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As compared to cement, epoxy is quick setting, has very low shrinkage, excellent adhesion, high strength, low viscosity to penetrate even hair cracks and good resistance to most of the chemicals. However, epoxy grouting, being expensive, should be used only when it is techno economically justified.

Composition : The epoxy grout consists of an epoxy resin and a hardener which react chemically when mixed. Epoxy resins are thermosetting and by suitably proportioning of the mix of resin, hardener and thinner (if necessary), the viscosity of the mix can be varied to suit all types of conditions. Grouting of wide cracks require large quantity of grout material. In such cases suitable fillers e.g. dry silicon flour etc. can be added based on manufacturer's recommendations.

Specification : Considering the width, depth and extent of cracks and other relevant details, the viscosity of the resin hardener mix, their

proportions, pot life, application procedure etc. should be chosen in consultation with the manufacturers. The shear strength on a specimen of two mild steel plates should not be less than 100 kg/cm2. The epoxy mortar should not be susceptible to fire and explosion during injection process and must be stable under varying climatic conditions.

Test certificates : The supplier should produce test certificates for Pot life test, strength test and shear test from approved test houses.

Equipments required :

Pneumatic or electric hole drilling equipment.

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 dia.

Polythene/plastic containers for mixing the epoxy formulation.

A portable generator.

Procedure for epoxy grouting (Annexure 2/8)

The area to be grouted should be dry and free from oil, grease, dust and all loose and unsound materials.

All cracks should be cut open to a 'V' groove about 10mm deep by mechanical or manual means. Loose material should be removed by using compressed air and groove fully sealed using epoxy mortar at least one day in advance.

Nails are driven into the cracks at 15 cm to 50cm intervals along the crack.

Holes of 7 - 10 mm dia should be drilled along the cracks and copper or aluminium or polythene pipe pieces of 6 - 9 mm dia fixed as grout nipples around the nails and allowed to rest on them.

Epoxy formulation is injected from the bottom most pipe, keeping all other pipes, except the adjacent ones, 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 per sq. cm is normally used. As soon as the epoxy comes out from the adjacent open pipes, they are plugged and the pressure 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 copper 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 consumed should be maintained.

Precautions while handling epoxy resins.

Manufacturer's detailed instructions should be followed for safe handling and processing.

Direct skin contact should be avoided and hand gloves (rubber) and protective goggles should be used.

The grease gun syringe should be washed with acetone immediately after use.