ATT Soundness & Durability Testing 3 — Questions and Answers
Question 1: The Los Angeles abrasion test (ASTM C131/C535) measures aggregate resistance to:
- Freeze-thaw deterioration
- Degradation by abrasion and impact (Correct answer)
- Chemical sulfate attack
- Alkali-silica reactivity
Correct answer: Degradation by abrasion and impact
The LA abrasion test measures an aggregate's resistance to degradation by abrasion and impact using steel balls in a rotating drum.
Question 2: In the Los Angeles abrasion test, after rotation the aggregate is washed over which sieve to determine percent loss?
- 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)
Material passing the No. 12 (1.70 mm) sieve after washing is considered loss in the LA abrasion test.
Question 3: ASTM C131 applies to coarse aggregate with particles predominantly retained on which sieve?
- 37.5 mm (1½ in.)
- 19.0 mm (¾ in.)
- 9.5 mm (⅜ in.) (Correct answer)
- 4.75 mm (No. 4)
Correct answer: 9.5 mm (⅜ in.)
ASTM C131 covers smaller coarse aggregates predominantly retained on the 9.5 mm (⅜ in.) sieve, while C535 covers larger aggregates.
Question 4: In the Micro-Deval test (ASTM D6928), what abrasive medium is used with the aggregate sample?
- Steel balls and water (Correct answer)
- Crushed quartz sand
- Hardened steel shot and a saline solution
- Steel balls and water
Correct answer: Steel balls and water
The Micro-Deval test uses steel balls and water in a rotating drum to determine aggregate wear resistance.
Question 5: Which LA abrasion percent loss value represents BETTER aggregate quality?
- 45%
- 35%
- 25% (Correct answer)
- 55%
Correct answer: 25%
A lower LA abrasion percent loss indicates a harder, more wear-resistant aggregate; 25% represents better quality than higher values.
Question 6: What is the typical maximum LA abrasion loss specified for coarse aggregate used in concrete pavement?
- 50%
- 40% (Correct answer)
- 30%
- 20%
Correct answer: 40%
Most pavement specifications limit LA abrasion loss to 40% or less for coarse aggregate in concrete pavement applications.
Question 7: How does the Micro-Deval test differ from the LA abrasion test in terms of the degradation mechanism it emphasizes?
- Micro-Deval emphasizes impact fracture while LA abrasion emphasizes polishing
- Micro-Deval emphasizes wet abrasion/attrition while LA abrasion includes significant impact (Correct answer)
- Micro-Deval uses heat cycling while LA abrasion is purely mechanical
- Micro-Deval tests fine aggregates while LA abrasion is for coarse only
Correct answer: Micro-Deval emphasizes wet abrasion/attrition while LA abrasion includes significant impact
The Micro-Deval test emphasizes wet abrasion and attrition at lower energy, while the LA abrasion test includes significant impact from the steel balls and the shelf inside the drum.
ATT Soundness & Durability Testing 3
The Los Angeles abrasion test (ASTM C131/C535) measures aggregate resistance to: