Fineness Modulus of Sand:

Objective:

  • To find mean size of particle in fine aggregate or sand.

What is Fineness modulus of Fine aggregate?

  • Fineness modulus of 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 is, all the sum of percentage cumulative retention of each sieve divided by 100, provides values of Fineness modulus.

Fineness modulus =

 

Fineness modulus of Sand
Fineness modulus of Sand

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. 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.
  5. Place the sample(W1), in top most sieve close the lid, pack the sieve stacker by fixing the clamps.
  6. And start mechanical sieve shaker for 10 to 15 minutes. And switch it off after the rotating period.
  7. Unpack the all sieves and measure the mass of each sieve to find out the weight of retain aggregates on each sieve.
  8. Calculate the wright of retained material on each sieve by subtracting the empty weight of that particular sieve.
  9. Analysis the all readings. Make sure that sum of all retained material should be equal to weight of sample taken.
  10. 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 SizeWeight Retained (gm)Cumulative weight retained (gm)Percentage weight retainedPercentage weight passing
    (C/W) x100 
14.75 mm000 100
22.36 mm15015015 85
31.18 mm14029029 71
4600 microns21550550.5 49.5
5300 microns31582082 18
6150 microns1801000100 0
   Total276.5 

Calculation:

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 2nd and 3rd 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 sandFineness modulus range
Fine sand2.2 – 2.6
Medium sand2.6 – 2.9
Coarse sand2.9 – 3.2

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

IS Sieve DesignationPercentage Passing
Grading Zone IGrading Zone IIGrading Zone IIIGrading Zone IV
10 mm100100100100
4.75 mm90 – 10090 – 10090 – 10095 – 100
2.36 mm60 – 9575 – 10085 – 10095 – 100
1.18 mm30 – 7055 – 9075 – 10090 – 100
600 microns15 – 3435 – 5960 – 7980 – 100
300 microns5 – 208 – 3012 – 4015 – 50
150 microns0 – 100 – 100 – 100 – 15

 

Read more on: Grading of aggregates>>>

 

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