PU Injection vs. Cementitious Grouting

Cementitious grouting and PU injection are two popular techniques for patching fractures and stopping leaks in concrete constructions. However, each approach has its unique benefits, uses, and drawbacks. The type of fracture, structural needs, and environmental circumstances all play a role in selecting the best one.

Compare cementitious and PU grouting, assisting you in choosing the optimum grouting option for your project.

Understanding PU Injection

PU injection involves injecting polyurethane resin into cracks using a grouting pump. The resin reacts with water, expanding to fill voids and forming a watertight seal. This method is widely used for waterproofing applications, particularly in structures exposed to moisture.

Advantages of PU Injection

1. Water-activated sealing – PU grout injection reacts with water, making it highly effective for sealing leaks in damp environments.

1. High flexibility – Unlike rigid grouts, polyurethane resin can expand and contract with structural movements, reducing re-cracking risk.

1. Fast curing time – PU injection cures quickly, minimising downtime and allowing structures to be used soon after application.

1. Strong adhesion – The resin bonds well with concrete, ensuring durability in leak-sealing applications.

1. Non-disruptive application – Requires small injection ports, avoiding extensive surface damage.

Limitations of PU Injection

• Not suitable for structural reinforcement – PU grouting is primarily for waterproofing and does not restore structural strength.

• Limited resistance to high pressure – Additional reinforcement may be required in cases of extreme water pressure.

• Requires specialised equipment – A grouting pump and precise injection techniques are needed for effective application.

Understanding Cementitious Grouting

Cementitious grouting uses a cement-based mixture injected into cracks or voids. This method is commonly used for structural repairs, soil stabilisation, and filling large gaps. Unlike PU injection, cementitious grouting does not expand but relies on solidification to restore integrity.

Advantages of Cementitious Grouting

1. Enhances structural strength – Cement-based grouts improve load-bearing capacity, making them ideal for repairing foundations and structural elements.

1. Cost-effective – The materials are widely available and generally cheaper than polyurethane resin.

1. Good resistance to high pressure – Cementitious grouts provide strong resistance against heavy loads and hydraulic pressure.

1. Versatile applications – Suitable for tunnels, dams, bridges, and large-scale infrastructure repairs.

1. Eco-friendly – Made from natural materials, reducing environmental impact.

Limitations of Cementitious Grouting

• Rigid and brittle – Does not accommodate structural movements, increasing the risk of future cracks.

• Slow curing time – Takes longer to set and fully cure compared to PU injection.

• Requires dry conditions – Moisture can affect adhesion and curing, limiting its use in wet environments.

• Higher material wastage – Cementitious grout may leak into surrounding voids, requiring more material to achieve full coverage.

Key Factors in Choosing the Right Method

1. Leak Sealing vs. Structural Repair

If the primary goal is waterproofing, PU injection is the better choice due to its ability to seal leaks effectively. For structural reinforcement, cementitious grouting provides greater load-bearing capacity.

2. Crack Size and Movement

For fine cracks and dynamic structures, PU grout injection is ideal since it remains flexible. For large cracks or voids, cementitious grouting is more effective due to its solid fill properties.

3. Moisture Conditions

PU grouting works in wet conditions, making it suitable for basements, tunnels, and water-retaining structures. Cementitious grouting requires dry conditions for proper bonding and curing.

4. Application Speed

For quick repairs, PU injection is preferable due to its fast curing time. Cementitious grouting takes longer to set, which can extend project timelines.

5. Equipment and Expertise

PU injection requires a grouting pump and trained professionals to ensure proper resin distribution. Cementitious grouting is easier to apply but may require additional support to prevent grout loss.

Conclusion

Both PU injection and cementitious grouting have specific advantages depending on the project requirements. While cementitious grouting is better suited for filling large spaces and providing structural reinforcement, PU grouting is ideal for waterproofing and leaking prevention. The decision is influenced by variables like project objectives, environmental circumstances, and crack size. Knowing the distinctions makes it easier to choose the best technique for effective and long-lasting repairs.

Visit Adcos Asia and let our experts help you protect your structure from water damage.