🏗️ Liquid limit wL and plastic limit wP of soil and plasticity index IP — fall cone method (60 g/60° or 80 g/30° cone) or Casagrande method and thread rolling, on the fraction below approx. 0,4 mm or natural soil, PN-EN ISO 17892-12

Construction PN-EN ISO 17892-12

Overview

WHAT THE STANDARD COVERS. Scope from the PKN catalogue card of PN-EN ISO 17892-12:2018-08 (Polish version), in full (our translation of the Polish card text): “This document specifies methods for the determination of the liquid and plastic limits of a soil. These comprise two of the Atterberg limits for soils. The liquid limit is the water content at which a soil changes from the liquid to the plastic state. This document describes the determination of the liquid limit of a specimen of natural soil, or of a specimen of soil from which material larger than about 0,4 mm has been removed. This document describes two methods: the fall cone method and the Casagrande method. NOTE The fall cone method in this document should not be confused with that of ISO 17892-6. The plastic limit of a soil is the water content at which a soil ceases to be plastic when dried further. The determination of the plastic limit is normally made in conjunction with the determination of the liquid limit. It is recognized that the results of the test depend largely on the judgement of the operator and that variability in results will occur.” We read the text of the standard in the preview of ISO 17892-12:2018 (first edition, 2018-06) from the cover to subclause 4.4.2 (rod or gauge for thread rolling, page 6) and the full text of amendment ISO 17892-12:2018/Amd 2:2022; of amendment 1 (EN ISO 17892-12:2018/A1:2021) we have only the European foreword and the title page.

ACCORDING TO THE TEXT OF THE STANDARD (foreword, introduction, clauses 1–4.4.2). The standard was prepared by CEN/TC 341 with ISO/TC 182 (Vienna Agreement); the first edition replaced ISO/TS 17892-12:2004 (technically revised) and incorporated Cor.1:2006; according to the introduction it is to present broad good practice, with no significant differences from national documents anticipated. Normative references: ISO 3310-1 (test sieves), ISO 14688-1 (identification and description of soils), ISO 17892-1 (determination of water content). Definitions: liquid limit wL and plastic limit wP — water contents determined by the respective test; plasticity index IP — the difference wL − wP; non-plastic soil — with IP of zero or one for which the plastic limit cannot be determined. Apparatus (4): balance accurate to 0,01 g or 0,1 % of the weighed mass (whichever is greater); containers not changing mass in repeated drying (glass, porcelain, corrosion-resistant metal), for the plastic limit — with close-fitting lids; distilled, de-ionized or demineralized water; spatulas, spray bottle, evaporating dishes, sieves according to ISO 3310-1, mixing plate (e.g. glass), metal straightedge approx. 100 mm. Fall cone apparatus (4.2): the cone is held firmly and released instantaneously to fall freely vertically; height adjustment until the tip just touches the specimen surface; measurement of penetration with a resolution of 0,1 mm or better — in the range 5 mm to 20 mm for the 60 g/60° cone or 10 mm to 30 mm for the 80 g/30° cone; both cones give essentially the same liquid limit, other devices may be used if comparable results are shown. Table 1 (typical manufacturing requirements): mass of cone plus shaft 60 ± 0,06 g or 80 ± 0,08 g; tip angle β 60° or 30° — in the 2018 edition ± 0,2°, after amendment A2 ± 0,3°; height of the conical tip h ≥ 20 mm or ≥ 30 mm; deviation from the geometrical tip at manufacture < 0,1 mm for both cones in the 2018 edition, after amendment A2 < 0,1 mm (60°) and < 0,2 mm (30°). Cone of stainless steel or chromium-plated, smooth (Ra < 0,8 µm as a manufacturing requirement), replaced when the surface is noticeably damaged; maximum tip wear b — in the 2018 edition < 0,3 mm, after amendment A2 < 0,3 mm for the 60 g/60° cone and < 0,6 mm for the 80 g/30° cone. Cup non-corrodible and rigid, spherical or cylindrical — cylindrical with a diameter of at least 50 mm and a depth of at least 25 mm (60 g/60° cone) or 40 mm (80 g/30°); timer read to 1 s. Casagrande apparatus (4.3): cup raised by a cam and dropped from a height of 10 mm onto a base, hand or motor driven (motor: 2 ± 0,25 revolutions per second, isolated from vibration); rubber base and feet according to Table 2 (hardness of feet Shore A 62–65, base Shore D at least 80, resilience of base S from 0,80 to 0,90); cup of brass or stainless steel in the shape of a segment of a sphere, not polished; cam raising the cup smoothly over at least 180° of rotation (a logarithmic spiral has been found satisfactory); grooving tool of plastic or metal with a bevelled tip (dimensions in Annex A); other apparatus may be used if comparability is shown. Thread rolling (4.4): flat, smooth plate without scratches (e.g. glass approx. 10 mm × 300 mm × 300 mm) and a rod of 3 mm to 3,5 mm diameter or a gauge with such an opening. The table of contents then lists: 5.1 — choice of liquid limit method, 5.2 — specimen preparation, 5.3 and 5.4 — liquid limit by the fall cone and Casagrande methods, 5.5 — plastic limit; 6.1 — proportion of sample smaller than 0,4 mm, 6.2 and 6.3 — liquid limit result by the fall cone and Casagrande methods, 6.4 — plastic limit, 6.5 — plasticity index; 7 — test report (mandatory and optional); Annex A (normative) — calibration, maintenance and checks, B (normative) — additional parameters.

AMENDMENT A2:2022 (full text). It replaces Table 1 and subclause 4.2.2.4 (values given above) and subclause A.3.6.1: before the first use on each day of use, the sharpness of the tip, the surface finish and the free fall of the cone are checked; the cone is replaced when the point can no longer be felt with the fingertip after pushing it through a hole of (1,50 ± 0,02) mm diameter in a metal plate (2,20 ± 0,02) mm thick for the 30° cone or (1,00 ± 0,02) mm thick for the 60° cone (Figure A.1; other dimensions allowed if the ratio of thickness to diameter is kept) — the maximum permitted wear corresponds to the tip being flush with the bottom of the plate; the surface of the cones is visually checked before use each day, and mass, dimensions and total tip wear are verified at least annually.

STATUS (cards as of 02.10.2026). The card of PN-EN ISO 17892-12:2018-08 (Polish version) has no “Withdrawn” header — the standard is CURRENT: Polish version published 20-11-2023, 34 pages, price group Q, Construction Sector, KT 254 for Geotechnics, ICS 13.080.20, 93.020, “Introduces: EN ISO 17892-12:2018 [IDT], ISO 17892-12:2018 [IDT]”, additional elements: amendments A1:2022-03 and A2:2022-08 (Polish versions). Card of amendment PN-EN ISO 17892-12:2018-08/A1:2022-03 (Polish version, published 21-12-2023, 6 pages, introduces EN ISO 17892-12:2018/A1:2021): “Scope”: “Figure A.2 was changed.”; card of amendment /A2:2022-08 (Polish version, published 31-01-2024, 7 pages, introduces EN ISO 17892-12:2018/A2:2022): “This document introduces changes in Table 1, 4.2.2.4 and A.3.6.1.” — both without a “Withdrawn” header. The PKN search for “PN-EN ISO 17892-12” (02.10.2026) shows the standard and both amendments in Polish and English versions and PKN-CEN ISO/TS 17892-12:2009 (Polish version; “Determination of Atterberg limits”) — card: “Withdrawn”, withdrawal date 01-08-2018. What A2 changes for the result: a wider angle tolerance (± 0,3° instead of ± 0,2°) and greater permitted wear of the 80 g/30° cone (0,6 mm instead of 0,3 mm) — a cone rejected under the 2018 edition may be accepted under A2; daily check of the tip with a gauge with a hole. We do not have the content of amendment A1 (Figure A.2). We have not checked the status of ISO 17892-12:2018 on the ISO website.

HOW MANY LABORATORIES AND IN WHAT FORM (copy of the accreditation scope database, data up to 17.09.2026, read 02.10.2026). The number 17892-12 appears in 19 records of 8 laboratories: AB 1770 (4), AB 1905 (3), AB 283, AB 962, AB 1416, AB 1750, AB 1778, AB 1914 (2 each). Current scopes on the PCA website (read 02.10.2026, scope issues from 24.09.2024 to 17.07.2026): 21 lines with the number — because entries break into two lines in the PDF (AB 1778: “PN-EN ISO 17892-12:2018-” and “08/A2:2022-08”), bilingual items are repeated (AB 1770 — two blocks of items), and at AB 1416 the number stands in four lines for two items. Edition: everywhere 2018-08; only AB 1778 adds amendment A2:2022-08, nobody cites amendment A1; AB 1770 indicates result points (“p. 6.2” for the liquid limit, “p. 6.4” for the plastic limit). Withdrawn documents stand alongside: PKN-CEN ISO/TS 17892-12:2009 (AB 1416 — for both limits) and PN-B-04481:1988 (AB 283 — p. 5.5 and p. 5.6.4, AB 1416 — p. 5.5). None of these items is suspended. The “Laboratories” tab searches for entries BEGINNING WITH “PN-EN ISO 17892-12” and shows 7 laboratories — without AB 1416, where the element of the reference field begins with “PN-88/B-04481 p. 5.5” or “PKN-CEN” (the copy glues three documents into one element); checked with the tab query on the production server labcoda.pl on 02.10.2026: “PN-EN ISO 17892-12” — 7, “PKN-CEN ISO/TS 17892-12” — 0, “EN ISO 17892-12” — 1 (a Czech laboratory accredited by ČIA, No. 1181); the tab finds AB 1416 under “PN-88/B-04481” (33 laboratories).

WHAT THE LABORATORIES TEST (items in PCA). Everywhere the object is soils (at AB 1770 with marine sediments and construction materials in adjacent items). Liquid limit: fall cone — 7 laboratories (AB 962 — “one-point and multi-point”), Casagrande method — AB 1905 (alongside the cone); plastic limit: “thread rolling method” (AB 1778, AB 1905), “weight method” (AB 283, AB 1750), unnamed (AB 962, AB 1416, AB 1770, AB 1914). At AB 283 both limits also have English names (“Plastic limit / Weight method”, “Liquid limit / Fall cone method”). The same scopes contain other parts of the series — water content according to PN-EN ISO 17892-1 and particle size distribution according to PN-EN ISO 17892-4 — which have separate entries in the Knowledge Base, as do soil tests according to PN-88/B-04481. Status (cards as of 02.10.2026): PN-EN ISO 17892-1:2015-02 (English version, with additional element A1:2022-11) and PN-EN ISO 17892-4:2017-01 (English version) — without a “Withdrawn” header; PN-B-04481:1988 — “Withdrawn”, withdrawal date 10-09-2015.

WHERE A SEEMINGLY CORRECT RESULT IS EASY TO GET. In preparation: the standard describes testing natural soil or the fraction from which particles larger than approx. 0,4 mm have been removed — these are two different test materials, and the proportion of the fraction smaller than 0,4 mm is a separate result in the table of contents (6.1); the water must be distilled, de-ionized or demineralized. In measurement: the 60 g/60° and 80 g/30° cones give according to the standard essentially the same liquid limit, but each has its own penetration range (5–20 mm or 10–30 mm) and its own cup (depth ≥ 25 mm or ≥ 40 mm) — a cup chosen for the 60 g/60° cone does not meet requirement 4.2.3 for the 80 g/30° cone; tip wear has a limit, and its daily check with a gauge was introduced by amendment A2 — a laboratory citing only the 2018 edition (7 of 8) does not have this requirement in the cited document; the fall cone method of this standard is easily confused with the cone method of ISO 17892-6 (the scope of the standard warns about this explicitly). In the Casagrande apparatus the drop height (10 mm), hardness and resilience of the rubber base and feet, the cam shape and the condition of the cup are requirements of the standard — an apparatus not meeting them may be used only after comparability of results has been shown. With the plastic limit: the result depends on the judgement of the operator (as the scope says), and the rod or gauge of 3 mm to 3,5 mm is the only numerical reference in the read text. In the calculation: wL and wP are water contents determined according to ISO 17892-1 (a separate standard), IP = wL − wP is a calculation from two results of this standard, and a soil for which wP cannot be determined is described as non-plastic, not by a number. Citing the withdrawn PN-B-04481 or PKN-CEN ISO/TS 17892-12 next to this standard (AB 283, AB 1416) gives two or three reference documents in one item; the scope does not show according to which one a given result was obtained.

WHAT WE DO NOT GIVE. From the read text we do not have Clauses 5–7 (choice of method, specimen preparation, procedures with the cone, Casagrande apparatus and thread rolling, calculations, report) or Annexes A and B (apart from A.3.6.1 as worded by amendment A2) — so we do not give times, number of determinations, the penetration corresponding to the liquid limit, the number of blows, the rolling procedure or formulae. We do not know the content of amendment A1 beyond the sentence on the PKN card (“Figure A.2 was changed”).

Method principle

The liquid limit is determined as the water content at which the soil passes from the liquid to the plastic state — by the fall cone method (penetration of a freely falling 60 g/60° or 80 g/30° cone into the specimen) or by the Casagrande method (cup with soil in which a groove is cut with the grooving tool, raised by a cam and dropped from a height of 10 mm); the plastic limit — as the water content at which the soil ceases to be plastic when dried further, by thread rolling with a 3–3,5 mm rod or gauge as the diameter reference. Water content is determined according to ISO 17892-1, and the plasticity index is calculated as IP = wL − wP; we do not have the test procedures (Clause 5).

Applications

• Classification and description of cohesive soils in geotechnical investigation — liquid and plastic limits in the scopes of 8 laboratories
• Liquid limit by the fall cone method (7 laboratories) and by the Casagrande method (AB 1905)
• Plastic limit by thread rolling (in the scopes also as “weight method”) and the plasticity index from both limits

Key parameters

Standard

Standard number

PN-EN ISO 17892-12:2018-08 (wersja polska z 20-11-2023 i wersja angielska; EN ISO 17892-12:2018, ISO 17892-12:2018 IDT) ze zmianami PN-EN ISO 17892-12:2018-08/A1:2022-03 i /A2:2022-08

Title (PL)

Rozpoznanie i badania geotechniczne — Badania laboratoryjne gruntów — Część 12: Oznaczanie granic płynności i plastyczności

Title (EN)

Geotechnical investigation and testing — Laboratory testing of soil — Part 12: Determination of liquid and plastic limits

Step-by-step procedure

1. Specimen preparation

   Natural soil or the fraction from which particles larger than approx. 0,4 mm have been removed; the proportion of the fraction < 0,4 mm is a separate result (6.1). PN-EN ISO 17892-12:2018-08 with A1 and A2 current (cards as of 02.10.2026). Details of subclause 5.2 NOT GIVEN.

2. Cone check

   Before first use each day: tip sharpness with the gauge with a hole, surface finish, free fall (A.3.6.1 according to amendment A2); mass, dimensions and wear — at least annually.

3. Liquid limit

   Fall cone or Casagrande method (choice — 5.1); the procedure of subclauses 5.3 and 5.4, the number of determinations and the way wL is obtained are NOT GIVEN.

4. Plastic limit

   Thread rolling on a smooth plate, with a 3–3,5 mm rod or gauge as the diameter reference; the procedure of subclause 5.5 is NOT GIVEN; the result depends on the operator’s judgement (scope of the standard).

5. Results

   wL and wP as water contents (according to ISO 17892-1); IP = wL − wP; non-plastic soil when IP = 0 or wP cannot be determined; report — Clause 7 (content NOT GIVEN).

Required equipment and apparatus

Reagents, media and consumables

Health and safety (OHS)

• Cone tip and grooving tool — take care when checking sharpness with a finger through the gauge hole; laboratory ovens for water content; the read text of the standard contains no health and safety warnings
• TECHNICAL NOTE: changing from the 60 g/60° cone to the 80 g/30° cone requires a different cup and penetration range; permitted wear and cone tolerances were changed by amendment A2, which only AB 1778 cites

Frequently asked questions