P.U. Foam Grouting | P.U. Injection Grouting is grouting with polyurethane [PU] resins which can be used to improve/enhance the mechanical and sealing properties of soil, and rock or to repair concrete structures. The principle of grouting is the injection of liquid grouting material into the subject environment under controlled pressure.
Advantages of Injection grouting
Injection grouting is a construction and maintenance technique used to fill voids, stabilize structures, and improve the integrity of various types of materials. Here are several advantages of injection grouting:
- Structural Reinforcement: Injection grouting can strengthen and stabilize structures such as foundations, retaining walls, and bridges by filling voids, cracks, and gaps in the material.
- Waterproofing: It is highly effective in preventing water infiltration and sealing leaks in underground structures, basements, and tunnels, making it an essential technique in waterproofing applications.
- Cost-Effective: Injection grouting can be a cost-effective alternative to major structural repairs or replacements, saving money in the long run by extending the lifespan of existing structures.
- Minimal Disruption: The process of injection grouting is relatively non-invasive and can often be completed without the need for extensive excavation or demolition, minimizing disruption to the surrounding environment or operations.
P.U Injection
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 the 1980s when it was used in the mining industry. In recent years, PU grouting technology has spread significantly from the mining industry into the field of civil engineering, since the application possibilities have been growing exponentially.
The Process
Civil construction widely uses grouting technology in fields such as underground constructions, tunnelling, anchoring soil and rocks, strengthening, stabilizing, and filling 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 polyurethane grouts are available, which are broadly classified into two categories, namely Hydrophilic and Hydrophobic, based on their reaction with water.
The challenge lies in choosing the right grout with the appropriate properties best suited for the given condition.
Hydrophilic Polyurethane
Hydrophilic polyurethane as the name goes, means love for water. It absorbs water like a sponge until it can’t hold any more.
Sometimes, additional water injection into the crack or joint enables the hydrophilic polyurethane to fully react and seal the crack. If there’s insufficient water, the grout shall not react fully.
Hydrophobic Polyurethane
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.