🛣️ Determination of the flow coefficient of aggregates — reference method (type testing, disputes): the time in seconds for a specified volume of aggregate to flow through a given opening in the standard apparatus; coarse aggregate 4–20 mm on a vibratory table (2970 rev/min, amplitude 0.18 mm) through a 40–60 mm opening into a channel sloping at 10°, fine aggregate up to 2 mm in a separate apparatus; result referenced to the CEREMA reference aggregate (coarse 6.3/10 mm — 100 s, fine 0.063/2 mm — 32 s); not for lightweight aggregates, PN-EN 933-6

Construction PN-EN 933-6

Overview

WHAT THE STANDARD COVERS. We read the text of the standard in the iTeh sample of SIST EN 933-6:2023 (text of EN 933-6:2022, English): from the title page through the contents, the European foreword and Clauses 1–5 up to and including 6.3.4.4 (flow channel of the coarse aggregate apparatus). Outside the sample remain the further items of Clause 6 (among others the fine aggregate apparatus, 6.4), Clauses 7 and 8 (preparation of test portions, procedure, calculation and test report for coarse and fine aggregate) and the informative Annexes A and C (example data sheets) and B (precision).

ACCORDING TO THE TEXT OF EN 933-6:2022 (foreword, Clauses 1–5, part of Clause 6). The standard was prepared by CEN/TC 154 “Aggregates” (secretariat BSI); CEN approved it on 7.11.2022; it supersedes EN 933-6:2014. Changes compared with the 2014 edition according to the foreword: the scope explicitly excludes lightweight aggregates; scope according to current rules, with three annexes and a warning; references to Annex A of EN 1097-6:2013 changed to undated (calculation of masses in 7.2.2, 7.3.1 and 8.2.2), with new notes that the method generally applies to aggregates with water absorption below about 1.5 %; Clause 5 on reference materials reworded; verification of the aperture dimension in 6.4.1 clarified (Figure 3); test reports in 7.5 and 8.5 updated; the expression of numerical results in 8.3, 8.4 and Annex C changed “for a better precision of the final result”. Scope (1): reference method used for type testing and in case of dispute; other methods (e.g. in factory production control) are allowed if their relationship with the reference method has been established; coarse aggregate 4–20 mm and fine aggregate up to 2 mm; not for lightweight aggregates; for coarse aggregate the flow coefficient is linked with the percentage of crushed or broken surfaces and can be used together with EN 933-5, and shape and surface texture also influence it (note 1); experience with the test has generally been limited to natural aggregates (note 2); warning about dust, noise and heavy lifts. Normative references (2): EN 932-2, EN 932-5, EN 933-2, EN 933-3, EN 1097-6. Definitions (3): aggregate size d/D, constant mass (weighings at least 1 h apart, difference up to 0.1 %; usually after drying at (110 ± 5) °C), laboratory sample, size fraction di/Di, test portion. Principle (4): the flow coefficient is the time in seconds for a specified volume of aggregate to flow through a given opening under specified conditions in the standard apparatus. Reference materials (5): reference coarse aggregate — size fraction 6.3/10 mm, flow time ER (100 ± 2) s with an opening of (42.0 ± 0.2) mm, in calculations ER = 100 s and particle density 2.70 Mg/m3; reference fine aggregate — size fraction 0.063/2 mm, flow time ERS (32 ± 2) s, in calculations ERS = 32 s and 2.70 Mg/m3; at present the only recognised source of both — aggregates controlled by CEREMA (regional laboratory in Rouen; coarse — quartzite, fine — siliceous sand from the Somme bay); another source may be used after cross-testing in at least 10 laboratories, and in case of dispute the CEREMA aggregate decides. Apparatus (6.1–6.3): general requirements of EN 932-5; sieves 0.063, 2, 4, 6.3, 8, 10, 14 and 20 mm according to EN 933-2; ventilated oven (110 ± 5) °C or drying equipment that does not break down particles; balance accurate to 0.1 % of the mass; stopwatch reading to 0.1 s; for coarse aggregate: bar sieves 4 mm and 5 mm according to EN 933-3, container of about 10 l, vibratory table with a bubble level, four rubber suspensions (160 ± 30) N/mm, an unbalanced-weight vibrator at (2970 ± 20) rev/min and amplitude (0.18 ± 0.02) mm with the flow unit empty, and a baseplate of (100 ± 10) kg; flow unit of total mass (42.3 ± 0.1) kg: plastic tube for the test portion with inside diameter (125 ± 2) mm and height (610 ± 10) mm, metal shutter adjusting the opening height from (40 ± 1) to (60 ± 1) mm (checked with a gauge block to ± 0.1 mm), metal movable flap releasing the flow, metal flow channel with a slope of (10.0 ± 0.5)° and width of (90 ± 1) mm with plastic sides.

STATUS (as of 03.10.2026). In the PKN search (term “PN-EN 933-6”, 03.10.2026) PN-EN 933-6:2023-06 (English version, “Introduces: EN 933-6:2022 [IDT]”) has no withdrawal note; PN-EN 933-6:2014-07 (English version) — “Withdrawn and replaced by PN-EN 933-6:2023-06 — English version”; PN-EN 933-6:2002 (Polish version) — “Withdrawn and replaced by PN-EN 933-6:2014-07”. What changed for the result between the 2014 and 2022 editions is listed in the foreword (above): above all the exclusion of lightweight aggregates, the indication of the water absorption limit of about 1.5 % and the changed expression of the result for fine aggregate (8.3, 8.4); we did not read the new expression itself.

HOW MANY LABORATORIES AND IN WHAT FORM (copy of the accreditation scope database, load up to 17.09.2026, read on 03.10.2026). The number 933-6 appears in 10 records at 8 laboratories: AB 442, AB 687, AB 937, AB 1344, AB 1414, AB 1532, AB 1545, AB 1685. In the current PCA documents (read on 03.10.2026, issues from 18.12.2025 to 19.08.2026) the number appears in 10 rows of the same 8 laboratories (AB 937 — 3 in the flexible scope “E”, the others 1 each). The form “PN-EN 933-6:2023-06” at five laboratories (at AB 1532 with “p. 8”, i.e. the clause on fine aggregate), “PN-EN 933-6” without year at AB 937; AB 1545 cites the withdrawn PN-EN 933-6:2014-07 — in a PCA document issued on 09.06.2026. None of these items is suspended. The “Laboratories” tab (“PN-EN 933-6”) shows the same 8 laboratories — checked with the tab query on the production server labcoda.pl on 03.10.2026.

WHAT THE LABORATORIES TEST (items in PCA). Aggregates. All items in which the type of aggregate or a range is given concern fine aggregate: “Flow coefficient of fine aggregates” (AB 442 — “flow method”, AB 1344, AB 1685), “of fine aggregate” (AB 937), “of fine-grained aggregate” (0.063–2.0) mm (AB 1545), “Flow coefficient” with the range (0–2) mm (AB 687, AB 1414) and with “p. 8” (AB 1532). There are no items for coarse aggregate 4–20 mm in the scopes.

WHERE A SEEMINGLY CORRECT RESULT IS EASY TO GET. With the reference aggregate: the result relies on the flow time of the reference aggregate (coarse — 100 s, fine — 32 s, density 2.70 Mg/m3), and aggregate from another source requires a comparison in at least 10 laboratories (5) — a result on an unverified aggregate is not comparable. With the type of aggregate: lightweight aggregates are excluded (1), and the method generally applies to aggregates with water absorption below about 1.5 % (foreword) — with more absorbent aggregates the result may be seemingly correct. With the coarse aggregate apparatus: vibration frequency and amplitude, mass of the unit, channel slope and opening height have tolerances (6.3) — getting them out of adjustment changes the flow time. With drying: the drying equipment must not break down particles (6.2.2). With the edition: a result according to PN-EN 933-6:2014 (AB 1545) and one according to the 2023 edition for fine aggregate differ in the way they are expressed (foreword, g).

WHAT WE DO NOT GIVE. We did not read the fine aggregate apparatus (6.4), Clauses 7 and 8 (test portion masses, number of repetitions, formulae) or Annex B (precision), so we do not give them. Nor do we give requirements of aggregate product standards (flow coefficient categories).

Method principle

A suitably prepared and dried test portion of aggregate of specified volume is placed in the standard apparatus and the time it takes to flow through an opening of a given height is measured with a stopwatch: coarse aggregate 4–20 mm — from a tube on a vibratory table through an opening under a shutter into a channel sloping at 10°; fine aggregate up to 2 mm — in a separate apparatus. The same measurement is made on the reference aggregate (CEREMA), and the flow coefficient is expressed in seconds.

Applications

• Coarse aggregates 4–20 mm and fine aggregates up to 2 mm — reference method for type testing and disputes (1)
• Assessment of the surface characteristics of particles; for coarse aggregate linked with the percentage of crushed particles (EN 933-5) (1, note 1)
• Fine aggregates (0–2 mm) — flow coefficient in the accreditation scopes of 8 laboratories in PCA

Key parameters

Standard

Standard number

PN-EN 933-6:2023-06

Title (PL)

Badania geometrycznych właściwości kruszyw — Część 6: Ocena właściwości powierzchni — Wskaźnik przepływu kruszyw

Title (EN)

Tests for geometrical properties of aggregates — Part 6: Assessment of surface characteristics — Flow coefficient of aggregates

Step-by-step procedure

1. Sample

   Reduction according to EN 932-2, drying to constant mass (usually (110 ± 5) °C). PN-EN 933-6:2023-06 current (PKN search, 03.10.2026).

2. Size fractions

   Separation of fractions by sieves; for coarse aggregate also by bar sieves; test portion masses (7.2, 8.2) — outside the sample.

3. Reference test

   Measurement of the flow time of the reference aggregate (coarse — about 100 s, fine — about 32 s).

4. Sample test

   Coarse aggregate: tube on the vibratory table, opening the flap, measuring the flow time with a stopwatch; fine aggregate — in the apparatus of 6.4.

5. Result

   Flow coefficient in seconds; we do not give the formulae (7.4, 8.4).

Required equipment and apparatus

Reagents, media and consumables

Health and safety (OHS)

• The standard warns about dust, noise and heavy lifts (1)
• Vibratory table with a baseplate of about 100 kg and a flow unit of about 42 kg — move following the rules for lifting heavy loads (6.3.3.4, 6.3.4)

Frequently asked questions