ATT Sampling Aggregates 2 — Questions and Answers
Question 1: When sampling aggregates from a conveyor belt, how many approximately equal increments must be taken to constitute one sample according to ASTM D75?
- At least 3 increments (Correct answer)
- At least 10 increments
- At least 5 increments
- A single large scoop
Correct answer: At least 3 increments
ASTM D75 requires a minimum of three approximately equal increments taken from the full cross-section of the belt to constitute a field sample.
Question 2: Which piece of equipment is specifically recommended for obtaining a cross-sectional cut of aggregate from a moving conveyor belt?
- A mechanical sampler frame (Correct answer)
- A front-end loader
- A grain probe
- A shovel held at belt edge
Correct answer: A mechanical sampler frame
A mechanical sampler frame that spans the full belt width is recommended to capture a complete cross-sectional cut without bias.
Question 3: Why is sampling aggregate directly from a stockpile surface considered a poor practice?
- Surface material has segregated and is not representative of the pile (Correct answer)
- It damages the stockpile structure
- ASTM prohibits surface sampling entirely
- Surface material is too dry to test
Correct answer: Surface material has segregated and is not representative of the pile
Segregation causes coarser particles to roll to the outer edges and base of a stockpile, making surface samples unrepresentative of the bulk material.
Question 4: What is the primary purpose of reducing a large field sample of aggregate to a smaller test sample?
- To obtain a specimen of manageable size that still represents the field sample (Correct answer)
- To remove oversized particles before testing
- To dry the aggregate before shipping
- To reduce transportation costs
Correct answer: To obtain a specimen of manageable size that still represents the field sample
Sample reduction produces a test specimen small enough for laboratory equipment while preserving the same particle size distribution as the original field sample.
Question 5: Which ASTM standard governs the practice of reducing samples of aggregate to testing size?
- ASTM C702 (Correct answer)
- ASTM D75
- ASTM C136
- ASTM C117
Correct answer: ASTM C702
ASTM C702 covers the standard practice for reducing samples of aggregate to testing size using methods such as mechanical splitting or quartering.
Question 6: When sampling from a flowing aggregate stream at a discharge point, when should increments be collected?
- At random time intervals throughout the entire flow period (Correct answer)
- Only at the beginning and end of the flow
- Only when flow rate is highest
- After the stream has been running for at least 10 minutes
Correct answer: At random time intervals throughout the entire flow period
Increments must be collected at random time intervals spanning the full duration of flow to ensure the composite sample represents all material discharged.
Question 7: For a field sample taken from a truck or rail car, from how many locations within the load should increments be collected?
- At least five locations (Correct answer)
- One central location
- Two opposite corners only
- The top center of the load only
Correct answer: At least five locations
ASTM D75 specifies collecting increments from at least five locations distributed across the load to account for segregation that occurs during transport.
ATT Sampling Aggregates 2
When sampling aggregates from a conveyor belt, how many approximately equal increments must be taken to constitute one sample according to ASTM D75?