Specific gravity of fine aggregate (sand) is the ratio of the weight of given volume of aggregates to the weight of equal volume of water.
The specific gravity of sands is considered to be around 2.65.
Apparatus for Specific Gravity Test
- A balance of capacity not less than 3kg ,readable and accurate to 0.5 gm and of such a type as to permit the weighing of the vessel containing the aggregate and water .
- A well ventilated oven to maintain a temperature of 100ºC to 110ºC
- Pycnometer of about 1 litre capacity having a metal conical screw top with a 6mm hole at its apex . The screw top shall be watertight .
- A means supplying a current warm air .
- A tray of area not less than 32cm².
- An airtight container large enough to take the sample.
- Filter papers and funnel.
Procedure of Test
- Take about 500g of sample and place it in the pycnometer.
- Pour distilled water into it until it is full.
- Eliminate the entrapped air by rotating the pycnometer on its side ,the hole in the apex of the cone being covered with a finger.
- Wipe out the outer surface of pycnometer and weigh it (W)
- Transfer the contents of the pycnometer into a tray , care being taken to ensure that all the aggregate is transferred .
- Refill the pycnometer with distilled water to the same level .
- Find out the weight (W1)
- Drain water from the sample through a filter paper .
- Place the sample in oven in a tray at a temperature of 100ºC to 110º C for 24±0.5 hours ,during which period ,it is stirred occasionally to facilitate drying .
- Cool the sample and weigh it (W2)