PU Grouting

Polyurethane (PU) Grouting is specially designed for providing water control in static joints or cracks in concrete structures. The grout material, when mixed with a certain amount of accelerator, will react with water or moisture and expand, to form a tough, closed-cell rubber that is essentially unaffected by corrosive environment.

In the application, PU reacts upon with the water in the slab and expands its volume and thus fills the cracks or pores in the slab. Therefore, it acts as a sealer over the cracks. The repairing process can be completed within half a day. Accelerator agents can be used to speed up the setting time of the grout.

Application Procedure

The method of repair is as follows:

1. Hack the surface plaster or skim coat at the affected area to exposed the concrete so to inspect the exact location of the crack.

2. Drill holes along the cracks and the distance between each crack is around 1 foot. The depth of the holes has to be less than that of the thickness of the basement wall.

3. Wet the area around the crack and the floor that is directly below the crack so to ensure that excess PU can be removed easily when dried.

4. Packer will than be installed to the holes.

5. Rinse the pump with water before mixing the chemical. Start pumping from one end of the crack and pump until the PU grout overflow from neighboring holes and cracks.

6. Remove the packer and plug the hole. Allow the PU to dry for around 1 hour and then scrip off the excess PU grout. Patch up the holes with mortar.

7. Wait for at least three days to check for any other leakages before re-plastering.

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Polyurethanes are products of the petrochemical industry. They are very durable when exposed to external conditions and retain their gloss well. They can be obtained as elastomers, solid and rigid materials or flexible coatings. Major cracks or localized porous concrete can be repaired by this method.

Polyurethane resin is most commonly used for water control, and usually used for one of the following:

a) Injected into cracks or joints to form a gasket;

b) Injection through a structure to form a barrier between structure and soil;

c) Injection into the soil to consolidate the soil into a monolithic impermeable barrier.

Polyurethane resins or grouts form gels, foams or solids, and or hydrophilic or hydrophobic. They are very stable, and have good resistance to acids and alkalis. Life expectancy of polyurethanes can be measured in one to two decades. These resins have many desirable qualities, such as expansiveness, adherence to wet or dry surfaces, controllable set times, a tenacious bonding ability, chemical resistance, and is reacted by the very water that you may be trying to stop.

The injection can be carried out at the either passive side (bottom up approach) or top side (top down approach) of the slab as illustrated below.

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