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Part three in our series on effective crack prevention, control, and repair discusses repairing cracks.

We’ve Learned Prevention and Control, So Now What Do We Do for Repairing?

If your efforts at prevention and control are unsuccessful, you may end up with a leaking crack that needs repairs. And you can start those repairs in a couple of ways.

Product Injections for Repairing and Waterproofing Dry Concrete

The most common repair method in this case is to inject a product into the crack in an attempt to fill it and make the crack waterproof. Typically, a series of holes are drilled along the crack length so that they intersect the crack beneath the surface. A port is then inserted into each hole, and a product is pumped into the crack.

Common product injections include slurry mixtures of cement and/or clay with water, which can be cost-effective for situations with minimal water flow and low pressure.

For more challenging repairs, hydrophilic urethane products are recommended. These react with water to produce a foam that quickly sets within the crack to block water flow. They will normally remain flexible and tolerate a slight amount of movement in the concrete. However, this flexibility deteriorates with time.

An injection product that should never be used for waterproofing is an epoxy. An epoxy injection is designed and used for restoring the strength and integrity of the structural elements in cracked concrete. These cracks must be relatively dry for the epoxy to achieve adhesion as the epoxy will not displace or react with water. As a result, it is largely ineffective at waterproofing a leaking crack.

All injection products suffer from the disadvantage of being somewhat hit and miss because both the hole drilling  and material injection is done blind. Although the success rate can be high, achieving 100% effectiveness is extremely difficult. Due to this, waterproofing and creating a completely dry structure are both equally challenging and unreliable. Attempting to re-inject missed and still leaking areas can also be very difficult.

A Crystalline Waterproofing System for Leaking Concrete

The only way to make certain a leaking crack is made completely waterproof is to open the crack and repair it directly. Cracks can be quickly chiseled open using an electric chipping hammer. The most common repair method in this situation involves chiseling the entire length of the crack to create a deep and narrow chase. The chase is then filled with hydraulic grout and preferably with a crystalline waterproofing system.

Crystalline waterproofing systems provide both a short-term physical barrier to water and long-term chemical waterproofing through the growth of pore-blocking crystals. Crystalline waterproofing is roughly equal to injection in the skill and time required. But it’s significantly cheaper and far more reliable. The limitation of this repair method is that it is not intended for cracks or joints experiencing movement.

Want a Refresher on the Rest of This Series?

With quality products and proper training, even badly cracked and leaking concrete can be successfully repaired to a dusty-dry state. Because repairs are inconvenient and often expensive, your best crack repair strategy is to focus on prevention and control.

If you’d like a refresher on those two aspects, check out our posts on crack prevention and crack control.

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