NETTCP Quality Control 4 — Questions and Answers
Question 1: Which AASHTO test method is used to determine the bulk specific gravity of compacted HMA specimens?
- AASHTO T 166 (Correct answer)
- AASHTO T 209
- AASHTO T 308
- AASHTO T 245
Correct answer: AASHTO T 166
AASHTO T 166 determines the bulk specific gravity (Gmb) of compacted bituminous mixtures using the saturated surface-dry (SSD) method.
Question 2: What is the acceptable range for the temperature of fresh Portland cement concrete at the point of delivery, per most state DOT specifications?
- Between 50°F and 90°F (10°C and 32°C) (Correct answer)
- Between 40°F and 100°F (4°C and 38°C)
- Between 60°F and 80°F (16°C and 27°C)
- Between 55°F and 95°F (13°C and 35°C)
Correct answer: Between 50°F and 90°F (10°C and 32°C)
Most transportation agency specifications require fresh concrete temperature at delivery to be between 50°F and 90°F to ensure proper hydration and workability.
Question 3: What is the significance of the 'percent within limits' (PWL) statistic in highway construction QA/QC?
- It estimates the percentage of a lot that meets specification requirements (Correct answer)
- It measures the standard deviation of test results
- It calculates the average test result for a lot
- It determines the maximum value in a data set
Correct answer: It estimates the percentage of a lot that meets specification requirements
PWL estimates the proportion of the production lot that falls within specification limits, and is used to determine pay factors in many state DOT contracts.
Question 4: During compaction of an embankment, field density tests show 91% relative compaction when 95% is required. Which action is most appropriate?
- Apply additional roller passes and retest (Correct answer)
- Accept the material because it is close to the specification
- Remove the entire lift and start over
- Change the Proctor method to T 180 to raise the standard
Correct answer: Apply additional roller passes and retest
When compaction is below the specified minimum, additional roller passes are made to increase density before the next lift is placed, then the area is retested.
Question 5: What information must be recorded on the concrete field test report at the point of sampling?
- Time of sampling, truck number, load number, air temperature, and test results (Correct answer)
- Only the compressive strength results and mix design number
- Slump and air content only
- Batch plant ticket number and truck arrival time only
Correct answer: Time of sampling, truck number, load number, air temperature, and test results
A complete concrete field report requires sampling time, truck and load identification, ambient conditions, and all field test results to ensure traceability.
Question 6: The term 'referee testing' in QA/QC programs refers to:
- Independent testing by a third party to resolve disputes between agency and contractor results (Correct answer)
- The first round of testing performed on any new material
- Retesting performed by the contractor after a failed test
- Testing required before a pay item can be certified
Correct answer: Independent testing by a third party to resolve disputes between agency and contractor results
Referee testing is performed by an independent laboratory to resolve disagreements between the contractor's QC and the agency's QA test results.
Question 7: What does a failing result on a boiling water soundness test (AASHTO T 103) indicate about aggregate?
- The aggregate is susceptible to disintegration when exposed to freeze-thaw cycles (Correct answer)
- The aggregate has low abrasion resistance
- The aggregate contains excessive fines
- The aggregate has high absorption capacity
Correct answer: The aggregate is susceptible to disintegration when exposed to freeze-thaw cycles
The boiling water soundness test identifies aggregate with clay coatings or weak particles that would break down under freeze-thaw weathering conditions.
NETTCP Quality Control 4
Which AASHTO test method is used to determine the bulk specific gravity of compacted HMA specimens?