LA Abrasion Test

A H M 531

Los Angeles Abrasion test

By: Ahmed Essam Mansour

Objectives: ¾ Measuring the hardness of coarse aggregate, i.e. the resistance of wear using Los Angeles method to determine the Los Angeles Abrasion Value (L.A.A.V)

Standards: ¾ ASTM C 131 - 69 ¾ ASTM C 535 – 69 ¾ AASHO T 96

General Discussion: A H M 531 Los Angeles abrasion test studies all possible reasons causing wear. In The Civil Engineering Center the L.A. abrasion machine Attrition, Abrasion, and crushing are all present as follows: • Attrition: By the friction between the aggregate particles. •

Abrasion: By the friction between the steel balls and the aggregates.

•

Crushing: By hitting the walls of the testing machine.

Los Angeles abrasion test is suitable for coarse aggregate of different sizes and it is not used for fine aggregate. Los Angeles Abrasion Value (L.A.A.V.): Is obtained from this test and it measures the wear of the material due to abrasion and attrition. L.A.A.V. = Original mass - retained mass (at sieve # 12) Original mass x 100%

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This value differs one grading to another, so there was specifications that specifies the samples grading with there masses and the charge of balls needed. We used grading B, our choice was based on that this grading is the most common. Grading B consists of two different sizes of aggregate, the first one passes through sieve 19 mm and retained at

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A H M 531

Los Angeles Abrasion test

By: Ahmed Essam Mansour

sieve 12.5 mm, the second size passes through the 12.5 mm sieve and is retained at 9.5 mm sieve. According to the specification the total weight of the aggregate that should be used in the test is 5000 ± 10 gm. For grading B it was specified that 11 steel balls shall be placed in the machine with the aggregates. According to the specifications if L.A.A.V. is less than 30% then this aggregate is suitable for all mixture, and if it is more than 50% this aggregate is unusable in any mixture.

Apparatus and Materials: 1.

Los Angeles Machine: It consists from: ₪ A steel drum, 28 inches in diameter and 20 inches in length. This drum rotates with its axis set horizontally at a speed of approximately 33 r.p.m.

A H M 531 The Civil Engineering Center

₪ A door closed by bolts and nuts, and an internal steel shelf that extend along the steel drum and it guarantees that the balls and aggregate will hit and so abrasion and attrition are done. ₪ Automatic counter switch, the number of wanted revolutions is set at the beginning of the test so that the machine will stop automatically when revolving the set number of revolutions.

2.

Steel balls.

3.

Weighing machine.

4.

Sieves (19 mm, 12.5 mm and 9.5 mm).

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A H M 531

Los Angeles Abrasion test

By: Ahmed Essam Mansour

Procedures: 1.

Getting specimen of grade B: Each group prepared one of the two sizes in the grading, The first group sieved the aggregate through 19mm sieve and 12.5 mm sieve, the aggregates passing through 19 mm sieve and retained at 12.5 mm sieve were take by an amount that equals 2500 gm. The second group sieved the aggregate through 12.5mm and 9.5mm sieve, the aggregates passing through 12.5mm sieve and retained at 9.5mm sieve were taken by an amount that equals 2500 gm. So the total weight of the specimen equals to 5000gm as the standard specifications.

2.

3.

A H M 531 The Civil Engineering Center We set the L.A. Machine to revolve 500 revolutions.

We placed the specimen in the machines drum with 11 steel balls.

4.

After it stopped the steel balls were taken first and then the specimen is filled in a tray.

5.

The specimen then is sieved at #12 (1.7mm), and the retained aggregate is weighted. (W)

Conclusion: The aggregate we used is suitable for all concrete mixtures as its L.A.A.V < 30. The L.A.A.V is direct proportional to the wear of aggregate.

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