How to inject polyurethane and epoxy resin (Part I)

Among the methods of repairing concrete structures is an injection of epoxy resin and polyurethane.
Resin injection: Resin injection is used to repair only concrete with cracks or spots, joints, and wet cracks. Two main methods are used to improve concrete using the resin injection technique:

A – Epoxy resin: Epoxy resins are solid treated with high strength and relatively high modulus of elasticity. The adhesion of epoxy resins to concrete is such that they can restore the original structural strength of cracked concrete with proper implementation. Epoxy resin is used to seal wet cracks. However, due to the low curing speed of epoxy resins, especially at low temperatures and in the presence of high water flow, it can not be used for sealing. Cracks in which epoxy resin is injected should be between 0.005 inches and 0.25 inches wide. Injecting epoxy resin into cracks 0.005 wide is difficult and impossible, and it is also challenging to maintain the injected resin in endeavors wider than 0.25 inches. However, this can sometimes be done successfully with high-density epoxy resin floors . Treated epoxy resins have a brittle state, with adhesion strength more significant than the shear and tensile strength of concrete. If these materials are used to reconnect cracked concrete exposed to loads greater than shear and tensile strength, it is to be expected that cracks will reappear along the epoxy joint. In other words, the epoxy resin should not be used to repair active cracks.
Success in applying epoxy resins to wet cracks varies. There are several unique and evolving techniques for re-bonding and sealing aqueous cracks with epoxy resin. These particular methods and techniques are very specialized and technical and are used in certain places. These methods are used only in repair projects when, after review and analysis, we conclude that other existing and standard methods are not responsive and suitable for repair.

B- Polyurethane resins: Polyurethane resin flooring is used to seal and eliminate water leakage from cracks and joints in concrete. They can also be injected into cracks that will allow small displacements. Except for solid two-component polyurethane systems, such systems have low strength and should not be used to reattach cracks. Polyurethane resin should not be used and injected into cracks less than 0.005 inches wide. So far, no limit has been set for the maximum crack size for injecting polyurethane resins. Polyurethane resins are available with a considerable variety in terms of physical properties. Some polyurethane resins become flexible after curing. Other systems of cured polyurethane resins become solid with relative flexibility. The high density that can be used to reattach seams with the possibility of Foamed polyurethane resins needing water to start the curing process is natural to use them for repairing only exposed to water or wet. To date, no standards have been set for polyurethane resins, such as those found invalid standards for epoxy resins. Due to the lack of standing on the one hand and extensive changes in the physical properties of polyurethane resins, on the other hand, it is necessary to be very careful in choosing this resin for repairing concrete. A practical guide for this type of resin is handy, and It is not successful. Some research and laboratory centers are conducting studies and research on this valuable type of resin. If you need advice and guidance on implementation methods, you can get help from these centers.

inject polyurethane resin
inject polyurethane resin

Due to the high cost of the injection method, these methods are not usually used to repair shallow and dry cracks. The technical and executive specifications of injectable resins are calibrated in the attached repair and restoration standards.
A- Preparation: Cracks, joints where resin is injected should be thoroughly cleaned of all contaminants and organic matter. Different methods with different efficiencies are used to clean the cracks. Repeated use of compressed air injection, and After that, water is an excellent way to wash and clean shots exposed to water leakage from the holes created for injection operations. Several practitioners have reported successful use of soaps in rinsing with water. Complete removal of the soap from the cracks is difficult, so it may not be reasonable or satisfactory to use it due to these problems. The use of acids to clean cracks in reconstruction operations is not permitted. Epoxy resin cracks, which are used to repair and re-adhesion, should not be injected with water. Epoxy domestic resin flooring can also be used for grouting in wet cracks to have higher adhesion when bonded to dry concrete.
B- Materials: Epoxy resin used for injection must contain 100% solids and comply with valid standards. If the purpose of the injection is to restore the original load-bearing conditions of the design, epoxy resins of type four should be selected and used. However, if the purpose of the repair is not to restore the original portability, epoxy resins of type one are sufficient. The use of any solvent or non-reactive diluent in polyurethane resin is not allowed.
Polyurethane resin used to repair cracks is a two-part system consisting of 100% of polyurethane resin as the first part and water as the second part. When mixed with water and treated in the form of foams, polyurethane resins are flexible or gel, which is related to the mixing ratio of the resin with water. However, if the polyurethane resin is mixed with a suitable amount of water, the cured and hardened resin foam has a minimum tensile strength of 20 psi with adhesion to 20 psi concrete and a minimum length of 400% during tensile rupture. Before using and injecting polyurethane resins, a certificate must be obtained from the manufacturer stating that the product has the minimum specifications.
C- Injection equipment: Resins can be injected with different types of equipment. In small repairs with epoxy resin, any system that can properly and successfully inject the required epoxy resin can be used. In these systems, two components of epoxy resin flooring for homes can be mixed in a separate container before application. Due to the short life of epoxy resin after mixing, this method can be critical in terms of time.
In large epoxy resin injection jobs, it is usually necessary to use a single-stage injection method. Two components of the epoxy are pumped separately from the tank to the nozzle and mixed there. Mixing in the nozzle makes it possible to mix the two components next to the repaired crack and then inject. The epoxy used in this method must first have a low viscosity, and the operation time must be carefully controlled. . Different manufacturers have their equipment (Figure 62 -. The set of epoxies and various methods developed allows repairs to be carried out in adverse conditions with satisfaction and success. If repairs are needed). These companies should be contacted mainly by the epoxy resin injection method.

If you need more information, contact our resin flooring company .

Photo Credit: Adobe Stock

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