Code of Practice Used : (IS: 2386(PART 1)-1963) AND (IS: 383-1970)
AIM:
To determine the grain size distribution of fine aggregates and to find grading zone of fine aggregates.
THEORY:
Sieve analysis is the method of dividing a sample of aggregates into various fractions each consisting of particles of same size. The sieve analysis is carried out to determine the particle size distribution in a sample of aggregate, which we call Gradation. The aggregate fraction from 4.75 to 75 micron is referred to as fine aggregates. Fine aggregate is the sand used in mortars, coarse aggregates is the broken stone or gravel, and all in one aggregate is the combination of fine and coarse aggregates. The coarse aggregates unless mixed with fine aggregates do not produce good quality of concrete.
Grading pattern of a sample is found out by sieving a sample successively through the entire sieve set mounted one over the other in order of size, with largest sieve on the top. The material retained on each sieve after shaking, represents the fraction of aggregates coarser than the below sieve. Sieving can be done either manually or mechanically. Fineness modulus is just a numerical index value of fineness giving some idea of the mean size of particles in the entire body of aggregates. Determination of fineness modulus may be considered as a method of standardization of the grading of aggregates. It is calculated by sieving a known mass of given aggregates on a set of standard sieves and by adding the cumulative percentages of mass of material retained on all the sieves and divide the total percentage by 100.
| Type of aggregate | Max. Size of aggregate in mm | Fineness Modulus | |
| Minimum | Maximum | ||
| Fine aggregate | 4.75 | 2.00 | 3.50 |
| Coarse aggregate | 20 40 75 | 6.00 6.90 7.50 | 6.90 7.50 8.00 |
| All in aggregate | 20 25 30 40 75 | 4.70 5.00 5.20 5.40 5.80 | 5.10 5.50 5.70 5.90 6.30 |
Limits of Fineness modulus for different aggregates
APPARATUS:
- Fine aggregates
- IS Sieve set from 4.75 mm to 75 micron.
- Mechanical sieve shaker
- Weighing balance
- Scoop
PROCEDURE:
- Take 1000 Gms of fine aggregates sample.
- Arrange the sieve set from top to bottom as follows 4.75 mm, 2.36 mm, 1.18 mm, 600 micron, 300 micron, 150 micron, 75 micron and Pan.
- After weighing the sample, transfer the sample to 4.75 mm sieve and cover it with lid.
- Place the assembly of sieve set on mechanical sieve shaker and sieve it for five to ten minutes.
- Remove the assembly from mechanical sieve shaker and weigh the sample retained on each sieve, simultaneously note down in observation sheet.
OBSERVATION AND CALCULATIONS:
Total Weight = 1000 grams
| IS Sieve Size | Weight of Fine aggregate | Percent Retained | Cumulative Percent Retained | Percent passing |
| 4.75 mm | ||||
| 2.36 mm | ||||
| 1.18 mm | ||||
| 600 micron | ||||
| 300 micron | ||||
| 150 micron | ||||
| 75 micron | ||||
| Pan | ||||
| ∑ F |
RESULT:
Fineness modulus of fine aggregates = ∑ F/100
REVIEW QUESTIONS:
- What are fine aggregates, coarse aggregates and all in aggregates?
- Define fineness modulus and state its objective.
- What is the significance of sieve analysis?
- Write the size of fine and coarse aggregates.
- Which is the common sieve which appears for both types of aggregates?
- What precautions are necessary while performing sieve analysis?
