Practice Test Geeks(ATT) ACI Aggregate Testing Technician Practice Test
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Los Angeles Abrasion Testing Flashcards

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  1. Many highway specifications require that coarse aggregate for base course have an LA abrasion loss no greater than:

    Answer: 50%

    A maximum LA abrasion loss of 50% is a common specification limit for coarse aggregate used in base course applications.

  2. Compared to base course aggregate, the maximum allowable LA abrasion loss for aggregate used in concrete wearing slabs is typically:

    Answer: Lower, because surface aggregate must resist traffic wear directly

    Wearing surfaces demand harder, more abrasion-resistant aggregate, so specifications set lower maximum LA loss values (often ≤30–40%).

  3. A project specification requires LA abrasion loss ≤ 40%. A test result of 38% means the aggregate:

    Answer: Passes because 38% is less than 40%

    The aggregate passes because 38% is below the 40% maximum limit; no additional safety margin is required by ASTM C131.

  4. The LA abrasion test primarily measures resistance to:

    Answer: Abrasion and impact degradation

    The test measures resistance to abrasion (grinding) and impact (tumbling with steel balls), simulating degradation during handling and service.

  5. Which of the following applications is MOST sensitive to aggregate LA abrasion loss?

    Answer: Concrete pavement wearing course

    Concrete pavement wearing courses experience direct traffic abrasion, making aggregate hardness critical and LA loss limits most restrictive.

  6. When two LA abrasion tests are run on samples from the same lot, the results are 34% and 39%. What action should the technician take?

    Answer: Report both values and check if the difference exceeds the allowable precision

    ASTM C131 provides precision statements; both results should be reviewed against the multi-laboratory or single-operator precision limits before averaging.

  7. A technician notices that some aggregate particles broke along pre-existing cracks during the LA test. This outcome indicates:

    Answer: The aggregate has inherent weaknesses, which is exactly what the test is designed to detect

    Pre-existing fractures represent real aggregate weakness; detecting them is a valid purpose of the LA abrasion test.