How to inject polyurethane and epoxy resin (Part II)

Polyurethane resins have a very short life after mixing, so mixing should be done when all components are ready and injection of special single-stage equipment such as that used for injection of epoxy resin in large repairs. Existing repair instructions do not allow the injection of 100% pure resin. A mixture of water and resin or type A and type B resin must be used in each step. This equipment component of the resin system causes mixing to take place just before the resin injection point into the crack. The size of polyurethane resin injection equipment varies from small and manual types to large commercial equipment that can inject large volumes of resin per hour (Figures 63 and 64). The pumping pressure of polyurethane resin injection equipment may be more than 3000 psi. Several manufacturers provide high-quality equipment, and it is rare to need to design another type of equipment for a repair project.

D – Execution method: The success of repair projects with resin injection directly depends on the experience and knowledge of the executive forces. A contractor selected for injection repair must have three years of experience in similar contracts or be involved in at least five projects. In a repair project, a less experienced contractor can be used if the manufacturer agrees to monitor the project’s implementation process full time and the manufacturer has five years of experience in providing resin to similar projects.

  1. How to apply epoxy resin flooring by pressure injection: The purpose of injecting epoxy resin flooring for homes is to fill the crack and maintain it until the curing and hardening stage is completed. The first step in the resin injection process is to thoroughly clean the adjacent concrete surfaces of loose, worn concrete and contaminants. The injection site and entrance are then inspected. Different types of injection methods can be used:
  • If the cracks are clearly visible and relatively open, the injection pack can be installed at appropriate intervals by direct drilling on the crack surface. When drilling to install the packer, care must be taken to prevent the formation of dust and remnants of drilling and thus blockage of the path and opening. There are special vacuum drills for this purpose. The crack surface between the packers should be closed with epoxy putty to allow the resin floors to harden in the crack. The injection operation starts from the lowest pack and continues to the highest pack.
  • A better way to install the pack is to alternate drilling holes from the top and bottom of the crack at an angle until it cuts and crosses the crack surface. This method ensures that the hole created intersects with the crack, even if cracks or slopes are in the crack. Then, as mentioned above, the surface of the crack should be closed with putty or epoxy paste.

Epoxy resin should be injected relatively low to allow the resin to move and fill all cavities. The use of high pressure in the resin injection closes the injection path and does not fill the crack, which is a sign of inexperience of the relevant contractor. The best way to ensure the quality of epoxy resin injection operations is to obtain and approve a detailed plan of preparation and execution of operations from the contractor and perform small-scale corrugation of the resin injection site in concrete. If more than 90% of the empty holes in the concrete are filled during the injection operation, they can be considered a complete injection. If the injection is not complete, the contractor must perform the re-injection operation without receiving any cost from the employer.

(2) Method of application of polyurethane resin by pressure injection: The main principles of polyurethane resin injection are based on controlling water penetration by using resin injection under pressure and closing cracks. Most of the issues related to polyurethane resin injection are similar to the cement slurry injection method.

To better control water flow, even holes drilled for injection on the concrete surface should be possible. The milky pack can be used on the holes to eliminate crack water pressure on the concrete surface during injection. To prevent the resin from leaking out too much during injection, the crack should be temporarily sealed using a wooden wedge, rock wool, hemp rope with resin, or epoxy putty.

The holes made for the resin injection should be alternately on the crack sides and with a maximum distance of 24 inches from each other. The holes are angled and 8 to 24 inches deep (the holes should be as deep as possible depending on the thickness of the concrete. Different packers (Figure 66) or Milky packs are used depending on the injection method and the amount of water.

Injection of polyurethane resin should be done according to predetermined procedures and steps. The injection system in terms of injection intervals is the same as successful cement slurry injection intervals. In this system, injection is done first from the initial holes and then from the middle holes. For example, first, the resin is injected through the initial holes of the sides, and then the third hole is drilled and injected in the middle of them. The injection pressure should be the minimum pressure suitable for moving the resin and filling the crack. However, a pressure of PSI 1500 to PSI 2000 is usually used for injection. The injection into a hole should be stopped when the flow of constant pressure injection has been stopped for a period of 10 to 15 minutes. This method in completing and stopping the injection provides the necessary guarantee for completing the crack, compaction, and proper repair. It is a mistake to stop injecting water as soon as it stops. If this method is used, performance can be improved by injecting a lower density resin under hydrostatic pressure and re-injecting in the event of a leak.

It is also common to use intermittent injections to seal cracks with high water intensity. In this method, an initial injection step is performed in several pre-selected packers, and after 15 minutes to 2 hours, the next injection step is performed. Sealing cracks with large volumes of water flow may require several stages of injection operations. Therefore, the exact number of injections required is unknown.

In polyurethane domestic resin flooring injection, it is done with different ratios of water to resin. For high water flows, a 0.5: 1 resin to water ratio can be desirable. It should be noted that the said resin and water may be mixed within 1 inch to 5 feet of the injection pipe and mixed before the exit, and the foaming reaction takes place after the current enters the network of cracks. Long packers can be used to inject resin in deep parts of the structure. If the mixed resin is used for injection in such holes, the reaction will occur along the hole before the resin reaches the desired crack depth. These special packers (Figure 67), by moving the components of the injected resin separately, allow the resin to move to the end hole of the packer in the depth of the crack.
In doing so, they need to use experienced contractors, and technical consultants become more important.

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

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