ISO 5091-2:2023

Structural intervention of existing concrete structures using cementitious materials — Part 2: Top‐surface overlaying

This document specifies the standards for design and construction using the top-surface overlaying method, which increases the thickness of existing concrete members by integrating cementitious materials onto the top surface of the members so as to improve the safety, serviceability, durability and other properties of a concrete structure. This document specifies structural intervention of existing concrete structures using cementitious materials design and execution principles, and strategies for defects and on-going deterioration including, but not limited to: a) mechanical actions, e.g. fatigue, 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.

Intervention structurelle sur les structures en béton existantes utilisant des matériaux cimentaires — Partie 2: Recouvrement de la surface supérieure

General Information

• Status: Published
• Publication Date: 20-Jul-2023
• ICS: 91.080.40 - Concrete structures
• Technical Committee: ISO/TC 71/SC 7 - Maintenance and repair of concrete structures
• Drafting Committee: ISO/TC 71/SC 7 - Maintenance and repair of concrete structures
• Current Stage: 6060 - International Standard published
• Start Date: 21-Jul-2023
• Due Date: 18-Jun-2023
• Completion Date: 21-Jul-2023

Standards Content (Sample)

INTERNATIONAL ISO
STANDARD 5091‐2
First edition
2023-07
Structural intervention of
existing concrete structures using
cementitious materials —
Part 2:
Top‐surface overlaying
Intervention structurelle sur les structures en béton existantes
utilisant des matériaux cimentaires —
Partie 2: Recouvrement de la surface supérieure
Reference number
ISO 5091-2:2023(E)
© ISO 2023

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ISO 5091‐2:2023(E)
COPYRIGHT PROTECTED DOCUMENT
© ISO 2023
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
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ISO 5091‐2:2023(E)
Contents Page
Foreword .v
Introduction . vi
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Investigation of existing structure.2
4.1 General . 2
4.2 Investigation . 2
4.2.1 Investigation using documents, records . 2
4.2.2 On-site investigation . 3
5 Intervention design. 3
5.1 General . 3
5.2 Structural plan . 3
5.3 Structural details . 3
6 Materials . 4
6.1 General . 4
6.2 Materials in existing structure . 4
6.3 Materials used in repairing or strengthening parts . 5
6.3.1 Cementitious materials . 5
6.3.2 Reinforcing materials . 5
6.3.3 Bonding products . 5
6.3.4 Waterproof materials . 5
6.3.5 Pavement materials . 5
6.4 Characteristic values and design values of materials for repaired or strengthened
parts . 6
6.4.1 General . 6
6.4.2 Cementitious materials . 6
6.4.3 Reinforcing materials . 6
6.4.4 Bonding products . 6
7 Actions . 6
7.1 General . 6
7.2 Actions for intervention design . 6
8 Performance verification for repaired or strengthened structure .6
8.1 General . 6
8.2 Calculation of response . 7
8.2.1 General . 7
8.2.2 Modelling of structure. 7
8.2.3 Structural analysis . 7
8.2.4 Calculation of response values . 7
8.3 Durability verification . 7
8.3.1 General . 7
8.3.2 Verification related to steel corrosion . 7
8.4 Safety verification . 7
8.4.1 General . 7
8.4.2 Verification related to failure . 7
8.4.3 Verification related to fatigue failure . 8
8.5 Serviceability verification . 9
8.5.1 General . 9
8.5.2 Stress level limit . 9
8.5.3 Verification related to appearance . 9
8.6 Restorability verification . 9
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ISO 5091‐2:2023(E)
8.6.1 General . 9
8.7 Structural details . 9
8.7.1 Thickness of top-surface overlaying parts . 9
8.7.2 Cover . 10
8.7.3 Placement of reinforcing materials. 10
8.7.4 Joints for reinforcing materials . 10
8.7.5 Structural details related to seismic performance . 10
9 Construction .11
9.1 General . 11
9.2 Prior investigation and construction plan. 11
9.3 Mix proportion of cementitious materials . 11
9.4 Preparation .12
9.5 Surface treatment . 12
9.6 Assembly of reinforcing materials . 13
9.7 Manufacture of cementitious materials . 13
9.8 Transportation, placement, compaction and finish . 13
9.9 Curing .13
9.10 Pavement . 13
9.11 Quality control . 14
9.12 Inspection . 14
10 Records . .14
11 Maintenance .14
Annex A (informative) Examples of design and execution .15
Bibliography .18
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ISO 5091‐2:2023(E)
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 pre-
stressed concrete, Subcommittee SC 7, Maintenance and repair of concrete structures.
A list of all parts in the ISO 5091 series can be found on the ISO website.
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.
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ISO 5091‐2:2023(E)
Introduction
As a repairing and strengthening method, attaching of cementitious material layer to surface of existing
concrete structures has been widely accepted. Since the cementitious layer does not have enough tensile
strength, tension reinforcement is generally placed in the cementitious layer. There are two types of
attaching way. For the first way, the cementitious layer is attached either on top surface or bottom
surface of horizontal concrete members, especially slabs, while, for the second way, the cementitious
layer is attached to jacket vertical concrete members, especially columns. There has not been any ISO
standard on design, execution, and maintenance for this method with attaching cementitious layer. The
ISO 5091 series serves as the first ISO standard for the intervention by attaching cementitious material
layer with tension reinforcement inside.
At the same time, the ISO 5091 series is the first ISO standard developed for a specific intervention
method, which conforms to the umbrella code, ISO 16311, especially ISO 16311-3 and ISO 16311-4.
The ISO 5091 series consists of four parts. ISO 5091-1 provides the issues common to all three parts,
while ISO 5091-2, 3 and 4 provide the issues specific to each attaching way of cementitious material
layers.
ISO 5091-2 describes a specific method of verifying the performance of a structure repaired or
strengthened by means of top-surface overlaying based on the currently available latest technologies.
Note, however, that the verification method described herein does not cover all kinds of verification.
For necessary information, reference need to be made to the relevant standard specifications and other
documents.
Given that members subject to intervention are mostly decks, the standard methods described herein
are considered the latest information on design and construction of top-surface overlaying using
fibre-reinforced concrete on overlaying parts. As technology advances, new materials and design and
construction methods are developed and methods for evaluating the post-intervention structural
performance with sufficient accuracy are established, making it possible to apply top-surface overlaying
for intervention parts and members other than decks, use materials other than fibre-reinforced
concrete, employ interface treatment methods other than cutting, cleaning and adhesive, etc., it is not
necessarily required to adhere to what is set forth in ISO 5091.
The ISO 5091 series can serve as a practical standard for construction industry, such as client, design
consultant and general contractor, to apply the structural intervention with externally attached
cementitious layer. Additional technical information, which is not provided explicitly in ISO 5091 series,
needs to be provided in each application case with consideration of the provisions of ISO 5091 series.
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INTERNATIONAL STANDARD ISO 5091‐2:2023(E)
Structural intervention of existing concrete structures
using cementitious materials —
Part 2:
Top‐surface overlaying
1 Scope
This document specifies the standards for design and construction using the top-surface overlaying
method, which increases the thickness of existing concrete members by integrating cementitious
materials onto the top surface of the members so as to improve the safety, serviceability, durability and
other properties of a concrete structure.
This document specifies structural intervention of existing concrete structures using cementitious
materials design and execution principles, and strategies for defects and on-going deterioration
including, but not limited to:
a) mechanical actions, e.g. fatigue, 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.
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 5091-1:2023, Structural intervention of existing concrete structures using cementitious materials —
Part 1: General principles
ISO 16311-3, Maintenance and repair of concrete structures — Part 3: Design of repairs and prevention
ISO 16311-4, Maintenance and repair of concrete structures — Part 4: Execution of repairs and prevention
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/
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ISO 5091‐2:2023(E)
3.1
top‐surface overlaying
method in which the thickness of the structural element associated with the top surface of the existing
concrete members is increased using cementitious materials, which will generally be reinforced
Note 1 to entry: The technique enhances the performance (e.g. strength, stiffness) of the existing concrete
structure and is applicable to highway bridge decks, etc.
3.2
bonding product
material, such as a primer or adhesive, that is applied to bond concrete and mortar
Note 1 to entry: The grouting material for bonding concrete and reinforcing material is also included in this term.
3.3
filling material
material injected to fill the gap between a reinforcing material, such as intermediate penetrating tie,
and concrete
3.4
filling property
degree of filling of cracks and adhesion of crack filling material to substrate
3.5
very high early strength cement
type of cement with a typical mix proportion that develops a compressive strength as high as 20 N/
2 2
mm to 30 N/mm within 2 h to 3 h of placement
3.6
reinforcing material
steel or FRP material used to sustain, restore or improve the mechanical performance of a structure
3.7
polymer hydraulic cement mortar
hydraulic composition made cementitious materials and fine aggregate modified by the addition of a
polymer
3.8
overlaying material
cementitious material, potentially reinforced, added on the top surface of an existing concrete structure
for the purpose of making an intervention to enhance the performance of that structure
3.9
FRP grid
resin-impregnated FRP reinforcing materials formed into a grid shape
4 Investigation of existing structure
4.1 General
The investigation of the existing structure for intervention using the top-surface overlaying method
shall be as set forth in ISO 5091-1:2023, Clause 4.
4.2 Investigation
4.2.1 Investigation using documents, records
The investigation of the existing structure using documents, records, etc. for top-surface overlaying
shall be as set forth in ISO 5091-1:2023, Clause 4.
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ISO 5091‐2:2023(E)
If the intervention has already been performed, maintenance records need to be inspected.
4.2.2 On‐site investigation
The on-site investigation for considering the application of top-surface overlaying shall be as set forth
in ISO 5091-1:2023, Clause 4.
To ensure smooth construction work with top-surface overlaying on the site, the storage space and
arrangement of construction machines and materials, traffic restrictions and so forth should be
checked in the prior investigation phase.
5 Intervention design
5.1 General
The intervention plan for considering the application of top-surface overlaying shall be as set forth in
ISO 5091-1:2023, Clause 5.
The structural plan for degraded part removal, patching repair, concrete replacement, etc. shall be
formulated based on the correct judgment of the degradation status to ensure that the performance
level and design service life of the structure required from the intervention are achieved.
In structural details, a bonding method shall be established that ensures the integrity between the
existing parts and overlaying parts so that the intervention effect of top-surface overlaying is obtained.
5.2 Structural plan
The structural plan for considering the application of top-surface overlaying shall be as set forth in
ISO 5091-1:2023, Clause 5.
In designing intervention work, appropriate decisions shall be made on the method to remove degraded
concrete, the materials and method for patching repair, whether partial concrete replacement is
necessary and the range of replacement, the construction method of top-surface overlaying, etc. before
starting construction with top-surface overlaying, considering these circumstances. Materials for
patching repair for the top surface of decks are required to shrink little, be excellent in crack resistance
and deformation-following capability and Young's modulus equal to or smaller than that of the existing
concrete.
The intrusion of water into the inside of decks needs to be completely prevented and it is important to
apply waterproofing and ensure water drainage on the waterproof top surface. In order to ensure that
the repaired or strengthened structure sustains its performance as mentioned above, it is necessary to
take measures to prevent re-degradation while taking into consideration the maintenance following
completion of intervention as well.
5.3 Structural details
The structural details for considering the application of top-surface overlaying shall be as set forth in
ISO 5091-1:2023, Clause 5. An increase in the self-weight due to the overlay shall also be considered
appropriately.
For a structure repaired or strengthened with top-surface overlaying to fulfil the required performance,
the existing parts and overlaying parts need to function together as a composite structure. Figure 1
shows examples of the cross-section of decks to which top-surface overlaying is applied.
If the stiffness of the existing part is vastly different from that of the overlaying part, the strength,
Young's modulus and other properties of the existing concrete and overlaying materials need to be
considered.
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ISO 5091‐2:2023(E)
Key
1 existing asphalt pavement
2 existing RC deck
3 asphalt pavement
4 overlaying concrete
5 water resistant layer
6 reinforcing steel
7 reinforcing FRP grid
8 overlaying concrete (concrete pavement)
a
Before overlaying.
b
After overlaying.
c
Top-surface overlaying with asphalt pavement.
d
Steel-reinforced top-surface overlaying with asphalt pavement.
e
FRP grid reinforced top-surface overlaying with asphalt pavement.
f
Top surface overlaying.
Figure 1 — Examples of the cross‐section of decks to which top‐surface overlaying is applied
6 Materials
6.1 General
The materials used for top-surface overlaying shall be of proven quality to ensure that the required
performance is fulfilled for a necessary period.
6.2 Materials in existing structure
The characteristic values and design values of t
...

DRAFT INTERNATIONAL STANDARD
ISO/DIS 5091‐2
ISO/TC 71/SC 7 Secretariat: KATS
Voting begins on: Voting terminates on:
2022-07-20 2022-10-12
Structural intervention of existing concrete structures
using cementitious materials —
Part 2:
Top‐surface overlaying
ICS: 91.080.40
THIS DOCUMENT IS A DRAFT CIRCULATED
FOR COMMENT AND APPROVAL. IT IS
THEREFORE SUBJECT TO CHANGE AND MAY
This document is circulated as received from the committee secretariat.
NOT BE REFERRED TO AS AN INTERNATIONAL
STANDARD UNTIL PUBLISHED AS SUCH.
IN ADDITION TO THEIR EVALUATION AS
BEING ACCEPTABLE FOR INDUSTRIAL,
TECHNOLOGICAL, COMMERCIAL AND
USER PURPOSES, DRAFT INTERNATIONAL
STANDARDS MAY ON OCCASION HAVE TO
BE CONSIDERED IN THE LIGHT OF THEIR
POTENTIAL TO BECOME STANDARDS TO
WHICH REFERENCE MAY BE MADE IN
Reference number
NATIONAL REGULATIONS.
ISO/DIS 5091-2:2022(E)
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. © ISO 2022

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ISO/DIS 5091-2:2022(E)
DRAFT INTERNATIONAL STANDARD
ISO/DIS 5091‐2
ISO/TC 71/SC 7 Secretariat: KATS
Voting begins on: Voting terminates on:

Structural intervention of existing concrete structures
using cementitious materials —
Part 2:
Top‐surface overlaying
ICS: 91.080.40
COPYRIGHT PROTECTED DOCUMENT
THIS DOCUMENT IS A DRAFT CIRCULATED
FOR COMMENT AND APPROVAL. IT IS
© ISO 2022
THEREFORE SUBJECT TO CHANGE AND MAY
This document is circulated as received from the committee secretariat.
All rights reserved. Unless otherwise specified, or required in the context of its implementation, no part of this publication may
NOT BE REFERRED TO AS AN INTERNATIONAL
be reproduced or utilized otherwise in any form or by any means, electronic or mechanical, including photocopying, or posting on STANDARD UNTIL PUBLISHED AS SUCH.
the internet or an intranet, without prior written permission. Permission can be requested from either ISO at the address below
IN ADDITION TO THEIR EVALUATION AS
or ISO’s member body in the country of the requester. BEING ACCEPTABLE FOR INDUSTRIAL,
TECHNOLOGICAL, COMMERCIAL AND
ISO copyright office
USER PURPOSES, DRAFT INTERNATIONAL
CP 401 • Ch. de Blandonnet 8
STANDARDS MAY ON OCCASION HAVE TO
BE CONSIDERED IN THE LIGHT OF THEIR
CH-1214 Vernier, Geneva
POTENTIAL TO BECOME STANDARDS TO
Phone: [phone]
WHICH REFERENCE MAY BE MADE IN
Reference number
Email: [e-mail]
NATIONAL REGULATIONS.
Website: www.iso.org ISO/DIS 5091-2:2022(E)
RECIPIENTS OF THIS DRAFT ARE INVITED
Published in Switzerland
TO SUBMIT, WITH THEIR COMMENTS,
NOTIFICATION OF ANY RELEVANT PATENT
RIGHTS OF WHICH THEY ARE AWARE AND TO
ii
  © ISO 2022 – All rights reserved
PROVIDE SUPPORTING DOCUMENTATION. © ISO 2022

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ISO/DIS 5091‐2:2022(E)
Contents Page
Foreword .v
Introduction . vi
1 Scope . 1
2 Normative references . 2
3 Terms and definitions . 2
4 Investigation of existing structure.3
4.1 General . 3
4.2 Investigation . 3
4.2.1 Investigation using documents, records, etc. . 3
4.2.2 On-site investigation . 3
5 Intervention design. 3
5.1 General . 3
5.2 Structural plan . 4
5.3 Structural details . 5
6 Materials . 6
6.1 General . 6
6.2 Materials in existing structure . 6
6.3 Materials used in repairing or strengthening parts . 6
6.3.1 Cementitious materials . 6
6.3.2 Reinforcing materials . 7
6.3.3 Bonding products . 7
6.3.4 Waterproof materials . 7
6.3.5 Pavement materials . 7
6.4 Characteristic values and design values of materials for repaired or strengthened
parts . 7
6.4.1 General . 7
6.4.2 Cementitious materials . 8
6.4.3 Reinforcing materials . 8
6.4.4 Bonding products . 8
7 Actions . 9
7.1 General . 9
7.2 Actions for intervention design . 9
8 Performance verification for repaired or strengthened structure .9
8.1 General . 9
8.2 Calculation of response . 10
8.2.1 General . 10
8.2.2 Modeling of structure . 10
8.2.3 Structural analysis . 10
8.2.4 Calculation of response values . 10
8.3 Durability verification . 10
8.3.1 General . 10
8.3.2 Verification related to steel corrosion . 10
8.4 Safety verification . 11
8.4.1 General . 11
8.4.2 Verification related to failure . 11
8.4.3 Verification related to fatigue failure . 13
8.5 Serviceability verification . 15
8.5.1 General .15
8.5.2 Stress level limit . 15
8.5.3 Verification related to appearance . 15
8.6 Restorability verification .15
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ISO/DIS 5091‐2:2022(E)
8.6.1 General .15
8.6.2 Structural details related to seismic performance .15
8.7 Structural details . 15
8.7.1 Thickness of top-surface overlaying parts . 15
8.7.2 Cover . 16
8.7.3 Placement of reinforcing materials. 16
8.7.4 Joints for reinforcing materials . 16
9 Construction .17
9.1 General . 17
9.2 Prior investigation and construction plan. 18
9.3 Mix proportion of cementitious materials . 19
9.4 Preparation . 19
9.5 Surface treatment . 20
9.6 Assembly of reinforcing materials . 20
9.7 Manufacture of cementitious materials . 20
9.8 Transportation, placement, compaction and finish . 20
9.9 Curing . 21
9.10 Pavement . 21
9.11 Quality control . 22
9.12 Inspection .22
10 Records . .23
11 Maintenance .23
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ISO/DIS 5091‐2:2022(E)
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 documents 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).
Attention is drawn to the possibility that some of the elements of this document may be the subject of
patent rights. ISO shall not be held responsible for identifying any or all such patent rights. Details of
any patent rights identified during the development of the document will be in the Introduction and/or
on the ISO list of patent declarations received (see www.iso.org/patents).
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 Organisation (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 pre-
stressed concrete, Subcommittee SC 7, Maintenance and repair of concrete structures.
A list of all parts in the ISO 5091 series can be found on the ISO website.
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.
v
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ISO/DIS 5091‐2:2022(E)
Introduction
As a repairing and strengthening method, attaching of cementitious material layer to surface of
existing concrete structures has been widely accepted. Since the cementitious layer does not have
enough tensile strength, tension reinforcement is generally placed in the cementitious layer. There are
two types of attaching way. For the first way, the cementitious layer is attached either on top surface
or bottom surface of horizontal concrete members, especially slabs, while, for the second way, the
cementitious layer is attached to jacket vertical concrete members, especially columns. There has not
been ISO standard on design, execution and maintenance for this method with attaching cementitious
layer. This ISO 5091 serves as the first ISO standard for the intervention by attaching cementitious
material layer with tension reinforcement inside.
At the same time, this ISO 5091 is the first ISO standard developed for a specific intervention method,
which conforms to the umbrella code, ISO 16311 Maintenance and repair of concrete structures,
especially ISO 16311-3 – Part 3: Design of repairs and prevention and ISO 16311-4 – Part 4: Execution of
repairs and prevention.
ISO 5091 Structural intervention of existing concrete structures using cementitious materials consists
of four parts; ISO 5091-1 – Part 1: General principles, ISO 5091-2 – Part 2: Top-surface overlaying,
ISO 5091-3 – Part 3: Bottom-surface (soffit) underlaying, and ISO 5091-4 – Part 4: Jacketing. ISO 5091-1
provides the issues common to all three parts, while ISO 5091-2, 3 and 4 provide the issues specific to
each attaching way of cementitious material layers.
It is expected that this ISO 5091 could serve as a practical standard for construction industry, such as
client, design consultant and general contractor, to apply the structural intervention with externally
attached cementitious layer. Additional technical information, which is not provided explicitly in
ISO 5091, needs to be provided in each application case with consideration of the provisions of ISO 5091.
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DRAFT INTERNATIONAL STANDARD ISO/DIS 5091‐2:2022(E)
Structural intervention of existing concrete structures
using cementitious materials —
Part 2:
Top‐surface overlaying
1 Scope
These guidelines specify the standards for design and construction using the top-surface overlaying
method, which increases the thickness of existing concrete members by integrating cementitious
materials onto the top surface of the members so as to improve the safety, serviceability, durability
and other properties of a concrete structure. The requirements not mentioned in the Top-Surface
Overlaying section shall be as set forth in the ISO/NP 5091-1 and relevant standard specifications for
concrete structures.
NOTE Top-surface overlaying is a construction method that increases the thickness of existing concrete
members by placing and integrating cementitious materials onto the top surface of the members so as to improve
the safety, serviceability, durability and other properties of a concrete structure.
NOTE Typical structures to which top-surface overlaying is applied as an intervention method are highway
bridge reinforced concrete decks (hereinafter decks) that are subject to the repeated action of relatively large
variable loads. The method is mainly applied to improve the safety and other properties of decks that have
degraded due to fatigue resulting from the repeated action of traffic loads. It may also be applied to improve
durability and utility for such purposes as to respond to design load changes taking place as vehicles become
larger and protect the top surface of decks against degradation due to de-icing substance. Examples of applications
other than those for decks include overlaying reinforcement of the top surface of footings aimed at improving the
seismic performance of bridge piers whose existing footings have an insufficient flexural load-carrying capacity
for ground motions. While the Top-Surface Overlaying section is not necessarily confined to a specific type of
structure, it mainly covers the standard design and construction methods for top-surface overlaying of decks.
NOTE For top-surface overlaying to produce the specified effect, it is indispensable to integrate the existing
members with the cementitious materials of the overlaying parts. In some cases, after the top surface of decks
is cut and cleaned, fiber-reinforced concrete is placed while adhesive is applied in order to achieve integrity. The
primary reason for using fiber-reinforced concrete on the overlaying parts is to improve the flexural resistance,
tensile resistance, shear resistance and cracking resistance of the concrete. For example, since the cross-section
layer of the top-surface overlaying parts is relatively thin, there is possibility of cracking occurring due to initial
drying or occurring and progressing due to active loads. Mixing fiber is expected to suppress the progress of
cracking. Also, in intermediate support points and overhanging decks of continuous girder bridges, reinforcing
materials such as reinforcing steel and FRP reinforcing materials are used to improve the negative flexural load-
carrying capacity. In top-surface overlaying for footings, the thickness is greater than for decks. In the case of
mass concrete, therefore, a measure needs to be taken to protect against thermal cracking due to hydration heat
of cement.
NOTE These guidelines describe a specific method of verifying the performance of a structure repaired
or strengthened by means of top-surface overlaying based on the currently available latest technologies. Note,
however, that the verification method described herein does not cover all kinds of verification. For necessary
information, reference shall be made to the relevant standard specifications and other documents. In the future,
as purposes for intervention, diversify and advances in technology are made, many different methods are
expected to be proposed.
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NOTE Given that members subject to intervention are mostly decks at present, the standard methods are
described herein that are considered the latest information on design and construction of top-surface overlaying
using fiber-reinforced concrete on overlaying parts. As technology advances, new materials and design and
construction methods are developed and methods for evaluating the post-intervention structural performance
with sufficient accuracy are established, making it possible to apply top-surface overlaying for intervention parts
and members other than decks, use materials other than fiber-reinforced concrete, employ interface treatment
methods other than cutting, cleaning and adhesive, etc., it is not necessarily required to adhere to what is set
forth in these guidelines.
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 16311-1:2014, Maintenance and repair of concrete structures — Part 1: General principles
ISO 16311-2:2014, Maintenance and repair of concrete structures — Part 2: Assessment of existing concrete
structures
ISO 16311-3:2014, Maintenance and repair of concrete structures — Part 3: Design of repairs and
prevention
ISO 16311-4:2014, Maintenance and repair of concrete structures — Part 4: Execution of repairs and
prevention
ISO 19338:2014, Performance and assessment requirements for design standards on structural concrete
ISO 1920-8, Testing of concrete — Part 8: Determination of drying shrinkage of concrete for samples
prepared in the field or in the laboratory
ISO 10406-2, Fibre-reinforced polymer (FRP) reinforcement of concrete — Test methods — Part 2: FRP
sheets
ISO 10406-3, Fibre-reinforced polymer (FRP) reinforcement of concrete — Test methods — Part 3: CFRP
strips
ISO 12473, General principles of cathodic protection in seawater
ISO 13823, General principles on the design of structures for durability
ISO 14484, Performance guidelines for design of concrete structures using fibre-reinforced polymer (FRP)
materials
ISO 22966, Execution of concrete structures
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
General
The definitions of the terms used in the Top-surface overlaying section shall be as defined in Clause 3 of
ISO / NP 5091-1.
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4 Investigation of existing structure
4.1 General
The investigation of the existing structure for intervention using the top-surface overlaying method
shall be as set forth in Clause 4 of the ISO/NP 5091-1.
NOTE Intervention using the top-surface overlaying method needs to be designed by understanding
the condition of the existing structure through a prior investigation, and plans for construction, construction
management and inspections need to be formulated based on the results of the design. The investigation of
the existing structure shall be as set forth in Clause 4 of the ISO/NP 5091-1 and involve an investigation using
documents, records, etc. and an on-site investigation. It is necessary to check the condition of the structure,
environmental conditions and conditions of use, as well as to understand the restrictions and problems on
intervention, through these studies.
4.2 Investigation
4.2.1 Investigation using documents, records, etc.
The investigation of the existing structure using documents, records, etc. for top-surface overlaying
shall be as set forth in Clause 4 of the ISO/NP 5091-1.
NOTE To check the performance that the existing structure possesses, it is necessary to understand such
information as the dimensions of members, steel arrangement and materials us
...