and the water seemed to just pool on top. This could reduce bond performance. This is different from the conclusion of Graybeal, who concluded prewet surfaces improved bond. However, Graybeal used wet burlap to moisten the surface of small, lab scale tests, so the surfaces would have had higher moisture contents. In this test the RT thought that trying to prewet a vertical surface for 24 hours was likely impractical in the field. 4. The compressive strength of the materials varies by a large amount. Sika 212 was the weakest and Masterflow 4316 was the strongest. Masterflow 928 and small aggregate concrete had similar compressive strengths. One important note: This test cannot be performed in a short amount of time. The surface material must set hard enough to be cored and that usually takes at least one day. Wet coring is used both to control dust and to prevent damage to the cores. This saturates the surface material which then must be allowed to dry, or the epoxy will not adhere. Simply drying the surface with a heat gun does not work as water in the pores continues to seep out for some time. The RT found that at least 24 hours needed to elapse for the cores to dry. Longer was better. Finally, the epoxy needs a full 24 hours to completely cure and provide a sufficient strength for the tests. The RT tried numerous epoxies. Many did not have sufficient strength and those that did needed a full 24-hour cure. Thus, the RT is suggesting that if this test is used to qualify material, it be performed at 7 days.

Experimental Program 117 Table C-4. Pull-off test results for panel I. Region Grout Material Surface Type and Condition Average Strength (psi) Standard Deviation COV Failure Mode 1 Masterflow 4316 Round exposed aggregate, Prewet 614 102 16.6 Substrate (a) 2 Masterflow 4316 Round exposed aggregate, Dry 504 74 14.7 Substrate (a) 3 Masterflow 4316 Steel formed, Dry 305 115 37.6 Bond (b) 4 Masterflow 4316 Steel formed, Prewet 392 70 17.9 Substrate (a) 5 Masterflow 928 Round exposed aggregate, Prewet 373 26 7.0 Grout (c) 6 Masterflow 928 Round exposed aggregate, Dry 247 57 23.1 Grout (c) 7 Masterflow 928 Steel formed, Dry 335 66 19.6 Grout (c) 8 Masterflow 928 Steel formed, Prewet 324 52 16.0 Grout (c) 9 Concrete Round exposed aggregate, Prewet 454 88 19.4 Bond (b) 10 Concrete Round exposed aggregate, Dry 405 39 9.6 Shear key concrete (c) 11 Concrete Steel formed, Dry 348 100 28.7 Bond (b) 12 Concrete Steel formed, Prewet 326 32 9.9 Bond (b) 13 Sika 212 Round exposed aggregate, Prewet 437 52 11.9 50% Grout (c) / 50% Bond (b) 14 Sika 212 Round exposed aggregate, Dry 338 9 2.8 Bond (b) 15 Sika 212 Steel formed, Dry 220 97 44.3 80% Bond (b) / 20% Grout (c) 16 Sika 212 Steel formed, Prewet 311 39 12.6 80% Bond (b) / 20% Grout (c)

118 Guidelines for Adjacent Precast Concrete Box Beam Bridge Systems Table C-5. Cube tests results for panel I. Material Strength (psi) Age (days) Masterflow 4316 13,972 29 Masterflow 928 8,339 30 Shear Key Concrete 8,462 26 Sika 212 5,217 30 C.3.2 Pull-off Test Panel II: Crushed Exposed Aggregate The rounded river gravel exposed aggregate finish used during first set of pull-off tests was chosen as a worst-case scenario. In one of the interim reports, a panel member suggested that testing angular aggregate would be worthwhile as it is expected to perform better than the round gravel finish. Therefore, another test panel with exposed, crushed aggregate finish was constructed (see Figure C-67). The panel was divided into four 1-ft x 8-ft strips for four different shear key materials. Each strip was further transversely divided into three sections. The first section was kept dry, the second section was prewet just before pouring the shear key material, and the third section was soaked with burlap for 24 hours. While prewetting with burlap is impractical in the field, the RT would at least like to provide data on this for any DOT that may want to consider this option. Figure C-68 shows the finished specimen with 12 different regions. The same procedure as previously discussed was used to obtain the pull-off strengths for each region. Cubes were tested at 14 days for compressive strengths of the shear key materials. Table C-6 shows the results of pull-off strength for each of the twelve regions. Table C-7 shows the compressive strengths for the four materials used in this test. The observations from these set of pull-off tests are summarized below: 1. The Masterflow 4316 again performed the best. Failures were in the substrate. The failure values were a bit lower in the second test series than in the first set, indicating that the substrate was slightly weaker. Since in both the original tests and the current tests the Masterflow 4316 tended to bond well enough to fail the substrate, the angular aggregate made no difference, nor did the wet or dry substrates. 2. The Masterflow 928 grout performed well. While casting the first pull-off panel, it was noted that this grout did not appear to set properly. However, for this panel, the grout set properly and there were no problems. The failures were mostly in the substrate. Wet surfaces performed better than dry. 3. The Sika 212 had similar performance in both sets of tests. The previous test showed that exposed aggregates perform better than steel formed surfaces and wet performs better than dry, but the angular aggregate did not appear to make a difference. Sika 212 and the Masterflow 928 had similar performance. This suggests that normal, non-shrink grouts would have similar performance. 4. The concrete performed a little worse in the current test than in the previous test. This was probably due to lower strength of the concrete overlay mix. There was one other interesting note. The concrete exhibited some plastic shrinkage cracking. This could be a factor in using this material in hot weather. 5. Wetting the substrate increased the pull-off strength in most cases. Using burlap to keep the surface wet did not seem to help as it did not seem that the burlap was very effective in keeping the surface saturated.

Experimental Program 119 Figure C-67. Pull-off test panel II with exposed crushed aggregate surface. Figure C-68. Final specimen (panel II) after grouting showing different grout types and surface condition.

120 Guidelines for Adjacent Precast Concrete Box Beam Bridge Systems Table C-6. Pull-off test results for panel II. Region Grout Material Surface Condition Average Strength (psi) Standard Deviation COV Failure Mode 1 Concrete Wet burlap 303 109 35.9 Bond (b) 2 Concrete Prewet 341 36 10.6 Bond (b) 3 Concrete Dry 224 86 38.2 Bond (b) 4 Sika 212 Wet burlap 474 64 13.5 80% Bond (b) / 20% Substrate (a) 5 Sika 212 Prewet 388 14 3.6 Substrate (a) 6 Sika 212 Dry 344 95 27.7 Grout (c) 7 Masterflow 928 Wet burlap 424 7 1.6 Substrate (a) 8 Masterflow 928 Prewet 388 47 12.1 Substrate (a) 9 Masterflow 928 Dry 378 115 30.5 80% Bond (b) / 20% Substrate (a) 10 Masterflow 4316 Wet burlap 426 76 17.8 Substrate (a) 11 Masterflow 4316 Prewet 486 65 13.3 Substrate (a) 12 Masterflow 4316 Dry 426 108 25.4 Substrate (a) Table C-7. Cube tests results for panel II. Material Strength (psi) Age (days) Shear Key Concrete 5,375 14 Sika 212 6,305 14 Masterflow 928 8,222 14 Masterflow 4316 11,779 14

Experimental Program 121 C.3.3 Pull-off Test Panel III: Surface Sandblasted to CSP–4 The concrete surface profile in the girder keyways for system testing was not fabricated with an exposed aggregate. A member of the International Concrete Repair Institute (ICRI) was consulted to evaluate the finished girder keyway surfaces. The consultant stated that the girder sides were prepared to at least a Concrete Surface Profile 3; but the actual method of determining the CSP is to compare the surface with standard chips provided by the ICRI. The RT made the comparison and judged the surface to be CSP-4. The previous pull-off tests were performed on exposed aggregate surfaces. Those tests are not representative of the actual girder being tested in full-scale system tests. Therefore, the RT asked the girder fabricator to prepare a separate 4-foot by 4-foot panel with the girder concrete. This panel was than sandblasted to generate a surface profile like the girder surface profile (see Figure C-69). Prior to casting the shear key material, the surface was lightly sandblasted to remove laitance or contamination. The panel was divided into three regions – one foot wide and four feet long – using wooden formwork. Water was sprayed to prewet the substrate prior to casting the overlay. A 1.5-inch-thick layer of Sika 212 and Masterflow 4316 were cast in the first two regions. These were the same grouts used in the Type IV shear key system tests and were placed in the panel at the same time that the Type IV shear keys were grouted. There were concerns about the quality of Sika 212 grout. The first bags of grout were in good condition, but the some of the bags had hard material with “lumps” when opened. About half the shear key in the full-sized specimens were cast with the “good” grout and about half with the “bad” grout. Unfortunately, the RT did not suspect or realize that some of the grout might have been bad and the pull-off specimen, cast last, used the poor-quality grout. The third region of the panel was cast with small aggregate concrete. It was the same mix that was used for Type V shear key system test and was placed in the panel at the same time when Type V shear keys were poured. One of the concerns that the RT had regarding the concrete mix placed in the panel was that it was poured in the end when the shear key pour was completed. By the time it was being placed in the panel, it already started to setup. Cubes were made to test the compressive strength of Sika 212 and Masterflow 4316. The compressive strength of the small aggregate concrete was measured using 6-inch by 12-inch cylinder specimens. The same procedure as previously detailed was used to obtain the pull-off strengths for each region. Table C-8 shows the results of pull-off strength for each region. Table C-9 shows the compressive strengths for the materials used in this test. The observations from these set of pull-off tests are summarized below: 1. The Masterflow 4316 performed better than Sika 212 and small aggregate concrete. Failures were in the substrate. The failure values were lower than the previous two tests indicating that the substrate was weaker. Since in all the pull-off tests the Masterflow 4316 tended to bond well enough to fail the substrate, it can be concluded that any surface with roughness equal to or greater than CSP-4 is adequate. 2. The Sika 212 performed worse for the CSP-4 surface among all the pull-off tests. This was expected as the grout was of poor quality and the failure mode changed from bond failure in previous tests to grout failure in this test. Despite its poor performance the average failure strength for Sika was 268 psi. This is sufficient to prove the adequate bond since a minimum of 150 psi bond strength has been suggested. 3. The small aggregate failed at an unexpectedly low bond strength of 136 psi for the CSP-4 surface. However, the RT strongly believes that the low bond strength is not because of the substrate surface roughness but because the concrete mix started to set when being placed and therefore could not

122 Guidelines for Adjacent Precast Concrete Box Beam Bridge Systems bond well with the substrate. In the full-scale test, the RT found the bond to be very good (see section on full-scale testing). 4. The compressive strength of Sika 212 was 4221 psi at seven days. This is lower than the manufacturer specified strength of 5500 psi at seven days. This further suggests that the grout received was of poor quality. Figure C-69. Pull-off panel III after sandblasting. Table C-8. Pull-off test results for panel III. Region Grout Material Surface Condition Average Strength (psi) Standard Deviation COV Failure Mode 1 Masterflow 4316 Prewet 391 49.3 12.6 Substrate (a) 2 Sika 212 Prewet 268 83.3 31.2 Grout (c) 3 Small aggregate concrete Prewet 136 10.2 7.5 Bond (b) Table C-9. Compressive strength test results for panel III. Material Strength (psi) Age (days) Masterflow 4316 (cube) 12,803 7 Sika 212 (cube) 4,221 7 Concrete (cylinder) 6,461 7

Experimental Program 123 C.3.4 Pull-off Testing IV: Girder Sides The girders were to have an exposed aggregate surface. As detailed previously, the fabricator was unable to achieve this surface, so a roughly sandblasted surface was used. All of the pull-off testing (ASTM C1583) conducted prior to casting the girders used exposed aggregate surfaces as the means of roughening the surface. The girder fabricator created a new panel for the pull-off testing, made of the same concrete and with the same sandblasted surface. The pull-off tests performed on this panel had some problems with the Sika 212 grout and the small aggregate concrete. As detailed in the previous section, some of the Sika 212 used in the Type IV shear key was of poor quality. This was not detected until most of the shear key had been cast. The poor-quality grout was used for the pull-off tests and failed mostly in grout during testing (average failure strength 268 psi). The concrete used in the Type V shear key appeared to become plastic by the time the RT casted the pull- off panel and showed bond failure at relatively low strengths during pull-off testing (average failure strength 136 psi). Therefore, to provide a more accurate information on the performance of these materials, the RT decided to perform additional pull-off tests. In order to dispose of the girders after the testing was complete, the girders were cut apart through the joints. This created a vertical, exposed girder side that surface was used to perform the testing. The pull-off tests were performed on the grout/concrete adhering to sides of the girders. The testing procedure was exactly like the original pull-off tests, except that instead of a horizontal panel surface, a vertical girder side surface was used. Figure C-70 shows various stages of a pull-off test procedure.

124 Guidelines for Adjacent Precast Concrete Box Beam Bridge Systems Figure C-70. (a) Drilling cores into the sides of the girder, (b) cores drilled in the girder sides, (c) pull-off disks attached to the cores, (d) pulling off the cores from girder sides. The testing was performed on a Sika 212 joint surface from a Type IV shear key in the region of the joint that was poured first during shear key casting and had good grout. Testing was also performed on a small aggregate concrete joint surface from a Type V shear key. Masterflow 4416 joint surface was not tested as it showed sufficient bond during original pull-off testing and there was no reason to retest. The results of all the tests performed are shown in Table C-10, but not all of the tests had the same failures. Consistent with the method used for the previous pull-off tests, Table C-11 shows the results of the most consistent tests. The average failure strength for concrete surface increased from 136 psi on pull-off panel to 306 psi on the girder surface. The failure was in the bond for both the cases. This verified the RT’s suspicion that the low failure strengths in the original pull-off tests were due to concrete becoming plastic before casting the panel. For Sika 212 surface, the failure strength increased from 268 psi on the pull-off panel to 464 psi on the girder surface. Also, the failure mode changed from grout failure to bond failure. This indicates that for a good quality Sika grout, the performance is adequate. It should also be noted that these tests were performed on joints exposed to extreme thermal loading and cyclic live load during full-scale testing. They were also cut apart. Thus, it is possible that there was some damage, meaning that initial strengths may have been even better.

Experimental Program 125 Table C-10. Pull-off test results on the sides of girder. Region Grout Material Test Number Average Strength (psi) Failure Mode 1 Small aggregate concrete 1 316.4 Bond (b) 2 316.2 Bond (b) 3 285.7 Bond (b) 4 375.5 Grout (c) 5 247.1 Bond (b) 6 397.2 Grout (c) 7 285.9 Substrate (a) 8 421.1 Substrate (a) 2 Sika 212 1 191.3 Bond (b) 2 174.9 Bond (b) 3 105.7 Bond (b) 4 671.9 Bond (b) 5 527.6 Bond (b) Table C-11. Summary of pull-off testing. Region Grout Material Average Strength (psi) Standard Deviation Coefficient of Variation (COV) Failure Mode 1 Small aggregate concrete 306 17.6 5.8 Bond (b) 2 Sika 212 464 246.5 53.2 Bond (b) C.3.5 Summary of Pull-off Testing A series of pull-off tests was performed to evaluate the tensile strength of various shear key materials and their bonding characteristics with the girder surface. A total of four shear key materials—one high bonding grout, two non-shrink grouts, and one small aggregate concrete mix—were tested. Effects of surface preparations such as surface roughness, prewetting the surface, and covering the surface with wet burlap were studied. The ASTM C1583 test was used as the standard testing procedure. The overall findings of the pull-off testing are as follows: 1. All the materials and surface conditions had a pull-off failure strength of at least 200 psi, and most were above 300 psi. De la Varga et al. (2016) suggested that a strength of 150 psi was needed, and all the grouts and all the conditions met this minimum. Lopez de Murphy et al. (2010) suggested 300 psi for bond and most of the specimens met this requirement as well. 2. Since all the combinations of grout and surface conditions showed a pull-off strength of at least 200 psi, the RT suggests using this value as the minimum to qualify any grout/surface combination. 3. The higher bonding grout performed the best and is recommended, however, other grouts also showed satisfactory performance and could be used.

126 Guidelines for Adjacent Precast Concrete Box Beam Bridge Systems 4. The surface roughness affected the bond performance. Both the exposed aggregate surfaces and the CSP-4 surface performed better than the steel formed surface. In many cases the failure modes were shifted from bond failure on steel formed surface to either substrate or grout failure on roughened surface. Any surface roughened to CSP-4, or more is recommended. 5. Prewetting the surface increased the pull-off strength in 10 out of 12 cases. In the remaining two cases, the strength remained almost identical in one case while in the other it was reduced. The reduction in strength was for the steel formed surface which as mentioned before caused prewetting water to pool and might have reduced the bond strength. Therefore, for roughened surface, prewetting of the girder surface is highly recommended.

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Bridges constructed with adjacent precast prestressed concrete box beams have been in service for many years and provide an economical solution for short and medium span bridges. A recurring problem is cracking in the longitudinal grouted joints between adjacent beams, resulting in reflective cracks forming in the asphalt wearing surface or concrete deck.

The TRB National Cooperative Highway Research Program's NCHRP Research Report 1026: Guidelines for Adjacent Precast Concrete Box Beam Bridge Systems presents guidelines developed for the design and construction of various adjacent precast box beam bridge systems to enhance the performance of connections and bridge service life and to propose design and construction specifications.

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