CTQP Materials Sampling and Testing 4 — Questions and Answers
Question 1: When performing a field density test using the nuclear gauge method, the gauge must be kept at least how far from any wall or vertical obstruction?
- 6 inches
- 12 inches (Correct answer)
- 18 inches
- 24 inches
Correct answer: 12 inches
Nuclear gauges must be kept at least 12 inches from walls or vertical obstructions to prevent backscatter interference that could affect readings.
Question 2: Which AASHTO standard governs the procedure for reducing field samples of aggregate to testing size?
- AASHTO T 2
- AASHTO T 11
- AASHTO T 248 (Correct answer)
- AASHTO T 304
Correct answer: AASHTO T 248
AASHTO T 248 covers the standard method of test for reducing samples of aggregate to testing size using splitting or quartering techniques.
Question 3: A bituminous mixture sample collected from behind the paver should be tested for temperature within how many minutes of sampling?
- 5 minutes
- 10 minutes (Correct answer)
- 15 minutes
- 30 minutes
Correct answer: 10 minutes
Mix temperature must be measured within 10 minutes of sampling to ensure the reading accurately reflects the in-place material condition.
Question 4: The term 'lot' in materials acceptance testing typically refers to:
- A single truckload of material
- A defined quantity of material for statistical acceptance purposes (Correct answer)
- One day's production output
- A random sample from the stockpile
Correct answer: A defined quantity of material for statistical acceptance purposes
A lot is a defined quantity of material (such as a specified tonnage or lane-miles) used as the statistical unit for acceptance sampling and testing.
Question 5: When sampling hot mix asphalt from a truck, the standard practice is to discard how much material from the tailgate before collecting the sample?
- No material needs to be discarded
- The first few shovelfuls (Correct answer)
- The top 6 inches of the load
- Half of the total load
Correct answer: The first few shovelfuls
The first few shovelfuls from the tailgate are discarded because edge material may be unrepresentative due to segregation during haul.
Question 6: Which test method is used to determine the percentage of crushed faces in coarse aggregate per FDOT and AASHTO specifications?
- AASHTO T 304
- AASHTO T 335 (Correct answer)
- AASHTO T 96
- AASHTO T 176
Correct answer: AASHTO T 335
AASHTO T 335 covers the standard method for determining the percentage of fractured particles in coarse aggregate, often required for HMA and base course specifications.
Question 7: If a concrete cylinder breaks at the cap rather than at the midpoint during a compressive strength test, the result is typically:
- Automatically invalid and must be discarded
- Acceptable if the break pattern meets ASTM C39 criteria (Correct answer)
- Always higher than the true strength
- Only valid if the cap thickness exceeds 1 inch
Correct answer: Acceptable if the break pattern meets ASTM C39 criteria
ASTM C39 defines acceptable fracture patterns; a cap break (Type 5 or 6) may still be reported if it meets the standard's criteria for an acceptable failure mode.
CTQP Materials Sampling and Testing 4
When performing a field density test using the nuclear gauge method, the gauge must be kept at least how far from any wall or vertical obstruction?