Sampling Aggregates Flashcards
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Which of the following situations represents 'biased sampling' of aggregate?
Answer: Consistently sampling only from the outside edges of a stockpile where fines accumulate
Sampling from stockpile edges introduces bias because coarse particles roll away, leaving fines concentrated at the periphery, making the sample unrepresentative.
What is the significance of the 'increment' in aggregate sampling terminology?
Answer: A single portion of material collected in one operation that is combined with others to form the field sample
An increment is one individual scoop or cut of material; multiple increments are combined to create the composite field sample used for testing.
Which ASTM standard provides the primary guidance for sampling aggregates from various sources including stockpiles, conveyor belts, and transportation units?
Answer: ASTM D75
ASTM D75 is the standard practice for sampling aggregates and covers procedures for obtaining samples from stockpiles, flowing streams, trucks, rail cars, and barges.
When sampling aggregate from a barge or ship hold, what is the recommended approach if material cannot be sampled from a flowing stream?
Answer: Sample from multiple locations within the hold at varying depths
Multiple sampling locations at varying depths within the hold help account for segregation caused by loading and settling during transport.
The required minimum mass of a field sample is primarily determined by which aggregate characteristic?
Answer: The nominal maximum size of the aggregate
ASTM D75 Table 1 ties minimum field sample mass directly to nominal maximum size because larger particles require more material to achieve statistical representativeness.
After collecting a field sample, what information must be recorded as a minimum on the sample identification tag?
Answer: Sample ID, material description, source location, date and time, and sampler's name
Complete identification including source, time, date, and sampler ensures traceability and allows results to be linked back to a specific lot of material.
Fine aggregate samples that will be tested for moisture-sensitive properties (e.g., absorption) should be transported in:
Answer: Sealed, moisture-proof containers to prevent drying or wetting
Sealed, moisture-proof containers preserve the as-sampled moisture state, which is essential for accurate absorption and surface moisture measurements.