🏗️ Shape, dimensions and tolerances for concrete specimens and moulds — PN-EN 12390-1

Construction PN-EN 12390-1:

Overview

WHY THE GEOMETRY OF A SPECIMEN IS A SEPARATE STANDARD. Compressive strength is calculated as the failure load divided by the cross-sectional area. If a specimen is not a cube but a slightly skewed parallelepiped, the cross-sectional area differs from the one assumed in the calculation, the load is distributed unevenly and the specimen fails earlier. A geometrical deviation therefore does not give a result that is "slightly worse" — it gives a systematically understated result, and without any trace in the number itself. Before a laboratory measures strength, it must therefore be certain that the specimen lies within tolerance.

THE SCOPE FROM THE PKN CATALOGUE CARD, IN FULL: "This document specifies the shapes, dimensions and tolerances for concrete specimens made as cubes, cylinders and prisms, and for the moulds required to make them. NOTE The tolerances specified in this standard are suited to the needs of strength testing, but may also be applied in tests of other properties."

THE NOTE IN THE SCOPE MATTERS MORE THAN IT LOOKS. The standard states plainly that the tolerances were established FOR STRENGTH TESTING, and that for other properties they "may be applied". That is permissive wording, not mandatory. A laboratory testing, say, water absorption or freeze-thaw resistance cannot therefore cite this standard as proof that its specimens are appropriate for that test — it must check what the standard for that test requires. This is the same class of distinction as between a product standard and a method standard: a document is sometimes invoked more widely than it warrants for itself.

THREE SHAPES AND THE DIFFERENCE THAT FOLLOWS. A cube and a cylinder give different strengths for the same concrete — the cylinder result is lower, because stresses are distributed differently and friction against the platens acts differently. This is not a measurement error but a property of the shape. That is why a concrete class is written with two numbers (for example C30/37: the first cylinder, the second cube), and why a report must state the shape and size of the specimen. A bare figure in megapascals without the shape is incomplete.

MOULDS ARE PART OF THE SUBJECT OF THE STANDARD, NOT AN APPENDIX. The scope lists "and for the moulds required to make them" on equal footing with the specimens. A worn, warped or leaking mould produces out-of-tolerance specimens in series, and the fault only comes to light when the finished specimens are measured — that is, after twenty-eight days of curing, when the material can no longer be reproduced. Periodic checking of moulds is therefore part of maintaining testing capability, not a housekeeping task.

PLACE IN THE EN 12390 SERIES. Part 1 specifies the geometry of specimens and moulds; part 2 — the making and curing of specimens; part 3 — compressive strength; part 4 — requirements for testing machines; part 7 — density of hardened concrete. In this database parts 4 and 7 are cited by existing entries, and part 1 stands at the beginning of the whole sequence.

A CHANGE OF LANGUAGE VERSION IN THE OPPOSITE DIRECTION. The 2021-12 edition is available in POLISH and replaced PN-EN 12390-1:2013-03 — the ENGLISH version. This is the reverse of the direction seen with PN-EN 482 and PN-EN 933-2, described in this database, where newer editions ceased to be translated. We note this so as not to entrench the impression that translations always disappear — it varies, and the card must be checked each time.

WHAT WE DO NOT GIVE. We do not have the text of the standard — PKN supplies it for a fee. We therefore DO NOT GIVE the values of the tolerances or the nominal dimensions of specimens: neither the permissible deviation of flatness of the loaded faces, nor the perpendicularity of the sides, nor the deviation of the edge dimension. Such values are sometimes quoted from memory or from earlier editions; an entry presenting them as the content of the standard would claim more than we have verified.

THE TAB SHOWED TWO LABORATORIES AND NEITHER OF THEM PERFORMS THIS TEST — CORRECTED (23.09.2026). The key read "PN-EN 12390-1" and was matched by the beginning of the value, so it also caught the thirteenth part: "PN-EN 12390-13" (AB 023) and "PN-EN 12390-13:2021-12" (AB 1251) — i.e. the determination of the modulus of elasticity in compression, a test with a completely different subject. Both laboratories shown got onto the list for the WRONG REASON — but one of them, AB 023, really does have this standard (see below), so it was shown rightly, only by accident. AND THE SAME ENTRY SHOWS A SECOND PHENOMENON, THE REVERSE OF THE FIRST: part 1 DOES NOT OCCUR AT ALL at the beginning of any value, and its only occurrence in the whole set reads "PN-EN 12390-2 PN-EN 12390-3 PN-EN 12390-1 PN-EN 12504-1" — four standards in one field, ours in third place. That laboratory is AB 023 — the same one that the key caught through the thirteenth part. One entry of its scope gave it a false hit, while another, hidden in third place in a field of four standards, really contained part 1. The key was supplemented with a colon ("PN-EN 12390-1:"), which cuts off the thirteenth part. The tab is now empty — and THIS FIX HAS A COST, WHICH WE STATE PLAINLY: it cut off one false hit (AB 1251) and one true hit under a false address (AB 023). No laboratory declares this standard as a SEPARATE entry of its scope, but AB 023 has it as an addition alongside other test standards — and a tab with a key matched by the beginning of the value will not show this single laboratory in any variant. FOR COMPARISON, THE 12390 FAMILY IN THE SCOPES: part 3 (compressive strength) 98 entries at 65 laboratories, part 8 (depth of penetration of water) 46 at 39, part 7 (density) 43 at 28, part 5 (tensile splitting) 23 at 21, part 6 — 23 at 20, part 13 — 2 at 2, and parts 1 and 2 — one entry each (both in the same field of four standards), part 4 — zero. PART 9 (freeze-thaw resistance) has 9 entries at 8 laboratories, but NOT ONCE as "PN-EN 12390-9": all occurrences are "PKN-CEN/TS 12390-9", i.e. a technical specification, not a European standard. The same family number, a different kind of document — a pattern looking for the "PN-EN" prefix would declare zero for it. THE PARTS DESCRIBING THE TEST ITSELF HAVE DOZENS OF LABORATORIES, THE PARTS ON THE SHAPE OF SPECIMENS AND ON MACHINES — ZERO. This is the same regularity that can be seen with PN-EN 932 and PN-EN 933: an accreditation scope lists tests, not the conditions for performing them.

Method principle

The result of a strength test is the quotient of load and cross-sectional area, and the distribution of stresses within the specimen depends on its geometry. The standard therefore establishes the permissible shapes (cube, cylinder, prism), their dimensions and the tolerances on deviations — of flatness of the loaded faces, of perpendicularity of the sides and of the dimensions — as well as requirements for the moulds in which the specimens are made. An out-of-tolerance specimen does not give a "less accurate" result but a systematically understated one, impossible to recognise from the figure alone.

Applications

• Making specimens for concrete strength testing — cubes, cylinders and prisms
• Verification and qualification of moulds used in a concrete laboratory
• Checking specimen geometry before testing — rejecting out-of-tolerance specimens
• Reviewing another laboratory's report: whether the shape and size of the specimen are stated, without which a strength figure is incomplete

Key parameters

Standard

Standard number

PN-EN 12390-1:2021-12 (wersja polska; wprowadza EN 12390-1:2021 [IDT])

Title (PL)

Badania betonu -- Część 1: Kształt, wymiary i inne wymagania dotyczące próbek i form

Title (EN)

Testing hardened concrete — Part 1: Shape, dimensions and other requirements for specimens and moulds

Step-by-step procedure

1. Choose the shape and size of specimen

   Match the shape to the test and to the way the result is expressed. Cylinder and cube strengths are not the same figure — the report must state which was measured.

2. Check the mould before use

   Moulds are the subject of this standard. A warped or worn mould produces whole series of out-of-tolerance specimens, and the fault only shows after curing.

3. Make and cure the specimens

   The moulding and curing themselves are carried out per PN-EN 12390-2 — this standard specifies the geometry, not the making.

4. Check the geometry before testing

   Measure the dimensions and the deviations of flatness and perpendicularity. THE TOLERANCES ARE NOT GIVEN HERE — they are in the text of the standard.

5. Handling an out-of-tolerance specimen

   A non-conforming specimen does not give a result understated "slightly" — it gives one carrying a systematic error. Decide on rejection or surface preparation before testing, not after seeing the figure.

6. Record in the report

   State the shape, the nominal size of the specimen and the full designation of the standard with its year.

Required equipment and apparatus

Reagents, media and consumables

Health and safety (OHS)

• Hardened concrete releases dust when the loaded faces are ground — respiratory and eye protection required
• Concrete specimens are heavy — risk of back injury when carrying them and when removing them from moulds; the mass depends on the size, which we do not state in this entry
• TECHNICAL NOTE: the tolerances of this standard are established for strength testing; for other properties check the requirements of the relevant test standard rather than transferring these

Frequently asked questions