Specific Gravity and Water Absorption Test


Objective

  1.  To calculate the strength or grade of the material
  2. To assess the water absorption of aggregates

Apparatus

The apparatus includes the following:

(a)  An equilibrium of capability about 3kg, to weigh precise 0.5g, and of such a variety and shape as to allow the weighing of the specimen container when discharged in water.

(b) A thermostatically balanced and monitored oven to uphold temperature at heat of 100-110° C.

(c) A wire not exceeding the length of  6.3 mm mesh or a punctured vessel of fitting size which consists  thin wire hangers for hanging it from the balance.

(d) A vessel for filling it with water and hanging the basked from height.

(e) An air tight vessel of capability comparable to that of the basket

(f) A hollow tray and two porous clothes, both of them not lesser than 75x45cm.

Theory

The explicit gravity of a total is assumed to be a measure of strength or grade of the substance. Stones with lower specific gravity are commonly weaker than those with greater specific gravity values.

Procedure

(i) Approximately 2 kg of total specimen is washed properly to get rid of any fines, sapped and are put in a wire basket and saturated in distilled water at a 22- 32º C temperature and a cover of minimum 5cm of water on top of the crest of basket.

(ii) Straight away after saturation the entrapped air is taken away from the specimen by lifting the container holding it 25 mm on top of the bottom of the container and letting it to plunge at the rate of approximately one drop per second. The basket and the total has to linger totally saturated in water for a timeframe of 24 hour later.

(iii) The container and the specimen are weighed whilst hanging in water at a 22° – 32°C temperature. The mass while hanging in water is noted =W1g.

(iv) The container and aggregates are detached from water and permitted to drain for some minutes, after which the aggregates are moved to the dry porous clothes. The hollow container is then taken back to the tank of water shaked 25 times and weighed in water=W2g. .

(v) The aggregates kept on the porous clothes are exterior dried till no additional moisture can be absorbed by this cloth. Then the aggregates are once again taken to the second porous dry piece of cloth spread in solitary layer and permitted to dry for minimum of 10 minutes unlessl the aggregates are entirely surface dry. The surface dried aggregate is then weighed =W3 g

(vi) The aggregate is now kept in a hollow tray and put in an oven whose temperature is maintained at 110° C for 24 hrs. It is then detached from the oven, let chilled in an air tight vessel and weighted=W4 g.

(1) Specific gravity = (dry weight of the aggregate /Weight of the same volume of water)

(2) Apparent specific gravity = (dry weight of the aggregate/Weight of the same volume of water exclusive of air voids in aggregate)

Observations

Weight of immersed aggregate floating in water with the container = W1 g

Weight of container hanging in the water = W2 g

Weight of immersed aggregate in water = W1 – Wg

Weight of immersed exterior dry aggregate in air = W3 g

Weight of water equivalent to the quantity of the aggregate = W3–(W1–W2)g

Weight of oven dry aggregate = W4 g

(1) Specific gravity = W/ (W3– (W1– W2))

(2) Apparent specific gravity = W4 / (W4– (W1– W2))

(3) Water Absorption = ((W– W4) / W4) X 100

Result

(1) Specific gravity =

(2) Apparent specific gravity =

(3) Water Absorption =

Recommended value:

The volume of the aggregate and whether or not the heat was artificially increased should be shown and specified. ISI has specified three techniques of testing for the calculation of the specific gravity of aggregates, in regards to the volume of the aggregates. The three size varieties used are aggregates greater than 10 mm, 40 mm and lesser than 10 mm. The specific gravity of aggregates usually applied in construction of roads varies from about 2.5 to 3.0 with a standard of about 2.68. Although high specific gravity is normally taken as a signal of high strength and quality, it is not wise to determine the appropriateness of a example road aggregate exclusive of discovering the mechanical properties such as aggregate crushing, impact and scrape values. Water absorption cannot exceed 0.6 per unit by weight.