prEN 18374

• 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
• Publication Date: 07-Jun-2028
• ICS: 93.020 - Earthworks. Excavations. Foundation construction. Underground works
• Technical Committee: CEN/TC 396 - Earthworks
• Drafting Committee: CEN/TC 396/WG 8 - Test methods
• Current Stage: 4060 - Closure of enquiry - Enquiry
• Start Date: 01-Oct-2026
• Due Date: 20-May-2027
• Completion Date: 01-Oct-2026
• Ref Project: oSIST prEN 18374:2026 - Earthworks - Geotechnical laboratory tests - Lime and/or hydraulic binder treated materials - Test for determining the treatment suitability of a soil

prEN 18374 is a CEN draft European Standard for geotechnical laboratory testing of soils and alternative materials treated with lime and/or hydraulic binders. It specifies a short laboratory test to check whether a soil is suitable for that treatment by looking at swelling and, where relevant, indirect tensile strength. The method is aimed at earthworks and related projects, and it shows whether a chosen soil-treatment combination is promising before more detailed study or use.

What does prEN 18374 specify?

prEN 18374 specifies a laboratory method for judging the treatment suitability of a soil treated with lime and/or hydraulic binders. The test looks for swelling risk and loss of mechanical performance, and it is intended for treated soils and alternative or anthropogenic materials used in embankments, capping layers, roads, railways, airports, industrial or commercial platforms, hydraulic works and road foundations.

The document is organized into scope, references, terms, abbreviations, test principle, apparatus, operating procedure, an alternative supplementary method, the test report, and two annexes.

Annex	What it covers
Annex A	Criteria used to define treatment suitability
Annex B	Example test report

A key limitation is that the result applies only to the tested combination of soil, treatment product and dosage, and it is not meant for structural design.

What are the key requirements of prEN 18374?

prEN 18374 is built around a controlled laboratory sequence: prepare representative specimens, expose them to defined curing and immersion conditions, then measure swelling and, for hydraulic-binder cases, indirect tensile strength. In practice, the method tells a project team whether a selected treatment is likely to behave acceptably before committing to field work.

Specimen preparation and test route

Clause 7.1 requires the mixture to be prepared from site-relevant material, water and the selected treatment product or products. The mixture is first characterized using normal Proctor references, then remade for specimen manufacture. This matters because the test is tied to the actual material condition and dosage under consideration.

Clause 7 also distinguishes two routes:

• lime only
• hydraulic binder, possibly combined with lime

That distinction matters because the conditioning period and the follow-up evaluation are not the same in the two cases.

Swelling assessment

Clause 7.3.1 measures volumetric swelling on specimens removed from the mould. The document allows volume measurement by hydrostatic weighing or by calliper measurement when the specimen condition allows it. This gives a direct check on expansion after curing and immersion, which is the main indicator of instability in treated material.

Annex A then interprets the swelling result as suitable, uncertain, or unacceptable. For the reader, this means the swelling value is not just recorded - it is used to decide whether the treatment remains plausible or needs reformulation or further study.

Strength assessment and supplementary testing

Clause 7.3.2 applies indirect tensile strength testing to the specimens kept in cases, using the indirect tensile test method referenced in the document. This is especially relevant when the treated material is intended for a capping layer or another application where mechanical performance matters.

Clause 8 adds an alternative supplementary method when the first result is uncertain or unacceptable. It allows a second test with a longer pre-immersion curing time, selected by the geotechnical engineer. In practice, this gives a way to check whether a slower-developing formulation can still become acceptable.

Reporting

Clause 9 requires the report to identify the document used, the organization and technician, dates, mixture description, source water, Proctor references, specimen manufacturing details, curing time, swelling and strength results, and the final suitability conclusion when applicable. That matters because the result is only valid for one exact tested configuration and must be traceable.

What terms does prEN 18374 define?

• curing time - the period between specimen preparation and immersion.
• immersion time - the period after curing during which the specimens stay fully underwater.
• material - soil or alternative or anthropogenic material.
• hydraulic binder - cement or hydraulic road binder; the term can also cover non-standard products.
• treatment product - the added product, which may be lime only, hydraulic binder only, or hydraulic binder with lime.
• Gv - volumetric swelling of the specimen after maturation, expressed as a percentage.
• R - indirect tensile strength, expressed in megapascals.

Who uses prEN 18374?

prEN 18374 is used by geotechnical engineers, laboratory technicians, earthworks designers, quality managers and project buyers who need to decide whether a soil can be treated with lime and/or a hydraulic binder. It is relevant to road, rail, airport, industrial platform, hydraulic works and foundation projects. The test supports mix selection, treatment screening and reporting before wider use of the treated material.

Which standards are used with prEN 18374?

prEN 18374 relies on several CEN standards for specimen preparation, material identification and test execution:

• EN 13286-2 - Proctor compaction and reference density/water content
• EN 459-1 - building lime definitions, specifications and conformity criteria
• EN 13282-1 and EN 13282-2 - hydraulic road binder specification
• EN 13286-42 - indirect tensile strength test for hydraulically bound mixtures
• EN 13286-53:2004 - manufacture of test specimens by axial compression
• EN 16907-4 - the broader method for soil treatment studies with lime and/or hydraulic binders
• EN 16907-2 - material classification used for identification in the report
• EN 197-1 and EN 196-3 - referenced for hydraulic binder terminology and rapid-setting binder timing

What does the prEN 18374 document contain?

prEN 18374 contains a defined apparatus set-up, including a moulding system, a thermostatic bath, hydrostatic weighing equipment and a crushing press. It also includes the specimen manufacturing steps, the two conditioning routes for lime-only and hydraulic-binder treatments, and the calculation route for swelling and indirect tensile strength.

The document gives figure-based guidance for the moulding set and for measuring initial specimen volume. Annex A provides the decision criteria, while Annex B gives an example test report format. Together, these parts support laboratory testing, project screening and technical reporting for treated soils.

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
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