For Hardened Concrete Preparation, how deep must removal occur?

• A. Within 0.5 inch
• B. Within 1 inch
• C. Within 2 inches
• D. Within 3 inches

Answer: (B)

When preparing hardened concrete for repair, the aim is to remove the weak, laitance-rich surface so the patch material can bond effectively to sound concrete. This surface preparation should be shallow enough to preserve the underlying structure but deep enough to eliminate loose or contaminated material and roughen the base for good mechanical interlock. The specified limit is within one inch. Sticking to this depth removes the weak layer without unnecessarily cutting into solid concrete, which could compromise the substrate or require more extensive repair. If you encounter damage deeper than an inch, the repair approach would change to address the deeper unsound material rather than simply removing more surface. In practice, you’d verify removal depth with a straightedge or gauge, ensuring the surface is clean, dry, and appropriately roughened to promote bonding.