The Epoxy Grouting is used for all structures built of stone or brick masonry or concrete gets affected by prolonged weathering action. The ingress of moisture associated with chemicals such as nitrates, chlorides, and sulphates accelerate the deterioration of the structures.
If the structures are built in the proximity of sea or on aggressive ground soils, then then the process of deterioration further accelerates.
Stonemasonry built with interior stones such as sandstones or laterite etc. suffers spalling by the ingress of moisture. Similarly, brick masonry built with porous bricks suffers spelling action. Leaching of cement and lime due to poor drainage further deteriorates the structures leading to their failure.
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It is a well-known fact that adhesion between old damaged masonry or concrete and newly laid masonry or concrete is very poor. Besides this, cement does not get enough time for setting and hardening before traffic is allowed over the newly repaired structures. This leads to frequent repairs at the same spot.
To overcome this drawback Epoxy grouting may be adopted.
Advantages of Epoxy resins
Epoxy resins have the following advantages over cement as the bonding material.
1. Quick setting 2. Low shrinkage
3. Low viscosity to fill up hair cracks 4. High adhesion to any material
5. Stable at all temperatures.
Epoxy resins consist of condensation products of Epichlorohydarin and Bisphenol-A, They are thermosetting with high adhesive strength. Practically they have no shrinkage and possess good resistance to wear and to most of the chemicals. The resin and hardener have to be mixed for starting the chemical reaction for hardening. The pot life of the mixture varies between 30 minutes to 120 minutes depending upon the ambient temperature
and the type of hardener. For preparing mortars, silica flour is added. Manufacturer’s recommendations should be followed for the best application procedure, temperatures, and pot life. For mixing Epoxy components plastic vessels should be used. Epoxy Grouting operation is shown in Fig.
Procedure for Epoxy grout
Followings are the requirement for the surface over which epoxy is to be applied
1. Strong and sound
2. Dry and clean
3. Free from oil, grease, and lose material
4. Latency free
5. Dust and debris free
External materials must be removed from the surface. If necessary compressed air may be used for this purpose. For thin cracks, low viscosity resins may be used. For vertica1 cracks to ensure complete filling the grouting should be done from the bottom to the top.
Before grouting a V-shaped groove is made all along the crack and all loose pieces of concrete are removed by using a jet of air. Nails are driven into the crack at interval 15 to 30 cms. Copper or aluminum pipes or M.S. sheath 40 to 50 mm long and 6 to 9 mm diameter arc inserted around the nails and allowed to rest on them.
Now all the cracks arc sealed along the groove with Epoxy putty. The tubes provide an unobstructed passage for the Epoxy resin into the cracks and also for an outlet for the entrapped air.
Epoxy of suitable formation is injected from the bottom-most pipe, keeping all pies except the adjacent one blocked by wooden plugs. For injecting the epoxy, suitable nozzles connected to an air compressor or another suitable machine may be used.
The pressure of 3.5 to 7 kg/cm2 usually is applied. As soon as Epoxy starts coming out from the adjacent open pipe, it is plugged and the pressure is increased to the desired level and maintained for 2 to 3 minutes.
This operation is continued for the other pipes also. Any surplus resin from copper pipes is scraped off with a spatula and the surface is cleaned with a rag soaked in noninflammable solvent. The worker doing this job should wear rubber gloves. The equipment used should be washed with acetone immediately after the completion of work.
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For a superficial network of fine cracks that do not endanger the stability of the structure, 300 to 4000-micron thick coating of solvent-free epoxy is sufficient. In case of wider cracks, which are not expected to endanger the suitability of structure can e partially filled with Epoxy putty, which a mixture of Epoxy, hardener and china clay.
Epoxy being a costly material, its use should be restricted to areas below and around the bed blocks, cracks in RCC/PSC slabs or girders, etc., where the dynamic forces are likely to be transmitted.
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