Polyurethane Grouting is a technique that involves the injection of expanding polyurethane to cut-off water flow through concrete joints or cracks or to fill voids under slabs or behind concrete walls. The grout is injected under low/high pressure through a pre-drilled hole. The grout then expands to fill the crack or void. This PU Grouting is used for expansion joints and concrete cracks that are actively leaking.