Epoxy injection grouting is a technique used for repairing cracks in concrete structures. This method is preferred over cement grouting due to its quick setting property, low shrinkage, high strength, and good resistance to chemicals. However, it is more expensive, so it should only be used when cement grouting is not suitable for crack repair.
The equipment required for epoxy injection grouting includes a high-pressure injection pump, hoses, packers, and epoxy resin and hardener. The process of grouting is determined by the type, width, and depth of the crack in the concrete structure. For wide cracks, fillers such as silicon four are used before epoxy grouting.
The filler material used should be chosen based on the manufacturer’s specifications. A very low viscosity epoxy resin and hardener composition is used for injection grouting of cracks. The viscosity of the resin hardener mix, their proportions, pot life, and application procedure are selected based on the width and depth of the crack and other relevant details in consultation with the manufacturer.
The selected epoxy mortar should be stable under varying climatic conditions and not susceptible to fire and explosion during the injection process. For grouting of wide cracks, a large quantity of grout material is required. Therefore, the appropriate fillers must be used before epoxy grouting.
Equipments Required for Epoxy Injection Grouting
The equipment required for hole drilling can either be pneumatic or electric. Additionally, pressure injection equipment with control valves and gauges is necessary. An air compressor with a capacity of 3 to 4 cubic meters per minute and a pressure of 10 kilograms per square centimeter is also required.
Polythene or metal pipe pieces with a diameter of 6 to 9 millimeters are needed as well. In addition, polythene or plastic containers will be necessary for mixing the epoxy formulation. Finally, a portable generator is required to power the equipment.
Procedure for Epoxy Injection Grouting in Concrete Structures:
Repairing cracks in concrete involves several important steps, and surface preparation is the first one. To ensure a successful repair, it is essential to remove any oil, grease, dust, and loose or unsound materials from the area to be repaired. Once the surface is clean, the cracks in the concrete must be cut open into a ‘V’ groove approximately 10mm deep, either manually or mechanically. Compressed air is then used to remove any loose materials.
Next, the ‘V’ groove cut is sealed completely with epoxy mortar at least one day before the epoxy injection. Nails are driven into the cracks at intervals of 15cm to 50cm along the crack. Holes of 7 – 10 mm diameter are drilled along the cracks, and pieces of copper, aluminium, or polythene pipe, measuring 6 – 9 mm in diameter, are fixed as grout nipples around the nails and allowed to rest on them.
Epoxy formulation is injected from the bottom-most pipe, with all other pipes except the adjacent ones being blocked by wooden plugs. The injection is performed using suitable nozzles connected to air compressors or by hand-operated modified grease guns. Typically, a pressure of 3.5 to 7 kg /cm2 is 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.
After the injection, the nozzle is withdrawn, and the hole is sealed with epoxy mortar. This process is repeated for the other pipes as well. Any resin that remains or overflows from the pipe is scraped off with a metal spatula, and the surface is cleaned with a rag soaked in non-inflammable solvent. By following these steps, cracks in concrete can be effectively repaired using epoxy grouting.
When working with epoxy, it is important to be mindful of its pot life, which is the amount of time it takes for the material to begin to harden after it is mixed. To avoid wasting epoxy and ensure proper curing, it is advisable to mix only small quantities of epoxy at a time.
To accurately measure the components of the epoxy, it is recommended to use a scale and weigh the materials rather than relying on volume measurements. Thorough mixing is crucial to ensure that the epoxy sets properly.
For thin cracks, low viscosity resins may be used. These resins are less thick and more easily flow into small spaces, making them ideal for filling narrow gaps.
To keep track of the materials used for epoxy grouting, it is important to maintain a record. This helps ensure that the correct materials are used in the correct quantities and can be useful for future reference.