ATT ATT Flat, Elongated Particles & Sand Equivalent 1 — Questions and Answers
Question 1: Which ASTM standard covers the test method for flat particles, elongated particles, or flat and elongated particles in coarse aggregate?
- ASTM C131
- ASTM D4791 (Correct answer)
- ASTM C142
- ASTM C29
Correct answer: ASTM D4791
ASTM D4791 is the standard test method for flat particles, elongated particles, or flat and elongated particles in coarse aggregate.
Question 2: In ASTM D4791, a particle is classified as 'flat' when the ratio of its width to thickness exceeds:
- 2:1
- 3:1 (Correct answer)
- 5:1
- 10:1
Correct answer: 3:1
Per ASTM D4791, a particle is classified as flat when the ratio of width to thickness is greater than a specified value, commonly 3:1 for standard testing.
Question 3: Why are flat and elongated particles undesirable in concrete aggregate?
- They reduce water demand significantly
- They tend to orient horizontally and create planes of weakness, increasing water demand (Correct answer)
- They improve workability of fresh concrete
- They have higher specific gravity
Correct answer: They tend to orient horizontally and create planes of weakness, increasing water demand
Flat and elongated particles orient themselves horizontally under compaction, creating planes of weakness and requiring more water for adequate workability.
Question 4: The proportional caliper device used in ASTM D4791 testing measures:
- The mass of individual particles
- The ratio between two dimensions of a particle (Correct answer)
- The surface area of particles
- The volume of particles
Correct answer: The ratio between two dimensions of a particle
The proportional caliper used in ASTM D4791 is set to a specific ratio (e.g., 1:3 or 1:5) and directly indicates whether a particle's dimensional ratio exceeds the threshold.
Question 5: In ASTM D4791, what is the minimum number of particles required for a valid flat and elongated test?
- 50 particles
- 100 particles (Correct answer)
- 200 particles
- 500 particles
Correct answer: 100 particles
ASTM D4791 requires a minimum of 100 particles per size fraction to achieve statistically reliable results.
Question 6: A particle classified as 'flat and elongated' in ASTM D4791 has a ratio of its maximum dimension to its minimum dimension exceeding:
- 2:1
- 3:1
- 5:1 (Correct answer)
- 1.5:1
Correct answer: 5:1
A particle is classified as flat and elongated in ASTM D4791 when the ratio of maximum to minimum dimension exceeds 5:1.
ATT ATT Flat, Elongated Particles & Sand Equivalent 1
Which ASTM standard covers the test method for flat particles, elongated particles, or flat and elongated particles in coarse aggregate?