SPECIFIC GRAVITY TEST OF COARSE AGGREGATE

 

SPECIFIC GRAVITY TEST OF COARSE AGGREGATE

AIM:

To determine the Specific gravity of the aggregate using Pycnometer.



APPARATUS REQUIRED:

1. Pycnometer of about 1 litter capacity

2. Weighing balance, with an accuracy of 1g.                 

3. Vacuum pump 

4. Oven                                                                                          

SAMPLE:

The sample of 2000g to 1000g of aggregate shall be taken for tested. The aggregate which have been heated artificially shall not be taken. Reference IS: 2386 (Part III) – 1963).

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PROCEDURE:

1. A sample of 1kg for 10mm to 4.75mm size and 500gm for less than 4.75mm size. The sample is placed in a tray and fully covered with distilled water for 24hours and the temperature of water to be maintained at 22º to 32ºc.

2. Soon after immersion by simple agitation with rod the air bubbles entrapped in the aggregate shall be removed.

3. After that water should be carefully drained by decantation through a filter paper, if any material retained being returned to the sample. The sample is exposed to gentle warm air and evaporates surface moisture.

4.   At frequent intervals, the sample is stirred for uniform drying until no free surface moisture is seen. After that the saturated and surface dry sample is weighed (A). 

5. Then the sample is placed in the Pycnometer and it should be filled with distilled water. Any entrapped air shall be removed by gently rotating the Pycnometer by covering the cone with finger. After that it should be weighed (B).

6. The sample in the Pycnometer is emptied to the tray and ensures that all the aggregate is transferred. Then the Pycnometer is filled with distilled water to the same level as before and weighed as (C).

7. The water should be carefully drained from the sample by decantation through a filter paper. Then the sample is placed in an oven at temperature of 100ºc and 110ºc for 24hours. 

8. After it shall be cooled in an air tight container and weighed as (D). 

OBSERVATION:

Sl. No.

Observations an Calculations

Determination No.

1

2

3

1

Weight of saturated surface dry sample  (A)

 

 

 

2

Weight of Pycnometer containing sample and filled with distilled water  (B)

 

 

 

3

Weight of Pycnometer filled with distilled water (C)

 

 

 

4

Weight of oven dried sample(D)

 

 

 
















CALCULATION:

Specific gravity = D/ (A-(B-C))

Water absorption = (100x (A-D)) / D

NOTE: Acceptable Value 

1. Specific Gravity – minimum 2.65
2. Water absorption – Should not exceed 2%

REFERENCE:

IS: 2386 (PART 3) – 1963

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