गिट्टी घर्षणमान मूल्य , AGGREGATE ABRASION VALUE

 AGGREGATE ABRASION VALUE

IS: 2386 (part 4)-1963

AIM: 

To determine the abrasion value of coarse aggregate as per IS: 2386 (part 4)-1963.

APPARATUS:  

1.         Los Angles Abrasion Testing Machine.

2.         IS Sieve of size – 1.7mm.

3.       Abrasive charge – 12 nos. cast iron or steel spheres approximately 48mm dia. And each weighing b/w 390 and 445 gm ensuring that the total weight of charge is 5000 ± 25 gm.

4.         Oven.

PREPARATION OF SAMPLE:

The test sample should consist of clean aggreagte which has been dried in an aven  at 105 to 110 ºc to a substantially constant weight and should conform to one of the gradings shown in the table below:

GRADING OF TEST SAMPLES: 

Sieve size (square hole)		Weight in gm of test sample for grade
		A	B	C	D	E	F	G
Passing through(mm)	Retained on (mm)
80	63	-	-	-	-	2500*	-	-
63	50	-	-	-	-	2500*	-	-
50	40	-	-	-	-	5000*	5000*	-
40	25	1250	-	-	-	-	5000*	5000*
25	20	1250	-	-	-	-	-	5000*
20	12.5	1250	2500	-	-	-	-	-
12.5	10	1250	2500	-	-	-	-	-
10	6.3	-	-	2500	-	-	-	-
6.3	4.75	-	-	2500	-	-	-	-
4.75	2.36	-	-	-	5000	-	-	-

* tolerance of ±2% permitted

PROCEDURE:

The test sample and the abrasive charge should be placed in the Los angles abrasion testing machine and the machine rotated at a speed of 20 to 33 rpm for 1000 revolutions. At the completion of test, the material should be discharged and sieved through 1.70mm IS sieve

REPORTING OF RESULTS:

1.      The material coarser than 1.70mm IS sieve should be washed, dried in an oven at a temp. Of  100 to 110ºc to a constant weight (weight B).

2.      The proportion of loss b/w weight A and weight B of the test sample should be expressed as a % of the original weight the test sample. This value should be reported as , 

3.       Aggregate abrasion value = {(A-B)/A} X 100%

 RESULT:

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