University of New Mexico
Civil Engineering Department
Civil Engineering Materials Laboratory, CE 305L
RESISTANCE TO DEGRADATION OF SMALL-SIZE COARSE AGGREGATE
BY ABRASION AND IMPACT IN THE LOS ANGELES MACHINE
ASTM C131
Scope
This test method covers a procedure for testing sizes of coarse aggregate smaller than 1-1/2 inch (37.5 mm) for resistance to degradation using the Los Angeles testing machine.
References
ASTM C136 Sieve Analysis of Fine and Coarse Aggregate
ASTM C535 Resistance to Degradation of Large-Size Coarse Aggregate by Abrasion and Impact in the Los Angeles Machine
ASTM E11 Specification for Wire-Cloth Sieves for Testing Purposes
Summary
The Los Angeles 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 L.A. Abrasion test is widely used as an indicator of the relative quality or competence of mineral aggregates.
Apparatus
Los Angeles testing machine
Sieves
Balance – accurate within 0.1% of range required for test
Charge – the charge shall consist of steel spheres averaging approximately 46.8 mm in diameter and each weighing between 390 and 445 g. The charge, depending upon the grading of the test sample, shall be as follows:
Grading |
Number of Spheres |
Weight of Charge, g |
A |
12 |
5000 +/- 25 |
B |
11 |
4584 +/- 25 |
C |
8 |
3330 +/- 20 |
D |
6 |
2500 +/- 15 |
Materials
The test sample shall be washed and oven-dried (105 to 115 °C) to substantially constant weight, separated into individual size fractions, and recombined to the grading (Table 1) most nearly corresponding to the range of sizes in the aggregate as originally furnished.
Los Angeles Testing Machine
Procedure
Download Procedure for the LA abrasion test
Download Excel form for the LA abrasion test
• Wash the coarse aggregate test sample, per ASTM C136, and oven-dry (105 to 115 °C) to substantially constant weight. Separate into individual size fractions, and recombine to the grading (Table 1) most nearly corresponding to the range of sizes in the aggregate as originally furnished. The weight of the sample prior to test shall be recorded to the nearest 1 g.
• Place the test sample and the charge in the Los Angeles testing machine
• Rotate the machine at a speed of 30 to 33 rpm for 500 revolutions.
• Discharge the material from the L.A. abrasion machine and separate the sample on a No. 12 sieve (1.70 mm).
• Weigh the material coarser than the No. 12 sieve and record this as the final weight.
Table 1. Gradings of Test Samples
|
Weight of Indicated Sizes, g |
||||
Sieve Size (Square Openings) |
Grading |
||||
Passing |
Retained on |
A |
B |
C |
D |
37.5 mm (1-1/2 in.) |
25.0 mm (1 in.) |
1250 +/- 25 |
|||
25.0 mm (1 in.) |
19.0 mm (3/4 in.) |
1250 +/- 25 |
|||
19.0 mm (3/4 in.) |
12.5 mm (1/2 in.) |
1250 +/- 25 |
2500 +/- 10 |
||
12.5 mm (1/2 in.) |
9.5 mm (3/8 in.) |
1250 +/- 25 |
2500 +/- 10 |
||
9.5 mm (3/8 in.) |
6.3 mm (1/4 in.) |
2500 +/- 10 |
|||
6.3 mm (1/4 in.) |
4.75 mm (No. 4) |
2500 +/- 10 |
|||
4.75 mm (No. 4) |
2.36 mm (No. 8) |
5000 +/- 10 |
|||
Total |
5000 +/- 10 |
5000 +/- 10 |
5000 +/- 10 |
5000 +/- 10 |
|
• Calculate the L.A. abrasion loss as the difference between the original weight and the final weight of the test sample as a percentage of the original weight of the test sample.
L.A. Abrasion Loss (%) = (Original Weight – Final Weight)*100/(Original Weight)
Report
1) The L.A. abrasion loss as a percentage (nearest 1%).
Questions• What is the maximum allowable abrasion loss for concrete coarse aggregate as specified in ASTM C33, Standard Specifications for Concrete Aggregates?
• Do your test results satisfy the abrasion loss requirements for concrete coarse aggregate as specified in ASTM C33, Standard Specifications for Concrete Aggregates?