Sieve Analysis and Fineness Modulus Determination for Aggregate Classification

Fineness Modulus of Fine Aggregate:

The sand fineness module (fine aggregate) is an index number describing the mean size of sand particles. By doing sieve analysis with normal sieves, it is measured.

The accumulated percentage kept on each sieve is applied and the sum of the fine aggregate is subdivided by 100. To find the fine aggregate fineness modulus, we require 4.75mm, 2.36mm, 1.18mm, 0.6mm, 0.3mm, and 0.15mm sieve sizes.

The fineness modulus of the finer aggregate is greater than the coarse aggregate fineness module.

Fineness Modulus of Coarse Aggregate

The fineness modulus of coarse aggregates is the index number of the total particle size of the coarse aggregate. By doing sieve analysis with normal sieves, it is measured. The accumulated percentage retained on each sieve is applied and the coarse aggregate valuation is given by subdividing it by 100.

The fineness module is larger than the fine aggregate, thus the fineness module of the coarse aggregate is greater than the fine aggregate. We require sieve sizes of 75mm, 37.5mm, 19mm, 9.5mm, 4.75mm, 2.36mm, 1.18mm, 0.6mm, 0.3mm and 0.15mm and determine the coarse aggregate fineness modulus.

The Fineness module is the number that is identified when we calculate the particle size from the lower order standard sieves to the higher-order sieve. So, we require all sizes of sieves in the coarse aggregate measurement.

Sieve Analysis

Analysis of the sieve helps to determine the distribution of the particle size of the coarse and fine aggregates. This is achieved by sieving the aggregates according to IS: 2386 (Part I)-1963. As standardized by the IS code, we use various sieves in this and then pass aggregates through them and thus collect various-sized particles leftover various sieves.

The equipment used are-

#1. 80mm, 63mm, 50mm, 40mm, 31.5mm, 25mm, 20mm, 16mm, 12.5mm, 10mm, 6.3mm, 4.75mm, 3.35mm, 2.36mm, 1.18mm, 600μm, 300μm, 150μm and 75μm.

#2. Balance or scale with precision to measure 0.1% of the test sample’s weight.

The available sample weight should not be less than the weight given below:

Procedure to Determine the Distribution of Aggregates by Particle Size.

1. The test sample is dried and measured at a steady weight at a temperature of 110 + 5⁰
2. A set of IS sieves is used to sieve the sample.
3. The substance on each sieve is weighed upon completion of the sieve.
4. As a proportion of the overall sample weight, the average weight moving through each sieve is measured.
5. The fineness module is obtained by applying to each sieve the total percentage of aggregates maintained and by dividing the sum by 100.

Sieve Analysis of Fine Aggregate:

One of the most relevant experiments conducted on-site is the Sieve analysis of Sand. Aggregates are neutral materials which are combined for mortar or concrete manufacture with binding materials such as cement or lime. It’s also found in mortar and asphalt as fillers.

The size of the aggregate ranges from several inches to the size of the smallest sand particle. In general, the aggregates occupy 60 to 75 percent of the concrete volume or 70 to 85 percent by weight and greatly affect the freshly mixed and hardened properties, mixture proportions, and economy of the concrete.

All IS 4.75 mm sieve pass aggregates and known as fine aggregates. In order to determine conformity with the design, quality control criteria, and verification parameters, all aggregate technicians use a sieve analysis (gradation test) to determine the gradation (particle size distribution, by size, within a given sample).

The sieve analysis is really useful for the monitoring and quality acceptance technique used in combination with other studies. Gradation implies the distribution of the scale of the particles within the overall size range. On a graph, gradation can be classified as well-graded, uniform, or gap graded (sometimes referred to as skip graded), listed below.

1. Well graded means the sizes are in nearly equal proportions across the whole range, although the largest and smallest particles would be very different.
2. Uniform gradation means that the particles have a significant proportion of the same dimension. Gap graded or skip graded means that with a few particles of an intermediate scale, most particles are high in size or tiny in size.
3. Targets: The whole sieve analysis technique is to determine the distribution of the particle size of the fine aggregates and to determine if it is appropriate for use in concrete mixing.

Equipment for Testing

#1. Sieves for IS 75 mm, 36 mm, 18 mm, 600 mic, 300 mic, 150 mic, 75 mic.

#2.Shovel and Skillet.

#3. Balance or scale with an accuracy representing 0.1 percent of the sample’s weight.

#4. Mechanical sieve shaker.

#5. Fine aggregates of 1000 grams.

Sieve Analysis Test Procedure-

Step 1. Dry the sample at a temperature of 110+ 5⁰ C at a constant weight.

Step 2. Next the sieve and put the sample on the top sieve in order to reduce the scale of the opening from top to bottom.

Step 3. Shake the sieves for a suitable time, say 15 times or 28 minutes, by hand or by mechanical apparatus. A correct series (forward and backward motion, left and right motion, clockwise (CW) and counter-clockwise (CCW) motion and regular jolting) should be done by the manual process.

Step 4. Restricted the volume of material on a given sieve such that all objects have the ability to enter the opening of the sieve several times during the sieving process. For sieves with openings greater than 4.75 mm, the weight maintained on each sieve shall not exceed 6 kg/m2 (4 g/in2) of the sieving surface at the end of the sieving operation.

Step 5. In the case of sieves with apertures of 4.75 mm and wider, the weight in kg/m of the sieving surface must not exceed 2.5 of the product (sieve opening in mm). In no case shall the weight be so high as to cause the sieve cloth to be permanently deformed.

Step 6. Continue sieving for a reasonable amount of time and in such a way that no more than 1 percent of the residue on any particular sieve can move through the sieve after 1 minute of continuous hand sieving after completion.

Step 7. Place the fine aggregate sample in the top sieve, place the cap on top of the sieve stack, and agitate for 10 to 15 minutes by using the mechanical sieve shaker.

Step 8. Carefully extract the sieves one at a time and, with its retained aggregate, measure each sieve. Calculate the material mass stored on each sieve, deducting the resulting sieve’s weight. Determine the weight of each rise in size by measuring the nearest 0.1 percent of the overall initial dry sample weight on a scale or balance.

Step 9. The overall substance weight after sieving should be carefully checked with the original sample weight put on the sieves. If depending on the initial dry sample weight, the sum varies by more than 0.3 percent, the data can not be considered for approval purposes.

Calculation of Sieve Analysis Test

1. Calculate passing ratios, cumulative percentage held, or percentages to the nearest 0.1 percent in separate scale fractions on the basis of the total weight of the original dry sample.
2. Calculate the fineness modulus (FM) by applying to the sample the average amount of content that is coarser than any of the normal flowing sieves (Cumulative percentage retained) and by dividing the number by 100:150-m (No. 100), 300-m (No. 50), 600-m (No. 30), 1.18-mm (No. 16), 2.23-mm (No. 8), 4075-mm (3/8-in), 37.5-mm (1.5-in) and wider (3 in or 6 in). If any non-standard sieve is used, apply the total percent retention of this sieve during FM measurement to the next lower-sized standard sieve.

Report of Sieve Analysis Test

The following are included in the report:

1. The absolute proportion of material moving through each sieve, or
2. The overall proportion of material retained on each sieve or on each sieve
3. Percentage of material between consecutive sieves maintained
4. Report the fineness modulus to the nearest 0.01 as necessary.

Sand Zone Classification:

Table for Fine Aggregate:

Table for Coarse Aggregate:

FAQ – Sieve Analysis and Fineness Modulus Determination for Aggregate Classification

What is sieve analysis?

Sieve analysis is a technique used to determine the particle size distribution of aggregates. It involves passing a sample of aggregate through a series of sieves with progressively smaller openings and measuring the amount of material retained on each sieve.

What is the purpose of sieve analysis in aggregate testing?

Sieve analysis helps in assessing the gradation (particle size distribution) of aggregates, which is crucial for designing concrete mixes. It ensures that aggregates meet specifications for strength, workability, and durability of concrete.

What is fineness modulus (FM) in relation to aggregates?

Fineness modulus is a measure that describes the average size of particles in an aggregate sample. It is calculated by summing up the cumulative percentages of aggregate retained on a series of sieves and dividing by 100.

How is fineness modulus (FM) used in practice?

FM helps in classifying aggregates into fine and coarse categories based on their particle sizes. It provides a numerical value that indicates the fineness or coarseness of an aggregate sample, influencing concrete mix proportions and performance.

What equipment is needed for sieve analysis?

Equipment includes standard sieves with various mesh sizes, a mechanical sieve shaker or hand sieves, a balance accurate to 0.1% of the sample weight, and containers for holding the aggregate samples.

What are the different zones of sand classification based on sieve analysis?

Sand is classified into four zones (Zone 1 to Zone 4) based on the percentage of aggregate retained on various sieve sizes (e.g., 10mm, 4.75mm, 2.36mm). These zones indicate the suitability of sand for different concrete applications.

Why is sieve analysis important in quality control of aggregates?

Sieve analysis ensures consistency and quality in aggregates used for concrete production. It helps in verifying compliance with specifications, optimizing mix designs, and achieving desired concrete properties.

How should one interpret the results of sieve analysis?

Results are typically presented as a gradation curve showing cumulative percentages passing or retained on each sieve. Engineers and concrete technologists use these curves to understand the distribution of particle sizes and make informed decisions about aggregate use.

What are the limitations of sieve analysis?

Sieve analysis may not accurately represent the shape and angularity of aggregate particles, which can affect concrete workability and strength. Additionally, very fine particles below 75 microns may not be effectively captured by standard sieves.

How can sieve analysis results be reported?

Results are reported by detailing the percentage of material retained on each sieve, cumulative percentages, and the calculated fineness modulus. Reports should adhere to standard methods and provide clear data for evaluation and comparison.