Determination of Water Absorption of Aggregates
Ref : IS 2386 (Part III)
Purpose : To determine the water absorption by aggregate.
Significance : Water absorption gives an idea of strength of rock. Stones having more water
absorption are more porous in nature and considered as unsuitable.
i). Balance of capacity about 3 Kg to weight accurate to 0.5 gm and of such a type
and shape so as to permit weigh of sample container when suspended in water.
ii). Thermostatically controlled oven to maintain temperature of 100oC to 110oC.
iii). A wire basket of not more than 6.3mm mesh.
iv). Container for filling water and suspending the basket.
v). As air tight container of capacity similar to that of the basket.
vi). A shallow tray and two dry absorbent cloths each not less than 75cm to 45cm.
- Take about 2 Kg of sample.
- Wash the sample in wire basket and in distilled water at a temperature between 22oC and 32oC, so that a cover of at least 5cm of water above the top of the basket.
- Place the drained sample in wire basket and immerse in distilled water at a temperature between 22oC and 32oC so that a cover of atleast 5cm of water above the top of the basket.
- Immediately after immersion the entrapped is removed from the sample by lifting the basket containing it 25mm above the base of the tank and allowing to drop 25 times at the rate of above one drop per second.
- Keep the basket and the aggregate completely immersed in water for a period of 24 + ½ hours.
- Weigh the basket and sample while suspended in water at a temp. of 22oC and 32oC (w1 g).
- Remove the basket and aggregate from the water and allowed to drain for a few minutes.
- Transfer the aggregate to one of the dry absorbent cloths.
- The empty basket is then returned to the of water jolted 25 times and weight in water (w2 g)
- Aggregates placed on the absorbent cloths are surface dried till no further moisture could be removed by them.
- Transfer the aggregates to another dry cloth and spread them in layer.
- Cover the aggregates and allow them to dry for at least 10 minutes until the aggregates are completely surface dry.
- The surface dried aggregates is then weighed (w3 g)
- Place the aggregate in a shallow tray and keep the tray in oven maintained at a temp. of 100oC for 24 hours.
- It is then removed from the oven in an air tight container and weighed (w4 g).
Water absorption – Percent by weight of water absorption in terms of oven dried weight of aggregates.
(W3 – W4) x 100 / (W4)
Frequency: Initially one set of 3 representative samples or each source of supply subsequently when warranted by changes in the quality of aggregates.