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Research Activities: 2007
Project 1b: Spalling Solution of Precast - Prestressed Bridge Deck Panels
Matching Research Agency
Missouri Department of Transportation (MoDOT) and Missouri University of Science and Technology (Missouri S&T)
|One graduate and one undergraduate student.|
The primary objectives of the proposed project are to investigate the causes for spalling in precast-prestressed panels and cost-effective mitigation solutions for existing bridge decks, as well as review improved design options for new construction. Alternative solutions will be proposed and evaluated. This will include fundamental laboratory studies to evaluate and validate the proposed design. It will also include the development of procedures for the design of prototype bridge deck panels that are corrosion-free to eliminate the spalling problem. Field implementation and performance monitoring of the bridge deck panel on new construction and/or replacement of existing bridge decks will constitute Phase II of the project.
Precast-prestressed concrete panels are commonly used in the construction of concrete bridge decks. Almost all prefabricated bridge decks in MoDOT’s inventory consist of precast-prestressed 3” thick deck panels and cast-in-place 5.5” thick slabs on top of the panels. The precast-prestressed concrete panels serve as formwork for the cast-in-place concrete slabs and accelerate the construction of bridge decks in a cost-effective way. Traditionally these panels are reinforced with mild steel temperature reinforcement in the traffic direction along with low-relaxation seven wire steel prestressing strands perpendicular to the traffic direction (along the length of the panel).
It was recently observed that some bridges in MoDOT inventory have experienced rusting of embedded steel reinforcement and concrete spalling issues in deck panels. The plausible reasons for spalling observed in many bridges currently in service likely include corrosion of the steel in the panels due to use of deicing salts, permeability/cracking in the panels, and inadequate concrete cover. Corrosion of steel reinforcement can be detrimental as it can result in shorter life spans for the deck panels.
Since the use of stay-in-place deck panels has proven to be a very cost-effective practice for concrete bridge deck constructions in Missouri, it is of interest to examine ways to mitigate spalling and the resulting service-life reduction associated with corrosion of embedded reinforcement in these panels. Hence an investigation of the causes and development of solutions including alternate design options for these panels will have a significant economic impact on MoDOT bridge construction practices. Further, as steel reinforcing bar prices continue climbing and more rusting/spalling issues appear, eliminating the steel in these panels could become cost effective. The idea proposed in this project is to replace the steel reinforcement, both prestressed and nonprestressed, by fiber reinforced polymer (FRP) bars and perform experimental testing of these panels to evaluate their long-term structural performance.
Deliverables from the proposed project include the final report described in Task 6, as well as quarterly progress reports. The quarterly report which will summarize the accomplishments during the quarter and also provide opportunities for the research investigators of three Missouri universities involved in this initiative and MODOT to provide technical and other input with regard to progress on the project. After the final report is submitted and approved, a one-half day workshop presentation on the findings and recommendations will be made to MoDOT bridge engineers.
Specifically, the final report will include, but not be limited to, a summary of the causes for spalling in precast prestressed panels, recommendations for mitigation, alternative panel designs with laboratory and field test performance data.
Relationship to other Research/Projects
A project under the Missouri S&T-UMC-UMKC MoDOT Structures Program Initiative.
Technology Transfer Activities
The technology transfer activities will include a final research report and dissemination of the findings through a national conference via technical presentation and publication(s).
Transportation Research Board Keywords
Corrosion, Coating Systems, Steel degradation