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Material Testing

Water Absorption Test of Aggregates

Why porous aggregate matters, and the wire-basket procedure for weighing a washed sample saturated and surface-dry, then oven-dry, to get its absorption as a percentage.

Constropedia Editorial First published October 2021 · Updated September 2026 · 2 min read

Objectives and Significance

Water absorption gives an idea of the internal structure of aggregate. Aggregates having more absorption are more porous in nature and are generally considered unsuitable, unless found to be acceptable based on strength, impact and hardness tests.

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Aim

Aim of this test is to determine the water absorption of coarse aggregates.

Apparatus

  1. Wire basket – perforated, electroplated or plastic coated with wire hangers for suspending it from the balance
  2. Water-tight container for suspending the basket
  3. Dry soft absorbent cloth – 75cm x 45cm (2 nos.)
  4. Shallow tray of minimum 650 sq.cm area
  5. Air-tight container of a capacity similar to the basket
  6. Oven
Perforated wire mesh basket with a wire handle for suspending aggregate in water
Blue frame with a digital balance on top and a wire basket hung from it into a black water container

Procedure

  1. The sample should be thoroughly washed to remove finer particles and dust, drained and then placed in the wire basket and immersed in distilled water at a temperature between 22 and 32 Degree Celsius
  2. After immersion, the entrapped air should be removed by lifting the basket and allowing it to drop 25 times in 25 seconds. The basket and sample should remain immersed for a period of 24 ± ½ hrs. afterwards.
  3. The basket and aggregates should then be removed from the water, allowed to drain for a few minutes, after which the aggregates should be gently emptied from the basket on to one of the dry cloths and gently surface-dried with the cloth, transferring it to a second dry cloth when the first would remove no further moisture. The aggregates should be spread on the second cloth and exposed to the atmosphere away from direct sunlight till it appears to be completely surface-dry. The aggregates should be weighed (Weight ‘A’).
  4. The aggregates should then be placed in an oven at a temperature of 100 to 110 Degree C for 24hrs. It should then be removed from the oven, cooled and weighed (Weight ‘B’)

Results and Calculations

Formula:

Water Absorption = (A-B)/B x 100%

Where A= Weight before Oven Dry

B = Weight after oven dry

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