NETTCP Quality Control 2 — Questions and Answers
Question 1: When performing a sieve analysis on aggregate, which sieve size is used to define the boundary between coarse and fine aggregate?
- No. 4 (4.75 mm) (Correct answer)
- No. 8 (2.36 mm)
- No. 10 (2.00 mm)
- 3/8 inch (9.5 mm)
Correct answer: No. 4 (4.75 mm)
The No. 4 sieve (4.75 mm) is the standard boundary between coarse and fine aggregate in ASTM and AASHTO specifications.
Question 2: What does the term 'plasticity index' (PI) represent in soil classification?
- The difference between liquid limit and plastic limit (Correct answer)
- The moisture content at which soil begins to flow
- The ratio of clay to silt content
- The maximum dry density of the soil
Correct answer: The difference between liquid limit and plastic limit
Plasticity index is calculated as PI = LL − PL, indicating the range of moisture content over which soil behaves plastically.
Question 3: Which QC test is used to determine the in-place density of compacted asphalt pavement using a nuclear gauge?
- AASHTO T 355 (Correct answer)
- ASTM C 138
- AASHTO T 180
- ASTM D 1556
Correct answer: AASHTO T 355
AASHTO T 355 covers the use of nuclear surface moisture-density gauges for testing asphalt mixtures in place.
Question 4: During concrete production, what is the primary purpose of performing a slump test?
- To measure workability of fresh concrete (Correct answer)
- To determine compressive strength
- To check air content
- To verify water-cement ratio
Correct answer: To measure workability of fresh concrete
The slump test (ASTM C 143) measures the consistency and workability of fresh concrete before placement.
Question 5: A QC technician finds that a batch of HMA has a voids in the mineral aggregate (VMA) value below the minimum specified. What is the most likely corrective action?
- Increase the percentage of coarse aggregate or adjust gradation (Correct answer)
- Increase the asphalt binder content immediately
- Reduce the mixing temperature
- Add more mineral filler
Correct answer: Increase the percentage of coarse aggregate or adjust gradation
Low VMA is typically corrected by adjusting the aggregate gradation, often by increasing the coarse fraction to create more void space.
Question 6: What is the standard curing period for concrete cylinders before testing compressive strength at 28 days?
- Cylinders must be moist-cured or sealed until the time of testing (Correct answer)
- Cylinders must be air-dried for the last 7 days
- Cylinders can be stored in any condition after 24 hours
- Cylinders must be heat-cured at 100°F
Correct answer: Cylinders must be moist-cured or sealed until the time of testing
ASTM C 31 requires that concrete test cylinders be moist-cured or sealed to prevent moisture loss until tested at 28 days.
Question 7: In statistical quality control, what does a control chart help a technician identify?
- Trends, shifts, or out-of-control points in a process (Correct answer)
- The exact compressive strength of each sample
- The required sample frequency per lot
- The minimum acceptable specification limit
Correct answer: Trends, shifts, or out-of-control points in a process
Control charts plot process data over time so technicians can identify non-random patterns that signal the process is going out of control.
NETTCP Quality Control 2
When performing a sieve analysis on aggregate, which sieve size is used to define the boundary between coarse and fine aggregate?