CCIL Concrete 2 — Questions and Answers
Question 1: According to CSA A23.1, what is the minimum curing period for concrete exposed to freezing temperatures before it can be considered adequately cured?
- 3 days at 10°C
- 7 days at 10°C (Correct answer)
- 14 days at 10°C
- 28 days at 10°C
Correct answer: 7 days at 10°C
CSA A23.1 requires concrete to be maintained at a minimum of 10°C for at least 7 days to achieve adequate early strength before exposure to freezing.
Question 2: When performing a slump test per ASTM C143/CSA A23.2-5C, the concrete is rodded in how many layers?
- 2 equal layers
- 3 equal layers (Correct answer)
- 4 equal layers
- 5 equal layers
Correct answer: 3 equal layers
The slump test requires filling the mold in 3 equal layers, each rodded 25 times with a tamping rod.
Question 3: What does a bleeding rate in fresh concrete primarily indicate?
- Water-to-cement ratio is too low
- Excess mix water migrating to the surface (Correct answer)
- Aggregate segregation at the bottom
- Insufficient cement content
Correct answer: Excess mix water migrating to the surface
Bleeding occurs when excess mix water rises to the surface of fresh concrete due to settlement of heavier solids.
Question 4: In CCIL concrete testing, what is the purpose of the air content test performed per ASTM C231?
- Measuring total porosity of hardened concrete
- Determining entrained and entrapped air in fresh concrete (Correct answer)
- Calculating the void ratio after curing
- Assessing bleed water channel volume
Correct answer: Determining entrained and entrapped air in fresh concrete
ASTM C231 (pressure method) measures the air content of freshly mixed concrete to verify adequate air entrainment for freeze-thaw durability.
Question 5: Which failure mode is expected during a standard compressive strength test of a properly made and tested concrete cylinder?
- Horizontal splitting along the mid-height
- Diagonal shear cone fracture or columnar cracking with end cones (Correct answer)
- Explosive shattering with no defined pattern
- Delamination along aggregate planes
Correct answer: Diagonal shear cone fracture or columnar cracking with end cones
Acceptable failure patterns for concrete cylinders include diagonal shear cones, columnar cracks, or combinations; these indicate valid test results per ASTM C39.
Question 6: What is the standard diameter-to-height ratio for a concrete test cylinder used in compressive strength testing?
- 1:1
- 1:2 (Correct answer)
- 2:1
- 1:3
Correct answer: 1:2
Standard concrete cylinders have a 1:2 diameter-to-height ratio (e.g., 100 mm × 200 mm or 150 mm × 300 mm) as required by ASTM C39.
Question 7: When capping concrete cylinders with sulfur mortar per ASTM C617, the cap thickness should not exceed:
- 3 mm
- 6 mm (Correct answer)
- 10 mm
- 13 mm
Correct answer: 6 mm
ASTM C617 limits sulfur mortar cap thickness to 6 mm (¼ inch) maximum to minimize eccentricity effects during loading.
CCIL Concrete 2
According to CSA A23.1, what is the minimum curing period for concrete exposed to freezing temperatures before it can be considered adequately cured?