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South Dakota Department of Transportation
Project Synopsis
SD2000-06


Title: Determination of Optimized Fly Ash Content in Bridge Deck and Bridge Deck Overlay Concrete
Project Researcher: V Ramakrishnan, SDSM&T
Project Manager: Daris Ormesher
Research Period: 2/14/2000 - 2/28/2002
Status:
Cost: $100,000.00

Problem Statement: Bridge engineers are challenged to construct bridges economically with increased performance. Although designers are confident of their bridge deck and bridge deck overlay designs, the materials that are used for construction may eventually cause problems. Bridge decks and bridge deck overlays should resist sulfate attack, be resistant to alkali-silica reactivity (ASR), have minimal drying and/or shrinkage cracking, and be nearly impermeable. If a concrete mix appropriately addresses each of these properties, then it is likely that bridge deck and bridge deck overlay maintenance will be reduced and their lives should be increased.

Although newly constructed bridge decks on the state highway system contain epoxy coated steel, a possible avenue for corrosion remains because the epoxy coating may experience some deterioration prior to installation due to ultraviolet radiation or it may get chipped during shipping, storage at the job site, or installation. The corrosion problem may be even worse for South Dakota cities and counties as they use black steel (not epoxy coated). Beyond, the possible corrosion problem, newly constructed bridge decks and bridge deck overlays may be constructed with concrete mixes having a higher than desired permeability. Also, the mixes may not adequately resist sulfate attack, ASR, and drying and/or shrinkage cracking. Restrained shrinkage cracks are easily identifiable in newly constructed bridge decks when the forms are removed. These cracks occur frequently over the length of the deck (approximately every 5 to 6 feet).

Bridge deck overlays are a frequent form of maintenance for older decks. Most generally, these older decks contain black steel with the steel possibly having some degree of corrosion. The bridge deck overlay concrete should have a low permeability to minimize corrosion, resist sulfate attack, resist ASR, and have a low crack potential so that the deck's life can be extended for as many as 15 years.

Studies indicate that the inclusion of fly ash in concrete can result in a higher resistance to chloride intrusion (due to reduced permeability), less surface cracking, greater resistance to freeze-thaw deterioration, and resistance to ASR and sulfate attack. Therefore, there is a potential to reduce repair and replacement costs. Understanding the possible benefits of fly ash in concrete, SDDOT's Bridge and Materials Engineers have a desire to evaluate bridge deck and bridge deck overlay concrete that contains fly ash.

Although studies have indicated that Class F fly ash can improve the quality of concrete, trial bridge deck and bridge deck overlay fly ash concrete batches should be prepared and tested to determine if the properties are significantly increased beyond that of SDDOT's normal mixes. In addition, testing should be conducted to determine the effects of air content on permeability. If the optimized bridge deck and bridge deck overlay fly ash concrete mixes have significant improvement in the properties above, then the optimized mixes should be used in their respective field application. It is likely that the optimized bridge deck concrete mix could be used in the southbound structure on I-29 which will be monitored as part of SD98-06. A bridge deck overlay project would have to be identified so that the optimized bridge deck overlay concrete could be field tested and evaluated as part of this project.



Findings:

Research Objectives:
1  To evaluate, optimize, and recommend concrete mix designs using Class F fly ash to reduce permeability, reduce drying and/or shrinkage crack potential, increase resistance to sulfate attack, and increase resistance to ASR for bridge deck and low slum
2  To evaluate the effects of varying air contents on the permeability for the optimized mixes.
3  To evaluate the constructability and performance of the optimized low slump dense overlay concrete mix.

Research Tasks:
1  Review and summarize literature relevant to air content and the use of Class F fly ash in concrete to determine their effects on concrete permeability, resistance to ASR and sulfate attack, and crack potential.
2  Meet with the Technical Panel to review the research scope and work plan.
3  Determine the optimized Class F fly ash concrete mix designs for bridge deck and bridge deck overlay concrete by testing trial batches. The optimized mixes should minimize concrete permeability and crack potential and increase resistance to sulfate a
4  Propose field sampling and testing programs for determining the field concrete’s fresh and hardened concrete properties for both the bridge deck and bridge deck overlay Class F fly ash mixes.
5  Submit a Technical Memorandum summarizing relevant literature, research methodology, test results, recommended concrete mix designs, and the recommended field sampling and testing programs. NOTE: Based on the findings up to this point, the Technical
6  Attend the bridge deck overlay preconstruction meeting to ensure the bridge deck overlay fly ash low slump dense concrete mix, sampling, testing, and monitoring are understood by all.
7  Attend the construction of the bridge deck overlay. Conduct the sampling and testing as approved in the tasks above. In addition, record weather conditions and observe and record construction methods.
8  Conduct performance tests of hardened concrete on the collected field samples for the bridge deck overlay as approved in an earlier task. Performance tests should include, but not be limited to, permeability, density, and bond strength.
9  Evaluate the performance of the constructed bridge deck overlay.
10  Recommend construction guidelines for using fly ash low slump dense concrete in bridge deck overlay applications based on results observed from this study.
11  Recommend mix designs and testing guidelines for the optimized fly ash bridge deck and low slump dense bridge deck overlay concrete based on results observed from this study.
12  Submit a final report summarizing relevant literature, research methodology, test results, findings, conclusions, and recommendations.
13  Make an executive presentation to the SDDOT Research Review Board summarizing the findings and conclusions.

Documents Available:

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