PU Grouting Injection & Construction Waterproofing is basically grouting with polyurethane [PU] resins which can be used to improve/enhance the mechanical and sealing properties of soil, rock or to repair concrete structures. The principle of grouting is the injection of liquid grouting material into the subject environment under controlled pressure.
Polyurethane foam can seal water leakage through cracks or joints. The PU grouting resin fills the tears and cracks or pores, and it subsequently hardens. During the grouting process, all the void spaces are filled with polyurethane grouting.
The technology dates back to 1980s where it was used in the mining industry. In the recent years, PU grouting technology has spread significantly from the mining industry into the field of civil engineering, since the application possibilities has been growing exponentially.
Grouting technology is widely used in the following fields of civil construction, i.e underground constructions, tunneling, anchoring of soil and rocks, strengthening and stabilization, and filling of voids.
After injection into a crack or joint,polyurethane grouts react quickly with water to form an expanding foam. This chemical reaction produces carbon dioxide gas that results in a volume expansion. After the expansion, the final product is a rigid or flexible closed-cell polyurethane foam that seals water leakage through cracks or joints.
Many different polyurethanes grouts are available, which are broadly classified into two categories, namely Hydrophilic and Hydrophobic, based on their reaction with water. The challenge is to choose the right grout with the right properties that will be best suited for the given condition.
Hydrophilic polyurethane as the name goes, it means love for water. It absorbs water like a sponge, until it can’t hold no more. Additional water is sometimes injected into the crack or joint to enable the hydrophilic polyurethane to fully react and seal the crack. If there's insufficient water, the grout shall not react fully.
Hydrophobic polyurethane grout does not require a lot of water. A small amount of water to begin the foaming reaction is sufficient.
The following videos will help you understand the process better.
1.Drilling to install injection ports,nozzles.
2.Installing injection ports (grout nipples) at intervals astride the crack.
3.High pressure hose attached.
4.Injection grouting in progress.