CCIL Concrete Field Testing Procedures 3 — Questions and Answers
Question 1: When consolidating concrete in a cylinder mold using internal vibration, what is the maximum diameter of the vibrator permitted?
- One-quarter the diameter of the mold
- One-third the diameter of the mold (Correct answer)
- One-half the diameter of the mold
- Two-thirds the diameter of the mold
Correct answer: One-third the diameter of the mold
Per ASTM C31, the vibrator diameter must not exceed one-third the diameter of the mold to allow proper consolidation without segregation.
Question 2: What is the purpose of the bleeding test described in ASTM C232?
- To measure water gain at the surface of freshly placed concrete (Correct answer)
- To determine aggregate absorption
- To assess cement hydration rate
- To measure segregation of coarse aggregate
Correct answer: To measure water gain at the surface of freshly placed concrete
ASTM C232 measures the relative quantity of mixing water that will bleed from a sample of fresh concrete.
Question 3: Which ASTM standard covers field-cured concrete specimens for acceptance testing?
- ASTM C39
- ASTM C31 (Correct answer)
- ASTM C192
- ASTM C617
Correct answer: ASTM C31
ASTM C31 covers both standard-cured and field-cured specimens made and cured in the field for acceptance and quality control.
Question 4: What is the maximum time allowed between sampling fresh concrete and completing the slump test?
- 2 minutes
- 3 minutes
- 5 minutes (Correct answer)
- 10 minutes
Correct answer: 5 minutes
Per ASTM C143, the slump test must be completed within 5 minutes after obtaining the composite sample.
Question 5: At what depth below the concrete surface must a thermometer probe be inserted when measuring concrete temperature per ASTM C1064?
- 25 mm (1 in.)
- 50 mm (2 in.)
- 75 mm (3 in.) (Correct answer)
- 100 mm (4 in.)
Correct answer: 75 mm (3 in.)
ASTM C1064 requires the thermometer to be inserted at least 75 mm (3 in.) deep to obtain a representative temperature reading.
Question 6: Which factor most directly affects the accuracy of the gravimetric air content calculation in ASTM C138?
- Aggregate gradation
- Accurate specific gravity of concrete ingredients (Correct answer)
- Water-to-cement ratio
- Ambient temperature
Correct answer: Accurate specific gravity of concrete ingredients
The gravimetric method calculates air content based on the theoretical density using specific gravities of all ingredients, making accurate SG values critical.
Question 7: How many composite samples must be obtained from a truck load when making a full set of test cylinders for acceptance per ASTM C31?
- One from the beginning of the load
- One composite from the middle portion of the load
- One from each third of the load combined (Correct answer)
- One from the end of the load
Correct answer: One from each third of the load combined
A composite sample is obtained by combining samples from at least three portions of the load, avoiding the first and last 10% of the batch.
CCIL Concrete Field Testing Procedures 3
When consolidating concrete in a cylinder mold using internal vibration, what is the maximum diameter of the vibrator permitted?