Abrasion and Impact in the Los Angeles Machine
Summary of Test Method
This test is a measure of degradation of mineral aggregates of standard gradings resulting from a combination of actions including abrasion or attrition, impact, and grinding in a rotating steel drum containing a specified number of steel spheres, the number depending upon the grading of the test sample. As the drum rotates, a shelf plate picks up the sample and the steel spheres, carrying them around until they are dropped to the opposite side of the drum, creating an impactcrushing effect. The contents then roll within the drum with an abrading and grinding action until the shelf plate picks up the sample and the steel spheres, and the cycle is repeated. After the prescribed number of revolutions, the contents are removed from the drum and the aggregate portion is sieved to measure the degradation as percent loss. Los Angeles Testing Machine shown in Figure 1.
- Place the test sample and the charge in the Los Angeles testing machine and rotate the machine at a speed of 30 to 33 r/min for 500 revolutions. After the prescribed number of revolutions, discharge the material from the machine and make a preliminary separation of the sample on a sieve coarser than the 1.70-mm (No. 12) sieve. Sieve the finer portion on a 1.70-mm (No. 12) sieve in a manner conforming to Standard Test Method for Sieve Analysis of Fine and Coarse Aggregates. Wash the material coarser than the 1.70-mm (No. 12) sieve and oven-dry at 110 ±5°C to a constant mass, and determine the mass.
- Calculate the loss (difference between the original mass and the final mass of the test sample) as a percentage of the original mass of the test sample.
Quote: ASTM C131, Standard Test Method for Resistance to Degradation of Small-Size Coarse Aggregate by Abrasion and Impact in the Los Angeles Machine.
Figure.1 Los Angeles Testing Machine