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MATERIAL TESTING
Resistance to Degradation of Small-Size Coarse Aggregate by Abrasion and Impact in the Los Angeles Machine

AASHTO T 96-02 / ASTM C 131-01

Standard Method of Tests

Resistance to Degradation of Small-Size Coarse Aggregate by Abrasion and Impact in the Los Angeles Machine

Standard AASHTO T 96-02 / ASTM C 131-01

The resistance to degradation of coarse aggregates with a maximum size smaller than 37.5 mm (1½ in.) is determined using the Los Angeles testing machine based on AASHTO T 96-02 / ASTM C 131-01 test method.

Test Summary: The Los Angeles Abrasion (LAA) 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 of spheres chosen for the abrasion tests depends on the grading of the test sample. The drum rotates creating an impact crushing effect with an abrading and grinding action. 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 on abrasion.

Los Angeles Machine


Sieves


Weigh Balance - conforming to AASHTO M 231, Class G 5.


Abrasion Charge - consisting of steel spheres or ball bearings each having a diameter of between 46 mm [ 1 13⁄16 in.] and 48 mm [1 7⁄8 in.] and each having a mass of between 390 and 445 g. Suitable abrasive charge shall be selected depending upon the grading of the test sample as given in table below.

Grading Number of Spheres Mass of Charge, g
A 12 5000±25
B 11 4580±25
C 8 3330±20
D 6 2500±15

Oven of appropriate size capable of maintaining a uniform temperature of 110 ± 5°C (230 ± 9°F).


Step 1: Sampling

Obtain the field sample in accordance with AASHTO T 2, and reduce the field sample to adequate sample size in accordance with AASHTO T 248.


Step 2:

Wash the reduced sample and oven dry at 110 ± 5°C (230 ± 9°F) to a constant mass. Separate the sample into individual size fractions, and recombine to the grading given in Table below. The gradings most nearly corresponding to the range of sizes in the aggregate as furnished for the work shall be selected. Record the mass of the sample prior to test to the nearest 1 g.


Gradings of Test Samples
Sieve Size Mass, g
Passing Retained on Grading A Grading B Grading C Grading D
37.5 mm (1½ 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 (½ in.) 1250±10 2500±10 --- ---
12.5 mm (½ in.) 9.5 mm (3/8 in.) 1250±10 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

Step 3:

Place the test sample and the charge in the Los Angeles testing machine and rotate the machine at a speed of 30 to 33 rev/min for 500 revolutions.


Step 4:

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. The finer portion is sieved through a 1.70-mm (No. 12) sieve in a manner conforming to AASHTO T 27. Wash the material coarser than the 1.70-mm (No. 12) sieve and oven-dry at 110 ± 5°C (230 ± 9°F) to a constant mass, and determine the 6ass to the nearest 1 g.



Calculation:

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. Report this value as the percent loss

Percent Loss =  ( C Y ) C × 100 where:
C = mass of original test sample, g, and
Y = final mass of the test sample, g.

LOS ANGELES ABRASION




Output:

Los Angeles Abrasion Percent Loss:

Report Section

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