PU Grouting Technology
The PU injection grouting is typically done using pressure pumps. Habitually, piston type pumps with electric or pneumatic drive are used. Initially, a series of holes are drilled through the structure along the cracks and in and around hollow spots. If there are several cracks, holes are drilled in a staggered manner. The grouting pump takes the components in the appropriate ratio and delivers them separately to the mixing chamber. In the mixing chamber, the dual components are mixed and subsequently injected through the packers into the structures to be grouted. Under pressure, the PU penetrates into surrounding fissures and cavities up to the distance of a few meters from the borehole. The grouting material flows through the structures first as a liquid and then instantly reacts with water causing excessive foams as the water reacts with the isocyanate groups of PU resin to form CO2 gas and the volume starts increasing. The flow then stops and when the viscosity of the material becomes so high that further pumping is impossible, and the resin becomes a hard foam. The grouting is carried till refusal or till grout starts oozing out from the adjacent holes.
The sealing and strengthening of the rock mass or construction is achieved when all the cavities and crevices are filled with PU grouts. The grout holes are then sealed with non-foaming PU resins. After finishing of the grouting, it is necessary to flush the pump, hoses and accessories and clean the equipment.