ATT Los Angeles Abrasion Testing 3

Question 1

The shelf (lifter) inside the LA abrasion machine drum is positioned:

Accepted Answer

Projecting inward along the full length of the drum

Answer

The shelf projects inward along the full interior length of the drum to lift and tumble the charge during rotation.

Question 2

If a technician finds that the LA machine drum rotational speed is 40 rpm instead of the specified range, the test result will likely:

Accepted Answer

Be invalid and must be discarded per ASTM C131

Answer

ASTM C131 specifies a speed of 30–33 rpm; results obtained outside this range are not valid per the standard.

Question 3

Which characteristic of the steel balls (charge) must be verified before each LA abrasion test?

Accepted Answer

Total mass of the charge within the specified tolerance

Answer

The total charge mass must meet the specification for the grading used (e.g., 5,000 ± 25 g for Grading A), verified by weighing.

Question 4

A technician performing the LA abrasion test washes and dries the test sample before testing. The drying temperature should be:

Accepted Answer

110 ± 5°C (230 ± 9°F)

Answer

The sample must be dried to constant mass at 110 ± 5°C (230 ± 9°F) before testing per ASTM C131.

Question 5

After running the LA abrasion test, the retained material on the No. 12 sieve should be:

Accepted Answer

Washed, dried to constant mass, then weighed

Answer

The material retained on the No. 12 sieve is washed and dried to constant mass at 110 ± 5°C before final weighing.

(ATT) ACI Aggregate Testing Technician Practice Test