Fineness Modulus of Fine and Coarse Aggregrate

AIM

To determine the fineness modulus of given fine and coarse aggregates.

APPARATUS

IS test sieves, square hole perforated plate 75mm, 40mm, 20mm, 10mm, and fine wire cloth of 4800, 2400, 1200, 600, 300, and 150 Microns. Weighing balance (Sensitivity 0.1 percent) sieve shaker, tray plates. fine wire cloth of 4800, 2400, 1200, 600, 300, and 150 Microns. Weighing balance (Sensitivity 0.1 percent) sieve shaker, tray plates.

THEORY

Fine aggregate is sand used in mortars. Coarse aggregate is broken stone used in concrete. The size of the fine aggregate is limited to maximum 4.75 mm (4800 microns) beyond which it is known as coarse aggregate. Fineness modulus is only a numerical index of fineness, giving some idea about, the mean size of the particles in the entire body of concrete. 

Determination of fineness modulus is considered as a method of standardization of grading of aggregates i.e. the main object of finding fineness modulus is to grade the given aggregate for the most economical mix and workability with minimum quantity of cement. It is obtained by sieving known weight of given aggregate in a set of standard sieves and by adding the percent weight of material retained on all the sieves and dividing the total percentage by 100 used in concrete. The size of the fine aggregate is limited to maximum 4.75 mm (4800 microns) beyond which it is known as coarse aggregate. 

Fineness modulus is only a numerical index of fineness, giving some idea about, the mean size of the particles in the entire body of concrete. Determination of fineness modulus is considered as a method of standardization of grading of aggregates i.e. the main object of finding fineness modulus is to grade the given aggregate for the most economical mix and workability with minimum quantity of cement. It is obtained by sieving known weight of given aggregate in a set of standard sieves and by adding the percent weight of material retained on all the sieves and dividing the total percentage by 100.

PROCEDURE
Coarse aggregate
1. Take 5Kgs of coarse aggregate (nominal size 20mm) from the sample by quartering.
2. Carry out sieving by hand, shake each sieve in order 75mm ,40mm, 20mm, 10mm, and No's 480, 240, 120, 60, 30, & 15 over a clean dry tray for a period of not less than 2 minutes.
3. The shaking is done with a varied motion backward and forward, left to right, circular, clockwise and anticlockwise and with frequent jarring.
4. So that material is kept moving over the sieve surface in frequently changing directions.
5. Find the weight retained on each sieve taken in order

Fine aggregate:
1. Take 1 Kg of sand from sample by quartering in clean dry plate.
2. Arrange the sieves in order of No. 480, 240, 120, 60, 30 and 15 keeping sieve 480 at top and 15 at bottom.
3. Fix them in the sieve shaking machine with the pan at the bottom and cover at the top.
4. Keep the sand in the top sieve no 480, carry out the sieving in the set of sieves and arranged before for not less than 10 minutes.
5. Find the weight retained in each sieve.

OBSERVATIONS:

Coarse aggregate: Wt. of coarse aggregate taken: Kgs.

S.No	Sieve size	Weight retained	% Weight retained	% weight passing	Cumulative % Weights retained
1.	75 mm
2.	40 mm
3.	20 mm
4.	10 mm
5.	4800 microns
6.	2400 microns
7.	1200 microns
8.	600 microns
9.	300 microns
10.	150 microns

 

Fine aggregate: Wt. of fine aggregate taken: Kgs

S.No	Sieve size	Weight retained	% Weight retained	% weight passing	Cumulative % Weights retained
1	4800 microns
2	2400 microns
3	1200 microns
4	600 microns
5	300 microns
6	150 microns

Fineness Modulus: Sum of Cumulative percentage Wt. retained /100

PRECAUTIONS:
1. The sample should be taken by quartering.
2. The sieving must be done carefully to prevent the spilling of aggregate.

RESULT

The fineness modulus of given fine aggregate:________
The fineness modulus of given coarse aggregate:_________

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