Sampling Methods Flashcards
7 cards from real NETTCP practice questions. Tap to flip, then mark Knew It or Still Learning — missed cards come back until you master them.
Read the first 7 Sampling Methods flashcards as text
What is the minimum number of grab samples typically combined to form a composite sample of Portland cement concrete during placement?
Answer: 3
AASHTO R 60 specifies that a composite concrete sample is made from at least three grab samples taken at regular intervals during discharge.
A field sample of aggregates taken from a stockpile must avoid the outer surface layer because:
Answer: Segregated or degraded material collects at the surface and edges
The outer layer of a stockpile accumulates segregated coarse particles and may contain contamination, making it unrepresentative.
For HMA acceptance testing, which sampling method involves collecting material directly from the paver's hopper?
Answer: Hopper sampling
Hopper sampling involves collecting HMA directly from the paver's hopper before it is laid, capturing a sample representative of incoming material.
When sampling soil from a test pit for density testing purposes, which layer is sampled first?
Answer: Deepest layer to avoid disturbance from upper layers
Sampling begins at the bottom of the excavation to prevent contamination from material falling from disturbed upper layers.
A lot acceptance plan for pavement base course uses systematic sampling, taking one sample every 500 tons. If a lot is 3,200 tons, how many samples are collected?
Answer: 7
3,200 tons ÷ 500 tons/sample = 6.4, which rounds up to 7 samples to cover the entire lot.
In the context of NETTCP testing, what does 'representative sample' mean?
Answer: A portion that reflects the same properties as the entire material mass
A representative sample accurately reflects the composition, gradation, and properties of the total material being evaluated.
Which tool is specifically recommended for sampling fine aggregate from a flowing stream (belt conveyor) rather than from a static stockpile?
Answer: Sampling pan passed through the full stream cross-section
A sampling pan or trough passed through the full width of a moving stream ensures all size fractions are captured equally.