CCIL Concrete Field Testing Procedures 4 — Questions and Answers
Question 1: Per ASTM C31, how soon after casting must concrete test cylinders be protected from vibration and disturbance?
- Immediately after casting (Correct answer)
- After 1 hour
- After initial set
- After 24 hours
Correct answer: Immediately after casting
Cylinders must be protected from vibration, shock, and disturbance immediately after casting until they are transported to the curing facility.
Question 2: What is the Kelly ball test used to evaluate in fresh concrete?
- Air content
- Consistency and workability (Correct answer)
- Unit weight
- Setting time
Correct answer: Consistency and workability
The Kelly ball test (ASTM C360, now withdrawn) measured the penetration depth of a weighted ball to assess concrete consistency as a slump alternative.
Question 3: When the ambient temperature exceeds 32°C (90°F), what additional precaution must be taken with freshly cast concrete cylinders?
- Immediately immerse in water
- Place in an insulated box to prevent overheating
- Store in shade and cover with wet burlap (Correct answer)
- Add ice to the mold
Correct answer: Store in shade and cover with wet burlap
In hot weather, freshly cast specimens must be stored in a shaded location and protected with wet burlap or similar moisture-retaining covers to prevent thermal cracking.
Question 4: What is the correct procedure when the slump of concrete exceeds the maximum specified for the project?
- Add aggregate to reduce slump
- Reject the load or notify the engineer (Correct answer)
- Re-test immediately with another sample
- Add cement to stiffen the mix
Correct answer: Reject the load or notify the engineer
If test results fall outside specified limits, the load should be rejected or the engineer of record notified immediately for a disposition decision.
Question 5: Which ASTM standard governs the making and curing of concrete test specimens in the laboratory?
- ASTM C31
- ASTM C192 (Correct answer)
- ASTM C39
- ASTM C172
Correct answer: ASTM C192
ASTM C192 covers the procedure for making and curing concrete test specimens in the laboratory under controlled conditions.
Question 6: In ASTM C231 pressure meter calibration, what is the purpose of the aggregate correction factor?
- To correct for aggregate size
- To account for air absorbed by porous aggregates (Correct answer)
- To adjust for aggregate specific gravity
- To compensate for aggregate surface texture
Correct answer: To account for air absorbed by porous aggregates
Porous aggregates absorb air during the pressurization step, so an aggregate correction factor is subtracted from the meter reading to get true air content.
Question 7: What is the minimum number of concrete cylinders typically cast per sample for compressive strength acceptance testing?
- One
- Two (Correct answer)
- Three
- Four
Correct answer: Two
A minimum of two cylinders are cast per sample, with the average of the two used as the test result for compressive strength acceptance.
CCIL Concrete Field Testing Procedures 4
Per ASTM C31, how soon after casting must concrete test cylinders be protected from vibration and disturbance?