An Overview of Concrete Crack Repair

 

Concrete repair is a four billion dollar a year business according to “Concrete Repair Digest” magazine. Concrete crack repair is one element of this market.

This article limits itself to the repair of concrete cracks in general and specifically to cracks of Teamviewer crack

structures 16 inches in thickness or less. Most typically, we are relating to basements, other building foundations, parking decks, swimming pools, and unique poured-wall structures such as sea walls.

These applications have in common the preferred method of repair – low pressure crack injection of a liquid polymer which hardens with time. Other applications, such as those involving very thick-walled structures (such as dams) and very long cracks (found on bridges and highways) may be more suited to high pressure injection.

By far the most frequent type of cracks is caused during construction by failure to provide sufficient working joints to accommodate drying shrinkage and thermal movement. Also common are those cracks caused by structural settlement, overload or earthquakes. Most cracks are formed in the first 30 days of the pouring of the concrete structure.

These cracks may initially be too small to be detected and to have any negative consequences at first, while at other times, never growing to be a problem at all. Other cracks become visible very early and cause problems, such as water leakage, almost immediately.

Even the early undetected cracks can, in time, become larger and cause problems, whether structural or more commonly a source of water leakage.

How this happens can be delineated as:

1. Especially in colder climates, moisture can permeate these tiny breaks in the concrete substrate and enlarge them to full-fledged leaking cracks by moisture expansion/contraction resulting from freeze/thaw cycle of the moisture.
2. In addition, as the ground around the foundation stabilizes, any movement can cause the rigid concrete substrate to separate at these tiny breaks in the concrete, enlarging then to a water- leaking size.
3. A more serious problem to solve is when the area around the foundation remains unsettled, resulting in an ongoing stress on the concrete structure. If this stress exceeds the strength of the concrete, cracks will form even where initial cracks did not exist (even after repair of these initial cracks).

The first two listed sources of crack formation and propagation are situations to which repair can readily be effective and complete. The third situation should not be addressed unless done jointly with soil stabilization, peering, or mud-jacking to eliminate the cause of continuing settling.

Even the first two situations require proper applications and procedure to effectively solve the problem. The materials proven to be most effective in concrete crack repair are:

1. Two-component epoxies, which effectively seal a crack and at the same time reinforce the repair area to be actually stronger than the un-repaired concrete area around it. Epoxies are always the preferred material when the structural integrity of the concrete is open to question.
2. Polyurethane elastomeric foams, when concrete structural integrity is not a problem and problem is only water leakage. Polyurethane foams harden very rapidly (unlike most epoxies) and are less likely to flow out the back of some cracks as epoxies may. Furthermore, polyurethane foams expand in the crack area and may reach areas that an epoxy may not if not properly injected.

Polyurethane, being elastomeric, may also handle concrete movement more effectively than the more rigid epoxies (although this is a debated point and not one that this report draws conclusions on).

The secret to effective crack injection, whether epoxies or polyurethanes, is patient, low-pressure introduction of the liquid into the cracks, Low pressure (20-40 PSI) allows the applicator to properly monitor the injection process. At this pressure range, the applicator can be confident that the crack has been saturated with the liquid polymer up to that point when liquid begins to collect at an adjacent surface port. If done at higher pressure, the liquid polymer may only be filling the larger sections of the crack, leaving smaller crack sections available for future deterioration.

Traditionally, crack injection required expensive, cumbersome proportioning equipment. These remain useful where high pressure and/or very large volumes of liquid polymer need to be injected.