Epoxy Injection
Epoxy injection is a procedure to “weld” cracks in concrete together, which improves its performance and extends its useful life. It involves a low viscosity epoxy resin mixed according to specifications and pumped under pressure through drilled holes that intersect the crack, and/or through injection ports mechanically or epoxied in place over the crack [1].
Advantages:
- Tenacious bond; a good adhesive
- Can be made very moisture tolerant
- Good resistance to wear
- Good to about 180F
- Outstanding resistance to alkali, inorganic acids and many solvents
- Can be made to cure under cold, wet conditions
- Excellent adhesion to most materials
- Can be highly filled with low shrinkage
The injection method generally consists of drilling holes at closer intervals along the cracks, in some cases installing entry ports, and injecting the epoxy under pressure.
Application Procedure [2]
1) Surface preparation
Remove skim coat or plastering along the cracks to expose concrete surface. Dirt in the cracks should be removed before applying any material. This can be done by blowing compressed air into the cracks. Clean the crack that have been contaminated by flushing with water or some other effective solvent. Water or solvent is then blown out using compressed air or adequate time is provided for air-drying.
Remove dust particles with a wire brush. Wipe up oil with thinner.
2) Sealing of Surface and adhesion of plug
Seal crack at lengths, stopping at intervals of 300mm for plug adhesion. (Interval length depends on crack width and depth).
Push plugs onto crack until sealing material comes out of the four holes of the plug.
3) Seal Curing
Allow seal to cure.
4) Installation of epoxy pipes
Drill holes approximately 3/4 in. diameter and fix pipe nipple or tire valve with epoxy adhesive
5) Preparation of epoxy
Mix the epoxy well according to the manufacturer’s instructions usually with a mechanical stirrer. Care must be taken to mix only the amount of adhesives that can be used prior to commencement of gelling of the material. When the adhesive begins to gel, its flow characteristics begin to change and pressure injection becomes difficult.
6) Injection of epoxy
Inject the epoxy with a constant pressure until epoxy level reaches the entry port above. Stop when the pressure indicator rises to the expected level. Proceed to the next point.
7) Allow the grout to cure.
8) Finishing
Remove injector and grind off sealing material.
References
[1] Maintenance and repair of concrete structures, Engineering Manual 1110-2-2002, US Army Corps of Engineering, Washington.
[2] http://www.unifor.com.sg/