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Particle size distribution of fine aggregates

Determination of particle size distribution of fine aggregates

Aim:

To determine fineness modulus of fine aggregate and classifications based on IS: 383-2016.

Reference codes:

• IS 2386 (Part I)-1963.
• IS: 383-2016.
• IS: 460-1962.

Equipment's Required:

• Test Sieves conforming to IS : 460-1962 Specification of 4.75mm, 2.36mm, 1.18mm, 600μ, 300μ, 150μ,150μ.
• Balance.
• Gauging Trowel.
• Trays, sieve brushes, mortar with a rubber covered pestle.
• Mechanical sieve shaker.
• Stop Watch.

Theory:

This is the name given to the operation of dividing a sample of aggregate into various fractions each consisting of particles of the same size. The sieve analysis is conducted to determine the particle size distribution in a sample of aggregate, which we call gradation. Many a time, fine aggregates are designated as coarse sand, medium sand and fine sand. These classifications do not give any precise meaning. What the supplier terms as fine sand may be really medium or even coarse sand. To avoid this ambiguity fineness modulus could be used as a yard stick to indicate the fineness of sand. Fineness modulus is an empirical factor obtained by adding the cumulative percentages of aggregate retained on each of the standard sieves ranging from 4.75 mm to 75μ and dividing this sum by an arbitrary number 100. Equation for fineness modulus, F_m is

\[\mathop F\nolimits_m = \frac{{\sum {\mathop c\nolimits_P } }}{{100}}\]

Where,

• F_m = Fineness modulus.
• ΣC_p = Total of cumulative percentage of retained (%)

Precautions:

• Clean the sieves set so that no sand particles were struck in them.
• While weighing put the sieve with sand sample on the balance in a concentric position.
• Check the electric connection of the sieve shaker before conducting the test.
• No particle of soil sample shall be pushed through the sieves.

Procedure:

1. The sample shall be brought to an air-dry condition before weighing and sieving. The air-dry sample shall be weighed and sieved successively on the appropriate sieves starting with the largest. Care shall be taken to ensure that the sieves are clean before use.
2. The shaking shall be done with a varied motion, backward sand forwards, left to right, circular clockwise and anti-clockwise, and with frequent jarring, so that the material is kept moving over the sieve surface in frequently changing directions.
3. Material shall not be forced through the sieve by hand pressure. Lumps of fine material, if present, may be broken by gentle pressure with fingers against the side of the sieve.
4. Light brushing with a fine camel hair brush may be used on the 150μ and 75μ IS Sieves to prevent aggregation of powder and blinding of apertures.
5. On completion of sieving, the material retained on each sieve, together with any material cleaned from the mesh, shall be weighed.

Table:

IS Sieve sizes.	Empty weight sieves weight (gm).	Sieve+Soil weight (gm).	Weight of soil retained (gm).	Percent retained(%).	Cumulative percent retained(%)	Cumulative % wt. passing
4.75mm
2.36mm
1.18mm
600μ
300μ
150μ
75μ
Pan

Result:

Fineness modulus, F_m = ______________.

Verification/ Validation:

The range of fineness modulus of different type of sand is as shown below table. From this table we can estimate the type of sand which given sample belongs to. Sand having a fineness modulus more than 3.2 will be unsuitable for making satisfactory concrete.

Sl.No	Types of sand	Fm
1.	Fine sand	2.2 - 2.6
2.	Medium sand	2.6 - 2.9
3.	Coarse sand	2.9 - 3.2

Conclusion:

• Fineness modulus of a given sample of fine aggregate is ______________.
• The type of sand is ______________.
• The given sample of fine aggregate is belong to Grading Zones I / II / III / IV.

Viva Questions:

1. What is the role of fine aggregate in concrete ?
2. How is fine aggregate classified as per IS-383 1970 ?
3. What is the basis of classification of fine aggregate ?
4. What is the practical significance of Grain Size Distribution Analysis ?
5. Could the quality of concrete enhanced by the grade of the sand ?

Determination of particle size distribution of fine aggregates

Aim:

To determine fineness modulus of fine aggregate and classifications based on IS: 383-2016.

Reference codes:

• IS 2386 (Part I)-1963.
• IS: 383-2016.
• IS: 460-1962.

Equipment's Required:

• Test Sieves conforming to IS : 460-1962 Specification of 4.75mm, 2.36mm, 1.18mm, 600μ, 300μ, 150μ,150μ.
• Balance.
• Gauging Trowel.
• Trays, sieve brushes, mortar with a rubber covered pestle.
• Mechanical sieve shaker.
• Stop Watch.

Theory:

This is the name given to the operation of dividing a sample of aggregate into various fractions each consisting of particles of the same size. The sieve analysis is conducted to determine the particle size distribution in a sample of aggregate, which we call gradation. Many a time, fine aggregates are designated as coarse sand, medium sand and fine sand. These classifications do not give any precise meaning. What the supplier terms as fine sand may be really medium or even coarse sand. To avoid this ambiguity fineness modulus could be used as a yard stick to indicate the fineness of sand. Fineness modulus is an empirical factor obtained by adding the cumulative percentages of aggregate retained on each of the standard sieves ranging from 4.75 mm to 75μ and dividing this sum by an arbitrary number 100. Equation for fineness modulus, F_m is

\[\mathop F\nolimits_m = \frac{{\sum {\mathop c\nolimits_P } }}{{100}}\]

Where,

• F_m = Fineness modulus.
• ΣC_p = Total of cumulative percentage of retained (%)

Precautions:

• Clean the sieves set so that no sand particles were struck in them.
• While weighing put the sieve with sand sample on the balance in a concentric position.
• Check the electric connection of the sieve shaker before conducting the test.
• No particle of soil sample shall be pushed through the sieves.

Procedure:

1. The sample shall be brought to an air-dry condition before weighing and sieving. The air-dry sample shall be weighed and sieved successively on the appropriate sieves starting with the largest. Care shall be taken to ensure that the sieves are clean before use.
2. The shaking shall be done with a varied motion, backward sand forwards, left to right, circular clockwise and anti-clockwise, and with frequent jarring, so that the material is kept moving over the sieve surface in frequently changing directions.
3. Material shall not be forced through the sieve by hand pressure. Lumps of fine material, if present, may be broken by gentle pressure with fingers against the side of the sieve.
4. Light brushing with a fine camel hair brush may be used on the 150μ and 75μ IS Sieves to prevent aggregation of powder and blinding of apertures.
5. On completion of sieving, the material retained on each sieve, together with any material cleaned from the mesh, shall be weighed.

Table:

IS Sieve sizes.	Empty weight sieves weight (gm).	Sieve+Soil weight (gm).	Weight of soil retained (gm).	Percent retained(%).	Cumulative percent retained(%)	Cumulative % wt. passing
4.75mm	521	521
2.36mm	491.8	504
1.18mm	426	450.5
600μ	401.8	490
300μ	375.5	478
150μ	355.3	410
75μ	351.1	368.2
Pan	364.2	365

Result:

Fineness modulus, F_m = .

Note: Fineness modulus is calculate exculding the pan cumulative percent retained.

Verification/ Validation:

The range of fineness modulus of different type of sand is as shown below table. From this table we can estimate the type of sand which given sample belongs to. Sand having a fineness modulus more than 3.2 will be unsuitable for making satisfactory concrete.

Sl.No	Types of sand	Fm
1.	Fine sand	2.2 - 2.6
2.	Medium sand	2.6 - 2.9
3.	Coarse sand	2.9 - 3.2

Conclusion:

• Fineness modulus of a given sample of fine aggregate is .
• The type of sand is .
• The given sample of fine aggregate is belong to Grading Zones I / II / III / IV.

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Refrence

1. Brooks, J.J & Neville A. M. (2019). Concrete Technology (2^nd ed.). Pearson Publishers Pvt Ltd.

2. Shetty, M. S & Jain, A. K. ( 2018). Concrete Technology: Theory And Practice (8^thed.).S Chand Publishers Pvt Ltd.