North Carolina Building Contractor License Practice Exam

Concrete block walls must be prepared in which manner before applying bond?

1. Rough and dry

2. Clean and sufficiently damp

3. Smooth and dry

4. Clean and excessively damp

The correct answer is: Clean and sufficiently damp

The preparation of concrete block walls before applying bond is crucial for ensuring a strong and effective adhesion of the materials used. The correct choice indicates that the walls must be clean and sufficiently damp. Cleaning the surface is essential because any dirt, dust, oil, or other contaminants could hinder the bonding process, preventing adhesives or mortars from properly adhering to the concrete. This step ensures that the surface is suitable for bonding. Sufficient dampness is equally important because most bonding agents, such as mortar or adhesives, benefit from a slightly moist surface. When concrete is too dry, it can absorb too much moisture from the bond, which may lead to a weak connection or premature setting of the adhesive before it has had a chance to properly bond with the blocks. Conversely, excessive moisture could lead to issues such as washing away of materials or improper curing. Therefore, the combination of a clean surface and sufficient dampness creates optimal conditions for achieving a solid bond, making this preparation method the most effective approach for concrete block walls prior to application.