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Section 5: Crack Repair – Pressure-Injected Epoxy

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Pressure-inject TxDOT Type IX low-viscosity epoxy resin into concrete cracks to restore structural integrity of damaged members or to prevent water and chloride infiltration.

Depending on the epoxy resin material, cracks as narrow as 0.002 inches can be injected with epoxy resin. However, it is often difficult to effectively fill cracks that are narrower than 0.005 inches. It is important to use a crack gauge to get accurate readings on crack widths.

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Crack Injection Material: TxDOT Type IX low-viscosity epoxy resin (ASTM C 881 Type IV, Grade 1) typically consists of two liquid components that are combined automatically during the pressure injection process.

Epoxy for Sealing the Surface of Cracks: TxDOT Type V or VII concrete epoxy adhesive. Use only material that is approved by TxDOT and the crack injection material manufacturer.

Refer to DMS 6110 and MPL for Epoxies and Adhesives for additional information. Also refer to approved manufacturers and products list.

Use material not included in the approved MPL only if authorized by the Engineer.

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Repair Procedure

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  • Surface Preparation.
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    • Drill holes to permit installation of the injection ports or mount the ports on the surface as required by the manufacturer. Space the ports at appropriate intervals as outlined in the Application section that follows.
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    • Clean the interior of vertical cracks from bottom to top using either compressed air or vacuum systems to remove all loose materials entrapped in the cracks.
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      • In some cases, it may be difficult or impossible to sufficiently remove dust or debris from inside the cracks.
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      • If the debris is only near the surface, drill holes for the injection ports away from the exposed portion of the crack. Drill the holes at an angle so the injection ports intersect the crack beneath the surface away from the dust and debris.
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      • When using compressed air ensure that the debris is not being forced deeper into the crack.
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      • Consult the Engineer if it appears that debris in the crack could hinder proper injection of the epoxy resin.
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    • Remove contaminants where the surface seal will be applied, including laitance, oil, dust, debris, or other foreign particles.
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    • Unless the manufacturer or the Engineer specifically requires otherwise, do not grind the concrete around the crack to remove contaminants or provide a V-shaped groove along the crack.
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      • Grinding can force dust into the crack and consequently hinder proper flow of the epoxy resin.
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      • If a V-shaped groove is cut into place along the crack, carefully remove the dust using compressed air and/or high-pressure water blasting. Do not commence the surface sealer application or injection work until the crack and concrete surface have dried.
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  • Mixing.

    Mix the epoxy surface seal as required in the manufacturer’s technical literature.

    Epoxy Injection Resin: Use portable injection equipment capable of automatically mixing the liquid components at the proper proportion during the pressure injection operation.

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  • Application.

    Install the injection ports.

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    • Place the ports directly on the crack or in drilled holes that intersect the crack.
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    • Install the injection ports at appropriate intervals along the crack.
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      • The port spacing should not exceed the depth of the crack. If the depth of the crack is not known, space the ports as recommended by the resin manufacturer.
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      • If the crack projects through the entire concrete section, the intervals between ports should not exceed the section depth.
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    • Ensure that the ports are placed in locations where the crack is not too narrow or clogged with debris to permit adequate flow of the epoxy resin.
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    • Anchor the injection ports and seal the surface of the crack between ports using a sealer as required by the resin manufacturer.
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    • Allow sufficient time for the sealer to cure before commencing the resin injection.
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    • The sealer must have adequate strength to hold the injection ports in place and withstand the pressure along the crack during the injection operations.
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    • Apply sealer over the surface of the crack on the backside if the crack extends completely through the concrete section.
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    • Pressure-inject the epoxy resin into the crack through the ports.
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    • Use a positive displacement pump, air -actuated caulking gun, or paint pressure pot as recommended by the epoxy resin manufacturer and approved by the Engineer.
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    • If working on a vertical surface, start injecting at the lowest port and work upwards.
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    • Maintain adequate pressure until resin emerges from the adjacent port.
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      • If resin does not emerge from the adjacent port, stop the work and reevaluate the crack.
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      • Ports may need to be placed more closely together or debris cleared from under the existing ports.
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      • As noted above, ports should be installed at an angle so they intersect the crack at a deeper point if debris is clogging the crack near the concrete surface.
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      • Inadequate flow of the epoxy resin may be a sign that the crack is either too shallow or too narrow for pressure injection to serve its purpose.
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    • If the epoxy begins to flow out of a nonadjacent port, temporarily plug that port until the epoxy begins to flow out of the adjacent port.
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    • Once the resin appears in an adjacent port, remove the injection nozzle, seal the port, and begin injecting in the adjacent port.
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    • Move the equipment to the adjacent port and proceed with the epoxy resin pressure injection.
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    • Remove the injection ports and surface sealer after the epoxy resin has been given adequate time to cure. Resin material should not flow from the crack after the surface sealer is removed.
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  • Finishing.
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    • Grind away any epoxy resin or surface sealer residue that is left on the concrete surface after the injected material has had sufficient time to cure.
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Injection of concrete cracks with epoxy resin takes a great deal of skill and expertise. The repair crew should receive hands-on training from a technical representative from the resin manufacturer before proceeding with the work, or the Contractor should retain a specialty firm to perform the work.

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