Sieve Analysis (Gradation) of Fine Aggregate and Fineness Modulus of Sand
Object: – TO DETERMINE THE ZONING OF A GIVEN SAMPLE OF FINE AGGREGATE
INTRODUCTION
What is Fineness Modulus of Sand?
Fineness modulus of (Fine aggregates) is an index number which represents the mean size of the particles in the Fine aggregate. It is calculated by performing sieve analysis with standard sieves. The cumulative percentage retained on each sieveis added and subtracted by 100gives the value of fineness modules.
Theoretical Background
Gradation of the fine aggregate i.e. sand. Whose fineness is checked by Gradation As there are different types of sand, so we will have to judge that which type of sand is the best to be used for concrete. The sand will be called graded if it consists of particles having a variety of dimensions; such type of sand is recommended for use because this type of sand will possess the capability to form a compact structure thus will have more strength as compared to fine sand. The fine sand will also form compact structure but will increase the amount of water needed in concrete, which will decrease the strength of the concrete.
So the degree of gradation will decide about the sand to be used. Degree of gradation is also called fineness modulus of sand. We find fineness modulus and compare it the standard recommended values.
Fine aggregate means the aggregate which passes through #4 (4.75mm) sieve. To find the fineness modulus of fine aggregate we need sieve sizes of #4 (4.75mm), #8 (2.38mm), #16 (1.2mm), #30 (0.6mm), #50 (0.3mm), and #100 (0.15 mm). Fineness modulus of finer aggregate is lower than fineness modulus of coarse aggregate.
The dividing line between the fine and coarse aggregate is #4 sieve. It means the particles of aggregate passing through #4 sieve are termed as fine aggregate and those retained on it are called coarse aggregate.
The sieves are arranged so that with the biggest Openings is at the top and the one with the smallest openings is at the Bottom. A sample of aggregate is allowed to pass through all the sieves and the weights retained on each sieve are noted town. The results are reported in a tabular form and a graph is plotted between the percentage passing on y-axis and sieve opening on x-axis on a semi-log scale.
Key words:
Sieve Numbers: A number assigned to designate the size of a sieve which corresponds to the number of opening per linear inch. The #4 sieve means the sieve has 4 openings in one linear inch. Similarly #100 sieve means the sieve has 100 openings in one linear inch. This is true for other sieves also.
Sieve Analysis: – The maximum Dimension of a particle that will pass through the square hole of a particular mesh.
Why to Determine Fineness Modulus?
Relative coarseness or fineness of material is called fineness modulus. This is only for fine aggregates to know its fineness. It is generally used to get an idea of how coarse or fine the aggregate is. More fineness modulus value indicates that the aggregate is coarser and small value of fineness modulus indicates that the aggregate is finer. The sand having more fineness modulus is relatively coarser sand as compared to the sand having low fineness modulus.
Apparatus:
Balance: For fine aggregate accurate for 0.1gm. For coarse aggregate accurate for 0.5gm.
Containers to carry the sample.
Oven.—capable of maintaining a uniform temperature of 110 + 5°C (230 + 9°F).
Mechanical Sieve shaker.
sets of sieve:-For fine aggregate [ #4 , #8, #16 , #30 , #50, #100]
Procedure:
1- Dry the sample in oven (at 110+5 °C. ) and then allow it to cool to a room temperature.
Determine the weight of the test sample after cooling (M1).
Nest the sieve in order of decreasing size of opening from top to bottom place the sample on the top sieve.
Agitate (shake) the sieve by hand or placing the set on the mechanical shaker for 10min.
Open the set of sieve carefully so that no loosing of materials is expected.
Determine the mass of material retained on each sieve to the nearest 0.1g (either individually or cumulatively) the material retained on each sieve (M2).
Calculations:
Retained % = (Cumulative Weight Retained / Total Weight of Sample) x 100
Passing % = 100 – Retained %
Note: Make sure that the summation of the residue weights equals to the original sample weight with a difference not more than 1% of the original weight.
Sieve Analysis of Fine Aggregate | ASTM C33 | ||||||
Total Weight of Sample (Oven Dry) 1000 Grams | Table No. 1 Specification Limits | ||||||
ASTM Sieves | Weight Retained on each Sieve (grams) | Cumulative | |||||
Retained weight (grams) | Retained % | Passing % | Min | Max | |||
Sieve No. | Opening mm | ||||||
3/8 | 9.5 | 0.0 | 0 | 0.0 | 100 | 100 | 100 |
#4 | 4.75 | 28 | 28 | 2.8 | 97.2 | 95 | 100 |
#8 | 2.36 | 115.5 | 143.5 | 14.35 | 85.65 | 80 | 100 |
#16 | 1.18 | 158.5 | 302 | 30.2 | 69.8 | 50 | 85 |
#30 | 0.60 | 142.5 | 444.5 | 44.45 | 55.55 | 25 | 60 |
#50 | 0.30 | 265 | 709.5 | 70.95 | 29.05 | 5 | 30 |
#100 | 0.150 | 207 | 916.5 | 91.65 | 8.35 | 0 | 10 |
#200 | 0.75 | 69 | 985.5 | 98.55 | 1.45 | 0 | 3.0 |
Pan | 5 | ||||||
Fineness modulus limits for various zones of sand according to IS 383-1970 are tabulated below.
Sieve No. | Opening mm | Zone 1 | Zone 2 | Zone 3 | Zone 4 | Passing |
3/8 | 9.5 | 100 | 100 | 100 | 100 | 100 |
#4 | 4.75 | 90 – 100 | 90 – 100 | 90 – 100 | 95 – 100 | 97.2 |
#8 | 2.36 | 60 – 95 | 75 – 100 | 85 – 100 | 95 – 100 | 85.65 |
#16 | 1.18 | 30 – 70 | 55 – 90 | 75 – 100 | 90 – 100 | 69.8 |
#30 | 0.60 | 15 – 34 | 35 – 59 | 60 – 79 | 80 – 100 | 55.55 |
#50 | 0.30 | 05 – 20 | 08 – 30 | 12 – 40 | 15 – 50 | 29.05 |
#100 | 0.150 | 00 – 10 | 00 – 10 | 00 – 10 | 00 – 15 | 8.35 |
Fineness Modulus | 4.0 – 2.71 | 3.37 – 2.1 | 2.78 – 1.71 | 2.25 – 1.35 | 2.544 | |
Fineness Modulus: Sum of Cumulative percentage Wt. retained /100
FM = Σ Retained % Sieve (3/8 + #4 + #8 + #16 + #30 + #50 + #100) / 100
FM = Σ Retained % Sieve (0.0 +2.8 + 14.35 + 30.2 + 44.45 + 70.95 + 91.65) / 100 = 2.544
Values of Fineness Modulus of Sand:
Fineness Modulus of fine aggregate varies from 2.0 to 3.5mm. Fine aggregate having fineness modulus more than 3.2 should not considered as fine aggregate.
Generally sand having fineness modulus more than 3.2 is not used for making good concrete.
The sand with FM less than this will be called fine sand which is not good for use. And FM greater than this will be called coarse sand, which is again not good for use
Various values of Fineness modulus of different sand are detailed below.
Type of Sand | Fineness Modulus Range |
Fine Sand | 2.2 – 2.6 |
Medium Sand | 2.6 – 2.9 |
Coarse Sand | 2.9 – 3.2 |
Specification of Sand Mortar
Sand used for Masonry (medium to fine) 100% passing # 8 Sieve & not more than 15% passing #100 Sieve
Sand used for Plaster (medium to fine) 100% passing #16 Sieve & not more than 15% passing #100 Sieve
Soil & clay content (not more than 6 % Passing # 200 sieve)
Fineness modulus F.M = 1.5 to 1.8
