BCE Construction & Building Materials 5 — Questions and Answers
Question 1: What is the primary reason for using air-entrained concrete in cold climates?
- Increase compressive strength
- Improve workability at high temperatures
- Resist freeze-thaw damage (Correct answer)
- Reduce cement content
Correct answer: Resist freeze-thaw damage
Entrained air voids provide pressure relief as pore water freezes and expands, preventing internal cracking from freeze-thaw cycling.
Question 2: Which glass product is produced by rapidly cooling molten glass to create compressive surface stresses, making it 4-5 times stronger than annealed glass?
- Laminated glass
- Tempered glass (Correct answer)
- Heat-strengthened glass
- Borosilicate glass
Correct answer: Tempered glass
Tempering creates surface compression that must be overcome before tensile cracking begins, increasing strength and causing the glass to dice into small cubes when broken.
Question 3: What is the minimum concrete cover over steel reinforcement in a building column exposed to weather per ACI 318?
- 3/4 in
- 1.5 in
- 2 in (Correct answer)
- 3 in
Correct answer: 2 in
ACI 318 requires a minimum 2-inch cover for concrete exposed to weather for bars larger than No. 5, protecting reinforcement from corrosion.
Question 4: Galvanizing steel involves coating it with which metal to provide sacrificial corrosion protection?
- Chromium
- Nickel
- Zinc (Correct answer)
- Aluminum
Correct answer: Zinc
Zinc galvanizing provides both a physical barrier and cathodic (sacrificial) protection, oxidizing preferentially to protect the base steel.
Question 5: What does 'slump' measure in fresh concrete?
- Air content
- Unit weight
- Workability/consistency (Correct answer)
- Setting time
Correct answer: Workability/consistency
The slump test (ASTM C143) measures the vertical drop of a standard cone of concrete, indicating its workability and relative water content.
Question 6: In green building, what is the embodied carbon of a building material?
- Carbon dioxide emitted during the building's operational energy use
- Total greenhouse gas emissions from material extraction, manufacturing, and transport (Correct answer)
- Carbon sequestered in timber products
- Emission from on-site construction equipment only
Correct answer: Total greenhouse gas emissions from material extraction, manufacturing, and transport
Embodied carbon encompasses all lifecycle GHG emissions (often expressed as CO₂e) associated with material production, transport, installation, and end-of-life.
Question 7: Which type of mortar joint finish is most durable and weather-resistant for exterior masonry?
- Trowel-cut (flush) joint
- Struck joint
- Concave (tooled) joint (Correct answer)
- Raked joint
Correct answer: Concave (tooled) joint
A concave (rodded) joint compresses the mortar surface, sealing it against water infiltration and creating the most weather-tight finish.
BCE Construction & Building Materials 5
What is the primary reason for using air-entrained concrete in cold climates?