NASCLA Accredited Commercial General ContractorMasonryMedium
A masonry wall is being constructed with brick units. To ensure proper bond and prevent issues like efflorescence, which of the following practices is most critical regarding the brick units themselves before laying?
- AApplying a waterproofing sealant to one face of each brick.
- BHeating the bricks to approximately 100°F (38°C).
- CControlling the initial rate of absorption (IRA) of the bricks.
- DSoaking all bricks in water for at least 24 hours.
Show answer & explanationAnswer & explanation
Correct answer: C. Controlling the initial rate of absorption (IRA) of the bricks.
Controlling the initial rate of absorption (IRA) of bricks, often through pre-wetting, is critical. If IRA is too high, the brick draws too much water from the mortar, leading to a weak bond; if too low, the brick can float, also affecting bond.
Why the other options are wrong
- A. Applying sealant is not a standard practice for ensuring proper bond and can interfere with mortar adhesion.
- B. Heating bricks is typically done in very cold weather, not as a general practice for bond and efflorescence prevention.
- D. Over-soaking can make bricks too wet, hindering proper mortar bond and potentially causing floating issues.
Initial Rate of Absorption (IRA)
The rate at which a brick absorbs water from mortar, measured in grams per 30 square inches per minute. Crucial for proper mortar bond.
- Also known as suction rate.
- Too high IRA leads to dry, weak mortar.
- Too low IRA can cause bricks to float.
- Controlled by pre-wetting.
Memory trick: IRA is the critical 'thirst' of the brick for a strong mortar bond.