In construction and dry-mix mortar formulations, silane-based water repellents play a crucial role in enhancing waterproofing performance, moisture resistance, and long-term durability. These organosilicon compounds significantly reduce water absorption while improving stain resistance and workability across a wide range of applications—including exterior wall plasters, tile adhesives, putty powder, tile grout, and waterproof coatings.
This article explores two major types of powdered silane water repellents commonly used in cement and gypsum-based dry-mix mortars and highlights the performance differences between Aquago® WP200 and Aquago® WP200H from Celotech.
1. Classification of Powdered Silane-Based Water Repellents
Type 1: Encapsulated Silane with Water-Soluble Protective Colloid
This type involves spray-drying silane with a water-soluble colloid and anti-caking agent. Once the powdered product is mixed into mortar with water, the protective colloid quickly dissolves and releases the silane into the mix water, ensuring efficient dispersion.
Advantages:
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Fast activation in wet mortar
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Compatible with automated dry-mix systems
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Enables uniform hydrophobic performance
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Ideal for applications requiring some surface water absorption (e.g., putty, tile adhesive)
Technical Expansion:
The release mechanism of silane occurs through colloid shell disintegration, after which silane reacts with hydroxyl groups in the cementitious matrix to form covalent bonds, creating a long-lasting hydrophobic barrier.
Example Products:
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Wacker’s SILRES® Powder D
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Celotech Aquago® WP200
Aquago® WP200 is recommended for cement-based mortars. It offers excellent water repellency (Lotus Effect), reduces surface water uptake, and maintains good workability. Dosage ranges from 0.1% to 0.5% depending on formulation requirements.
Type 2: Silane on Inorganic Carrier
In this case, organosilicon actives are adsorbed onto inorganic carriers (e.g., silica, calcium carbonate). When mixed with water, the release of silane is slower due to the water-repelling nature of the active component, slightly extending the mixing time. The inorganic carrier itself may also participate in cement hydration, offering a synergistic effect on mechanical strength and workability.
Advantages:
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Improves thick-layer mortar anti-sagging
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Enhances cohesion and open time
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Strengthens durability and water barrier effect
Technical Expansion:
Some carriers (like reactive silica) may enhance calcium silicate hydrate (C-S-H) gel formation, which contributes to mechanical strength and adhesion. The interaction between silane and carrier can improve mortar stability and reduce efflorescence.
Example Products:
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ROOKWOOD Nanothix® B1490
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Celotech Aquago® WP200H
Aquago® WP200H is suitable for both cement- and gypsum-based mortars. It improves anti-sag properties, extends open time, and is ideal for spray-applied and machine-applied mortars. It provides long-lasting water repellency and is suitable for exterior plasters and waterproof renderings.
2. Comparison Table: WP200 vs WP200H
| Property / Feature | Aquago® WP200 (Type 1) | Aquago® WP200H (Type 2) |
|---|---|---|
| Release Mechanism | Fast (via water-soluble shell) | Gradual (via inorganic carrier) |
| Ideal Use Cases | Putty, tile adhesive, grout | Plasters, thick mortars |
| Water Absorption Reduction | Moderate to High | High |
| Workability | Excellent | Excellent (esp. for thick layers) |
| Dosage Range | 0.1% – 0.5% | 0.1% – 0.5% |
| Special Performance | Lotus effect, stain resistance | Anti-sagging, enhanced durability |
3. Selecting the Right Water Repellent
When selecting a silane-based water repellent for mortar, it’s critical to match the product type with the intended application, workability requirements, and long-term durability goals. While both types effectively reduce water ingress and surface porosity, their performance in different systems may vary due to release dynamics, carrier reactivity, and interaction with other additives like HPMC.
Best Practice Tip:
For optimal performance, ensure compatibility tests are conducted when combining silane-based hydrophobic agents with cellulose ethers (HPMC, MHEC) or redispersible powders (RDP), especially when formulating high-flexibility mortars.
Conclusion
Both types of powdered silane water repellents offer unique strengths for modern mortar systems. Whether you need fast-dispersing hydrophobicity for tile adhesive or long-lasting moisture resistance in thick plaster coatings, products like Aquago® WP200 and WP200H offer reliable solutions for enhanced waterproofing performance, improved workability, and long-term durability.
