A crack, obviously, is a sign of failure caused by stresses, inadequate design, or improper curing of the concrete during construction. One of the dangers of a structural crack is the effect that it has on the reinforcing bar inside. The reinforcing bar or “rebar” represents one of the main structural components of any concrete structure. Cracks left un-repaired allow moisture, salts and other contaminants to penetrate into the concrete and attack the rebar. The rebar oxidizes or deteriorates, losing its structural integrity. If left unchecked loss of the entire concrete structure can often be the result.

Epoxy injection (picture) protects the rebar and stops water leakage and is a technique for "welding" cracks in concrete back together. This often restores the concrete structure to its original strength and load design specifications.

In other words - under most conditions epoxy injection makes the concrete as good as new. It creates an impervious seal to air, water, chemicals, debris, and other contamination.