LAB TEST FOR DETERMINATION OF SPECIFIC GRAVITY AND WATER ABSORPTION OF AGGREGATE

OBJECTIVE: To determine the specific gravity and water absorption of aggregate.

APPARATUS: balance of 0.5gm accuracy; pycnometer of 500ml and 1000ml capacities of 4.75mm or any other if required.

PROCEDURE:

1.      Take a representative air-dried sample by quartering method or by a sample driver.

2.      Take a sample about 1000gm for 10mm, 500gm for finer than 4.75mm.

3.      Place in a tray and immerse with water at a temperature 22-32 cel.

4.      Remove the entrapped air or bubbles with gentle agitation, and keep the sample immersed for 24 +- ½ hours.

5.      After the time elapsed carefully drain water from sample by decantation through filter paper, any material retained to be returned to the sample.

6.      Expose the aggregate including any solid matter to warm air to remove surface water.

7.      Ensure uniform drying until no free surface moisture can be seen and material just attains a free running condition.

8.      Required the weight of the saturated surface dry aggregate.

9.      Place the aggregate in the pycnometer to its side, by closing the hole in apex of the cone with finger.

10.  Top the pycnometer, refill it with water and remove any access water from the surface so that the surface of the water in the hole is flat.

11.  Record the weight of pycnometer with water and sample.

12.  Empty the pycnometer, refill it with only water to the same level as before, and record the weight.

13.  Carefully drain water from sample by decantation through filter paper ,any material retained ,to be returned to the sample.

14.  Place the sample in the oven at 100-110 cel for 24+- ½ hours.

15.  After the time elapsed, cool the aggregate to room temperature and record its weight.

16.  Bulk specific gravity=d/[a-(b-c)], apparent specific gravity=d/[d-(b-c)],water absorption(%)=[100(a-d)]/d

17.  A=weight of saturated surface dry sample (gm), b=weight of pycnometer filled with sample and water (gm).

18.  C=weight of pycnometer filled with water only (gm), d=weight of oven dry sample (gm).