Why Low-Pressure Concrete Crack Injection Wall Repair?

The Standard method of Low-pressure Crack Injection with Polyurethane or Epoxy

When repairing foundation walls

The effective way is to use low-pressure crack injection for basement wall crack repair. Using either epoxy or polyurethane foam - is a gradual introduction of the liquid polymer into the crack at low pressures (20 to 50 psi). This method requires some patience, but it allows the applicator to monitor the injection process and ensure that the crack is completely filled. An incomplete injection of a crack is the most common reason for crack repair failure. This method of foundation repair has become the industry standard.

Typical Foundation Crack Repair

To fill a typical concrete foundation crack in a residential basement wall, injecting at pressures above 50 PSI may not be effective. Liquids prefer to take the path of the least resistance. At higher pressures, the liquid can have enough force to travel up the crack without completely filling the wall crack to the soil side. This is often narrower than the front of the crack. The user can determine how the crack is injected by watching the progress of the liquid traveling from surface port to surface port. 

During injection, It begins to fill from the bottom and when the product appears at the next port above, that section is completed. At high pressures, the liquid can overcome gravity and go port to port without filling small sections of the wall crack. Injection ports are spaced at the same thickness of the wall. An eight-inch thick concrete wall will have the surface ports placed 8 inches apart.

The Recommended Method for Repairing Foundation Cracks

The following is a basic guide for cracked foundation repairs and waterproofing procedures for poured foundation cracks. The methods of repair have been compiled from several professionals throughout North America who utilize epoxies and polyurethanes for reconstruction. In general, Epoxy can be used in all cases and for structural repair, and polyurethane foam can be used for non-structural leaking foundation cracks. Polyurethane can be more cost-effective for leaking foundation walls.

Concrete Surface Preparation

 Remove loose or flaking concrete with a wire brush or grind the surface to ensure proper bond of the surface seal paste. Always wire brush the surface prior to applying surface seal no matter what method of removal is used (i.e. grinding, wire brushing, scraping, etc). The surface must be dry to use epoxy paste and surface crack injection ports.

Installing Injection Surface Ports

Surface ports are most commonly used for low-pressure injection into concrete wall cracks. The ports placed 8-10 inches apart on 10-inch width concrete. Corner ports are used with wider foundation cracks or in corners where surface ports cannot mount flat. Specialized corner ports are also a viable approach for hard-to-reach corners. Surface ports eliminate the chore of drilling into the concrete, reducing labor, time, and clean-up.

Sealing the crack surface

Use Epoxy surface seal paste to seal over the surface ports and exposed cracks. The paste is formulated to cure in anywhere from half an hour to two hours. The more paste that is mixed at one time, the faster it will cure. Mix in small amounts to avoid waste.

The fast-setting paste gives an excellent surface seal with high bond characteristics which allows injection easily at 30-50 PSI pressures. The entire exposed crack should be covered with surface seal leaving only the porthole uncovered. Seal paste should extend one to two inches on either side of the cracked surface and be feathered edged to reduce seepage.

Surface Seal

The surface seal paste is cured and ready for injection when you cannot make an impression in it with your fingernail. In any case, do not begin injection until the surface seal resists your fingernail. Structural cracks move when concrete goes through a temperature cycle, which occurs normally over a 24-hour period. Surface seals will frequently crack from the movement if not restrained by epoxy injection. This condition requires the scheduling of injection within six hours after sealing the crack.

Injection Material, Tubes, and Dispensing Systems

After the surface, the crack has been sealed and the injection ports installed on it. It is a good idea to flush water into the ports to clean out the crack and prepare for an injection of Polyurethane. Flushing not required for epoxy injections. Using water to flush into the surface ports can test how well the surface was sealed. This will help, as you do not want to lose product from a leak, but not required if injecting Epoxy. Generally, our products are dispensed with a standard dual-tube injection dispensing tool supplied in the more advanced kits.

Foundation Crack Repair Injection

Start the Injection at the lowest port on the wall until the epoxy or polyurethane foam begins to flow from the port above it. Plug with the surface port cap provided and move up to the next port. Repeat this process until the entire crack has been filled with epoxy or polyurethane. Epoxy injections should be re-applied after 20 min. This will replace any product that has escaped or drained out into the soil on the outside. Most of our Epoxy gels after 20 minutes and will allow for re-injection for lost product.

Application of Injection Materials

Wide cracks will accept epoxy or urethane foam freely and do not require high pressure. Tight cracks, however, also require slow, continuous pressure of 20-50 PSI to reduce the possibility of leaks or blow-outs. If you feel pressure building within the cartridge, allow time for the material to seep into the crack before applying additional pressure. Remember, liquids cannot be compressed and need time to penetrate the crack. The optional spring-loaded compression spring on the “Jake” dispensing tool will push the material into the crack. Pump the trigger mechanism only as required to keep the compression spring actuated.

Hairline cracks will require special care. Hairline cracks will accept a smaller volume of epoxy in a given period of time but will penetrate a larger area of crack surface. Patience is required to effectively seal a hairline crack. Ultra-small cracks require our Ultra-low Viscosity Epoxy.

Finishing the Repaired Crack Repair

The injection surface ports can be removed after 1 to 2 days at room temperature when using epoxies. One to two hours with urethane foam. This allows adequate time for the epoxy or urethane foam to cure and penetrate into the cracks. The ports can be removed by striking with a trowel or hammer. If cosmetic appearance is preferred, the surface seal can be chipped, ground (with sanding disk), or burned off. The surface seal can be painted if grinding is not desired. Wear protective clothing and breathing apparatus while grinding. If cosmetic appearance is preferred, the surface seal can be chipped or grounded off (with sanding disk).

To save the time of grinding or chipping off the surface seal, NextStar offers a removable surface seal, 322 Seal-n-Peel Surface Seal. It easily removes from the top in one easy step, leaving an almost invisible repair job.

Special Crack Repairs

Snap ties or wire tie repairs and very small concrete cracks injected with Ultra-Low Viscosity Epoxy require up to 4 days to cure. Optionally auto-injectors can be used to allow for extended injection times that will save labor and time. This also applies to gravity feed repairs, such as concrete pillars, concrete statues, and other architectural concrete items.

Product Offers

Nextstar Technologies offers many different solutions to solve nearly any problem for the homeowner or contractor alike. Call us today if you need any assistance choosing the correct solution to your cracked or broken concrete foundation needs.

Phone 866-445-3986 NextstarTech.com and NextStar.ca