🏗️ Test sieves, nominal size of apertures for aggregates — PN-EN 933-2

Construction PN-EN 933-2

Overview

WHAT THIS STANDARD SETTLES. Determining particle size distribution consists of sieving a sample through a set of sieves and weighing what remains on each. The result therefore depends not only on the aggregate but also on WHICH sieves were used. If every laboratory chose sizes freely, grading curves could be compared neither with one another nor with the requirements of product standards, which are expressed as percentages passing specific sieves. PN-EN 933-2 establishes that common set.

THE SCOPE FROM THE PKN CATALOGUE CARD, IN FULL: "This document specifies the nominal sizes of apertures of test sieves used for the determination of the particle size distribution of aggregates. The document applies to: a) test sieves of perforated metal plate having square apertures of size from 4 mm to 125 mm; b) test sieves of woven metal wire cloth with aperture size smaller than 4 mm down to 0.063 mm."

TWO KINDS OF SIEVE AND THE 4 mm BOUNDARY — EASY TO OVERLOOK. Above 4 mm these are PERFORATED PLATE sieves with square apertures; below 4 mm — WOVEN WIRE MESH. This is not a manufacturing detail: a particle passes through an aperture in a plate and through a mesh opening in different ways, because the thickness of the material and the shape of the edges differ. A set of sieves assembled "any way, as long as the sizes are right" may therefore give a result departing from the reference, even though the numbers on the frames agree. When ordering and calibrating sieves, the type of construction matters as much as the size.

NOMINAL VERSUS ACTUAL SIZE. The standard specifies NOMINAL sizes — the values by which the set is described and named. The actual spread of aperture sizes of a particular sieve is the subject of requirements and verification in other documents and in calibration. A sieve therefore has two numbers: the one from the standard, quoted in the report, and the one from the calibration certificate, which states how far the individual item departs from it. Quoting the nominal size alone in a report is correct; passing over calibration in silence is not.

CHANGE OF EDITION AND CHANGE OF LANGUAGE. The 2021-01 edition replaced PN-EN 933-2:1999 — the POLISH version — and is itself available in English only. This is the same situation as with PN-EN 482, described in this database: a laboratory wishing to read the document in Polish must reach for a text that is no longer in force. We note this because both designations are encountered in accreditation scopes, and "PN-EN 933-2" without a year does not settle which is meant.

PLACE IN THE SEQUENCE OF TESTING. The order is: take the sample, reduce it per PN-EN 932-2 (a separate entry in this database), select sieves sized per PN-EN 933-2, sieve and calculate the grading per PN-EN 933-1. Requirements for aggregates for concrete, for asphalt mixtures or for unbound materials are given by separate product standards — PN-EN 12620, PN-EN 13043, PN-EN 13242 — and it is they that state which percentages passing are acceptable; 933-2 says only on which sieves this is measured.

WHAT WE DO NOT GIVE. We do not have the text of the standard — PKN supplies it for a fee (9 pages, TC 108, ICS 91.100.15). We therefore DO NOT LIST the series of sizes itself. Series circulating in secondary publications are sometimes copied from earlier editions or mixed with series from standards of other fields; an entry presenting them as the content of this standard would claim more than we have verified.

Method principle

Particle size distribution is expressed as the mass fractions retained on successive sieves of a set, so the result is described not only by numbers but also by which sieves the set contained. The standard establishes a common series of nominal sizes, dividing it according to the construction of the sieve: above 4 mm perforated plate with square apertures, below 4 mm woven wire mesh down to 0.063 mm. A grading curve from one laboratory can thereby be compared with one from another and with the requirements of product standards, which are expressed as percentages passing those very sizes.

Applications

• Selecting and assembling a set of sieves for determining the grading of aggregates
• Determining the particle size distribution of aggregates for concrete, asphalt mixtures and unbound mixtures
• Verifying conformity of an aggregate with product standard requirements expressed as percentages passing specified sieves
• Assessing the comparability of grading curves from two laboratories — a discrepancy often results from a different set of sieves, not a different aggregate

Key parameters

Standard

Standard number

PN-EN 933-2:2021-01 (wersja angielska; wprowadza EN 933-2:2020 [IDT])

Title (PL)

Badania geometrycznych właściwości kruszyw -- Oznaczanie składu ziarnowego -- Nominalne wymiary otworów sit badawczych

Title (EN)

Tests for geometrical properties of aggregates — Determination of particle size distribution — Test sieves, nominal size of apertures

Step-by-step procedure

1. Establish the required sieves

   Check in the product standard or specification through which sieves the requirements for the given aggregate are expressed. The set is assembled for those sieves, not the other way round.

2. Verify the type of construction

   Above 4 mm — perforated plate with square apertures; below 4 mm — woven wire mesh. A sieve of the right size but the wrong type is not a sieve from this set.

3. Check the calibration

   The nominal size describes the sieve; the calibration certificate states how far the item departs from it. A worn or deformed sieve keeps the nominal value on its frame but not in its apertures.

4. Sieve and calculate

   The sieving itself and the calculation of grading are carried out per PN-EN 933-1 — this standard supplies only the sieve sizes.

5. Record in the report

   Give the nominal sizes of the sieves used and the full designation of the standard with its year — "PN-EN 933-2" alone does not distinguish the 1999 edition from that of 2021.

Required equipment and apparatus

Reagents, media and consumables

Health and safety (OHS)

• Dust release when sieving fine fractions — respiratory protection required for aggregates containing crystalline silica
• Noise from the sieve shaker — in continuous work in a small room it can become a harmful agent
• TECHNICAL NOTE: agreement of nominal sizes does not prove comparability — worn sieves give inflated passing percentages while retaining the nominal marking

Frequently asked questions