CTQP Concrete Field Inspector 2 — Questions and Answers
Question 1: According to ASTM C31, what is the required curing temperature range for standard-cured concrete cylinders?
- 50°F to 60°F (10°C to 16°C)
- 60°F to 80°F (16°C to 27°C) (Correct answer)
- 70°F to 90°F (21°C to 32°C)
- 40°F to 70°F (4°C to 21°C)
Correct answer: 60°F to 80°F (16°C to 27°C)
ASTM C31 requires standard-cured cylinders to be maintained at 60°F to 80°F (16°C to 27°C) during initial curing.
Question 2: What does the term 'bleed water' refer to in concrete?
- Water added during mixing to improve workability
- Water that rises to the surface due to settlement of solids (Correct answer)
- Water lost through evaporation during hot weather
- Water absorbed by dry aggregates after batching
Correct answer: Water that rises to the surface due to settlement of solids
Bleed water is the water that migrates to the top surface of freshly placed concrete as the heavier solid particles settle.
Question 3: Which ASTM standard governs the sampling of fresh concrete?
- ASTM C138
- ASTM C172 (Correct answer)
- ASTM C231
- ASTM C143
Correct answer: ASTM C172
ASTM C172 is the standard practice for sampling freshly mixed concrete from the point of delivery.
Question 4: When testing air content by the pressure method (ASTM C231), which aggregate type makes this method NOT applicable?
- Granite
- Limestone
- Lightweight aggregate (Correct answer)
- River gravel
Correct answer: Lightweight aggregate
The pressure method cannot be used with lightweight or porous aggregates because they absorb air pressure, giving inaccurate readings.
Question 5: A concrete load arrives at 8:00 AM and mixing began at 7:00 AM. Under ASTM C94, what is the latest this concrete can be discharged?
- 8:30 AM
- 9:00 AM (Correct answer)
- 9:30 AM
- 10:00 AM
Correct answer: 9:00 AM
ASTM C94 requires concrete to be discharged within 90 minutes of mixing or before the drum has revolved 300 times, whichever comes first.
Question 6: What is the minimum number of composite samples that should be taken to make one set of test cylinders per ASTM C172?
- 1
- 2
- 3 (Correct answer)
- 4
Correct answer: 3
ASTM C172 requires the composite sample to be obtained from at least three approximately equal portions taken throughout the middle portion of the load.
Question 7: During hot weather concreting, which factor most directly increases the rate of slump loss?
- Lower water-to-cement ratio
- Higher concrete temperature (Correct answer)
- Coarser aggregate gradation
- Increased cement fineness
Correct answer: Higher concrete temperature
Higher concrete temperature accelerates cement hydration and evaporation, both of which cause more rapid slump loss.
CTQP Concrete Field Inspector 2
According to ASTM C31, what is the required curing temperature range for standard-cured concrete cylinders?