SUMMARY

Take approximately 5000g sample of aggregate retained on the No. 12 (1.70 mm)

sieve is placed inside a rotating steel drum containing a specified number of steel spheres

or "charge". As the drum rotates, a shelf inside the drum picks up the aggregate and steel

spheres. The shelf carries them around until they drop on the opposite side of the drum,

subjecting the aggregate to impact and crushing. Then, the aggregate is subjected to

abrasion and grinding as the drum continues to rotate until the shelf picks up the contents,

and the process is repeated. The drum is rotated for a 500 number of revolutions at 30-

33rpm. Afterward, the aggregate is removed from the drum and sieved on a No. 12 (1.70

mm) sieve. The aggregate retained on the sieve is weighed and the difference between

this weight and the original weight is expressed as a percentage and reported as the L.A.

abrasion loss value.

INTRODUCTION

Tests for resistance to abrasion in crushed rock, slag, crushed and uncrushed

gravel can using Los Angeles testing method. Features welded structural steel frame,

fabricated 1/2”-thick (913mm) abrasion-resistant steel drum, removable shelf bolted to

drum and balanced drum assembly for easy rotation by hand. Enclosed chain drive rotates

drum without conventional slip clutch. Positive drive delivers greater accuracy. Self-

contained worm-drive motorized speed reducer has anti-friction bearings and sealed

lubrication. Soft aggregate will be quickly ground to dust; while as harder aggregate are

resistances to crushing effect. This test method covers a procedure for testing sizes of

coarse aggregate smaller than 37.5 mm for resistance to degradation using the Los

Angeles testing machine.

OBJECTIVE

The objective of the experiment is:

i. To ascertain the degradation property of aggregates by abrasion.

Apparatus:

Los Angeles Abrasion machine, sieve shaker, sieve sizes of 25mm, 20mm, 14mm,

10mm, 1.7mm, and pan, balance accurate to 0.01g and fine haired brush(3mm).

THEORY

A common test used to characterize toughness and abrasion resistance is the Los

Angeles (L.A.) abrasion test.  For the L.A. abrasion test, the portion of an aggregate

sample retained on the 1.70 mm (No. 12) sieve is placed in a large rotating drum that

contains a shelf plate attached to the outer wall (the Los Angeles machine).  A specified

number of steel spheres are then placed in the machine and the drum is rotated for 500

revolutions at a speed of 30 - 33 revolutions per minute (RPM).  The material is then

extracted and separated into material passing the 1.70 mm (No. 12) sieve and material

retained on the 1.70 mm (No. 12) sieve.  The retained material (larger particles) is then

weighed and compared to the original sample weight.  The difference in weight is

reported as a percent of the original weight and called the "percent loss". For many

decades throughout the world, the L. A. Abrasion test (ASTM and AASHTO) has been

the standard for evaluating coarse aggregate degradation and toughness in dry conditions.

It also is a standard in the EU. Rogers wrote, “Despite the name, the Los Angeles test

does not measure abrasion but rather impact resistance.” Many believe that this dry test is

a measure principally of breakdown due to impact and degradation during handling,

batching and lay-down operations.

PROCEDURE

i. Approximately 5000g of aggregates including 2500±10g of 20mm to 14mm, and

2500±10g of 14mm to 10mm sizes are used in the test.

ii. The sample washed, dried and then weighted.

iii. Place the sample in the Loss Angeles Abrasion machine.

iv. Add eleven (11) steel balls in the machine.

v. Rotated the drum for 500 revolution at 30-33rpm.

vi. After the drum stopped, the sample was removed and sieved on No. 12. The

sample that was retained on the sieve was washed and dried at temperature of 105

to 110. Then weigh the sample once its cool to room temperature.

SAMPLE CALCULATION

Calculate the "Percent Wear" to the nearest % using the following equation:

Percent wear (%) = (weight loss/initial weight) x 100

= [(A - B)/A)] x 100

Where:

A = Mass of original test specimen to the nearest 1 g

B = Mass retained on the 1.70-mm sieve after the specified number of revolutions, to the

nearest 1 g

RESULT

Aggregate size(mm)

Weight of sample (g)

before test(initial

weight)

Weight sample (g) after test/ before enter the oven

Weight of sample (g)

after enter the oven

Loss

20 - 14

5002 3323 3315 168714 - 10

Percent wear (%)

33.73

DISCUSSION

A good and better road aggregate for a nominal 20mm maximum size should be

getting the percentage of wear between 10 to 45%. After the experiment, we get a result

at value 33.73 % wear. So, the sample aggregate applicable to make road. While done

the experiment we have to be carefully to prevent an error. The errors including while

handle the Loss Angeles Abrasion machine. Occasionally, check machine for worn gears

improperly tensioned belts, worn bearings for to reduce possibility of improper

operations. The safety also should be the priority and must take important. Soils and

aggregates may contain bacteria and organisms which can be harmful to one’s health.

Dust masks and protective gloves are required when handling materials.

Dust, noise, lifting and the operation of equipment are encountered in this testing

procedure. It is not possible to completely eliminate these risks, but steps should be taken

to minimize them as much as possible.

CONCLUSION

From the experiment above, we can conclude that this test is succeed related to

the theory saying that the aggregate abrasion test can be used to determine the percent

wear. However, the safety and errors should be the priority to get a correct result.

From the experiment, student is able to identify the characteristic of the aggregate and

can to ascertain the degradation property of aggregates by abrasion. Characteristic of the

aggregates used in the construction of roads must be durable, abrasion resistant, and

freeze-thaw resistant in order to perform well in pavement or as base course. So the

objective in the experiment was achieved.

REFERENCES

i. Laboratory manual.

ii. http://training.ce.washington.edu/wsdot/modules/03_materials/03-2_body.htm

iii. http://pavementinteractive.org/index.php?title=Los_Angeles_Abrasion

APPENDIX

Los angeles abrasion tester sieve

Weighing machine