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Background :
Bridge deck overlays (such as asphalt concrete, Portland cement-based concrete, latex-modified concrete, epoxy polymer concrete, or polyester polymer concrete) can degrade and separate from the underlying concrete decks, a common issue known as debonding. A survey was conducted among ODOT staff including Bridge Maintenance Engineers and Bridge Construction Engineers from Districts 1 – 8. Some important aspects understood from the survey are: (1) membranes are needed when asphalt overlays are placed on concrete decks; (2) exposed concrete decks are often overlaid with asphalt concrete, for example, the bridges on US-60 between Tonkawa and Ponca City; (3) asphalt concrete was used a lot as bridge overlays however, without a membrane, they cannot be laid. Even if the overlay appears intact, the concrete deck beneath may suffer from hidden deterioration, such as rebar corrosion and delamination. New materials must be researched to evaluate their effectiveness in bonding to concrete bridge decks.
Objective :
The Objective of this project is to examine the potential of advanced thermoplastic woven Fiber Reinforced Polymer (FRP) tapes that can develop a cohesive bond with overlays due to their fundamental exothermic behavior allowing crosslinking action. Highly exothermic bridge deck overlays (>50ºC (122ºF)) (such as asphalt concrete, latex-modified concrete, epoxy polymer concrete, or polyester polymer concrete) generate high amounts of heat upon mixing its constituents.
Scope :
Task 1 – Material Collection :
The FRP membranes will be collected from WEAVE3D, an industry partner committed to donating the material needed for this study. FRP membrane of two different mess sizes will be used. Asphalt, cementitious and polymeric overlays mix designs will be established for use in this study.
Task 2 – Quantification of Interlayer Shear Strength
In this task, the interlayer shear strength test will be conducted using a Louisiana Interlayer Shear Strength Tester (LISST) (Fig 4). A 150-mm diameter cylindrical sample, comprising two layers, will be sheared under pre-established normal loads, and shearing stress at failure will be reported as the interlayer shear strength. The bottom half of the cylinder will be 50-mm thick, and will be compacted to 4% (± 0.5%) target air voids in a Superpave Gyratory Compactor (SGC). The cylindrical specimen will be placed back in the bottom of the SGC mold and an upper layer (50-mm thick with a target air void of 7% ± 0.5% will be compacted on top of it. The composite specimen will be cooled overnight before testing in a LISST device. This process will be performed for FRP membranes with the three different overlay materials, with three replicates per combination. Through the LISST tests proposed, debonding effects will be studied and observations will be reported for all three overlay types proposed that is asphalt concrete, Portland cement-based concrete and epoxy polymer concrete.
Task 3 – Conduct Microscopic Alalysis
Advanced light microscopy will be performed using a Keyence VHX-7000 ultramicroscope. The microscope is fully automated and has the ability to capture high magnification of up to 6500x images. Precision of interface physical characteristics formed during interaction of overlay materials and the membrane used in this study will be assessed by cutting cross sections of each fabricated specimen.
Task 4 – Analysis of Laboratory Test Results.
The data collected from the interlayer shear strength test and microscopic tests will be analyzed and important trends will be identified. Also, the effect of mess size of the FRP membrane on the interlayer shear strength will be assessed.
Task 5 – Project Reporting
Quarterly progress reports will be submitted on schedule, followed by a project final report after completion of all tasks. The final report will include all test data, analysis, discussions, as well as recommendations on the use of FRP membrane for bridge deck maintenance.
Research Team:
Principal Investigator: Shreya Vemuganti, Ph.D.
Co-Principal Investigators: Syed Ashik Ali, Ph.D.