Specific Gravity Test for Fine Aggregate

ASTM C128 outlines standard procedures for the determination of specific gravity and absorption capacity of fine aggregate.

Equipment:

1. Balance

2. Pycnometer

3. Oven

Sample:

Approximately 500g of fine aggregate.

Procedure:

1. Dry the sample in oven to constant mass at temperature of 110±5°C, then cool in air at room temperature until the sample reaches comfortable handling temperature i.e. 50°C.

2. Immerse the sample in water, or add minimum 6% moisture to the sample for 24±4 hours.

3. Pour out the excessive water while avoiding the loss of fines. Spread the sample on a flat non-absorbent surface and expose it to gently moving current of warm air. Stir frequently to ensure the drying process is carried out homogeneously. Continue until the sample is near free-flowing condition, and dry until the sample reaches surface-dry condition. The sample is now in saturated surface dry (SSD) condition.

4. Weigh the sample and record it as A (g).

5. Partially fill the pycnometer with wate, then add in about 500g of sample. Fill the apparatus with additional water to approximately 90% of capacity.

6. Roll, invert or agitate the pycnometer to remove all visible air bubbles.

7. Bring the water level in the pycnometer to calibrated capacity. Weigh the pycnometer + sample + water and record it as B (g).

8. Remove the sample from pycnometer. Dry the sample in oven to constant mass at temperature of 110±5°C, then cool in air at room temperature for 1±0.5 hours.

9. Weigh the sample and record it as C (g).

10. Fill the pycnometer with water to its calibrated capacity. Weight the pycnometer + water and record it as D (g).

Calculation:

1. Specific gravity (oven dry) = C/(D+A-B)

2. Specific gravity (SSD) = A/(D+A-B)

3. Apparent specific gravity = C/(D+C-B)

4. Absorption = [(A-C)/C]x100%