Epoxy Injection
Repair using epoxy injection
One of the most versatile, crack repair method is epoxy injection. This method has been successfully used in buildings, bridges, dams etc., due to following characteristics:
– Outstanding adhesive qualities to materials such as concrete and steel
– Resistance to a wide range of acids and alkalis and other chemicals, except acids such as nitric which have high oxidizing characteristics
– Rather vulnerable to organic solvents
– Low shrinkage when the compound course and changes from the liquid to the solid state
– High coefficient of thermal movement compared with concrete
– High compressive, tensile and flexural strength
– Appreciable loss of strength at temperatures over about 80oC
– High rate of gain of strength which can be varied to suit the particular application
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.
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
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 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.
The site conditions under which the resin will be applied must be stated to the formulator. Unless specially formulated, most epoxide resins must be applied to dry surfaces and the ambient air temperature and relative humidity during application must be kept within fairly narrow limit.
Quality Checking of Grouting
The following guideline can be used to check the efficacy of the completed injection process:
Replace failed Waterstop around existing Pipe Penetrations
(1) Hack old grout or deteriorated concrete from the circumference of the pipe penetrations until sound area is found.
(2) Clean to remove grease and dirt using a wire brush, air blower, or vacuum cleaner to eliminate any remaining dust or loose particles. Provide surface preparation to receive the new waterstop or grout according to the specification of the supplier..
(3) Installation of the repair products according to the specification of the supplier.