Testing of aggregates with respect to its resistance to wear is an important test for aggregates. Abrasion Test is the measure of aggregate toughness and abrasion resistance such as crushing, degradation and disintegration. Resistance to Degradation of small-size Coarse aggregates by Abrasion and Impact in Los Angeles Machine. There are three methods in use for testing abrasion resistance:
Deval attrition test for aggregate
In this method, particles of known weight are subjected to wear in an iron cylinder rotated 10000 times at a certain speed. Then we express the percentage of particles finer than 1.7 mm as a percentage of original particles.
Dorry abrasion test for aggregates
In India we don’t normally go for this test. The test involves in subjecting a cylindrical specimen of 25 cm height and 25 cm diameter to the abrasion against rotating metal disk sprinkled with quartz sand. Then determine the loss in weight of the cylinder after 1000 revolutions. Express the hardness of the rock in terms of an empirical formula.
Los Angeles test for aggregates
This is a modification over Deval test. It is relatively a faster method. The applicability of the method to all types commonly used aggregate makes this this method popular.
Procedure of abrasion test for aggregates:
- Consider a specified amount of aggregate (5 kg), which is larger than 1.7 mm size.
- In this test we should consider charge balls (as per table 1) of specific weight which depends on the grading of aggregate.
- Place the aggregates and abrasive charge balls on the cylinder and fix the cover.
- The number of revolution also depends on the grading type (A, B, C and D – 500 revolution ; E, F and G – 1000 revolutions).
- Then we start the machine at a specific speed and after the specific number of rotations, we stop the machine.
- Then collect the aggregates in a tray and sieve them through 1.7 mm sieve.
- Weigh the aggregates passing through 1.7 mm sieve, and express it as a percentage of total weight of aggregate.
- This percentage is the abrasion value.
The abrasion value should not be more than 30 % for wearing surfaces, and not more than 50 % for concrete.
Check this post for different tests available for aggregate.
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