Crack injection is a precision-focused leak seal approach for smaller cracks or joints. Contractors repair these defects by drilling holes into the wall and inserting injection ports at an angle to intersect the crack inside the wall. Next, they inject polyurethane grout directly into the center of the crack through the ports. The resin rapidly reacts with water to form a flexible watertight seal.
This process also protects the rebar inside the wall. Water intrusion through the cracks can lead to rebar corrosion and concrete spalling. Rusting rebar can expand six to ten times the original volume of the steel. This creates internal pressure on the concrete. While concrete is very strong in compression, it has a low tensile strength, and the expanding rebar will cause it to crack. When polyurethane resin is injected under pressure, it can encapsulate rebar and slow down the corrosion process.