ISO 16311-3:2014

INTERNATIONAL ISO
STANDARD 16311-3
First edition
2014-04-15
Maintenance and repair of concrete
structures —
Part 3:
Design of repairs and prevention
Entretien et réparation des structures en béton —
Partie 3: Conception des réparations et prévention
Reference number
©
ISO 2014
© ISO 2014
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ii © ISO 2014 – All rights reserved

Contents Page
Foreword .iv
Introduction .v
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Minimum considerations before repair and prevention design. 2
4.1 General . 2
4.2 Initial risk assessment . 2
4.3 Assessment of defects and their causes . 3
5 Strategies for maintenance, repair, and prevention . 4
5.1 General . 4
5.2 Options . 4
5.3 Factors . 4
5.4 Choice of appropriate strategy . 5
6 Basis for the choice of specific repair and prevention design principles, strategies,
remedies, and methods . 6
6.1 General . 6
6.2 Repair remedies and methods of maintenance, repair, and prevention . 6
7 Properties of products and systems required for compliance with repair and
prevention remedies . 8
8 Design documentation requirements . 9
9 Compliance with health, safety, and environmental requirements .9
10 Competence of personnel . 9
Annex A (informative) Design of repairs and prevention .10
Bibliography .22
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
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to Trade (TBT) see the following URL: Foreword - Supplementary information
The committee responsible for this document is ISO/TC 71, Concrete, reinforced concrete and pre-stressed
concrete, Subcommittee SC 7, Maintenance and repair of concrete structures.
ISO 16311 consists of the following parts, under the general title Maintenance and repair of concrete
structures:
— Part 1: General principles
— Part 2: Assessment of existing concrete structures
— Part 3: Design of repairs and prevention
— Part 4: Execution of repairs and prevention
iv © ISO 2014 – All rights reserved

Introduction
The repair and prevention of defects and deterioration in concrete structures requires complex design
work. This part of ISO 16311 defines the design principles, strategies, remedies, and methods for
preventing accelerated deterioration and the repair of concrete structures that have suffered or may
suffer damage or deterioration. It gives guidance on the choice of repair design principles, strategies,
remedies, methods, and selection of products and systems which are appropriate for the intended use.
This part of ISO 16311 identifies key stages in the repair process:
— the need for assessment of the condition of the structure;
— the need for identification of the causes of deterioration;
— evaluating the options for repair and prevention, and decision-making;
— the selection of the appropriate remedies for repair and prevention;
— the selection of methods;
— the definition of properties of products and systems;
— the specification of maintenance requirements following repair and prevention.
This part of ISO 16311 does not deal with matters related to structural design and the verification of
structural performance in both deteriorated and repaired condition. The information related to the
deteriorated condition is presented in ISO 16311-2.
This part of ISO 16311 contains an Annex A which provides guidance and background information on
the normative text.
INTERNATIONAL STANDARD ISO 16311-3:2014(E)
Maintenance and repair of concrete structures —
Part 3:
Design of repairs and prevention
1 Scope
This part of ISO 16311 defines basic considerations and decision-making for the specification of repair and
prevention remedies, and management strategies for reinforced and unreinforced concrete structures
using products and systems specified in other International Standards or Technical Specifications. This
part of ISO 16311 covers only atmospherically exposed structures, and buried or submerged structures,
if they can be accessed.
This part of ISO 16311 specifies repair and prevention design principles, and strategies for defects and
on-going deterioration including, but not limited to:
a) mechanical actions, e.g. impact, overloading, movement caused by settlement, blast, vibration, and
seismic actions;
b) chemical and biological actions from environments, e.g. sulfate attack, alkali-aggregate reaction;
c) physical actions, e.g. freeze–thaw, thermal cracking, moisture movement, salt crystallization, fire,
and erosion;
d) reinforcement corrosion;
e) original construction defects that remained unaddressed from the time of construction.
The execution of maintenance and repairs is covered in ISO 16311-4.
Further background information on the scope of this part of ISO 16311 is given in Annex A.
2 Normative references
The following documents, in whole or in part, are normatively referenced in this document and are
indispensable for its application. For dated references, only the edition cited applies. For undated
references, the latest edition of the referenced document (including any amendments) applies.
ISO 14040, Environmental management — Life cycle assessment — Principles and framework
ISO 14044, Environmental management — Life cycle assessment — Requirements and guidelines
ISO 16311-1, Maintenance and repair of concrete structures — Part 1: General principles
ISO 16311-2, Maintenance and repair of concrete structures — Part 2: Assessment of existing concrete
structures
ISO 16311-4, Maintenance and repair of concrete structures — Part 4: Execution of repairs and prevention
ISO 22965-1, Concrete — Part 1: Methods of specifying and guidance for the specifier
3 Terms and definitions
For the purposes of this document, the terms and definitions given in ISO 16311-1 and the following
apply.
3.1
defect
fault, or deviation from the intended level of performance of a structure or its parts
[SOURCE: ISO 15686-1:2000]
3.2
design service life
specified period of time for which a structure or its members is to be used for its intended purpose
without major repair being necessary
[SOURCE: ISO 16311-1]
3.3
maintenance
set of activities undertaken to check, evaluate the performance of a structure and preserve/restore it so
as to satisfy its performance requirements in service
[SOURCE: ISO 13823:2008]
3.4
passivity
state in which steel in concrete is protected by a thin film and the corrosion rate is minimized
Note 1 to entry: This film is destabilized or lost when concrete carbonates to the level of the reinforcing steel,
when aggressive salts concentrate and attack the steel, or atypically, when all oxygen is depleted at the surface of
the steel (i.e. submerged concrete members after many years).
3.5
prevention
remedial action to prevent or slow down further deterioration of a structure or structural member and
reduce the possibility of damage to the user or any third party, inhibiting the progress of deterioration,
and proactively preventing deterioration
3.6
protection
measure that is intended to prevent or reduce the development of defects in the structure
3.7
repair
restoration of a structure or its components to an acceptable condition by the renewal or replacement of
worn, damaged, or deteriorated components
[SOURCE: ISO 13823:2008]
4 Minimum considerations before repair and prevention design
4.1 General
This clause outlines procedures that shall be undertaken to assess the current condition of a concrete
structure prior to designing repair and prevention programs.
General guidance is given in Annex A.
4.2 Initial risk assessment
The risks to health and safety from falling debris or localized structural failure due to removing
deteriorated materials, and the effect of deterioration upon the mechanical stability of the concrete
structure shall be assessed pre-repair work, as well as the anticipated loads and forces during repair
work.
2 © ISO 2014 – All rights reserved

Where the concrete structure or a portion thereof is considered to be unsafe, appropriate actions and
sequences shall be specified to make it safe before other prevention or repair work is undertaken and
while underway, taking into account any additional risks that can arise from the repair work itself.
Such action can include local prevention or repairs, the installation of support or other temporary
stabilization measures, or partial or even complete demolition.
4.3 Assessment of defects and their causes
An assessment shall be made of the defects in the concrete structure, their causes, and of the ability of
the concrete structure to perform its function per the detailed guidance provided in ISO 16311-2. This
information is briefly summarized in the subsequent paragraphs.
The process of assessment of the structure shall include, but not be limited to, the following.
a) Documentation of the materials and systems comprising the structure.
b) The visible condition of the existing concrete structure.
c) Testing to determine the condition of the concrete and reinforcing steel.
d) The original design approach and potential design deficiencies.
e) The environment, including exposure to deleterious species.
f) The history of the concrete structure, including environmental exposure, and previous maintenance
and repair programs.
g) The conditions of use, (e.g. loading or other actions).
h) Requirements for future use.
The nature and causes of defects and deficiencies, including combinations of causes, shall be identified
and recorded (see Figure 1).
The approximate extent and likely rate of increase of defects shall then be assessed. An estimate shall
be made of when the member or concrete structure would no longer perform as intended, with no
prevention or repair measures (other than maintenance of existing systems) applied.
The results of the completed assessment shall be valid at the time that the prevention and repairs are
designed and carried out. If, as a result of passage of time or for any other reason, there are doubts about
the validity of the assessment, a new assessment shall be made.
Figure 1 — Common causes of defects and deterioration
5 Strategies for maintenance, repair, and prevention
5.1 General
This clause identifies options and factors to be considered when choosing a strategy for the management
of the structure.
5.2 Options
Per ISO 16311-1, the following options shall be taken into account in deciding the appropriate action to
meet the future requirements for the life of the structure.
a) Do nothing for a certain time while monitoring the structure.
b) Re-analyse the structural capacity, possibly leading to a downgrade in function.
c) Prevent or reduce further deterioration.
d) Strengthen or repair and protect all or part of the concrete structure.
e) Reconstruct all or part of the concrete structure.
f) Demolish all or part of the concrete structure.
5.3 Factors
The factors that shall be considered when choosing a management strategy include, but are not limited
to the following categories.
5.3.1 General
4 © ISO 2014 – All rights reserved

a) The intended use and remaining service life of the structure.
b) The required performance of the structure.
NOTE This can include, for example, fire resistance and watertightness.
c) The likely service life of the repair and prevention work.
d) The required availability of the structure, permissible interruption to its use and opportunities for
additional prevention, repair, and monitoring work.
e) The acceptable number and cost of repair cycles during the design life of the concrete structure.
f) The comparative whole life cost of the alternative management strategies, including future
inspection and maintenance or further repair cycles.
g) Properties and possible methods of preparation of the existing substrate.
h) The appearance of the protected and repaired structure.
5.3.2 Structural
The actions and how they will be resisted, including during and after implementation of the strategy.
5.3.3 Risk assessment
a) The consequences of structural failure.
b) Health and safety requirements.
c) The effect on occupiers or users of the structure and on adjacent structures and the general public.
5.3.4 Environmental
a) The exposure environment of the structure and whether it can be changed locally.
NOTE Exposure classes are given in ISO 22965-1, Annex A.2.
b) The need or opportunity to protect part or all of the concrete structure, from weather, pollution,
salt spray, etc., including protection of the substrate during the repair work.
5.4 Choice of appropriate strategy
The choice of strategy for the structure shall be based on the above assessment of the structure, client
requirements, and relevant provisions (e.g. safety requirements) valid in the place of execution. All
repair and prevention work undertaken as part of a structure management strategy shall comply with
this part of ISO 16311.
A repair and prevention remedy or remedies shall be chosen according to Clause 6, that is:
a) appropriate to the type, cause or combination of causes and to the extent of the defects;
b) appropriate to the future service conditions.
6 Basis for the choice of specific repair and prevention design principles, strate-
gies, remedies, and methods
6.1 General
This clause specifies the basic repair and prevention strategies and remedies which shall be used,
separately or in combination, to protect, maintain, or repair concrete structures. Determining the
suitability of these remedies and methods for a particular condition can only be assessed after a thorough
evaluation of the component or structure per ISO 16311-2 and reconciling repair and prevention design
principles that include, but are not limited to:
a) do no harm to the structure or member;
b) adopt proven techniques and products with a documented record of success in similar projects;
c) harmonize prevention, repair, and maintenance strategies with budgets and planning.
6.2 Repair remedies and methods of maintenance, repair, and prevention
6.2.1 General
Maintenance, repair, and prevention remedies are based on chemical, electrochemical, or physical
remedies that can be used to prevent or stabilize the deterioration of concrete, or corrosion of the steel
or other embedded metals, or to strengthen the concrete structure.
Table 1 contains examples of repair and prevention methods which apply the remedies. Only methods
which comply with the remedies shall be selected, taking into account any possible undesirable
consequences of applying a particular method or combination of methods under the specific conditions
of the individual repair.
Execution of the repairs and prevention is addressed in ISO 16311-4.
6.2.2 Remedies and methods addressing defects in concrete and reinforcement corrosion
Remedies 1 to 6 in Table 1 address defects in the concrete or concrete structures that can be caused by
the following actions, separately or in combination:
a) mechanical: e.g. impact, overloading, movement caused by settlement, vibration, seismic actions,
and blast;
b) chemical and biological: e.g. sulfate attack, alkali-aggregate reaction;
c) physical: e.g. freeze–thaw action, fire, thermal cracking, moisture movement, salt crystallization,
and erosion.
Remedies 7 to 11 in Table 1 address reinforcement corrosion caused by:
a) physical loss of the protective concrete cover;
b) chemical loss of alkaline pH in the protective concrete cover as a result of reaction with atmospheric
carbon dioxide (carbonation);
c) contamination of the protective concrete cover with corrosive agents (usually chloride ions) which
were incorporated in the concrete when it was mixed or which have penetrated into the concrete
from the environment;
d) stray electrical currents conducted or induced in the reinforcement from neighbouring electrical
installations;
e) stress corrosion cracking of prestressed members;
6 © ISO 2014 – All rights reserved

f) galvanic corrosion (e.g. dissimilar metals, differential environments).
Where there is existing corrosion of reinforcement or a danger that corrosion will occur in the future,
one or more of remedies of corrosion repair and prevention shall be selected.
In addition, the concrete itself shall be repaired, where necessary, according to Remedies 1 to 6.
Table 1 — Remedies and Methods for repair and prevention of concrete structures
Remedy Examples of Repair Strategies and Methods
1. Protection against ingress 1.1 Hydrophobic impregnation
1.2 Impregnation
1.3 Coating
1.4 Surface bandaging of cracks
1.5 Filling of cracks
1.6 Transferring cracks into joints
a
1.7 Erecting external panels
a
1.8 Applying membranes
2. Moisture control 2.1 Hydrophobic impregnation
2.2 Impregnation
2.3 Coating
2.4 Erecting external panels
2.5 Electrochemical treatments
3. Concrete restoration 3.1 Hand-applied, localized patches
3.2 Recasting members with concrete or mortar
3.3 Spraying concrete or mortar
3.4 Replacing members
4. Structural strengthening 4.1 Adding or replacing embedded or external reinforcing bars
4.2 Adding reinforcement anchored in pre-formed or drilled holes
4.3 Bonding plate reinforcement
4.4 Adding mortar or concrete
4.5 Injecting cracks, voids, or interstices
4.6 Filling cracks, voids, or interstices
4.7 Prestressing - (post tensioning) or FRP strengthening
5. Increasing physical resistance 5.1 Coating or membranes
5.2 Impregnation
5.3 Adding mortar or concrete
5.4 Applying a membrane
6. Resistance to chemicals 6.1 Coating
6.2 Impregnation
6.3 Adding mortar or concrete
7. Preserving or restoring passivity 7.1 Increasing cover to reinforcement with additional mortar or concrete
(preservation only) or applying a coating
7.2 Replacing contaminated or carbonated concrete
7.3 Electrochemical realkalisation of carbonated concrete
7.4 Realkalisation of carbonated concrete by diffusion
7.5 Electrochemical chloride extraction
7.6 Applying a membrane (preserving passivity only)
Table 1 (continued)
Remedy Examples of Repair Strategies and Methods
8. Increasing resistivity 8.1 Hydrophobic impregnation
8.2 Impregnation
8.3 Coating
9. Cathodic control 9.1 Limiting oxygen content (at the cathode) by saturation or surface
coating
10. Cathodic protection 10.1 Applying an electrical current to achieve a protective electrochemi-
cal potential
11. Control of anodic areas 11.1 Active coating of the reinforcement
11.2 Barrier coating of the reinforcement
11.3 Applying corrosion inhibitors in or to the concrete
11.4 Installation of discrete galvanic anodes
a
These methods may also be applied to other remedies.
6.2.3 Protection and repair of concrete and reinforcement by methods not mentioned in this
International Standard
The absence from this part of ISO 16311 of a specific method, or the application of a method to a new
situation, shall not be taken to mean that such a method or application is necessarily unsatisfactory. The
application of methods to situations unforeseen in this part of ISO 16311, or the use of methods which do
not have a substantial history of successful performance and are not specified in this part of ISO 16311,
may be satisfactory in appropriate circumstances.
7 Properties of products and systems required for compliance with repair and
prevention remedies
Once the repair approach is determined per Clause 6, the products and systems to be used shall be
selected in accordance with requirements given in one or more of the following:
a) International standards;
b) Regional standards;
c) National standards;
d) National technical approvals;
e) Approvals according to project specification.
Descriptions and acceptance values of properties, in relation to specific products and systems, have to
be documented by test methods valid in the place of use and specified in the project specification.
Care shall be taken that products and systems do not undergo adverse physical or chemical reactions
with each other and with the concrete structures.
Repair products that are part of a system for repair shall not normally be tested individually unless one
or more of the repair products are intended to meet particular performance requirements in its own
right.
ISO 16311-4 gives details of site application requirements. If on-site application conditions cannot
reasonably be made to fulfil the application conditions specified for the product or system, alternative
products (if any) or alternative repair remedies or methods shall be specified to avoid such a conflict.
8 © ISO 2014 – All rights reserved

8 Design documentation requirements
Unless otherwise agreed, the following shall be provided to the owner of the structure at the conclusion
of the design effort:
1) documentation of the repair and prevention design, including any test results pertinent to the
design;
2) documentation of any quality control and assurance requirements for the execution of the repair
and prevention design;
3) instructions for inspection and maintenance to be undertaken during the remaining design service
life of the repaired part of the concrete structure.
9 Compliance with health, safety, and environmental requirements
The repair and prevention design shall comply with the requirements of relevant health and safety,
environmental protection, and fire regulations valid in the place of use.
Where there is a conflict between the properties of specific products or systems and environmental
protection or fire regulations, use shall be made of alternative repair remedies or methods which avoid
such a conflict.
10 Competence of personnel
This part of ISO 16311 presupposes that personnel have the necessary skill and adequate equipment
and resources to design, specify, and execute the work in accordance with the relevant parts of this
International Standard and the requirements of the project specification.
NOTE In some countries, there are special requirements regarding the level of knowledge, training, and
experience of personnel involved in the different tasks.
Annex A
(informative)
Design of repairs and prevention
A.1 General
This Annex provides guidance and background information on the normative text.
A.2 Scope
Some aspects of the scope will require specialized knowledge and structural design. Examples include
structural requirements of fire-damaged concrete, assessment and repair of pre-stressed concrete,
damage due to seismic actions and increasing structural capacity by replacement or addition of
embedded or external reinforcement, electrochemical and materials concerns.
The scope does not include non-structural construction materials used in conjunction with concrete,
such as floor screeds or render and plaster finishes.
a) The scope of this part of ISO 16311 does not include detailed guidance on inspection, testing, and
assessment before and after repair. This is covered by ISO 16311-2.
b) In well designed and constructed concrete structures built according to standards for design,
execution and materials valid in the place of use, the concrete cover should normally protect
reinforcement from corrosion under conditions of normal exposure in natural environments,
including marine environments and where de-icing salts are used. With older structures, previous
standards may not have been adequate for normal exposure. In particular, “inadequate design,
specification or construction or use of unsuitable construction materials” may lead to a poor
quality cover concrete, poor compaction and hence reduced durability of reinforced concrete. Other
mechanisms may cause premature deterioration, including fire, mechanical actions, or chemical
attack.
c) For waterproofing of vertical surfaces, vapour-permeable materials are normally used; for
waterproofing horizontal surfaces, materials that are impervious to water and water vapour are
normally used, but this depends on the intended use of the structure and vapour transmission
requirements.
d) Site application and details of methods of repair and prevention are provided in ISO 16311-4,
including the preparation of the concrete and reinforcement before application of products and
systems.
Products and systems may be applied for purposes other than repair and prevention, for example solely
or mainly to improve appearance, or to modify a concrete structure for a different use.
A.3 Minimum considerations before repair and prevention
A.3.1 General
This clause is not a detailed guide to undertaking a structural appraisal or a condition assessment of the
concrete structure. This information is presented in ISO 16311-2. To help users of this part of ISO 16311,
Figure A.1 gives an example of the phases of a repair project.
10 © ISO 2014 – All rights reserved

PROJECTPHASES
INFORMATION PROCESS OF MANAGEMENT DESIGN OF EXECUTION OF ACCEPTANCE OF
ABOUT THE ASSESSMENT STRATEGY REPAIRSand REPAIRS and REPAIRS
STRUCTURE PREVENTATIVE PREVENTATIVE
MEASURES MEASURES
Basic consideratio
...