EXPERIMENT ON DETERMINATION OF LOS ANGELES ABRASION VALUE

TITLE OF THE EXPERIMENT

Aggregate Abrasion Value 

AIM OF THE EXPERIMENT

To determine the aggregate abrasion value of coarse aggregate. 

APPARATUS AND MATERIAL

1.     An Abrasion machine

2.     11 Abrasion charges.

3.     BS test sieve of aperture sizes 20.00mm, 14.00mm, 10.00mm and 1.70mm

4.     Fine and stiff brushes

5.     Digital Weighing Balance

6.     Oven

                      
         

The Los Angeles test is a measure of degradation of mineral  aggregates of standard gradings coming about including abrasion or attrition, impact, and grinding in a rotating steel drum containing a specified number of steel spheres. The Los Angeles (L.A.) scraped area test is a typical test strategy used to show total strength and scraped area attributes. Total scraped spot attributes are imperative in light of the fact that the constituent total in HMA must oppose pounding, debasement and breaking down with a specific end goal to deliver a great HMA.

                                

Principle of the Test:

To produce the abrasive action by utilization of standard steel balls which when blended with the total and pivoted in a drum for particular number of unrest cause affect on total. The %age wear because of rubbing with steel balls is resolved and is known as scraped area esteem.

REASON FOR THE TEST

• Aggregate utilized as a part of roadway asphalt ought to be hard and must oppose wear because of the stacking from compaction gear, the cleaning impact of activity and the inner scraped area impact. 
• The road aggregate ought to be sufficiently hard to oppose the scraped spot of total. Protection from scraped area is resolved in research center by misfortune points scraped spot test.
• 
  
• USES & SIGNIFICANCE OF LA ABRASION TEST :

1. For a aggregate to perform attractive in asphalt, it must be adequately difficult to oppose the grating impact of activity over drawn out stretch of time. The delicate totals will be rapidly ground to clean, while the hard totals are very impervious to smashing impact. 

2. The test likewise will decide the nature of the aggregate.


3. The L.A. Scraped spot test is broadly utilized as a marker of the relative quality or capability of mineral aggregate.

PROCEDURE

SAMPLE PREPARATION

1.     The sample was air dry at a temperature not exceeding 110ᵒc and not exceeding 4 hours.

2.     2500gm(X) of sample passing 20mm sieve but retained on 14mm sieve was weighed.

3.     Also 2500gm(Y) of sample passing 14mm sieve but retained on 10mm sieve was weighed.

EXPERIMENT PROPER

1.     The cover of the machine was removed and sample X and Y above was put in the machine.

2.     The abrasive charges was placed on the sample and the cover was fixed back firmly.

3.     The machine was switched on and allowed to undergo 500 revolutions at 28rev/mm or 30rev/mm.

4.     The machine was switched off and the content was emptied into a tray at the base of the machine.

5.     The sample was sieved to separate the fines using 2.36mm sieve until no significant amount passed in 1 minute.

6.     The fractions retained retained(A) on sieve 2.36mm and passing (B) sieve.

CALCULATION

AGGREGATE RETAINED ON SIZE		WEIGHT OF       SAMPLE BEFORE TEST(Gm)	WEIGHT OF       SAMPLE AFTER TEST(Gm)	DIFFERENCE IN WEIGHT(Gm)
14mm	2500Gm	5000	2691	2309
10mm	2500Gm

The difference between the original weight and the final weight of the test sample is expressed as a percentage of the original weight of the test sample.

aggregate abrasion value = (A-B)/A  × 100%

where A= original weight

B =final weight

(5000-2691)=2309 

=2309/5000 × 100% = 0.4618 × 100%

=46.18% = 46%

The aggregate abrasion value is 46%

PRECAUTION

§  Before testing, machine was checked and ensures proper fixing.

§  After test electric supply was switched off.

§  Thoroughly clean & dry the container before testing.

§  Accurate timing was allowed and the correct revolution.

§  Student was not staying very close to the machine during the test.

§  The content in the machine was properly collected into the tray.

  

ERROR

o   Machine error

o   Inability to have the total mass collected after the whole experiment.

o   There is a little loss in the collection which gives error.

OBSERVATION

A mixture of fine content and coarse aggregate was obtained after the content was collected in the tray after the complete revolution of the machine.

CONCLUSION

From the aggregate abrasion value of the coarse aggregate gotten which is 46% indicates that the coarse aggregate is totally weak and its implies that it can only be used for concrete. This aggregate cannot resist abrasive effect if used for road pavement.