LAB TEST FOR DETERMINATION OF PARTICLE SIZE DISTRIBUTION OF FINE AND COARSE AGGREGATE

OBJECTIVE: To determine the particle size distribution of fine and coarse aggregate.

APPARATUS: balance of 0.1gm accuracy, IS sieves  63mm ,40 mm, 20mm, 12.5mm, 10mm, 4.75mm, 2.36mm, 1.18mm, 600 micron, 300 microns and 75 microns.

PROCEDURE:

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

2.      Record its weight before sieving.

3.      Sieve the samples successively on the sieves for which the site distribution to be analyzed, starting from the largest.

4.      Shake each sieve separately on a clean tray until two minutes.

5.      The sieving shall be done backward, forward, circular, clockwise and anti-clockwise with frequent jarring, so that the material kept on sieve frequently changes its direction.

6.      Material other than 20mm shall not be forced through.

7.      Lumps of fine material present can be broken by gentle pressure by hand.

8.      Fine camel hairbrush may be used to clean the underside of the IS sieve 150 & 75 microns.

9.      Weights the materials retained on each sieve and record them again.

10.  The cumulative mass of the aggregate fraction shall be calculated and percentage of passing in each sieve shall then be reported.

Minimum weights of sample for sieve analysis

Maximum size of aggregate                                  Minimum weight of sample to be taken (gm)

63mm                                                                                                                               50,000

50mm                                                                                                                               35,000

40mm                                                                                                                               15,000

25mm                                                                                                                               5,000

20mm                                                                                                                               2,000

12.5mm                                                                                                                            1000

10mm                                                                                                                               500

4.75mm                                                                                                                            200

2.36mm                                                                                                                            100