Dr E. Ramanathan PhD
For cementitious waterproof coatings, special cements like Sulphate Resistant Cement, White Portland Cement, or High Alumina Cement are often preferred over ordinary Portland cement (OPC), depending on performance needs.
🔍 Comparison Table: Normal Cement vs Special Cements in Waterproof Coating
| Property | Ordinary Portland Cement (OPC) | Special Cement (White/High Alumina/Sulphate Resistant) |
|---|---|---|
| Grade Used | OPC 43 or 53 | White cement (33–43 grade), High Alumina Cement, SRPC |
| Setting Time | Initial: ~30 min; Final: ~10 hrs | Similar or faster (High Alumina Cement sets quicker) |
| Water Demand | Higher | Lower (smoother particle size, better fineness) |
| Durability | Moderate | High resistance to chemicals, salts, and aggressive environment |
| Shrinkage | Higher, prone to cracks | Lower, less prone to micro-cracking |
| Alkalinity | Normal (~pH 12-13) | Same or higher; White cement is purer |
| Color | Grey | White or buff; better aesthetics in coating |
| Compatibility with Polymers | Moderate | Higher; white cement and HAC mix better with SBR, acrylic, etc. |
| Water Penetration Resistance | Moderate | Improved due to dense hydration (especially with HAC or additives) |
| Cost | Lower | Higher (but justifiable in performance applications) |
🔧 Recommended for Cementitious Waterproof Coatings:
- White Portland Cement
– Better compatibility with polymers (SBR, Acrylic).
– Offers aesthetic benefit and denser matrix. - High Alumina Cement (HAC)
– Fast setting and high early strength.
– Excellent in aggressive environments. - Sulphate Resistant Portland Cement (SRPC)
– Suitable for foundations and basements exposed to sulphates. - Pozzolanic or Blended Cement (PPC)
– Can be used with polymer additives; lower permeability.
🧪 Note on Cement Grade:
- 53 Grade OPC: Higher strength, faster setting, more prone to cracking if not cured properly.
- 43 Grade OPC: More suitable for slow hydration and waterproof coatings when used with polymers.
- Special Cements: Tailored for reduced porosity, better adhesion, and chemical resistance.
NOTE:
White cement or High Alumina Cement with polymer additives is generally more suitable for high-performance cementitious waterproofing due to superior durability, adhesion, and water impermeability.
Pros and Cons fo Pozzolanic Portland Cement
