Fineness Modulus of Fine aggregate?

Fineness Modulus of Fine Aggregates: Definition

• Fineness Modulus of Fine Aggregates or sand is a index number, which represent the mean size of particle in sand.
• Fineness modulus is found by performing the sieve analysis.
• The formula to find out the Fineness Modulus of Fine Aggregates is, all the sum of percentage cumulative retention of each sieve divided by 100, provides values of Fineness modulus.

Test to find Fineness Modulus of Fine Aggregates

Objective:

To determine the average particle size in fine aggregate or sand.

Fineness modulus =

Determination of Fineness modulus of Sand:

Test to find out Fineness modulus of Sand:

• Generally, sieve analysis is done to find out fineness modulus of fine aggregates as well as coarse aggregate. (As per IS 2083 Part 4)

IS Code for Fineness Modulus of fine aggregate : IS : 383 -1970

Sample Preparation:

• Take the aggregates sample of exact 1kg by weighing it. (Make sure that all aggregates should be oven dried at 110℃ before measurement) and note down the measurement as W1 (1kg or 1000gm)

Sieve Analysis: Test procedure (IS : 2386 (Part 1) and IS : 2386 (Part 4))

Apparatus:

• Different type of sieves (As per IS standards)
  • Weighing Balance (Accuracy upto 0.01gm)
  • Mechanical Sieve shaker
  • Oven

Procedure:

Following steps are need to follow for sieve analysis:

1. Take the aggregates sample of exact 1kg by weighing it. (Make sure that all aggregates should be oven dried before measurement) and note down the measurement as W1 (1kg or 1000gm)
2. If the particles are lumped then crush the lumps with hand or pestle.
3. Weigh all the empty sieves and record their weight in gms.
4. Prepare the all sieves for testing by dusting all. And stack them all together with respect to their size.
5. Note that the largest sieve size should be at top and smallest at bottom by arranging them in descending order, it shall collect the sieved samples from above sieve.
6. Place the sample(W1), in top most sieve close the lid, pack the sieve stacker by fixing the clamps.
7. And start mechanical sieve shaker for 10 to 15 minutes. And switch it off after the rotating period.
8. Unpack the all sieves and measure the mass of each sieve to find out the weight of retain aggregates on each sieve.
9. Calculate the wright of retained material on each sieve by subtracting the empty weight of that particular sieve.
10. Analysis the all readings. Make sure that sum of all retained material should be equal to weight of sample taken.
11. Calculate the cumulative percentage of retention on each sieve.

Data Recording and Calculation:

1. Sample Details:______________
2. Sample weight taken(W):  __________gms
3. Day & date:_______
4. Time:______________

Table for Reading Reference: (Fine Aggregates only)

Sr. No.	Sieve Size	Weight Retained (gm)	Cumulative weight retained (gm)	Percentage weight retained	Percentage weight passing
				(C/W) x100
1	4.75 mm	0	0	0	100
2	2.36 mm	150	150	15	85
3	1.18 mm	140	290	29	71
4	600 microns	215	505	50.5	49.5
5	300 microns	315	820	82	18
6	150 microns	180	1000	100	0
			Total	276.5

Fineness modulus of Sand = Sum of cumulative percentage retained/ 100 = 276.5/100= 2.76

Therefore, the Fineness modulus of sand is 2.76.

Result:

• The Fineness modulus of sand is 2.76.
• It means the mean size of particle in sand is between the 2^nd and 3^rd sieve.
• It simply means the average or mean particle size of sand lies is in between 300 micron to 600 micron.

General range of Fineness modulus of sand:

Type of sand	Fineness modulus range
Fine sand	2.2 – 2.6
Medium sand	2.6 – 2.9
Coarse sand	2.9 – 3.2

Grading Limits for Fine Aggregates: (Based on Clause 4.3 of IS: 383 – 1970)

IS Sieve Designation	Percentage Passing
	Grading Zone I	Grading Zone II	Grading Zone III	Grading Zone IV
10 mm	100	100	100	100
4.75 mm	90 – 100	90 – 100	90 – 100	95 – 100
2.36 mm	60 – 95	75 – 100	85 – 100	95 – 100
1.18 mm	30 – 70	55 – 90	75 – 100	90 – 100
600 microns	15 – 34	35 – 59	60 – 79	80 – 100
300 microns	5 – 20	8 – 30	12 – 40	15 – 50
150 microns	0 – 10	0 – 10	0 – 10	0 – 15