**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 =**

**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:

- 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)
- If the particles are lumped then crush the lumps with hand or pestle.
- Weigh all the empty sieves and record their weight in gms.
- 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.
- Place the sample(W1), in top most sieve close the lid, pack the sieve stacker by fixing the clamps.
- And start mechanical sieve shaker for 10 to 15 minutes. And switch it off after the rotating period.
- Unpack the all sieves and measure the mass of each sieve to find out the weight of retain aggregates on each sieve.
- Calculate the wright of retained material on each sieve by subtracting the empty weight of that particular sieve.
- Analysis the all readings. Make sure that sum of all retained material should be equal to weight of sample taken.
- Calculate the cumulative percentage of retention on each sieve.

**Data Recording and Calculation:**

- Sample Details:______________
- Sample weight taken(W): __________gms
- Day & date:_______
- 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 |

**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 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 |

Read more on: Grading of aggregates>>>