ATT Los Angeles Abrasion Testing 2 — Questions and Answers
Question 1: How many steel balls (charge) are used for ASTM C131 Grading A?
- 6 balls
- 8 balls
- 10 balls
- 12 balls (Correct answer)
Correct answer: 12 balls
Grading A in ASTM C131 requires a charge of 12 steel balls weighing 5,000 ± 25 g.
Question 2: What is the standard number of revolutions for the LA abrasion test on aggregates tested per ASTM C131?
- 100 revolutions
- 300 revolutions
- 500 revolutions (Correct answer)
- 1000 revolutions
Correct answer: 500 revolutions
The standard test per ASTM C131 requires exactly 500 revolutions of the LA machine drum.
Question 3: The Los Angeles abrasion loss is expressed as:
- The mass retained on the No. 12 sieve divided by original mass × 100
- The mass passing the No. 12 sieve divided by original mass × 100 (Correct answer)
- The mass of steel balls lost divided by original mass × 100
- The difference in drum diameter before and after testing × 100
Correct answer: The mass passing the No. 12 sieve divided by original mass × 100
LA abrasion loss (%) = (mass passing the No. 12 sieve ÷ original sample mass) × 100.
Question 4: ASTM C535 is used instead of ASTM C131 when aggregate is:
- Smaller than 3/8 inch (9.5 mm)
- Larger than 1½ inch (37.5 mm) (Correct answer)
- Contaminated with clay
- Lighter than 2.4 specific gravity
Correct answer: Larger than 1½ inch (37.5 mm)
ASTM C535 covers larger aggregates with particles greater than 1½ in. (37.5 mm), while C131 covers smaller sizes.
Question 5: After the LA abrasion test, the aggregate and charge are separated using a sieve with an opening size of:
- No. 4 (4.75 mm)
- No. 8 (2.36 mm)
- No. 12 (1.70 mm) (Correct answer)
- No. 16 (1.18 mm)
Correct answer: No. 12 (1.70 mm)
The material is removed from the machine and sieved over a No. 12 (1.70 mm) sieve to determine loss.
Question 6: The inside diameter of the Los Angeles abrasion machine drum is approximately:
- 457 mm (18 in.)
- 711 mm (28 in.) (Correct answer)
- 508 mm (20 in.)
- 610 mm (24 in.)
Correct answer: 711 mm (28 in.)
The LA machine drum has an inside diameter of 711 mm (28 in.) and an inside length of 508 mm (20 in.).
Question 7: When preparing a grading B sample for ASTM C131, which sieve sizes define the retained fractions?
- 1 in. to 3/4 in. and 3/4 in. to 1/2 in.
- 3/4 in. to 1/2 in. and 1/2 in. to 3/8 in. (Correct answer)
- 1/2 in. to 3/8 in. and 3/8 in. to No. 4
- 3/8 in. to No. 4 and No. 4 to No. 8
Correct answer: 3/4 in. to 1/2 in. and 1/2 in. to 3/8 in.
Grading B uses material retained between 3/4–1/2 in. and 1/2–3/8 in. sieves with a total mass of 2,500 g each fraction.
ATT Los Angeles Abrasion Testing 2
How many steel balls (charge) are used for ASTM C131 Grading A?