AIM

To determine the specific gravity of given sample of fine and coarse aggregates.

 

SPECIFIC GRAVITTY OF COARSE AGGREGATE.

Apparatus

  1. A balance or scale of capacity not less than 3 kg, readable and accurate to 0.5 g and of such a type and shape as to permit the basket containing the sample to be suspended from the beam and the weighed in water.
  2. A well ventilated oven thermostatically controlled to maintain a temperature of 100oC to 110oC.
  3. A wire basket of not more than 6.3 mm mesh or a perforated container of convenient size.
  4. A stout water tight container of convenient size.
  5. Two dry soft absorbent cloths each not less than 75×45 cm
  6. A shallow tray of area no less than 650 cm2
  7. An air tight container of capacity similar to that of the basket.

 

Procedure

(I) Take 2 kg of aggregate. Sample larger than 10mm

(ii)Wash the sample thoroughly to remove finer particle and dust.

(iii) Place the sample in a wire basket and immerse it in distilled water at a temperature between 22oC and 32oC with a cover of at least 5 cm of water above the top of the basket.

(iv) Remove the entrapped air by lifting the basket containing the sample 25 mm above the base of the tank and allowing it to drop per second, care being taken to see that the sample is completely immersed in water during the operation.

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

(vi) Remove the basket and aggregate from water and allow To drain for a few minutes.

(vii) Empty the aggregate from the basket to a shallow tray.

(viii) Immerse the empty basket in water jolt 25 times and than the weight in water (w2).

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

(x) Remove it from the oven and cool it 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

Apparatues

1.A balance of capacity not less than 3kg ,readable and accurate to 0.5 gm and of such a type as to permit the weighing of the vessel containing the aggregate and water .

2.A well ventilated oven to maintain a temperature of 100ºC to 110ºC

3.Pyconometer of about 1 littre capacity having a metal conical screw top with a 6mm hole at its apex . The screw top shall be water tight .

4.a means supplying a current warm air .

5.A tray of area not less than 32cm².

6.An air tight container large enough to take the sample.

7.Filter papers and funnel.

pycnometer

 

Procedure

(I) Take about 500g of sample and place it in the pycnometer.

(II) Pour distilled water into it until it is full.

(III) Eliminate the entrapped air by rotating the pycnometer on its side ,the hole in the apex of the cone being covered with a finger.

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

(V) Transfer the contents of the pycnometer into a tray , care being taken to ensure that all the aggregate is transferred .

(VI) Refill the pycnometer with distilled water to the same level .

(VII) Find out the weight (W1)

(VIII) drink water from the sample through a filter paper .

(IX) Place the sample in oven in a tray at a temperature of 100ºC to 110º C for 24±0.5 hours ,during which period ,it is stirred occasionally to facilitate drying .

(X) Cool the sample 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 =…………………..