Aggregate Water Absorption Test

Determine Aggregate Water Absorption

g
g
1.5 %
Water Absorption %

Aggregate Water Absorption
Aggregate Water Absorption = WB - WAWA×100

Aggregate Water Absorption = 2000 - 19701970×100

Aggregate Water Absorption = 1.5 %

Water Absorption value is less than 2%
Material is suited for construction

What is Aggregate Water Absorption Test?

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


Apparatus
  1. Balance - A balance or scale of capacity not less than 3 kg, readable and accurate to O-5 g and of such a type and shape as to permit the basket containing the sample to be suspended from the beam and weighed in water.
  2. Oven - A well ventilated oven, thermostatically controlled, to maintain a temperature of 100 to 110°C.
  3. A wire basket of not more than 6.3 mm mesh or a perforated container of convenient size, preferably chromium plated and polished, with wire hangers not thicker than one millimetre for suspending it from the balance.
  4. A stout watertight container in which the basket may be freely suspended.
  5. Two dry soft absorbent cloths each not less than 75 x 45 cm.
  6. A shallow tray of area not less than 650 cm2.
  7. An airtight container of capacity similar to that of the basket

Sample

A sample of not less than 2000 g of the aggregate shall be tested. Aggregates which have been artificially heated shall not normally be used. If such material is used the fact shall be stated in the report. Two tests shall be made, and it is recommended that the two samples should not be tested concurrently.


Procedure

The sample shall 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°C and 32°C with a cover of at least 5 cm of water above the top of the basket.

  • Immediately after immersion the entrapped air shall be removed from the sample by lifting the basket containing it 25 mm above the base of the tank and allowing it to drop 25 times at the rate of about one drop per second. The basket and aggregate shall remain completely immersed during the operation and for a period of 24 ± 1/2 hours afterwards.
  • The basket and the sample shall then be jolted and weighed in water at a temperature of 22 to 32°C. If it is necessary for them to be transferred to a different tank for weighing, they shall be jolted 25 times as described above in the new tank before weighing.
  • The basket and the aggregate shall then be removed from the water and allowed to drain for a few minutes, after which the aggregate shall be gently emptied from the basket on to one of the dry clothes.
  • The aggregate placed on the dry cloth shall be gently surface dried with the cloth, transferring it to the second dry cloth when the first will remove no further moisture. It shall then be spread out not more than one stone deep on the second cloth, and lest exposed to the atmosphere away from direct sunlight or any other source of heat for not less than 10 minutes, or until it appears to be completely surface dry (which with some aggregates may take an hour or more ). The aggregate shall be turned over at least once during this period and a gentle current of unheated air may be used after the first ten minutes to accelerate the drying of difficult aggregates. The aggregate shall then be weighted (weight WB).
  • The aggregate shall then be placed in the oven in the shallow tray, at a temperature of 100 to 110°C and maintained at this temperature for 24 ± 1/2 hours. It shall then be removed from the oven, cooled in the airtight container and weighed (weight A).

Water absorption percentage of aggregates is calculated as
Water absorption (percent of dry weight) = WB - WAWA×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 surkedry 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.

Specifications: Water absorption Values

Maximum Permissible Water absorption % for the different types of pavements
Sr. Type of Pavements Maximum Water absorption %
(IRC Recommendations)
1 Granular Sub Base (GSB) 2%
2 Base course W.B.M (Water Bound Macadam) 2%
3 Base course W.M.M. (Wet Mix Macadam) 2%
4 Base course Crusher Run Macadam 2%
5 Base course / Binder course B.M. (Bituminous Macadam) 2%
5 Base course / Binder course D.B.M. (Dense bituminous Macadam) 2%
6 Surface course / Wearing course S.D.B.C. (Semi Dense Bituminous Concrete) 2%
7 Surface course / Wearing course B.C. (Bituminous Concrete) 2%
8 Cement Concrete Pavement (Wearing Surface) 2%
9 Cement Concrete Pavement (Other than Wearing Surface) 2%