Epoxy Injection resin is a system for welding cracks back together. This welding restores the original strength and loading originally designed into the concrete. Epoxy injection restores the structural qualities the concrete design intended. In other words under most conditions it makes the concrete as good as new. It creates an impervious seal to air, water, chemicals, debris, and other contamination.
A crack, obviously, is a sign of failure caused by stresses, inadequate design, improper curing, sinking foundation or even a leaning concrete wall. One of the dangers of a structural crack is the effect that it has on the reinforcing bar. The reinforcing represents one of the main structural values of the concrete.
Cracks left unprepared allow moisture and other contaminants to penetrate and attack the rebar. The rebar deteriorates, losing the structural value.
Epoxy injection resin has two purposes. First, it effectively seals the crack to prevent the damaging moisture entry. Secondly, it monolithically welds the structure together. Most people assume that this welding of the structure is the most important result of the repair. Actually what is most important is the sealing.
The sealing properties of the injection prevents premature deterioration of the reinforcing. This can be of equal, or in some cases greater importance than the structural welding. It would theoretically always be desirable to get this welding effect.
CLI Concrete Leveling also offers carbon fiber staples for added strength to epoxy injections.