CCIL Concrete Field Testing Procedures 5 — Questions and Answers
Question 1: When using a penetration resistance apparatus per ASTM C403, what does a penetration resistance of 500 psi (3.5 MPa) indicate?
- Initial set of concrete (Correct answer)
- Final set of concrete
- Complete hydration
- Loss of workability only
Correct answer: Initial set of concrete
Per ASTM C403, initial set is defined as the time required to reach a penetration resistance of 500 psi (3.5 MPa).
Question 2: According to ASTM C172, what portion of a truck load must be excluded when sampling fresh concrete?
- First and last 5%
- First and last 10% (Correct answer)
- First and last 15%
- First and last 25%
Correct answer: First and last 10%
ASTM C172 requires that samples be taken after discarding the first and last 10% of the batch to ensure a representative sample.
Question 3: What is the acceptable temperature range for fresh concrete at the time of delivery per most North American specifications?
- 5°C to 25°C (41°F to 77°F)
- 7°C to 32°C (45°F to 90°F) (Correct answer)
- 10°C to 30°C (50°F to 86°F)
- 15°C to 35°C (59°F to 95°F)
Correct answer: 7°C to 32°C (45°F to 90°F)
Many specifications and ACI 305/306 recommend concrete delivery temperatures between 7°C (45°F) and 32°C (90°F) to prevent cold- or hot-weather placement problems.
Question 4: Which test method is used to determine the time of setting of concrete mixtures by penetration resistance?
- ASTM C191
- ASTM C403 (Correct answer)
- ASTM C494
- ASTM C940
Correct answer: ASTM C403
ASTM C403 covers the test method for time of setting of concrete mixtures by penetration resistance on mortar sieved from the mix.
Question 5: When casting 100×200 mm (4×8 in.) concrete cylinders using rodding, how many times must each layer be rodded?
- 10 times
- 15 times
- 25 times (Correct answer)
- 50 times
Correct answer: 25 times
Per ASTM C31, each layer in a 100×200 mm cylinder is rodded 25 times uniformly distributed over the cross-section.
Question 6: What action is required when the concrete temperature exceeds the maximum limit specified for the project during field testing?
- Proceed with placement and note on report
- Add water to cool the mix
- Reject the load and document non-conformance (Correct answer)
- Test another cylinder to confirm
Correct answer: Reject the load and document non-conformance
Non-conforming temperature results require rejection of the load and documentation on the field report; water addition is not permitted as it alters the mix design.
Question 7: Which document provides the standard specification for sampling freshly mixed concrete as the primary sampling standard referenced in North American practice?
- ASTM C172 (Correct answer)
- ASTM C31
- ASTM C1064
- ASTM C143
Correct answer: ASTM C172
ASTM C172 is the primary standard for sampling freshly mixed concrete, referenced by virtually all other field test methods.
CCIL Concrete Field Testing Procedures 5
When using a penetration resistance apparatus per ASTM C403, what does a penetration resistance of 500 psi (3.5 MPa) indicate?