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Section 6: Crack Repair – Gravity-Fed Epoxy

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Description

Use TxDOT Type IV low-viscosity, gravity-fed epoxy to fill cracks to help prevent water and chloride infiltration into concrete.

Depending on the epoxy material, cracks with widths as narrow as 0.004 inches can be filled using gravity-fed material. Use a crack gauge to get accurate readings on crack widths.

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Material

TxDOT Type IV low-viscosity, gravity-fed epoxy typically is made by combining two proprietary liquid components in the ratio required by the 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 when specified on the plans or if authorized by the Engineer.

Provide dry, coarse sand to apply to deck surface when flood coating with sealant is specified.

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Repair Procedure

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  • Surface Preparation.
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    • Remove contaminants where the epoxy will be pooled around the crack, including laitance, oil, dust, debris, or other foreign particles.
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    • The epoxy will not work effectively in cracks that are filled with contaminants. Use compressed air to remove debris and other foreign particles from inside the crack.
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    • Ensure that concrete is sufficiently dry prior to applying the epoxy.
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    • For cracks that extend completely through the concrete section, seal the crack on the back or underside of the concrete to prevent the epoxy material from flowing out. Remove the surface sealer after the gravity-fed epoxy has had adequate time to cure.
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  • Mixing.
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    • Measure the proper quantity of each component per the manufacturer’s requirements, then dispense into a clean container. Do not estimate the proper amounts while adding the different components.
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    • Mix the components thoroughly for 3 minutes using a low-speed electric drill (400 – 600 rpm) and a clean “Jiffy” type mixing paddle. Ensure that the material is well-blended after mixing.
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    • Do not mix gravity-fed epoxy material by hand.
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  • Application.
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    • Pour sealant directly on cracks within the treatment area. Distribute the sealant over the surface to be treated within the lot size that can be accommodated for the particular sealant being sealed. Brush grooved cracks with heavy nap roller. Pull additional sealant material onto crack using squeegee or broom and then re-brush crack with heavy nap roller.
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    • If applying on grooved surface, remove excess sealant from deck surface and brush or broom out epoxy from texture grooves. Do not allow the ponded sealant to stiffen, and do not allow sealant to remain in the grooves on the bridge deck.
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    • Broadcast or spread sand onto the still tacky sealant within 10 to 20 minutes of the last application of sealant. Apply the sand at a rate of 15 to 20 lb. per 100 sq. ft. of area.
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    • Contractor may propose alternate application techniques that meet manufacturer requirements.
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    • When sealing isolated cracks and flooding the surface will not be done, install temporary dams around the crack so the pressure head of the gravity-fed epoxy will build up. Install the dams using a material that will prevent the epoxy from spreading over the concrete surface, and that can be removed after the repairs have been completed. Leave the pooled epoxy in place for at least one hour. Refill the dammed area as necessary if the epoxy drains completely into the crack.

      NOTE: Although a wide variety of materials will work for constructing temporary dams for pooling gravity-filled epoxy, plumbers putty is a good option because it does not require any curing time and it can be very easily removed after use.

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Commentary

Gravity-feeding epoxy is an effective method for filling the tops of cracks. However, the depth of penetration can be variable. Limit its use to shallow cracks or locations where deeper cracks are acceptable, but protection from water and chloride infiltration is necessary.

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