Epoxy injection is an economical method of repairing non-moving cracks in concrete walls, slabs, columns and piers and is capable of restoring the concrete to its pre-cracked strength. Prior to doing any injection it is necessary to determine the cause of the crack. If the source of cracking has not been determined and remedied, the concrete may crack again.
Clean the crack and the surface surrounding it to allow the paste-over to bond to sound concrete. At a minimum, the surface to receive paste-over should be brushed with a wire brush. Oil, grease or other surface contaminant must be removed in order to allow the paste-over to bond properly. Take care not to impact any debris into the crack during cleaning. Using clean, oil-free compressed air, blow out the crack to remove any dust, debris or standing water. Best results will be obtained if the crack is dry at the time of injection. If water is continually seeping from the crack, the flow must be stopped in order for epoxy injection to yield a suitable repair. Other materials such as polyurethane resins may be required to repair an actively leaking crack.
For many applications, additional preparation is necessary in order to seal the crack. Where a surfacing material has been removed using an acid or chemical solvent, prepare the crack as follows:
If a coating, sealant or paint has been applied to the concrete, it must be removed before placing the paste-over epoxy. Under the pressure of injection, these materials may lift and cause a leak. If the surface coating is covering the crack, it may be necessary to route out the opening of the crack in a “V” shape using a grinder in order to get past the surface contamination.
While this method may appear to leave some ports uninjected, it provides maximum pressure to force the epoxy into the smaller areas of the crack. Moving to the next port as soon as epoxy appears will allow the epoxy to travel along the wider parts of the crack to the next ports rather than force it into the crack before it travels to the next ports.
This can indicate that either the crack expands and/or branches off under the surface of the concrete. Continue to inject and fill these voids. In situations where the crack penetrates completely through the concrete element and the backside of the concrete element cannot be sealed (e.g., basement walls, or footings with backfill) longer injection time may not force the epoxy to the next port. This most likely indicates that epoxy is running out of the unsealed back side of the crack. In this case the application may require a gel viscosity injection epoxy (CI-GV) or may not be suitable for epoxy injection repair without excavation and sealing of the back side of the crack.
Stop injecting. If using a fast cure paste-over material (CIP-F, CIP-LO or ETR), wipe off the leaking injection epoxy with a cotton cloth and re-apply the paste over material. Wait approximately 10 to 15 minutes to allow the paste-over to begin to harden. If the leak is large (e.g., the port broke off of the concrete surface) it is a good idea to wait approximately 30 minutes, or longer as necessary, to allow the paste over to cure more completely. Check to see that the paste-over is hard before reinjecting or the paste-over or ports may leak. Another option for small leaks is to clean off the injection epoxy and use paraffin or crayon to seal the holes.
This may indicate that the crack either expands or branches off below the surface. Continue to inject and fill these voids. This may also indicate that epoxy is running out of the back side of the crack. If the crack penetrates completely through the concrete element and cannot be sealed, the application may not be suitable for injection repair.
This can indicate several situations:
This may indicate that the crack is shallower than originally thought, or the epoxy is not penetrating the crack sufficiently before moving to the next port. Reinject some ports with a lower viscosity epoxy to see if the crack will take more epoxy. Another option is to heat the epoxy to a temperature of 80-100°F which will reduce its viscosity and allow it to penetrate into small cracks easier. The epoxy should be heated uniformly, do not overheat cartridge.
This can indicate there is not enough water present to react with the polyurethane and generate foam. Introduce water into the port and continue to inject. Introduce water into subsequent ports prior to injection. This can indicate that either the crack expands and/or branches off under the surface of the concrete. Continue to inject and fill these voids. This can indicate that the crack either expands and/or branches off under the surface of the concrete. Continue to inject and fill these voids. In situations where the crack penetrates completely through the concrete element, and the back-side of the concrete element cannot be sealed (e.g., basement walls, or footings with backfill), longer injection time may not force the epoxy to the next port. This most likely indicates that epoxy is running out the unsealed back side of the crack. In this case, the application may require a gel viscosity injection epoxy (CI-GV) or may not be suitable for injection repair without excavation and sealing of the back side of the crack.
This can indicate several situations:
Stop injecting. If using a fast cure paste-over material (CIP-F, CIP-LO or ETR), wipe off the leaking polyurethane with a cotton cloth and reapply the paste over material. Wait a approximately 10–15 minutes to allow the paste-over to begin to harden. If the leak is large (e.g., the port broke off of the concrete surface), it is a good idea to wait approximately 30 minutes, or longer as necessary, to allow the paste-over to cure more completely. Check to see that the paste-over is hard before reinjecting or the paste-over or ports may leak.
Another option for small leaks is to clean off the injection adhesive and use paraffin or crayon to seal the holes.
This may indicate there is not enough water present to react with the polyurethane and generate foam. Introduce water into the port and continue to inject. Introduce water into subsequent ports prior to injection. This may indicate that the crack either expands or branches off below the surface. Continue to inject and fill these voids.
This may indicate that the crack is shallower than originally thought, or the polyurethane is not penetrating the crack sufficiently before moving to the next port.
Some horizontal applications where complete penetration is not a requirement can be repaired using the gravity-feed method.
Samples of Simpson Strong-Tie® epoxies were immersed in the chemicals shown below for a maximum of three months. The samples were then tested according to ASTM D543 Standard Practices for Evaluating the Resistance of Plastics to Chemical Changes, Procedures I & II, and ASTM D2240 Standard Test Method for Rubber Property–Durometer Hardness.
Samples showing no visible damage and demonstrating statistically equivalent hardness as compared to control samples were classified as “Resistant” (R). These epoxies are considered suitable for continuous exposure to the identified chemical.
Samples exhibiting slight damage, such as swelling or crazing, or not demonstrating equivalent hardness as compared to control samples were classified as “Non-Resistant” (NR). These epoxies are considered suitable for periodic exposure to the identified chemical if the chemical will be diluted and washed away after exposure. Some manufacturers refer to this as “limited resistance” or “partial resistance” in their literature.
Samples that were completely destroyed by the chemical, or that demonstrated a significant loss in hardness after exposure were classified as “Failed” (F). These epoxies are considered unsuitable for exposure to the identified chemical.
Note: In many actual service conditions, the majority of the injection epoxy is not exposed to the chemical and thus some period of time is required for the chemical to saturate the entire mass of repair material. The repair would be expected to maintain integrity and load-bearing capability until a significant portion of the injection epoxy is saturated.
Chemical | Concentration | CSS-EP | CSS-ES | CI-LV | CI-LVFS | CI-LPL | CI-GV | CI-SLV |
---|---|---|---|---|---|---|---|---|
|
||||||||
Acetic Acid | 10% | F | F | F | F | F | F | F |
pH = 3 | 10% | R | R | R | R | R | R | |
Acetone | 100% | NR | NR | F | F | F | NR | F |
Aluminum Ammonium Sulfate (Ammonium Alum) | 10% | R | R | R | — | — | — | — |
Aluminum Chloride | 10% | R | R | R | — | — | — | — |
Aluminum Potassium Sulfate (Potassium Alum) | 10% | R | R | R | — | — | — | — |
Aluminum Sulfate (Alum) | 15% | R | R | R | — | — | — | — |
Ammonium Hydroxide (Ammonia) | 20% | R | R | R | R | R | R | R |
pH = 10 | R | R | R | R | R | R | R | |
Ammonium Sulfate | 15% | R | R | R | — | — | — | — |
Antifreeze | 100% | R | R | R | R | R | R | R |
Aviation Fuel (JP5) | 100% | R | R | R | R | R | R | R |
Break Fluid | 100% | R | R | R | R | R | R | R |
Calcium Hydroxide | 10% | R | R | R | R | R | R | R |
Calcium Hypochlorite | 15% | R | R | R | R | R | R | R |
Calcium Oxide | 5% | R | R | R | R | R | R | R |
Chlorine (Sodium Dichloro-s-triazinetrione) | 2,000 ppm | R | R | R | R | R | R | R |
Detergent (ASTM D543) | 100% | R | R | R | R | R | R | R |
Diesel Oil | 100% | R | R | R | R | R | R | R |
Ethyl Alcohol | 95% | R | R | F | F | NR | NR | F |
50% | R | R | NR | NR | R | R | NR | |
Fluorosilicic Acid | 25% | R | R | R | — | — | — | — |
Gasoline | 100% | R | R | NR | NR | R | R | NR |
Hydrochloric Acid | 10% | R | R | NR | R | R | R | F |
pH = 3 | R | R | R | R | R | R | R | |
Hydrogen Peroxide | 12% | R | R | F | R | NR | R | F |
Iron (II) Chloride (Ferrous Chloride) | 15% | R | R | R | — | — | — | — |
Iron (III) Chloride (Ferric Chloride) | 15% | R | R | R | — | — | — | — |
Isopropanol | 100% | R | R | R | R | R | R | R |
Machine Oil | 100% | R | R | R | R | R | R | R |
Methyl Ethyl Ketone | 100% | R | R | F | F | F | NR | F |
Mineral Spirits | 100% | R | R | R | R | R | R | R |
Motor Oil | 100% | R | R | R | R | R | R | R |
Potassium Permanganate | 10% | R | R | R | — | — | — | — |
Seawater (ASTM D1141) | 100% | R | R | R | R | R | R | R |
Soap (ASTM D543) | 100% | R | R | R | R | R | R | R |
Sodium Bicarbonate | 10% | R | R | R | — | — | — | — |
Sodium Bisulfite | 15% | R | R | R | — | — | — | — |
Sodium Carbonate | 15% | R | R | R | — | — | — | — |
Sodium Fluoride | 10% | R | R | R | — | — | — | — |
Sodium Hexafluorosilicate (Sodium Silicon Floride) | 50% | R | R | R | — | — | — | — |
Sodium Hydrogen Sulfide | 15% | R | R | R | — | — | — | — |
Sodium Hydroxide | 20% | R | R | R | R | R | R | R |
pH = 10 | R | R | R | R | R | R | R | |
Sodium Hypochlorite | 15% | R | R | R | R | R | R | R |
Sodium Nitrate | 15% | R | R | R | — | — | — | — |
Sodium Phosphate (Trisodium Phosphate) | 10% | R | R | R | — | — | — | — |
Sodium Silicate | 10% | R | R | R | — | — | — | — |
Sulfuric Acid | 10% | NR | NR | NR | R | R | NR | F |
pH = 3 | R | R | R | R | R | R | R | |
Toluene | 100% | R | R | R | R | R | R | R |
Water | 100% | R | R | R | R | R | R | R |