Aggregate Sampling & Reduction Flashcards
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Per ASTM C702, which reduction method is NOT recommended for fine aggregate because it can introduce segregation errors?
Answer: Miniature stockpile method
The miniature stockpile method is not recommended for fine aggregate because fine particles can segregate when formed into a small conical pile.
What minimum sample mass of coarse aggregate (3/4-in. maximum size) is typically required for a field sample per ASTM D75?
Answer: 25 kg (55 lb)
ASTM D75 specifies approximately 25 kg (55 lb) as the minimum field sample mass for coarse aggregate with a 3/4-in. nominal maximum size.
When sampling freshly mixed concrete at a job site for aggregate content verification, which standard governs obtaining the composite sample of fresh concrete?
Answer: ASTM C172
ASTM C172 covers sampling freshly mixed concrete, from which aggregate-related tests such as unit weight and air content are then performed.
What effect does over-drying an aggregate sample before splitting have on test results?
Answer: It prevents accurate moisture content determination of the field sample
If a field sample is oven-dried before splitting, its original field moisture is destroyed, making it impossible to determine the as-received moisture content.
Which of the following best describes a 'composite sample' as defined in ASTM D75?
Answer: A sample made up of several increments combined together
A composite sample is formed by combining multiple individual increments collected from different points or times to represent a lot of material.
When sampling from a truck or rail car, at how many approximately equal depth-interval locations across the load should increments be taken?
Answer: At least three locations across the load
ASTM D75 recommends collecting increments from at least three locations across the load at approximately equal depth intervals to account for variation within the unit.
Why is it important to sample aggregate from a moving conveyor belt rather than from a stationary pile whenever possible?
Answer: Moving belt samples capture the full cross-section of material flow, reducing segregation bias
Sampling from a moving belt captures the complete cross-section of aggregate being conveyed, avoiding the segregation bias inherent in stockpile sampling.