🪨 Uniaxial compressive strength of natural stone — at least 10 cubes or cylinders with a side/diameter of 70 or 50 mm, dried at 70 °C, loaded at a constant rate of stress increase of 1 ± 0.5 MPa/s; PN-EN 1926

Construction PN-EN 1926

Overview

WHAT THE STANDARD COVERS. EN 1926:2006 (clause 1): a method for determining the uniaxial compressive strength of natural stones. The standard was prepared by committee CEN/TC 246 "Natural stones"; the 2006 edition superseded EN 1926:1999. Normative Annex A describes the determination of the compressive strength of armourstone, informative Annex B — the point load strength index and its correlation, normative Annex C — the statistical evaluation of results. References: EN 197-1 (cement for capping with mortar), EN 12390 (all parts — testing machine), EN 12670:2001 (terminology of natural stone), EN 13383-1:2002 (armourstone — specification). The "Scope" field of the PKN card of PN-EN 1926:2007, in full (our translation): "A method for determining the uniaxial compressive strength of natural stones is specified. The apparatus, the preparation of test specimens, the expression of results and the test report are specified. The annexes give the determination of the compressive strength of stone for engineering works, the determination of the point load strength index of natural stone, the statistical calculation of test results" (without a full stop on the card; "stone for engineering works" is armourstone from Annex A in the text of the standard).

PROCEDURE (EN 1926:2006, clauses 3–10 — text read in full; the sample does not include Annexes A–C). Principle: specimens, after mechanical preparation of the faces or — if necessary — after capping with mortar, are placed centrally on the platen of the machine and loaded with a uniformly distributed force increased continuously until failure. • Apparatus (6): surface grinder; lapping machine if a finish is needed; testing machine of adequate capacity, according to EN 12390 and calibrated according to that standard; timer accurate to 1 s; ventilated oven maintaining 70 ± 5 °C; balance accurate to 0.1 g; length-measuring device accurate to 0.05 mm; air-conditioned room at 20 ± 10 °C. • Specimens (7.1–7.2): sampling is not the responsibility of the laboratory unless requested; at least 10 specimens, with the direction of the planes of anisotropy recorded; cubes with an edge of 70 ± 5 mm or 50 ± 5 mm or cylinders with a diameter and height of 70 ± 5 mm or 50 ± 5 mm; lateral dimension or diameter at least ten times the largest grain of the rock — with grains larger than 7 mm more specimens are recommended; the specimen axis perpendicular to the planes of anisotropy (bedding, foliation), and when loading parallel to them is required — a separate set of specimens. • Faces (7.3): loaded faces flat to a tolerance of 0.1 mm per 100 mm, the upper face between two planes parallel to the lower one, not more than 1 mm per 100 mm apart; sides smooth, straight to within 0.3 mm over the full length; finishing on a lathe or grinder, lapping if necessary. Capping with mortar of CEM I 52,5 R cement (EN 197-1) — only when the tolerance cannot be achieved by machining, and it has to be stated in the report. • Conditioning (7.4): drying at 70 ± 5 °C to constant mass (difference between two weighings 24 ± 2 h apart not greater than 0.1 % of the mass), then storage at 20 ± 5 °C until thermal equilibrium and testing within 24 h. • Test (8): cross-section dimensions to the nearest 0.1 mm as the mean of two perpendicular measurements in the upper and two in the lower part of the specimen; height to the nearest 1.0 mm; machine platens and specimen cleaned, the specimen centred under the spherically seated platen, without any packing; continuous loading at a constant rate of stress increase of 1 ± 0.5 MPa/s; the maximum force is recorded "to the nearest 10 kN" (as written in 8.3), and in the report the failure force of each specimen is given in kN without decimal places (clause 10 i). • Result (9, 10): R = F/A (failure force / cross-sectional area before testing), in MPa with at least two significant figures; the mean — to the nearest 1 MPa; the report also gives the standard deviation (to 1 MPa) and the coefficient of variation, the surface preparation and conditioning, the orientation of the loading axis relative to anisotropy; data on the stone (petrographic and commercial name, country and region of extraction, supplier, direction of anisotropy marked on the specimen with two parallel lines) are supplied by the client.

STATUS (state of the PKN cards on 10.10.2026). The card of PN-EN 1926:2007 (English version) carries no withdrawal label: title "Metody badań kamienia naturalnego -- Oznaczanie jednoosiowej wytrzymałości na ściskanie" (Natural stone test methods — Determination of uniaxial compressive strength; our translation), publication 09-03-2007, 17 pages, Sector of Construction and Building Structures, KT 108 Aggregates and Building Stone, "Replaces: PN-EN 1926:2001 - Polish version", "Introduces: EN 1926:2006 [IDT]", ICS 91.100.15. The card of PN-EN 1926:2001 (Polish version, "Metody badań kamienia naturalnego -- Oznaczanie wytrzymałości na ściskanie", introduced EN 1926:1999, replaced PN-B-04110:1984): withdrawn on 30-06-2007 and replaced by PN-EN 1926:2007. The current edition is therefore available in English only; the 2001 edition had a Polish version. In the PKN search engine (query "EN 1926", 10.10.2026) there are also the cards PN-EN 61926-1 and PN-ISO 1926 — these are different standards. In the iTeh catalogue (read on 10.10.2026) EN 1926:2006 has the status "Published", the last stage of the CEN periodic review — "9093 – Decision to confirm" dated 07.10.2026.

HOW MANY LABORATORIES AND IN WHAT FORM (copy of the accreditation scope database of 10.10.2026 and current PCA documents read on 10.10.2026). "EN 1926" appears in 9 records at 8 laboratories: AB 005, AB 298, AB 1251, AB 1344 (2 records), AB 1416, AB 1525, AB 1641 and AB 1778; the standard is present in all 8 current PCA documents, no entry is suspended. Form — everywhere "PN-EN 1926:2007"; AB 005 has it in one cell after PN-G-04303:1997 and before its own procedure. The "Laboratories" tab ("PN-EN 1926") shows 7 laboratories; AB 005 is outside it, because its entry begins with PN-G-04303. The same number 1926 is also borne by ASTM E1926 (longitudinal profiles and roughness of road pavements — 6 laboratories in the copy) — a completely different standard.

WHAT THE LABORATORIES TEST (copy and PCA documents). (Uniaxial) compressive strength of natural stone (AB 1251, AB 1344, AB 1416, AB 1641), of rocks and compact rocks and of stone elements (AB 298, AB 1525, AB 1778), of rocks and stone materials (AB 005 — also residual strength, force range 25–1000 kN) and of stone for hydraulic engineering works (AB 1344). Force ranges are given by each of the eight laboratories: 0–2000 kN (AB 1778), 1–1000 kN (AB 1416), 2.4–1200 kN (AB 1251), 4–3000 kN (AB 298, AB 1641), 5–500 kN (AB 1525), 25–1000 kN (AB 005), 30–1975 kN (AB 1344).

WHERE A SEEMINGLY CORRECT RESULT IS EASY TO GET. First — anisotropy: a bedded stone has a different strength perpendicular and parallel to the bedding; the standard requires testing perpendicular and recording the orientation, and preparing a separate set for the parallel direction — a result without orientation is not comparable. Second — too large a grain: with a specimen dimension smaller than ten times the largest grain the result is not representative; with grains over 7 mm more specimens are needed. Third — moisture: the result applies to specimens dried at 70 °C to constant mass and tested within 24 h; a moist specimen gives a different strength. Fourth — faces: failing flatness or parallelism lowers the result through stress concentration; capping with mortar has to be reported, packing must not be used. Fifth — armourstone: the standard has a separate, normative Annex A for it, not clauses 3–10 (AB 1344 has this subject in its scope). Sixth — rate: 1 ± 0.5 MPa/s is the rate of STRESS increase; the conversion to kN/s depends on the cross-sectional area (50 mm cube — 2500 mm², hence 2.5 kN/s; 70 mm — 4900 mm², hence 4.9 kN/s; our calculation).

WHAT WE DO NOT GIVE. The sample does not include the content of Annexes A (armourstone), B (point load index) and C (statistical evaluation of results) — we do not give them.

Method principle

At least 10 stone cubes or cylinders of 70 or 50 mm, with flat and parallel loaded faces and the axis perpendicular to the planes of anisotropy, are dried at 70 ± 5 °C to constant mass, placed centrally under a spherically seated platen without packing and loaded continuously at a constant rate of stress increase of 1 ± 0.5 MPa/s until failure; R = F/A in MPa, the individual results, the mean, the standard deviation and the coefficient of variation are reported (EN 1926:2006, clauses 3, 7–10).

Applications

• Natural stone — blocks, slabs, stone elements for building and roads (EN 1926:2006, clause 1)
• Armourstone — according to normative Annex A
• In the accreditation scopes: 8 laboratories; force ranges from 5–500 kN to 4–3000 kN

Key parameters

Standard

Standard number

PN-EN 1926:2007 (wersja angielska; wprowadza EN 1926:2006 [IDT])

Title (PL)

Metody badań kamienia naturalnego — Oznaczanie jednoosiowej wytrzymałości na ściskanie

Title (EN)

Natural stone test methods — Determination of uniaxial compressive strength

Step-by-step procedure

1. Preparation of specimens

   At least 10 cubes or cylinders 70 ± 5 or 50 ± 5 mm, axis perpendicular to anisotropy (a separate set for the parallel direction); grinding and lapping to a flatness of 0.1 mm/100 mm.

2. Drying

   70 ± 5 °C to constant mass (two weighings 24 ± 2 h apart differ by ≤ 0.1 %); then 20 ± 5 °C until thermal equilibrium.

   🌡 Temperature: 70 ± 5 °C

3. Measuring dimensions

   Cross-section to 0.1 mm (two perpendicular measurements at the top and two at the bottom), height to 1.0 mm.

4. Compression

   Within 24 h of conditioning: clean the platens, centre the specimen under the spherically seated platen, without packing; load continuously at 1 ± 0.5 MPa/s until failure; record the maximum force.

5. Result and report

   R = F/A (MPa, at least two significant figures); mean, standard deviation (to 1 MPa), coefficient of variation; orientation relative to anisotropy, surface preparation, conditioning. PN-EN 1926:2007 current, PN-EN 1926:2001 withdrawn on 30-06-2007 (state of the PKN cards on 10.10.2026).

Required equipment and apparatus

Reagents, media and consumables

Health and safety (OHS)

• Brittle failure of stone — fragments; machine guards and eye protection
• Grinding and cutting stone — dust (crystalline silica in many rocks), noise; respiratory and hearing protection

Frequently asked questions