Particle Size Distribution of Aggregates

7.2.1 Dry sieving test

7.2.1.1 Introduction. This test is primarily used to determine the grading of materials proposed

for use as aggregates or being used as aggregates. The results are used to determine compliance with the particle size distribution with applicable specification requirements and to provide necessary data for the control of the production of various aggregate products and mixtures containing aggregates.

7.2.1.2 Scope. This test covers the determination of the particle size distribution (PSD) or

sieve analysis of fine and coarse aggregate by sieving. An accurate determination of the amount finer than the 75 micron sieve cannot be achieved by this method. Test method 7.1.5 should be used to determine the amount of material finer than the 75 micron sieve.

7.2.1.3 Equipment

a) Balance, of appropriate capacity for the size of sample and capable of accuracy to 0.1% of the mass of the sample.

b) Test sieves. A complete nest of sieves in accordance with the sizes required by the specification and which must comply with the relevant standards. Sieves with openings larger than 125mm shall have a permissible variation in average opening of plus or minus 2% and shall have a nominal wire diameter of 8.0mm or larger. A set of the sizes and apertures given in Table 7.2.1 will cover most applications of the method.

c) Mechanical sieve shaker (Optional).

d) Oven, of appropriate size capable of maintaining a uniform temperature of 110ºC plus or minus 5ºC.

e) Trays and containers.

Table 7.2.1 Particulars of sieves for sieve analysis

Square perforated plate, 450 mm or 300mm diameter mm Wire cloth, 300 mm or 200 mm diameter mm (unless stated) 75.0 63.0 50.0 37.5 28.0 20.0 14.0 10.0 6.30 5.00 3.35 2.36 1.70 1.18 850 micron 600 micron 425 micron 300 micron 212 micron 150 micron 75 micron

Table 7.2.2 Minimum mass of test portion required for sieve analysis

Nominal size of material mm Minimum mass of test portion Kg.

63 50 40 28 20 14 10 6 5 3 less than 3 50 35 15 5 2 1 0.5 0.2 0.2 0.2 0.1

7.2.1.4 Sampling. Sample the aggregate in accordance with test procedure described in

Chapter 2.1. The test portion shall comply with the values given in Table 7.2.2. Reduction of the sample shall be made in accordance with 2.9.1.1.

7.2.1.5 Procedure

a) If the test sample has not been subjected to testing using method 7.1 (material finer than the 75 micron test sieve by washing), dry it to constant mass at a temperature of 100ºC plus or minus 5ºC and determine the mass of it to the nearest 0.1% of the total original dry sample mass.

b) Select the sieve sizes suitable to furnish the information required by the specification covering the material to be tested. Nest the sieves in order of decreasing opening size from top to bottom and place the sample, or portion of a sample if it is to be sieved in more than one increment, on the top sieve. Agitate the sieves by hand or by mechanical means for a sufficient period, established by trial or checked by measurement on the actual sample, to meet the criteria for adequacy of sieving described in the note below.

Note. Adequacy of sieving criteria : Sieve for a sufficient period and in such manner that, after completion, not more than 0.5% by mass of the total sample passes any sieve during 1 minute of continuous hand sieving performed as follows :

Hold the individual sieve, provided with a snug-fitting pan and cover, in a slightly inclined position in one hand. Strike the side of the sieve sharply and with an upward motion against the heel of the other hand at the rate of about 150 times per minute, turn the sieve about one-sixth of a revolution at intervals of about 25 strokes. In determining sufficiency of sieving for sizes larger than the 4.75 mm sieve, limit the material on the sieve to a single layer of particles. If the size of the mounted testing sieves makes the described sieving motion impractical, use 200mm diameter sieves to verify the sufficiency of sieving.

c) Limit the quantity of material on a given sieve so that all particles have opportunity to reach the sieve opening a number of times during the sieving operation. For sieves with opening smaller than 4.75 mm the mass retained on any sieve at the completion of the sieving operation shall not exceed 6 kg/m2 , equivalent to 4 g/in2 of sieving surface. For sieves with opening 4.75 mm and larger, the mass in kg/m2 of sieving surface shall not exceed the product of (2.5) x (sieve opening in

Note. The 6 kg/m amounts to 194 g for the usual 200mm diameter sieve. d) Determine the mass of each size increment by weighing to the nearest 0.1% of the

total original dry sample mass. The total mass of the material after sieving should be checked closely with original mass of sample placed on the sieves. If the amounts differ dry more than 0.3%, based on the original dry sample mass, the results should not be used for acceptance purposes.

e) If the sample had previously been tested by 7.1.5 add the amount finer than the 75 micron sieve determined by that method to the mass passing the 75 micron sieve by dry sieving of the same sample in this method.

7.2.1.6 Calculation. Calculate percentages passing, total percentages retained, or

percentages in various size fractions to the nearest 0.1% on the basis of the total mass of the initial dry sample.

7.2.1.7 Report. The report shall include the following information:

a) Total percentage of material passing each sieve. b) Total percentage of material retained on each sieve.

c) Report percentages to the nearest whole number, except if the percentage passing the 75 micron sieve is less than 10%, it shall be reported to the nearest 0.1%. A data sheet is given as Form 7.2.1.

7.2.2 Fineness modulus of fine aggregate

7.2.2.1 Using the procedure for sieve analysis of fine aggregate described in 7.2.1 above, calculate the fineness modules by adding the total percentages of material in the sample that is coarser than each of the following sieves (cumulative percentages retained) and dividing the sum by 100.

Sieve size Sieve size

150 micron 4.75mm

300 micron 9.5 mm

600 micron 19.0mm

1.1mm 37.5mm

2.3mm and larger, increasing the ratio of 2 to 1