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Aggregates · Fine aggregate (sand) and coarse aggregate for concrete, mortar and road work

Sieve Analysis of Aggregates (Grading and Fineness Modulus)

An oven-dried aggregate sample is shaken through a nest of standard sieves. The mass retained on each sieve gives the grading curve, the fineness modulus and, for sand, the IS 383 grading zone.

  • Construction materials
  • Dry sieving through a nest of standard test sieves
  • Sieve shaker
  • Hot air oven
  • Analytical balance

Reference: Typical method based on IS 2386 (Part 1) and ASTM C136; grading limits from IS 383. Always follow the current editions and your approved SOP.

PRINCIPLE

Why this method works

Aggregates are a mix of particle sizes. Passing a known mass through sieves with square openings that get smaller from top to bottom separates the particles into size fractions. The mass on each sieve is turned into a percentage retained, a cumulative percentage retained and a percentage passing. The grading controls how well the particles pack, so it affects the workability, cement demand and strength of concrete. The fineness modulus (FM) is a single number that summarises the grading: it is the sum of the cumulative percentages retained on the standard sieves divided by 100. A higher FM means a coarser material.

Instruments used

MATERIALS

Reagents & standards

ReagentGrade / specification
Test sievesIS sieves (or ISO / ASTM equivalent) with valid aperture verification, e.g. 80, 40, 20, 10, 4.75, 2.36, 1.18 mm, 600, 300 and 150 µm, with lid and pan
Sample dividerRiffle box or quartering equipment to reduce the field sample
BrushesSoft brass or nylon brush for cleaning fine sieves
SAMPLE PREPARATION

Preparing the sample

  1. 01

    Reduce

    Riffle or quarter the field sample to the test mass.

  2. 02

    Dry

    Oven-dry at 100–110 °C to constant mass and cool.

  3. 03

    Weigh

    Weigh the dried test portion.

  4. 04

    Sieve

    Shake through the nest until little more passes.

  5. 05

    Weigh fractions

    Weigh the material on each sieve and the pan.

  6. 06

    Calculate

    Work out % passing, grading zone and FM.

Procedure

  1. 1Reduce the field sample by riffling or quartering to the minimum mass the standard gives for the largest particle size. A test portion of about 500 g is common for sand; coarse aggregate needs several kilograms (for example about 2 kg for 10 mm and 5 kg for 20 mm nominal size; see the current table in IS 2386 Part 1).
  2. 2Dry the test portion in the oven at 100–110 °C to constant mass, cool it and weigh it to 0.1% of its mass.
  3. 3If the material has clay or dust coatings, wash it over a 75 µm sieve first, dry it again and record the loss (material finer than 75 µm).
  4. 4Stack the clean, dry sieves in order with the largest opening at the top and the pan at the bottom. Pour in the sample and fit the lid.
  5. 5Shake on the sieve shaker for a set time (for example 10–15 minutes, or as your SOP states), then finish each sieve by hand until not more than about 0.1% of the mass passes in one minute.
  6. 6Do not overload any sieve. If a sieve is overloaded, split the material and sieve it in portions.
  7. 7Weigh the material retained on each sieve and in the pan. The total should agree with the starting mass within about 0.3% (or the limit in your SOP).

Standard preparation

  1. 1Use sieves whose apertures have been verified within the calibration interval; check for torn or bulging mesh before each use.
  2. 2Check the balance with a standard weight before the test.

Notes for analysts

  • Only the standard sieve series counts towards the fineness modulus. Intermediate sieves such as 12.5 mm are reported but not added into FM.
  • Always dry the sample first: damp fines stick to coarse particles and to the mesh, which makes the sand look coarser than it is.
  • Plot % passing against sieve size on a log scale and draw the specification envelope; it shows at once where a sample is out of grading.
  • Do not force particles through the mesh by hand. It damages the sieve and changes the result.
TEST CONDITIONS

Method parameters (typical)

Drying temperature100–110 °C to constant mass
Sieves for fine aggregate10 mm, 4.75 mm, 2.36 mm, 1.18 mm, 600 µm, 300 µm, 150 µm and pan
Sieves for coarse aggregateFor example 40, 20, 16, 12.5, 10, 4.75 mm, chosen for the nominal size
Test portion (sand)Typically about 500 g; see the current table for coarse aggregate
ShakingMechanical shaking for a set time, then hand finishing
Balance readability0.1% of the test mass or better
Mass balance checkSum of fractions within about 0.3% of the starting mass
BEFORE YOU REPORT

System suitability & sequence

ParameterLimit
Sieve conditionNo torn, stretched or blocked mesh; apertures verified
Mass recoverySum of retained masses close to the starting mass (e.g. within 0.3%)

Typical sequence

  1. 1Reduce and dry the sample
  2. 2Weigh the test portion
  3. 3Wash over 75 µm if required, dry and re-weigh
  4. 4Sieve through the nest
  5. 5Weigh each fraction and check the mass balance
  6. 6Calculate and plot the grading curve
CALCULATION

Calculation with a worked example

Formula
% retained = mass on sieve ÷ total mass × 100; Fineness modulus FM = Σ (cumulative % retained on 150 µm, 300 µm, 600 µm, 1.18 mm, 2.36 mm, 4.75 mm and larger standard sieves) ÷ 100

Where

Mᵢ
Mass retained on sieve i (g)
M
Total oven-dry mass of the test portion (g)
CRᵢ
Cumulative % retained on sieve i
FM
Fineness modulus (no unit)

Given

Total dry mass of sand
500 g
Retained on 4.75 mm
10 g
Retained on 2.36 mm
40 g
Retained on 1.18 mm
80 g
Retained on 600 µm
120 g
Retained on 300 µm
140 g
Retained on 150 µm
85 g
Pan
25 g (total 500 g)

Working

  1. 1

    Cumulative mass retained: 10, 50, 130, 250, 390 and 475 g

  2. 2
    Cumulative % retained = cumulative mass ÷ 500 × 100: 2, 10, 26, 50, 78 and 95%
  3. 3

    % passing = 100 − cumulative % retained: 98, 90, 74, 50, 22 and 5%

  4. 4

    Sum of cumulative % retained = 2 + 10 + 26 + 50 + 78 + 95 = 261

  5. 5
    FM = 261 ÷ 100 = 2.61
  6. 6

    Passing 600 µm = 50%, which falls in the band IS 383 uses for a medium sand (commonly Zone II)

Fineness modulus = 2.61; 50% passes the 600 µm sieve, so the sand is a medium sand (typically IS 383 Zone II).

ACCEPTANCE CRITERIA

What result passes

  • Percentage passing each sieve within the grading limits in IS 383 (current edition) or the project specification for that nominal size.
  • Fine aggregate is placed in a grading zone (I to IV, coarse to fine) mainly by the percentage passing the 600 µm sieve; check the full zone table in the current edition.
  • Fineness modulus within the range stated in the mix design or specification. As a rough guide, fine sands are about 2.2–2.6, medium sands about 2.6–2.9 and coarse sands about 2.9–3.2.
  • Material finer than 75 µm within the limit in IS 383 or the specification (different limits apply to natural, crushed and manufactured sand).
METHOD VALIDATION

Validation parameters (ICH Q2(R2))

ParameterTypical requirement
ApproachStandard method; laboratories show competence by repeat tests and proficiency testing
RepeatabilityDuplicate tests on split samples should give FM values that agree closely (e.g. within about 0.1)
Equipment controlSieve aperture verification and balance calibration within their due dates
In LimsPulse · Sample Management

Run this method in LimsPulse: specifications and STPs under version control, results calculated and checked against limits, and a signed Certificate of Analysis.

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