Construction Concrete and Masonry 2 — Questions and Answers
Question 1: What is the standard size of a modular brick in the United States?
- 3-5/8" × 2-1/4" × 7-5/8" (Correct answer)
- 3" × 2" × 8"
- 4" × 2-2/3" × 8"
- 3-1/2" × 2-1/2" × 7-1/2"
Correct answer: 3-5/8" × 2-1/4" × 7-5/8"
A standard modular brick measures 3-5/8 inches wide × 2-1/4 inches tall × 7-5/8 inches long, which equals 4" × 2-2/3" × 8" with mortar joints.
Question 2: What is the purpose of control joints in a concrete slab?
- To allow expansion due to heat
- To provide locations where cracking can occur in a controlled manner (Correct answer)
- To accommodate pipe penetrations
- To increase the slab's load capacity
Correct answer: To provide locations where cracking can occur in a controlled manner
Control joints create weakened planes in concrete slabs that guide shrinkage cracking to occur at planned locations rather than randomly across the slab.
Question 3: What is the minimum concrete cover required for rebar in a slab exposed to weather in the US?
- 3/4 inch
- 1-1/2 inches (Correct answer)
- 2 inches
- 3 inches
Correct answer: 1-1/2 inches
ACI 318 requires a minimum of 1-1/2 inches of concrete cover over reinforcing steel in slabs exposed to weather to protect against corrosion.
Question 4: What is the correct mortar type for load-bearing masonry walls?
- Type N
- Type O
- Type M or S (Correct answer)
- Type K
Correct answer: Type M or S
ASTM C270 specifies Type M or Type S mortar for load-bearing and below-grade masonry due to their higher compressive strengths.
Question 5: What is 'admixture' in concrete mix design?
- The aggregate portion of the mix
- A material added to concrete to modify its properties (Correct answer)
- The type of cement used
- Water added at the job site
Correct answer: A material added to concrete to modify its properties
Admixtures are materials added to concrete in small quantities to modify properties like workability, setting time, air content, or durability.
Question 6: What is the purpose of air entrainment in concrete mixes used in freeze-thaw climates?
- To increase compressive strength
- To reduce the weight of concrete
- To create microscopic air bubbles that relieve freeze-thaw pressure (Correct answer)
- To speed up curing time
Correct answer: To create microscopic air bubbles that relieve freeze-thaw pressure
Air-entrained concrete contains microscopic air bubbles that provide relief space for water expansion during freezing, preventing surface scaling and cracking.
Construction Concrete and Masonry 2
What is the standard size of a modular brick in the United States?