WATER ABSORPTION TEST FOR COARSE AGGREGATES?

To determine the water absorption of coarse aggregates as per IS: 2386 (Part III) – 1963. 

Absorption capacity represents the maximum amount of water the aggregate can absorb.Water absorption gives an idea on the internal structure of the aggregate and strength of aggregates. Aggregates having  more absorption are more porous in nature and are generally considered unsuitable, until it is found acceptable based on strength, impact and hardness tests. 

Apparatus Required 

1. Wire Mesh Bucket (Perforated type)

Wire basket of not more than 6.3mm mesh or a perforated container of convenient size with thin wire hangers for suspending it from the balance.

 

2. Setup of Water Absorption Test 

The setup consists of container for filling water and suspending the wire basket in it and an airtight container of capacity similar to that of basket, a shallow tray and two dry absorbent clothes (each not less than 75 x 45 cm).

Sample:

A sample not less than 2000g should be used.

Procedure:

1.Approximately 2 kg of collected sample is taken, washed to remove the fine and then placed in a wire basket.The wire basket is then immersed in water, which is at a temperature of 220 to 320℃.

2. Immediately after immersion, the entrapped air is lifted from the sample by lifting the  basket 25mm above the base of the tank and allows it to drop, 25 times at a rate of approximately one drop per second.

3.  The basket, with aggregate are kept completely immersed in water for a period of 24 ± 0.5 hour.

4. The basket and aggregates are weighed while suspended in water, which is at a temperature of 220 from 320℃

5. The basket and aggregates are removed from the water and dried with a dry absorbent cloth.

6. Surface dried aggregates are also weighed.

7. The aggregates are placed in a shallow tray and heated to 100 to 1100℃ in an oven for 24 ± 0.5 hours.Later, it is cooled and weighed in an airtight container.

 

Calculation :

Water absorption percentage of aggregates is calculated as:

Water absorption (percent of dry weight) = $\frac{W_B-W_A}{W_A}\times 100$ %

Where,

• WA is Dry weight of aggregate (The weight in g of ovendried aggregate in air)
• WB is Weight of aggregate immersed in water (The weight in g of the saturated dry aggregate in air).

Note:
Water absorption shall not be more than 2% per unit by weight.
In case in Water absorption is higher than 2% than soundness test is required.

Observations:

1.

Water absorption value(%)=1.5  i.e <2%,so material is suited for construction

2.

Water absorption value(%)=0.4 i.e <2%,so material is suited for construction

For Testing:

Slump cone test, Silt content, Water absorption, Bulking of sand
Compaction factor test of concrete
Los Angeles Abrasion test on Aggregate