Polyurethane grouting fluid is widely used in various tunnel projects, underground engineering, subway engineering, and basement leakage plugging. Polyurethane grouting fluid is divided into oil-based polyurethane grouting fluid and water-based polyurethane grouting fluid. What is the difference between them? Kindy check Sinomaco Waterproofing answers where the differences between them lies. The difference between oil-based and water-based polyurethane grouts is fundamental and dictates their entire application strategy.
Here’s a detailed breakdown of their differences.
At a Glance: Key Differences
| Feature |Oil-Based Polyurethane | Water-Based Polyurethane |
| :— | :— | :— |
| **Chemical Reaction** | Moisture-**Independent** (reacts with itself) | Moisture-**Dependent** (reacts with water) |
| **Expansion** | Very high (can exceed 20x volume) | Low to moderate (mostly 2-5x volume) |
| **Flexibility** | Becomes a rigid, solid foam | Remains flexible and elastomeric |
| **Water Resistance | Excellent, hydrophobic (repels water) | Good, but can swell and soften with prolonged immersion |
| **Primary Use | Stopping active, rushing water** | **Sealing leaks & dampness, soil stabilization** |
| **Viscosity | Typically very low (thin, like water) | Can be formulated in a wider range (thin to thick) |
| **Tack-Free Time | Slower (minutes to hours) | Faster (seconds to minutes) |
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### Detailed Explanation of Differences
#### 1. Chemical Reaction and Curing Mechanism
This is the most critical difference.
* **Oil-Based (MDI or “Hydrophobic” Grout):** The curing reaction is **internal**. The two components (polyol and isocyanate) are mixed at the pump or injection gun. Once mixed, they begin to react and expand on their own timeline, **regardless of environmental moisture**. They are often called “hydrophobic” because they repel water and will not incorporate it into their chemical structure.
* **Water-Based (“Hydrophilic” Grout):** The curing reaction is **external**. The pre-mixed liquid resin is a single component. When it is injected, it **actively seeks out and reacts with water** in the soil or crack. Without water, it will not fully cure. They are “hydrophilic” because they have an affinity for water.
#### 2. Expansion
* **Oil-Based:** Undergoes **extremely high chemical expansion** (often 15-25 times its original volume). This creates tremendous outward pressure, allowing it to push into tiny fissures and forcefully displace water to seal a leak. This high pressure can sometimes cause damage (e.g., lifting slabs or cracking masonry) if not used carefully.
* **Water-Based:** Expands primarily through a foaming action as it reacts with water. Its expansion is **much lower** (typically 2-5 times). This makes it less forceful and better for applications where controlled, gentle filling is required.
#### 3. Final Cured Properties
* **Oil-Based:** Cures into a **rigid, closed-cell foam**. It is very strong and durable, acting like a hard plastic. It is highly resistant to chemicals and long-term water immersion.
* **Water-Based:** Cures into a **soft, flexible, open-cell foam** that resembles a kitchen sponge. While it seals water out, the foam itself can absorb water and swell, which can be a benefit for self-healing minor cracks. It remains elastomeric, allowing it to accommodate minor shifting and movement without cracking.
#### 4. Primary Applications
* **Oil-Based is the “Stopper”:** Use it when you have a **high-volume, active leak** that needs to be shut off immediately. Think of water rushing through a crack in a basement wall, a leaking tunnel, or a pipe penetration.
* **Pros:** Stops big water fast, very strong.
* **Cons:** Can be overkill, is rigid (can crack if substrate moves), and is generally more expensive.
* **Water-Based is the “Sealer”:** Use it for **dampness, seepage, and slow leaks**. It’s ideal for general crack injection in foundations, soil stabilization (void filling), and creating a flexible watertight gel curtain.
* **Pros:** More versatile, flexible, excellent for soil, generally less expensive.
* **Cons:** Cannot stop a large, high-pressure leak on its own; the foam can degrade with constant water immersion over time.
### Analogy: Plumber vs. Landscaper
* An **Oil-Based** grout is like a **plumber**. You call it for an **emergency burst pipe** (a major active leak). It uses forceful, direct methods to stop the flow immediately.
* A **Water-Based** grout is like a **landscaper**. You hire it to **regrade your yard** (soil stabilization) and **install a drainage system** (sealing dampness and seepage) to prevent water from getting to the foundation in the first place.
### Which One Should You Choose?
* **Choose Oil-Based Polyurethane if:**
* Water is **actively flowing or gushing** into a structure.
* You need to create a **high-strength, rigid plug**.
* The environment is **completely dry** (as it doesn’t need water to cure).
* **Choose Water-Based Polyurethane if:**
* You are dealing with **dampness, seepage, or a slow leak**.
* You need to fill **voids in soil or under slabs** (e.g., mudjacking).
* The crack is in a area that might experience **minor shifting or movement**.
* The goal is to create a **flexible, water-tight barrier**.
**Professional Note:** In many complex leaks, professional contractors will use a combination: first injecting a small amount of **oil-based** grout to stop the major flow, and then following up with **water-based** grout to create a complete, flexible seal and fill any remaining voids.
Post time: Sep-12-2025