Water Absorption Test of Aggregate: Lab Procedure, Result and Precautions

The water absorption test of aggregate is carried out to calculate the water absorption capacity of Aggregate.

The aggregate used in this test should be dust-free.

The main aim of this test is to,

a. To calculate the strength and quality of the aggregate.

b. To calculate the water absorption capacity of aggregate.

1. Water Absorption Test of Aggregate: Formula

✔ The formula that we need to utilize to calculate aggregate water absorption is as follows:

Weight of saturated aggregates in the air (A) =

Weight of oven-dry aggregates in the air (B) =

Water Absorption = (A-B)/B x100%

✔ If the Water Absorption value is less than 2%, aggregate can be used in construction.

2. Apparatus Required  

✔ The apparatus required for the test of water absorption of aggregate is mentioned below:

a. Weighing Balance

b. Thermostatically controlled oven

c. Wire basket

d. Container

e. A shallow tray and two absorbent clothes

3. Procedure  

1. About 2 kg of aggregate sample is taken, washed to remove fines, and placed in a wire basket. The basket is then immersed in water between 22°C and 32°C.
2. After submerging the sample, remove trapped air by lifting the basket 25mm above the tank base and dropping it 25 times at one drop per second.
3. The basket with aggregate is wholly immersed in water for 24 ± 0.5 hours.
4. The basket and aggregate are weighed while suspended in water at a temperature between 22°C and 32°C.
5. Firstly, the basket and aggregates are carefully removed from the water and dried thoroughly using an absorbent cloth to begin the process. Once dry, the weight of the surface of the aggregates is measured.
6. Next, the aggregates are placed in a shallow tray and subjected to a controlled heating process in an oven set at 100 to 110 degrees Celsius for 24 hours, with a tolerance of plus or minus 0.5 hours.
7. Lastly, the aggregates are allowed to cool in an airtight container and then weighed again.

Weight of saturated aggregates in the air (A) =

Weight of oven-dry aggregates in the air (B) =

Water Absorption = (A-B)/B x100%

4. Result  

The water absorption should not exceed 2%, although up to 3% may be acceptable in some instances.

5. Precautions  

a. The sample must be washed thoroughly to separate finer particles and dust.

b. Multiple dry cloths should be used to clean aggregate surfaces.

6. Advantages  

a. Knowing the water absorption capacity of aggregates can help us determine whether to use it as a construction material.

b. Used to prepare workable concrete.

c. Used to define water-cement ratio.

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