Quality Control Flashcards

When performing a sieve analysis on aggregate, which sieve size is used to define the boundary between coarse and fine aggregate?

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.

What does the term 'plasticity index' (PI) represent in soil classification?

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.

Which QC test is used to determine the in-place density of compacted asphalt pavement using a nuclear gauge?

Answer: AASHTO T 355

AASHTO T 355 covers the use of nuclear surface moisture-density gauges for testing asphalt mixtures in place.

During concrete production, what is the primary purpose of performing a slump test?

Answer: To measure workability of fresh concrete

The slump test (ASTM C 143) measures the consistency and workability of fresh concrete before placement.

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?

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.

What is the standard curing period for concrete cylinders before testing compressive strength at 28 days?

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.

In statistical quality control, what does a control chart help a technician identify?

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.