AIM: To find out the specific gravity and water absorption of the given aggregate
APPARATUS:
- Balance
- Oven to maintain temp of 100oC to 110oC
- Wire basket
- Container with water
- Trays
About 2 Kg of the aggregate sample is washed thoroughly and placed in the wire basket when immersed in distilled water.
The basket and the sample are then weighed (W1) while suspended in water at a temp of 22 degree to 32 degree.
The aggregates are then placed on the absorbent clothes and should be cleaned. The surface dry aggregates is then weighed (W2).
The aggregate is placed in a shallow tray and kept in an oven maintained at a temp of 110 degree for 24 hours.
It is then removed from the oven, cooled in an air tight container and weighted (W4).
OBSERVATIONS:
Weight of saturated aggregate suspended in water with the basket = W1
Weight of basket above suspended in water = W2
Weight of saturated aggregate in water = (W1-W2)
Weight of saturated surface dry aggregate in air = W3
Weight of Water equal to the volume of the aggregate = W3–W5
CALCULATIONS:
Specific Gravity= dry weight of aggregate/ weight of equal volume of water = W4 /(W3 -W5)
Water Absorption % = Percentage by weight of water absorbed in terms of oven dried weight of aggregate
= [(W3 -W4) / W4] x 100
INTERFERENCE:
The specific gravity of aggregates normally used in road construction ranges from about 2.5 to 3.0 with an average value of 2.68.
Water absorption value ranges from 0.1 to 2.0 % for aggregates normally used in road surfacing IRC has specified the maximum water absorption valves as 10 percent for aggregate used in bituminous surface dressing and built up spray grow.
