Appendix E – Method for Epoxy Crack Injection

Step 1:

Clean the cracks

Oil, grease, dirt, efflorescence and concrete particles will prevent desired epoxy penetration and bonding. Mechanical means or appropriate solvents should remove these foreign substances. Acids and corrosives are not permitted. Cracks should be water-jetted to clean out solvents and then blown out with compressed air and allowed to air-dry.

Step 2:

Seal the surface

Surface cracks are to be sealed in order to prevent leakage of the epoxy before it has gelled. Where the crack face cannot be reached, but where there is backfill, the backfill material is often an adequate seal. Where

extremely high injection pressures are needed, cracks should be cut out to a depth of about 13mm and about 20mm wide in a V-shape. This groove should then be filled with epoxy and finished flush with the concrete surface. Step 3:

Installation of injection ports

Three methods are generally used:

(a) Drilled holes with a fitting inserted. Commonly a pipe nipple or tire valve is bonded into the hole

(b) Bonded flush fitting. These fittings are commonly used when the cracks are not cut before sealing

(c) Interruption in seal. With the use of a special gasket epoxy can be injected directly into the crack

Step 4:

Mixing of epoxy

Mixing takes place continuously or in batches. When using the batch mixing procedure, care should be taken that the amount mixed should match the amount that can be used before gel of the epoxy takes place. In the continuous mixing system the two components of the epoxy pass through

individual driving and metering pumps before passing through an automatic mixing head. Preferably injection equipment should be equipped with

sensors on both the component A and B reservoirs that will automatically stop the machine when only one component is being pumped to the mixing head.

Step 5:

Injection of the epoxy

Hydraulic pumps, paint pressure pots and air-actuated caulking guns can be used. Pressure of injection should be selected carefully. Increased pressure often has no significant increase in filling rate of the crack. Excessive

injection pressure may cause propagation of the crack, causing further damage to the structure. Vertical cracks should be filled from the lowest port upwards. When epoxy reaches the upper port, the lower one can be capped and injection continued at the upper one. Horizontal cracks are filled in a similar manner – from one end to the other. A crack can be regarded as filled when the injection pressure can be maintained, if not, epoxy is still filling the crack, or a leak may be present.

Step 6:

Seal removal

The epoxy seal can be removed by means of grinding or other appropriate method. Fitting holes should be patched with an epoxy compound.

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