oSIST prEN 18374:2026

• Abstract:

  This document specifies a test method to determine the suitability of a soil to be treated with lime and/or hydraulic binders, with regard to volumetric swelling and mechanical strength, within a period not exceeding two to three weeks.; This test can be integrated into the general method of a study of treatment of materials with lime and/or a hydraulic binder, in compliance with standard EN 16907 4.; It is applicable to soils and alternative (or anthropogenic) materials treated with lime and/or hydraulic binders for the construction of embankments and capping layers; in the areas of roads, railways and airports; industrial or commercial platforms; hydraulic works and road foundations.; The results of this test:; — are only valid for the configuration tested (soil, treatment product, dosage);; — are in no case usable for dimensioning a structure including treated materials.; The values currently accepted to define treatment suitability are indicated for information in Annex A.

• Status: Not Published
• Public Enquiry End Date: 20-Sep-2026
• ICS: 93.020 - Earthworks. Excavations. Foundation construction. Underground works
• Technical Committee: ZEM - Earthworks
• Current Stage: 4020 - Public enquire (PE) (Adopted Project)
• Start Date: 22-Jul-2026
• Due Date: 09-Dec-2026
• Ref Project: prEN 18374 - Earthworks - Geotechnical laboratory tests - Lime and/or hydraulic binder treated materials - Test for determining the treatment suitability of a soil

oSIST prEN 18374:2026 is the Slovenian version of the draft European Standard prEN 18374 from CEN. It specifies a geotechnical laboratory test for judging whether a soil or alternative material is suitable for treatment with lime and/or hydraulic binders by checking swelling and, when needed, indirect tensile strength over a short test period of about two to three weeks.

What does oSIST prEN 18374:2026 specify?

oSIST prEN 18374:2026 specifies a laboratory method for treatment suitability, focused on volumetric swelling and mechanical strength. It applies to soils and alternative, including anthropogenic, materials used in embankments, capping layers, roads, railways, airports, industrial or commercial platforms, hydraulic works and road foundations.

The result is only valid for the exact configuration tested, meaning the specific soil, treatment product and dosage. It is not used to dimension a structure made with treated material.

The document is organized into clauses 1 to 9, followed by Annex A and Annex B.

Annex	What it covers
Annex A	Normative criteria for deciding whether a soil is suitable for treatment
Annex B	Informative example of a test report

What are the key requirements of oSIST prEN 18374:2026?

The test is built around controlled specimen preparation, accelerated curing and immersion, then measurement of swelling and, for some uses, indirect tensile strength. In practice, laboratories have to control the mixture, the moisture, the specimen geometry and the curing conditions closely, because the result applies only to that tested formulation.

Specimen preparation and mixture control

Clause 7.1 requires the mixture to be characterized using site data and Normal Proctor references from EN 13286-2. The treated mixture is prepared after removing particles larger than 6.3 mm, and the specimen mixture is made with a dry density of 96 % of the reference dry density and a water content between the reference water content and that value plus 2 %. This matters because the test is intended to represent a controlled formulation, not a loose field mixture.

Clause 7.1 also requires the water used in the mix to avoid elements that would harm setting or hardening. That means water quality can change the outcome of the suitability check.

Specimens for swelling and strength

Clause 7.1.2 calls for three swelling specimens, each 50 mm by 50 mm, released from the mould immediately after manufacture. Clause 7.1.3 calls for three strength specimens, made in the same way but kept in the case during curing and immersion. This split is important because swelling and strength are measured on different specimen conditions.

Curing and immersion sequence

Clause 7.2 sets different curing times depending on the treatment product. For lime only, specimens cure for 72 h at 20 °C and above 90 % humidity, then immerse for 168 h at 40 °C. For hydraulic binder, possibly combined with lime, curing is 24 h under the same temperature and humidity conditions, then the same immersion follows.

For rapid setting hydraulic binders, the curing time may be shortened using the setting start time on pure paste, based on the manufacturer’s sheet or EN 196-3, with a minimum of 4 h. The chosen curing time must be stated in the report.

Measurements and calculations

Clause 7.3.1 defines swelling measurement from the specimen volume before and after immersion, using callipers or hydrostatic weighing. Clause 7.3.2 defines indirect tensile strength testing by diametral compression in accordance with EN 13286-42. In practice, the first measurement checks whether the material expands too much, while the second checks whether the treated material develops enough strength for the intended use.

Interpretation and repeat testing

Annex A gives the criteria used to classify the material as suitable, uncertain or unacceptable. It uses swelling for all cases and adds an indirect tensile strength criterion when mechanical performance of a capping layer is being studied. Clause 8 allows a supplementary test with a longer curing time, up to 7 days, when the first result is uncertain or unacceptable.

What terms does oSIST prEN 18374:2026 define?

• Curing time - the period between completion of specimen preparation and immersion.
• Immersion time - the period after curing when the specimens are kept completely underwater.
• Material - soil or alternative, including anthropogenic, material.
• Hydraulic binder - cement or hydraulic road binder, and the term can also apply to non-standard products.
• Treatment product - the added product, made of hydraulic binder only, hydraulic binder with lime, or lime only.
• Volumetric swelling (G_V) - the percentage change in specimen volume after maturation and immersion.
• Indirect tensile strength (R) - the mechanical strength measured by diametral compression.

Who uses oSIST prEN 18374:2026?

Geotechnical engineers use oSIST prEN 18374:2026 to decide whether a soil treatment should be accepted, adjusted or repeated with a different dosage or product. Laboratory technicians use it to prepare specimens, run curing and immersion, and calculate the results.

It is also relevant to quality managers, consultants and buyers involved in earthworks for embankments, capping layers, roads, railways, airports, industrial platforms, hydraulic works and road foundations. They use the report to document whether a specific soil-treatment combination behaves acceptably in the laboratory.

Which standards are used with oSIST prEN 18374:2026?

Standard	What it contributes
EN 13286-2	Proctor compaction and reference density and water content
EN 459-1	Definitions, specifications and conformity criteria for building lime
EN 13282-1	Composition, specifications and conformity criteria for rapid hardening hydraulic road binders
EN 13282-2	Composition, specifications and conformity criteria for normal hardening hydraulic road binders
EN 13286-42	Indirect tensile strength test for hydraulically bound mixtures
EN 13286-53	Manufacture of test specimens by axial compression
EN 16907-4	General method for studies of soil treatment with lime and/or hydraulic binders
EN 16907-2	Material classification and identification used in the report and term source

What does the oSIST prEN 18374:2026 document contain?

The document contains the test principle, apparatus requirements, specimen manufacturing steps, curing and immersion procedures, and methods for swelling and strength calculation. It also includes the moulding set shown in Figure 1 and the volume-measurement method shown in Figure 2.

Annex A provides the interpretation criteria for treatment suitability, including the swelling criterion and the mechanical criterion for capping layers. Annex B provides an example report format listing the mixture, the manufacturing conditions, the results and the final suitability conclusion.

SLOVENSKI STANDARD
01-september-2026
Zemeljska dela - Geotehnični laboratorijski preskusi - Materiali obdelani z apnom
in/ali hidravličnim vezivom - Preskus za določitev primernosti obdelave tal
Earthworks - Geotechnical laboratory tests - Lime and/or hydraulic binder treated
materials - Test for determining the treatment suitability of a soil
Erdarbeiten - Geotechnische Laboruntersuchungen - Mit Kalk und/oder hydraulischem
Bindemittel behandelte Materialien - Prüfung zur Bestimmung der Behandlungsfähigkeit
eines Bodens
Terrassements - Essais de laboratoire géotechniques - Matériaux traités à la chaux et/ou
au liant hydraulique - Essai visant à déterminer l'aptitude d'un sol au traitement
Ta slovenski standard je istoveten z: prEN 18374
ICS:
93.020 Zemeljska dela. Izkopavanja. Earthworks. Excavations.
Gradnja temeljev. Dela pod Foundation construction.
zemljo Underground works
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

DRAFT
EUROPEAN STANDARD
NORME EUROPÉENNE
EUROPÄISCHE NORM
July 2026
ICS 93.020
English Version
Earthworks - Geotechnical laboratory tests - Lime and/or
hydraulic binder treated materials - Test for determining
the treatment suitability of a soil
Terrassements - Essais de laboratoire géotechniques - Erdarbeiten - Geotechnische Laboruntersuchungen -
Matériaux traités à la chaux et/ou au liant hydraulique Mit Kalk und/oder hydraulischem Bindemittel
- Essai visant à déterminer l'aptitude d'un sol au behandelte Materialien - Prüfung zur Bestimmung der
traitement Behandlungsfähigkeit eines Bodens
This draft European Standard is submitted to CEN members for enquiry. It has been drawn up by the Technical Committee
CEN/TC 396.
If this draft becomes a European Standard, CEN members are bound to comply with the CEN/CENELEC Internal Regulations
which stipulate the conditions for giving this European Standard the status of a national standard without any alteration.

This draft European Standard was established by CEN in three official versions (English, French, German). A version in any other
language made by translation under the responsibility of a CEN member into its own language and notified to the CEN-CENELEC
Management Centre has the same status as the official versions.

CEN members are the national standards bodies of Austria, Belgium, Bulgaria, Croatia, Cyprus, Czech Republic, Denmark, Estonia,
Finland, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway,
Poland, Portugal, Republic of North Macedonia, Romania, Serbia, Slovakia, Slovenia, Spain, Sweden, Switzerland, Türkiye and
United Kingdom.
Recipients of this draft are invited to submit, with their comments, notification of any relevant patent rights of which they are
aware and to provide supporting documentation.

Warning : This document is not a European Standard. It is distributed for review and comments. It is subject to change without
notice and shall not be referred to as a European Standard.

EUROPEAN COMMITTEE FOR STANDARDIZATION
COMITÉ EUROPÉEN DE NORMALISATION

EUROPÄISCHES KOMITEE FÜR NORMUNG

CEN-CENELEC Management Centre: Rue de la Science 23, B-1040 Brussels
© 2026 CEN All rights of exploitation in any form and by any means reserved Ref. No. prEN 18374:2026 E
worldwide for CEN national Members.

Contents Page
European foreword . 3
Introduction . 4
1 Scope . 5
2 Normative references . 5
3 Terms and definitions . 5
4 Abbreviations and symbols . 6
5 Principle of the test . 6
6 Apparatus . 7
7 Operating procedure . 8
7.1 Manufacturing of the specimens . 8
7.1.1 Preparation and characterization of the mixture . 8
7.1.2 Specimens for measurement of swelling. 9
7.1.3 Specimens for measurement of strength . 9
7.2 Experiment procedures . 9
7.2.1 Treatment with lime only . 9
7.2.2 Treatment with a hydraulic binder possibly combined with lime . 9
7.3 Measurements and calculations . 10
7.3.1 Determination of swelling . 10
7.3.2 Determination of indirect tensile strength . 11
8 Alternative supplementary method . 11
9 Test report . 12
Annex A (normative) Criteria for definition of the treatment suitability of a soil . 13
Bibliography . 16

European foreword
This document (prEN 18374:2026) has been prepared by Technical Committee CEN/TC 396
“Earthworks”, the secretariat of which is held by AFNOR.
This document is currently submitted to the CEN Enquiry.
Introduction
The purpose of the test for determining the treatment suitability of a soil is to detect the risk of swelling
and/or failure to a set of material treated with lime and/or hydraulic binders. In fact, the
material/treatment product reaction can sometimes be disrupted, even inhibited, by mineral or chemical
elements present in the material or in the water supplied, making the treatment uncertain or
unacceptable. The interaction of the material with the treatment product tested then creates a pathology
that might manifest as significant swelling and/or insufficient hydraulic setting or even non-setting.
This test also specifies the criteria considered for treatment suitability, in Annex A.
NOTE This test does not allow identification of the specific nature of the possible disruption.
1 Scope
This document specifies a test method to determine the suitability of a soil to be treated with lime and/or
hydraulic binders, with regard to volumetric swelling and mechanical strength, within a period not
exceeding two to three weeks.
This test can be integrated into the general method of a study of treatment of materials with lime and/or
a hydraulic binder, in compliance with standard EN 16907-4.
It is applicable to soils and alternative (or anthropogenic) materials treated with lime and/or hydraulic
binders for the construction of embankments and capping layers; in the areas of roads, railways and
airports; industrial or commercial platforms; hydraulic works and road foundations.
The results of this test:
— are only valid for the configuration tested (soil, treatment product, dosage);
— are in no case usable for dimensioning a structure including treated materials.
The values currently accepted to define treatment suitability are indicated for information in Annex A.
2 Normative references
The following reference documents are indispensable for the application of this document. For dated
references, only the edition cited applies. For undated references, the latest edition of the referenced
document (including any amendments) applies.
EN 13286-2, Unbound and hydraulically bound mixtures - Part 2: Test methods for laboratory reference
density and water content - Proctor compaction
EN 459-1, Building lime - Part 1: definitions, specifications and conformity criteria
EN 13282-1, Hydraulic road binders - Part 1: Rapid hardening hydraulic road binders - Composition,
specifications and conformity criteria
EN 13282-2, Hydraulic road binders - Part 2: Normal hardening hydraulic road binders - Composition,
specifications and conformity criteria
EN 13286-42, Unbound and hydraulically bound mixtures - Part 42: Test method for the determination of
the indirect tensile strength of hydraulically bound mixtures
EN 13286-53:2004, Unbound and hydraulically bound mixtures - Part 53: Methods for the manufacture of
test specimens of hydraulically bound mixtures using axial compression
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
3.1
curing time
time period between the completion of preparation of test specimens and their immersion
3.2
immersion time
time period after the end of curing, during which the test specimens are kept completely underwater
3.3
material
soil or alternative (or anthropogenic) material
[SOURCE: EN 16907-2]
3.4
hydraulic binder
cement or hydraulic road binder
Note to entry: This term can also apply to non-standard products.
[SOURCE: EN 197-1, EN 13282 (all parts) and EN 16907-4.]
3.5
treatment product
product added to a material and composed of either a hydraulic binder only, or a hydraulic binder with
lime, or lime only
4 Abbreviations and symbols
For the purposes of this document, the following abbreviations and symbols apply to the entire
document, unless otherwise specified.
d diameter of tested specimens, expressed in centimetres
h height of tested specimens, expressed in centimetres
ρ density of water, expressed in grams per cubic centimetre
w
Initial volume immediately after the specimen is released from the mould, expressed in
V
cubic centimetres
sum of the final volume of the specimen after immersion, the volume of all elastics and
V
containment band, expressed in cubic centimetres
V volume of all elastics and containment band, expressed in cubic centimetres
V final volume of the specimen after immersion, expressed in cubic centimetres
volumetric swelling of the specimen after maturation, expressed as a percentage
GV
R indirect tensile strength, expressed in megapascals
it
ρ dry density at optimum normal Proctor
dOPN
w water content at optimum normal Proctor
OPN
m submerged mass of the whole determined by hydrostatic weighing
m mass in open air of the whole ‘specimen, containment bands and elastics’ after immersion
5 Principle of the test
This test makes it possible to accelerate the phenomena of hydraulic setting and any potential swelling
by application of particular conditions (curing time, immersion in water at 40°C for 7 days) in accordance
with the terms indicated in articles 7 and 8 of this document.
Annex A gives an example of criteria used to define the treatment suitability of a soil following use.
6 Apparatus
The equipment shall comprise of:
— a mixer such as the one suggested in EN 13286-2 which is able to make a homogeneous mixture of
the material with the treatment product(s) under consideration;
— a press, used for manufacture of specimens, as defined in EN 13286-53;
— a moulding set comprising (see Figure 1):
o a counter-mould,
o two compacting pistons,
o five cases (at a minimum),
o a pair of spacer half shells as defined in Table 2 of EN 13286-53:2004,
o a thermostatic device capable of keeping a volume of water sufficient for complete immersion of
the specimens being tested at (40 ± 2)°C,
o a hydrostatic weighing set for the specimens, fitting on a scale whose precision is compatible
with the requirements defined in 6.3,
o a press, used for crushing of specimens, as defined in EN 13286-42;
— other common devices and materials:
o at least 3 containment bands for the specimens, cut from a
...