STANDARD
- IS:2386(Part3) 1963.
DEFINITION
Specific gravity is the ratio of the mass of a given volume of the substance to the mass of an equal volume of water.
APPARATUS
- Standard Pycnometer of one liter capacity.
- Balance of capacity 5kg and sensitivity 0.5 gram.
- Thermostatically controlled oven with capacity up to 250 °C.
PROCEDURE
- Take representative sample of aggregates approximately about 1000 grams passing 10mm IS Sieve and retained on 4.75 micron or 500 grams if finer than 4.75 mm place in tray and immerse in distilled water at a temperature of 22 to 32°C.
- Soon after immersion, remove entrapped air in bubbles on the surface of the aggregate by gentle agitation with a rod.
- Allow the sample to remain immersed in water for 24±1/2 hour.
- After the specified period of soaking drain off water from the sample by decantation through a filter paper, any material retained being returned to the sample.
- Expose the aggregate including any solid matter retained on the filter paper to a gentle current of warm air to avoid surface moisture and stir at frequent intervals to ensure uniform drying until no free surface moisture can be seen and the material just attains a free running condition.
- Weigh (A) the saturated surface dry sample.
- Place the aggregates in the pycnometer and fill with distilled water .
- Remove any entrapped air by rotating the pycnometer on its side by covering the hole in the apex of the cone with the finger.
- Remove any foam from the surface by tipping up with distilled water so that the surface of the water in the hole is flat.
- Dry the pyconometer out side and weigh (B).
- Empty the contents of the pyconometer in to a tray care being taken to ensure that all the aggregate is transferred.
- Refill the pyconometer with distilled water to the same level as before, dry on the out side and weigh (C)
Carefully drain off the water from the sample by decantation through a filter paper. - Surface dry the sample by exposing to the atmosphere away from direct sunlight or any other source of heat for not less than 10 minutes or until it appears to be completely surface dry.
- Keep the sample in the oven in a tray maintained at a temperature of 105° to 110 ˚C for 24 ± 1/2 hour.
- After the specified period remove the material from the oven cool in the airtight container and weigh (D).
- Make at least two determinations for each test.
CALCULATIONS
Specific gravity on oven dry basis = D/( A – (B – C) )
Specific gravity on SSD basis = A/( A – (B – C))
Apparent Specific gravity = D/( D – (B – C))
Water absorption, % x 100 = (A-D) /D
A = Weight of saturated surface dry sample.
B = Weight of pycnorneter filled with sample and filled with distilled water.
C = Weight of pycnometer filled with distilled water.
D = Weight of oven dried sample.
REPORT
- Report the individual and the mean results to the nearest second decimal.
PRECAUTION
- The difference in temperature of the water in the pycnometer during the first and second weighing shall not exceed 2°C.
DETERMINATION OF SPECIFIC GRAVITY OF AGGREGATES ( LESS THAN 10MM)
IS :2386 (Part 3)1963
| Description |
Units |
Test 1 | Test 2 |
Average |
| Weight of saturated surface dry sample (A) |
gms |
|||
| Weight of pycnometer filled with sample and filled with distil)ed water(B) |
gms |
|||
| Weight of pycnometer filled with distilled water only (C) |
gms |
|||
| Weight of oven dried sample ( D ) |
gms |
|||
| Apparent Specific gravity D/ D-( B -C) |
— |
|||
| Specific gravity on SSD basis A / A-(B-C) |
— |
|||
| Specific gravity on oven dried basis D/A-(B-C) |
— |
|||
| Water absorption (A-D)/D x 100 |
% |
. | ||
| Remarks: | ||||