Crack injection uses either chemical grouts or epoxies to stop water intrusion or address structural concerns. CJGeo specializes in crack injection using polyurethane, chemical and acrylic grouts to stop water infiltration. We also do some epoxy grouting to address structural cracks, but that’s not our specialty.
Crack Injection Indications
Water coming through a well-defined crack is the best indication that it may benefit from the crack injection repair process. If there are a lots of cracks, it may be more efficient to perform curtain grouting. If a leak develops because a structure is moving, polyurethane compaction grouting may be needed to stabilize the structure and reduce movement, in addition to crack injection.
There are two broad classes of chemical grouts. Both are suitable for crack injection:
- hydrophilic, and
Hydrophilic grouts require water to react, and then integrate the water into the cured grout. Because of this, they tend to expand less, but have higher elongation once cured. Dynamic cracks generally require hydrophilic grouts, because of their higher elongation. When hydrophilics react and mix with water, it reduces their viscosity. Therefore, hydrophilic grouts are well suited for very tight cracks.
Hydrophobic grouts require water (just a few % by volume) to react. However, they do not integrate water into their cured state. This generally gives hydrophobics higher expansion, and a more rigid structure. Rigidity helps to increase bearing capacity, but reduces elongation.
With the right grout selection, injecting cracks with chemical grout can be a very long term repair. There are a few things which can reduce the design life of a repair:
- Movement greater than elongation. If a structure is moving more than the grout can stretch, the grout can tear, allowing leaks to resume.
- Dimensional instability. If not constantly exposed to water, hydrophilic grouts can shrink with time. If the area suddenly becomes wet again, leaks can resume. If the grout doesn’t swell all the way back up, or tore as it shrank, the crack injection won’t provide long term protection.
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