Specific Gravity of coarse and fine aggregates


Objective: For assessment of the specific gravity of specified specimen of fine and coarse aggregates.

Specific gravity of coarse aggregate

Apparatus

  1. An equilibrium or scale of volume of minimum 3 kg, decipherable and precise to 0.5 g and it has to be of such shape and kind that it allows the basket holding the specimen to be discharged from the beam and the measured in the water.
  2. A properly ventilated oven which is thermostatically functioned to uphold a temperature of 100oC to 110oC.
  3. A wire basket not exceeding 6.3 mm mesh or a punctured vessel of suitable dimensions.
  4. A firm water tight container of suitable dimensions
  5. Two dry porous piece of clothes each minimum of 75×45 cm
  6. A hollow tray of dimensions’ minimum of 650 cm2
  7. An air tight vessel of dimensions’ familiar to that of the basket.

Procedure

I) For beginning the procedure, first take a 2 kg of aggregate specimen which is greater than 10mm.

(ii)Filter the specimen meticulously to get rid of any kind of finer particle and dust particles.

(iii) Put the specimen in a wire basket and dip it in purified water at a temperature ranging from 22oC and 32oC with a cover of minimum 5 cm of water on the top of the basket.

(iv) Now get rid of the trapped air by pulling up the basket comprising the specimen 25 mm taller than the base of the tank and permitting it to drop per second, with meticulous care being taken in each step in order to see that the specimen is fully engrossed in water in the process of operation.

(v) Immerse the sample in water at a temper of 220C-32oC (W).

(vi) Detach the basket and aggregate from the water and permit it to trench for a short period of time.

(vii) Shift the aggregate from the basket to a hollow tray.

(viii) Completely immerse empty basket in water and jolt it at least 25 times than the mass in water (w2).

(ix) Put the aggregates in oven at a very hot temperature of 100oC to 110oC for approximately 24+- 0.5 hours.

(x) Detach it from the oven and let it cool in room temperature and find the weight. (w2)

Calculations

Apparent Specific Gravity = (Weight of a substance/ wt of an equal vol of water)

= W3/ (W3- (w1-w2))

Result

S specific gravity of given coarse aggregate= ……

Specific Gravity of Fine Aggregate

Apparatus

1.An equilibrium of size minimum of 3kg, decipherable and precise to 0.5 gm and has to be of such a kind that it permits the weighing of the container comprising the aggregate and water.

2.A properly ventilated oven to preserve the hot temperature of 100ºC to 110ºC

3.Pyconometer of approximately 1-liter volume consisting a metal conical screw top with a minimum of 6mm hole at its top. The screw top should be water tight.

4.A mean providing a current warm air.

5.A tray of area minimum of 32cm².

6.An air tight vessel which is big enough to take the specimen.

7.Filter papers and funnel.

Procedure

(I) At first, take approximately 500g of specimen and put it in the Pycnometer.

(II) Now gently pour the distilled water into it up-to its brim.

(III) Get rid of the trapped air by revolving the pycnometer on its side. The hole in the crest of the cone has to me carefully covered with a finger.

(IV) Thoroughly wipe out the outer surface of pycnometer and weigh it (W)

(V) Shift the fillings of the pycnometer into a flat tray, and meticulously take care in order to ensure that all the aggregate is shifted properly.

(VI) Now refill the pycnometer with distilled water to the same horizontal level

(VII) Find out the mass (W1)

(VIII) Now drink the water from the specimen through a process of filter paper.

(IX) Put the specimen in oven in a tray at a very hot temperature of 100ºC to 110º C for approximately 24±0.5 hours, and in that period, the specimen is stirred intermittently to facilitate the process of drying.

(X) Allocate some time for the specimen to cool and weigh it (W2)

Calculation

Apparent specific gravity = (weight of dry sample/weight of equal volume of water)

= W2/(W2- (W-W2))

Result

Specific gravity of fine aggregate =………