Epoxy Injection Grouting of Cracks in Structures

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Epoxy injection grouting is a method of repairing cracks in concrete structures. Equipment required for epoxy based injection grouting, procedure for grouting will be discussed here. Epoxy based grouting is preferred to cement due to property of quick setting, very low shrinkage, excellent adhesion, high strength, low viscosity to penetrate even hair cracks and good resistance to most of the chemicals. But epoxy grouting being expensive, should be used when cement grouting is not suitable for crack repair for the required functioning of the structure. Epoxy grouting is done based on the type of crack, width and depth of crack in concrete structure. Grouting of wide cracks requires large quantity of grout materials. In such cases fillers are used to fill the cracks before epoxy grouting. Silicon four is one of the filler material used. The filler material to be used should be based on the manufacturers specification. Very low viscosity epoxy resin and hardener composition is used for injection grouting of cracks. Based on the width of crack, depth and extent of cracks and other relevant details, the viscosity of the resin hardener mix, their proportions, pot life, application procedure etc. is selected in consultation with the manufacturer. The epoxy mortar selected should not be susceptible to fire and explosion during injection process and must be stable under varying climatic conditions.

Equipments Required for Epoxy Injection Grouting

• Hole drilling equipment, can be pneumatic or electric based.
• Pressure injection equipment of standard make with necessary control valves and gauges, etc.
• Air compressor of capacity 3 to 4 cum/min. and pressure of 10 kg/cm².
• Polythene or metal pipe pieces 6 - 9mm diameter.
• Polythene / plastic containers for mixing the epoxy formulation.
• A portable generator.

Procedure for Epoxy Injection Grouting in Concrete Structures:

Surface preparation is the first step in repair of cracks in concrete. The area to be epoxy grouted should be made free from oil, grease, dust and all loose and unsound materials. Then cracks in concrete is cut open into a 'V' groove about 10mm deep by mechanical or manual method. Loose materials are removed by using compressed air. The ‘V’ groove cut is fully sealed with epoxy mortar at least one day in advance before epoxy injection. Nails are driven into the cracks at 15 cm to 50cm intervals along the crack. Holes of 7 - 10 mm diameter is then drilled along the cracks and copper or aluminium or polythene pipe pieces of 6 - 9 mm diameter is fixed as grout nipples around the nails and allowed to rest on them. Epoxy formulation is injected from the bottom most pipe. All other pipes, except the adjacent ones are blocked by wooden plugs. The injection is done using suitable nozzles connected to air compressors or by hand operated modified grease guns. Pressure of 3.5 to 7 kg /cm² is normally used. As soon as the epoxy comes out from the adjacent open pipes, they are plugged and the pressure is increased to the desired level and maintained for 2 to 3 minutes. The injection nozzle is then withdrawn and the hole sealed with epoxy mortar. This operation is repeated for the other pipes also. Any resin that remains or overflows the pipe is scraped off with a metal spatula and the surface cleaned with a rag soaked in non-inflammable solvent.

Due to restriction of pot life, it is advisable to mix only small quantities of epoxy at a time. All proportioning should be by weight and mixing should be thorough.

Low viscosity resins may be adopted for thin cracks. A record of materials used for epoxy grouting should be maintained.