ISO 18985:2025

Recycled aggregates for concrete

This document provides principles and framework for use of recycled aggregates for concrete, which are produced from used resources primarily in the form of waste concrete. This document is intended to accelerate the use of recycled aggregates produced from construction and demolition wastes such as waste concrete and demolished masonry units. This document complements ISO 19595, natural aggregates for concrete, which does not include the minimum requirements for the recycled aggregates for concrete.

Titre manque

General Information

• Status: Published
• Publication Date: 30-Jun-2025
• ICS: 91.100.30 - Concrete and concrete products
• Technical Committee: ISO/TC 71/SC 3 - Concrete production and execution of concrete structures
• Drafting Committee: ISO/TC 71/SC 3 - Concrete production and execution of concrete structures
• Current Stage: 6060 - International Standard published
• Start Date: 01-Jul-2025
• Due Date: 24-Mar-2026
• Completion Date: 01-Jul-2025

Overview

ISO 18985:2025 - Recycled aggregates for concrete - provides a unified framework and minimum requirements for using recycled aggregates produced from construction and demolition waste (primarily waste concrete and demolished masonry). The standard is intended to accelerate the safe, consistent uptake of recycled concrete aggregate (RCA) and recycled fine aggregate (RFA) in concrete production while complementing ISO 19595 (natural aggregates for concrete).

Key topics and technical requirements

ISO 18985 defines principles and technical topics that govern the production, testing and use of recycled aggregates for concrete. Major topics include:

• Scope and definitions: Key terms such as adhered mortar, recycled coarse aggregate (RCA), recycled fine aggregate (RFA), recycled mix aggregate and waste concrete.
• Types and classes: Classification framework for types and classes of recycled aggregates to match intended concrete applications (see Clause 5).
• Geometric requirements: Grading, particle shape, fines content and other size/shape criteria (Clause 6).
• Physical properties: Oven-dry density, water absorption, resistance to fragmentation (LA abrasion) and impurity limits (Clause 7).
• Chemical requirements: Limits and test approaches for chlorides, sulfates and other chemical risks relevant to durability (Clause 8).
• Durability considerations: Soundness, freeze–thaw performance and alkali–silica reactivity evaluation (Clause 9 and Annex C).
• Logistics and QA: Guidance on transportation, storage, sampling, test methods, inspection, marking, labeling and reporting (Clauses 10–14).
• Normative & informative annexes: Annex A (test method for impurity contents), Annex B (application to concrete), Annex C (freezing and thawing tests).

Practical applications and users

ISO 18985 is directly useful for:

• Aggregate producers converting construction and demolition waste into RCA/RFA
• Concrete manufacturers and ready-mix suppliers specifying recycled content and ensuring mix performance
• Contractors, specifiers and design engineers selecting appropriate recycled aggregates for structural and non-structural concrete
• Testing laboratories and quality managers implementing sampling, physical/chemical tests and inspection plans
• Regulators and sustainability programs setting procurement or circular-economy targets to reduce landfill and preserve natural aggregates

Benefits include standardized quality controls, clearer acceptance criteria for recycled materials, improved durability risk management, and facilitation of sustainable concrete use.

Related standards

ISO 18985 complements and references other standards for test methods and sampling, including:

• ISO 19595 (natural aggregates for concrete)
• ISO 20290 series (aggregate test methods)
• ISO 24684-2 (soluble sulfate determination)
• ISO 2859-2 (sampling procedures)
• ASTM C88/88M, EN test methods for aggregate properties

For implementation, consult the full ISO 18985:2025 text and your national standards body for local adoption and conformity requirements.

Standards Content (Sample)

International
Standard
ISO 18985
First edition
Recycled aggregates for concrete
2025-07
Reference number
© ISO 2025
All rights reserved. Unless otherwise specified, or required in the context of its implementation, no part of this publication may
be reproduced or utilized otherwise in any form or by any means, electronic or mechanical, including photocopying, or posting on
the internet or an intranet, without prior written permission. Permission can be requested from either ISO at the address below
or ISO’s member body in the country of the requester.
ISO copyright office
CP 401 • Ch. de Blandonnet 8
CH-1214 Vernier, Geneva
Phone: [phone]
Email: [e-mail]
Website: www.iso.org
Published in Switzerland
ii
Contents Page
Foreword .iv
Introduction .v
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Symbols and abbreviated terms. 2
5 General requirements . 3
5.1 General .3
5.2 Type of recycled aggregates .3
5.3 Class of recycled aggregates .3
6 Geometric requirements . 3
6.1 General .3
6.2 Grading .3
6.3 Particle shape .3
6.4 Fines content .3
7 Physical requirements . 4
7.1 General .4
7.2 Oven dry density .4
7.3 Water absorption .4
7.4 Resistance to fragmentation by LA abrasion .4
7.5 Impurities . .4
7.5.1 Organic impurity .4
7.5.2 Inorganic impurity .5
7.6 Others .5
8 Chemical requirements . 5
8.1 General .5
8.2 Chloride .5
8.3 Sulfate .5
9 Durability . 6
9.1 General .6
9.2 Soundness .6
9.3 Alkali-silica reactivity.6
10 Transportation and storage . 6
10.1 Transportation .6
10.2 Storage .6
11 Sampling and test methods . 6
11.1 Sampling .6
11.2 Test methods .6
12 Inspection . 7
13 Marking and labeling . 7
14 Reporting . 7
Annex A (Normative) Test method for impurity contents of recycled aggregates . 8
Annex B (Informative) Application to concrete .12
Annex C (Informative) Method for freezing and thawing test of recycled coarse aggregate Class
1 and Class 2.13
Bibliography . 17

iii
Foreword
ISO (the International Organization for Standardization) is a worldwide federation of national standards
bodies (ISO member bodies). The work of preparing International Standards is normally carried out through
ISO technical committees. Each member body interested in a subject for which a technical committee
has been established has the right to be represented on that committee. International organizations,
governmental and non-governmental, in liaison with ISO, also take part in the work. ISO collaborates closely
with the International Electrotechnical Commission (IEC) on all matters of electrotechnical standardization.
The procedures used to develop this document and those intended for its further maintenance are described
in the ISO/IEC Directives, Part 1. In particular, the different approval criteria needed for the different types
of ISO document should be noted. This document was drafted in accordance with the editorial rules of the
ISO/IEC Directives, Part 2 (see www.iso.org/directives).
ISO draws attention to the possibility that the implementation of this document may involve the use of (a)
patent(s). ISO takes no position concerning the evidence, validity or applicability of any claimed patent
rights in respect thereof. As of the date of publication of this document, ISO had not received notice of (a)
patent(s) which may be required to implement this document. However, implementers are cautioned that
this may not represent the latest information, which may be obtained from the patent database available at
www.iso.org/patents. ISO shall not be held responsible for identifying any or all such patent rights.
Any trade name used in this document is information given for the convenience of users and does not
constitute an endorsement.
For an explanation of the voluntary nature of standards, the meaning of ISO specific terms and expressions
related to conformity assessment, as well as information about ISO's adherence to the World Trade
Organization (WTO) principles in the Technical Barriers to Trade (TBT), see www.iso.org/iso/foreword.html.
This document was prepared by Technical Committee ISO/TC 71, Concrete, reinforced concrete and
prestressed concrete, Subcommittee SC 3, Concrete production and execution of concrete structures.
Any feedback or questions on this document should be directed to the user’s national standards body. A
complete listing of these bodies can be found at www.iso.org/members.html.

iv
Introduction
The construction industry generates waste from various activities throughout the life cycle of buildings and
civil engineering works. The wastes from the construction phase and the demolition phase, often called
the construction and demolition waste, contain resources suitable for potential reuse in new construction.
Concrete constitutes a major portion of construction and demolition waste in many countries. Landfilling
of waste concrete is increasing in many countries and causes a shortage of available land area. It can also
contaminate water and soil in the vicinity of the landfill site, usually due to alkalinity, and bring about social,
economic, and environmental issues.
The waste concrete can be recycled in the form of aggregates for concrete after processing by crushing
and sorting. This document primarily deals with the recycling of waste concrete in the form of recycled
aggregates that can be used to produce concrete as a replacement for natural aggregates. This is the subject
of growing interest due to increasing concrete construction and dwindling natural resources which are used
as constituent materials to produce concrete. In some countries, the most abundant form of construction
and demolition waste may not be the waste concrete, but other forms of waste such as demolished masonry
units. This document sets the minimum requirements for the recycled aggregates made from waste concrete
and others, used to produce concrete in a unified manner. Figure 1 shows how to use this document with
other ISO standards.
Key
information flow: standard A provides information to standard B
hierarchy: standard B complements standard A
Figure 1 — Relationship of this document to other International Standards

v
International Standard ISO 18985:2025(en)
Recycled aggregates for concrete
1 Scope
This document provides principles and framework for use of recycled aggregates for concrete, which
are produced from used resources primarily in the form of waste concrete. This document is intended to
accelerate the use of recycled aggregates produced from construction and demolition wastes such as waste
concrete and demolished masonry units. This document complements ISO 19595, natural aggregates for
concrete, which does not include the minimum requirements for the recycled aggregates for concrete.
2 Normative references
The following documents are referred to in the text in such a way that some or all of their content constitutes
requirements 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.
ISO 19595:2017, Natural aggregates for concrete
ISO 20290-1, Aggregates for concrete — Test methods for mechanical and physical properties — Part 1:
Determination of bulk density, particle density, particle mass-per-volume and water absorption
ISO 20290-2, Aggregates for concrete — Test methods for mechanical and physical properties — Part 2: Method
for determination of resistance to fragmentation by Los Angeles Test (LA-Test)
ISO 20290-5, Aggregates for concrete — Test methods for mechanical and physical properties — Part 5:
Determination of particle size distribution by sieving method
ISO 24684-2, Aggregates for concrete — Test methods for chemical properties — Part 2: Determination of
soluble sulfate salts
ISO 2859-2, Sampling procedures for inspection by attributes — Part 2: Sampling plans indexed by limiting
quality (LQ) for isolated lot inspection
ISO 565, Test sieves — Metal wire cloth, perforated metal plate and electroformed sheet — Nominal sizes of
openings
ASTM C88/88M, Standard Test Method for Soundness of Aggregates by Use of Sodium Sulfate or Magnesium Sulfate
EN 1744-5, Tests for chemical properties of aggregates — Part 5: Determination of acid soluble chloride salts
EN 933-3, Tests for geometrical properties of aggregates — Part 3: Determination of particle shape —Flakiness index
EN 933-4, Tests for geometrical properties of aggregates — Part 3: Determination of particle shape —Shape index
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
ISO and IEC maintain terminology databases for use in standardization at the following addresses:
— ISO Online browsing platform: available at https:// www .iso .org/ obp
— IEC Electropedia: available at https:// www .electropedia .org/

3.1
adhered mortar
old mortar from original concrete that is attached to natural coarse aggregate and old cement paste attached
to natural fine aggregate
Note 1 to entry: Properties such as absorption, density, and abrasion resistance of recycled aggregate are influenced
by the adhered mortar.
3.2
recycled coarse aggregate
RCA
recycled concrete aggregate (3.6) and/or recycled mix aggregate (3.7) with aggregate size greater than 4,75 mm
3.3
recycled fine aggregate
RFA
recycled concrete aggregate (3.6) and/or recycled mix aggregate (3.7) with aggregate size equal to 4,75 mm
or smaller
3.4
inorganic impurity
inorganic substance which is included during the collection of source materials for recycled aggregate
production
Note 1 to entry: The inorganic impurity which negatively affects properties of recycled aggregate concrete includes
asphalt concrete, pottery, glass, gypsum, steel, and others.
3.5
organic impurity
organic substance which is included during the collection of source materials for recycled aggregate
production
Note 1 to entry: The organic impurity which negatively affects properties of recycled aggregate concrete includes
wood, vinyl, cloth, plastic, paper, and others.
3.6
recycled concrete aggregate
recycled aggregate produced by processing waste concrete (3.8)
3.7
recycled mix aggregate
recycled aggregate that includes both recycled concrete aggregate (3.6) and recycled aggregate produced
from source materials other than concrete
3.8
waste concrete
concrete which is used for production of recycled concrete aggregate (3.6) through crushing, classification,
and removal of impurity
Note 1 to entry: The waste concrete includes concrete originated from construction and demolition waste and
reclaimed concrete that has not been previously used for construction such as pre-cast concrete products and
returned ready-mixed concrete which was subsequently hardened.
4 Symbols and abbreviated terms
RCA recycled coarse aggregate
RFA recycled fine aggregate
R
freeze-thaw resistance index
ft
5 General requirements
5.1 General
Recycled aggregates in this document shall include recycled concrete aggregates produced from waste
concrete and aggregates produced by processing waste materials other than concrete including demolished
masonry units.
5.2 Type of recycled aggregates
Recycled aggregates are categorized into two types: Recycled coarse aggregates and recycled fine
aggregates.
5.3 Class of recycled aggregates
Each type of recycled aggregates shall be divided into Class 1, Class 2, and Class 3 aggregates by performance
requirements and purpose of use. Class 1 aggregates can replace natural aggregates in significant quantity
to fabricate structural concrete. Class 2 aggregates can replace natural aggregates in limited quantity
to fabricate structural concrete. Class 3 aggregates are used to fabricate concrete for non-structural
applications.
Class 1 aggregates shall be recycled concrete aggregates. Class 2 aggregates shall be recycled concrete
aggregates or recycled mix aggregates.
6 Geometric requirements
6.1 General
Recycled aggregates shall satisfy requirements on grading, particle shape, and fines content.
6.2 Grading
The grading of the recycled aggregates shall conform to ISO 19595:2017, 5.3.2 and 5.3.3.
6.3 Particle shape
The particle shape shall be determined using the proper shape index.
The particle shape of recycled aggregates shall conform to ISO 19595:2017, 5.6.
NOTE The crushing procedures of waste concrete and other source materials to produce recycled aggregates can
generate angular particles of irregular shape which affect the performance of recycled aggregate concrete.
6.4 Fines content
The fines content in recycled aggregates shall conform to Table 1.
Amount finer than 0,063 mm shall be determined by ISO 20290-5.
Table 1 — Fines in recycled aggregates (maximum values by mass)
Type Class 1 Class 2 Class 3
RCA 1 % 2 % 3 %
RFA 7 % 10 % value to be declared

7 Physical requirements
7.1 General
Recycled aggregates shall satisfy requirements on density, water absorption, resistance for fragmentation
and impurities.
Adhered mortar content of recycled aggregates decreases density and increases water absorption of
recycled aggregates and is controlled in this document by setting limit values on density, water absorption,
and abrasion resistance per each type and class of recycled aggregates.
7.2 Oven dry density
Density of recycled aggregates shall conform to Table 2.
Table 2 — Oven dry density of recycled aggregates (minimum values): unit = kg/m
Type Class 1 Class 2 Class 3
RCA 2 500 2 350 2 100
RFA 2 300 2 100 value to be declared
7.3 Water absorption
Absorption of recycled aggregates shall conform to Table 3.
Table 3 — Water absorption of recycled aggregates (maximum values)
Type Class 1 Class 2 Class 3
RCA 3 % 4,5 % 8 %
RFA 5 % 9 % value to be declared
7.4 Resistance to fragmentation by LA abrasion
Resistance to fragmentation of recycled coarse aggregates by LA abrasion shall conform to Table 4 when
recycled coarse aggregates are used for concrete subjected to abrasive environment including pavement.
Table 4 — LA abrasion of recycled coarse aggregates (maximum values)
Type Class 1 Class 2 Class 3
RCA 40 % 45 % value to be declared
7.5 Impurities
7.5.1 Organic impurity
Total sum of various organic impurities included in recycled aggregates shall conform to Table 5.
Table 5 — Total organic impurities (maximum values by volume)
Type Class 1 Class 2 Class 3
RCA 0,3 % 0,3 % 1 %
RFA 0,3 % 0,3 % 1 %
NOTE: Refer to Annex A for test method of impurities.

7.5.2 Inorganic impurity
Total sum of various inorganic impurities included in recycled aggregates shall conform to Table 6.
Table 6 — Total inorganic impurities (maximum values by mass)
Type Class 1 Class 2 Class 3
RCA 1 % 2 % value to be declared
RFA 2 % 3 % value to be declared
NOTE: Refer to Annex A for test method of impurities.
7.6 Others
Original concrete with potential radioactive contamination shall not be used as source material for the
production of recycled aggregates.
NOTE Source of contamination by radioactive substances includes nuclear power plant, hospitals, etc.
8 Chemical requirements
8.1 General
Recycled aggregates shall be free of potentially harmful chemical reactions due to chlorides and sulfates.
8.2 Chloride
The contents of chlorides in recycled aggregates to be used in reinforced concrete components shall conform
to Table 7.
Table 7 — Acid soluble chloride content of recycled aggregates (maximum values by mass)
Type Class 1 Class 2 Class 3
RCA 0,04 % 0,1 % value to be declared
RFA 0,04 % 0,1 % value to be decla
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