Here's Why Concrete Surface Preparation Should Not Be Overlooked
The cleanliness and condition of a concrete surface play a vital role in ensuring its durability and the effectiveness of any coating applied to it. Proper surface preparation is crucial for the success of waterproofing coatings. Coatings can only last when they securely bond to the surface. Conversely, insufficiently prepared concrete surfaces can lead to debonding of the protective coating, resulting in water ingress and costly damages.
In cases where the concrete is unsound, the unsound layer will gradually detach itself, causing further deterioration. On the other hand, when a coating is applied to a properly prepared surface, the material and concrete will bond together as a unified unit.
Signs of Unsound Concrete Substrate:
1) Visible cracks or micro-cracks in the concrete.
2) Presence of laitance.
3) Blisters formed by trapped air bubbles under the concrete surface.
4) Scaling created by frozen water expanding the concrete.
5) Spalling (peeling or flaking concrete).
6) Delamination (separation of the surface’s paste layer).
7) Greasy surface due to oil and chemical contamination.
9) Moisture or wet spots on the floor.
10) Tapping with a hammer results in indents or damage for unsound concrete, while sound concrete causes the hammer to bounce.
One can also check for unsound concrete by tapping it with a hammer and observing if any resulting indents or damage occur. Sound concrete will cause the hammer to bounce.
Common Concrete Surface Preparation Methods:
• Abrasive blasting.
• Acid etching.
• Chip hammering.
• Detergent scrubbing.
• High and ultra-high-pressure water jetting.
• Low-pressure water cleaning.
• Needle scaling.
• Flame blasting.
• Surface retarders.
Standards for concrete substrate preparation are defined by the Society for Protective Coatings’ standard SSPC SP-13/NACE No. 6 Surface Preparation of Concrete. According to SSPC SP-13, surface preparation involves the methods used to clean the concrete surface, remove loose and weak materials and contaminants, repair the surface, and roughen it to promote adhesion. An acceptable prepared concrete surface should be free of contaminants, laitance, loosely adhering concrete, and dust, and should provide a sound, uniform substrate suitable for the application of protective coatings or lining systems.
The International Concrete Repair Institute’s ICRI 310.2 provides guidance on selecting and specifying concrete surface preparation methods for sealers, coatings, polymer overlays, and concrete repair. ICRI 310.2 offers a straightforward method of visually classifying surface profiles using replica chips. These rectangular rubber coupons resemble typical surfaces produced by the ICRI standard’s methods, serving as visual examples for specification, execution, and verification.
In conclusion, adequate surface preparation is often overlooked or neglected, as it lacks the appeal of applying the final coat of sealer and admiring the finished work. However, this neglect primarily arises from competent installers who follow a specific surface preparation standard for each job without a comprehensive understanding of the how and why. Consequently, a wide range of slabs and substrates end up being treated in the same manner, despite their inherent differences.
Achieving proper surface preparation involves thoroughly assessing the substrate, understanding the materials involved, identifying all potential variables, and accounting for them. Conducting this exercise effectively prior to installation will significantly reduce the chances of waterproofing failures.
“Proper surface preparation is the foundation for a successful coating application and the key to long-lasting protection.”