Aggregate Sampling & Reduction Flashcards
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Read the first 7 Aggregate Sampling & Reduction flashcards as text
After mechanical splitting of an aggregate sample, the technician notices one half is significantly heavier than the other. What is the most likely cause?
Answer: The splitter chutes were of unequal width or material bridged during splitting
Unequal chute widths or bridging during mechanical splitting are the most common causes of uneven mass distribution between the two halves.
When sampling aggregate from a flowing discharge stream, increments should be collected:
Answer: At regular time intervals throughout the entire discharge period
Collecting increments at regular intervals throughout the entire discharge period ensures that material from all phases of the discharge is represented in the composite sample.
Per ASTM C702, when using the quartering method, after how many completed quartering cycles is the sample typically considered reduced to testing size?
Answer: As many cycles as needed until the remaining mass meets the minimum test requirement
Quartering cycles are repeated until the retained portion reaches the minimum required test sample mass; there is no fixed number of cycles specified.
A technician collects only a single grab of material from the top of a stockpile and submits it as the field sample. This practice violates ASTM D75 primarily because:
Answer: A single grab cannot constitute a composite sample and the stockpile surface is subject to segregation
ASTM D75 requires composite samples formed from multiple increments; additionally, the stockpile surface is segregated and unrepresentative of the bulk material.
Which of the following aggregate sampling locations is generally considered the MOST representative of the material going into a pavement?
Answer: From the discharge end of the cold feed conveyor belt
The cold feed conveyor belt captures aggregate in motion before it enters the dryer, giving a representative cross-section of the material actually being fed into production.
What does ASTM D75 recommend doing when a sample must be shipped by mail or freight to a distant laboratory?
Answer: Double-bag the sample in moisture-resistant bags and seal securely to prevent loss and moisture change
ASTM D75 recommends double-bagging and secure sealing to protect the sample from loss of fines and moisture changes that would affect test results during transit.
When the field sample size exceeds what is needed but the technician has no mechanical splitter available, ASTM C702 recommends which alternative reduction method?
Answer: Use the quartering method as an approved alternative to mechanical splitting
ASTM C702 explicitly recognizes quartering as an approved alternative when mechanical splitters are unavailable, provided the procedure is followed correctly.