Which preparation step is essential before applying a bonding agent to an existing concrete surface?

• A. Roughen the surface
• B. Clean the surface
• C. Apply a bonding agent
• D. Roughen the surface and clean the surface

Answer: (D)

Preparing a concrete surface for a bonding agent requires both mechanical roughness and removal of contaminants. Roughening the surface creates tiny grooves and increases surface area, giving the bonding agent a better mechanical grip. Cleaning removes dust, laitance, oil, grease, curing compounds, and other residues that can form a barrier to adhesion. If you only roughen, residual contaminants may prevent bonding; if you only clean, a smooth surface may not provide enough key for the bond. So, the essential prep is to roughen and clean the surface (and ensure it’s dry) before applying the bonding agent.