Practice Test Geeks(ATT) ACI Aggregate Testing Technician Practice Test
← All ATT Flashcard Decks

Los Angeles Abrasion Testing Flashcards

7 cards from real ATT practice questions. Tap to flip, then mark Knew It or Still Learning — missed cards come back until you master them.

Read the first 7 Los Angeles Abrasion Testing flashcards as text

  1. How does the LA abrasion test differ from the Micro-Deval abrasion test (ASTM D6928)?

    Answer: LA uses a dry drum with large steel balls; Micro-Deval uses water and small steel balls

    The LA test uses a dry rotating drum with large steel balls, while the Micro-Deval test uses water and small steel balls to simulate wet abrasion conditions.

  2. An aggregate source produces two gradations: one tested per Grading C and one per Grading D of ASTM C131. Which statement about comparing the results is correct?

    Answer: Results may not be directly comparable because gradation and charge differ between gradings

    Different gradings use different steel ball charges and particle sizes, so LA loss values between gradings are not directly comparable.

  3. What is the purpose of washing the aggregate sample before the LA abrasion test?

    Answer: To remove dust and fines that would falsely inflate the abrasion loss

    Pre-existing dust and fines would pass the No. 12 sieve regardless of abrasion, inflating the measured loss; washing removes them before testing.

  4. The single-operator precision (1s%) for the LA abrasion test per ASTM C131 is approximately:

    Answer: 2%

    ASTM C131 precision data show a single-operator coefficient of variation of approximately 2%, meaning repeat tests by the same operator should be within about 6% of each other.

  5. A recycled concrete aggregate (RCA) source is suspected to have high abrasion loss. Which grading would most likely be selected for an LA abrasion test if the RCA is all passing 3/4 in. (19 mm) and retained on No. 4 (4.75 mm)?

    Answer: Grading C

    Grading C covers material passing 3/8 in. and retained on No. 4, while Grading B covers 3/4–3/8 in.; for material all passing 3/4 in. and retained on No. 4, the composite falls under Grading C.

  6. During an LA abrasion test, the drum is accidentally stopped at 450 revolutions due to a power outage. The technician should:

    Answer: Discard the sample and start the test over with a fresh specimen

    ASTM C131 requires exactly 500 revolutions; an incomplete run compromises the result and the test must be restarted with a fresh sample.

  7. Which scenario would cause the LA abrasion loss to be artificially LOWER than the true value?

    Answer: Failing to wash fines off the sample before testing

    If pre-existing fines are not washed off, they remain in the sample mass (denominator) without being lost, mathematically reducing the calculated percent loss.