Inspection and assessment of concrete structures in which the presence of ASR is suspected or has been established

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CUR - Recommendation 102

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Recommendation 102

Inspection and assessment of
concrete structures in which the
presence of ASR is suspected
or has been established

An alkali-silica reaction (ASR) is a reaction between the alkalis present in the pore
water of concrete and certain components of the aggregate that contain reactive silica.
The reaction leads to the formation of a gel, which expands when it absorbs water. As a
result of this expansion cracks are formed and the mechanical properties of the concrete
may change. This may have an adverse effect on the behaviour and the load-bearing
capacity of the structure. ASR is characterised by a crazed pattern of cracks. Depending
on the design of the structure and stresses in the material, however, more or less straight
cracks may also occur.

It is important to recognise the presence of ASR in view of its potential consequences
for the load-bearing capacity and the structural safety of the structure. This
Recommendation provides a procedure on the basis of which it can be established
whether cracks that are present are actually caused by an alkali-silica reaction in the
concrete. To be able to estimate the effect on structural safety a procedure is described
in this Recommendation for gathering all the material characteristics required of the
structures in question, including strength properties. In this CUR Recommendation
guidelines are provided for the structural assessment of a number of specific structures
on the basis of these material properties. Finally, this Recommendation also discusses
the maintenance measures that are to be taken when ASR is present.

At the time this Recommendation was published CUR Research Committee C 106,
“Structural aspects of alkali-silica reaction in concrete structures”, had the following
members:
ir. J.D. Bakker (chair), ir. C.A. van der Steen (secretary and reporter), ir. G. Chr.
Bouquet, dr. M.A.T.M. Broekmans (corresponding member), ing. J. Dudar, ir. J.
Hartogsveld*, ing. N. Kaptijn*, ir. E.J.C. Rademaker, ir. R. van Selst, ir. A.J.M.
Siemes*, dr. ir. C. van der Veen*, drs. E. Vega (coordinator) en W. Buist (mentor).
The structural section, chapter 8, of this Recommendation was prepared by a designer’s
working group, consisting of the committee members above indicated by an *, together
with ir. G.G.A. Dieteren, ir. U. Förster, ir. F.B.J. Gijsbers, dr. ir. E. Schlangen and ir.
J.A. den Uijl. Furthermore, an important contribution to establishing the calculation
methods in this Recommendation was made by ir. A.J. Wubs.

CUR Recommendation 102 was approved by the General Regulations Committee
“Concrete” and is supported by NEN/CUR Committee 353 039 / RC 12 “Concrete” and
NEN/CUR Committee 353 001 09 / RC 20 “TGB concrete structures”.
This Recommendation was found to be consistent with NEN 6702, NEN 6720, NEN
6723, NEN-EN 206-1 and NEN 8005.


CUR - Recommendation 102

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content

1

Subject 4

2

Area of application 4

3

Terms and definitions 4


4

Classification 5

4.1

Inspection and study classes 5

4.2

Reporting 8

4.3

Specification of study and reporting, data 8

5

Nature and scale of the study 9

5.1

General information 9

5.2

Exploratory inspection 9

5.2.1

Contents of inspection 9

5.2.2

Performance method 10

5.3

Technical study 10

5.3.1

Contents of study 10

5.3.2

Performance method 10

5.4

Targeted study 11

5.4.1

Contents of study 11

5.4.2

Performance method 11

5.4.3

Establishing the reinforcement configuration 12

5.5

Structural study 12

5.5.1

General information 12

5.5.2

Contents of study 13

6

Sample-taking 13

6.1

General information 13

6.2

Marking and drilling 14

6.3

Treatment of drilled cores 14

6.4

Repairing drilled holes 14

7 Measuring and assessment methods 14
7.1

Crack pattern, crazing 14

7.2

Cumulative crack width 14

7.3

Assessment of data and structure 16

7.3.1

Assessment of data 16

7.3.2

Assessment of structure 17

7.4

Polarisation and fluorescence microscopy (PFM) 17

7.4.1

Procedure 17

7.4.2

Aspects to be established 17

7.4.3

Microscope requirements 18

7.5

Uniaxial tensile strength 18

7.5.1

Determination of the uniaxial tensile strength 18

7.5.2

Verification of uniaxial tensile strength measured 18

7.6

Compression strength 19

CUR - Recommendation 102

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8 Structural analysis 19
8.1

Analysis principles 19

8.2

Deflection verification 19

8.3

Verification of shear forces 19

8.3.1

Principles 19

8.3.2

Design value of shear stress according to NEN 6720, based on average tensile strength 20

8.3.3

Design value of shear stress based on experimental research 20

8.3.4

Upper limit of the design value of shear stress 21

8.3.5

Special load combinations 22

8.4

Punch and torsion 22

9 Reporting 22
9.1

Class A 22

9.2

Class B 22

9.3

Class C 22

9.4

Control strategy and control measures 23

9.4.1

Data required for control measures 23

9.4.2

Specification of control measures 23

Titles of standards and CUR Recommendations stated 25

Appendix A Preparation of fluorescent epoxy 26

Appendix B Preparation Of Thin Sections 28


CUR - Recommendation 102


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1 Subject
This CUR Recommendation provides procedures and guidelines for:
• establishing whether an alkali-silica reaction (ASR) is present in concrete;
• establishing the relevant material properties;
• assessing a concrete structure for ASR, whereby methods are given for the structural
assessment of a number of specific structures.
In addition to this, possible control measures are discussed. These depend on the extent
of the damage by ASR.
2 Area of application
This CUR Recommendation applies to concrete structures in the Netherlands. The
structural assessment methods in chapter 8 of this Recommendation are only valid for
certain structures with structurally deleterious ASR. More specifically, the calculation
methods determined from experimental research (8.3.3) may only be used if:
• it concerns plate-shaped structures (plates, walls) with a thickness of at least 400
mm;
• a bidirectional reinforcement (in one plane) is used in these plates;
• the damage by ASR has resulted in delamination parallel to the plane of the plate;
• this has resulted in “anisotropy” of the uniaxial tensile strength.


3 Terms and definitions
3.1 Alkali-silica reaction (ASR):
the reaction of certain components of aggregate containing
reactive silica with the alkalis that are present in the pore water of concrete, which leads
to the formation of gel-like reaction products.



3.2 Structurally deleterious ASR:
the situation whereby the occurrence of ASR results in
deterioration of the mechanical properties of the concrete to such an extent that this
affects structural safety and usability.
3.3 Exploratory inspection:
a mainly visual assessment of the structure with the aim to
establish whether any (deleterious) ASR may be present.
3.4 Technical study:
a study performed on the structure and in a laboratory to establish
whether ASR is actually present, including exploratory tests to determine whether
material properties, such as compression and tensile strength, have been adversely
affected.
Explanation
These reaction products may absorb pore water, which makes them swell up and
exert pressure within the concrete. As a result of this, some of the mechanical
properties will initially deteriorate, including the tensile strength, and the concrete
may eventually start to crack. The deterioration of mechanical properties can be
deleterious to the structure.
Explanation
For newly to be built concrete structures, please refer to CUR Recommendation 89
“Measures to prevent damage to concrete by alkali-silica reaction (ASR)”.
The limitation to concrete structures in the Netherlands is necessary, as the
calculation methods were derived from Dutch calculation regulations or as these
calculation regulations are used for the assessment. The limited applicability of
calculation methods determined by experimental research stems from the fact that
only the structure described was studied.
CUR - Recommendation 102


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3.5 Targeted study:
a study with the aim to determine the strength properties of the concrete
affected by ASR more extensively.

3.6 Structural study:
a study into the structural consequences for the concrete affected by
ASR.
3.7 PFM (polarisation and fluorescence microscopy):
a microscopic research technique that
is applied on very thin, impregnated preparations of concrete in order to obtain an image
of the microstructure of the cement paste, the water-cement ratio, the type of cement,
the lithological composition of the aggregate and any converted substances in it, the
presence of cracks as well as the spatial distribution and the homogeneity of these
properties.
3.8 Reactive silica:
the amorphous or low-crystalline silica present in some aggregates that
reacts faster with alkalis on the basis of its less well-ordered crystal structure and/or its
greater specific surface area compared to coarse crystalline quartz.



3.9 Relative cumulative crack width
ε
ASR
:
an indicative measure for the extent to which
cracks have formed that is determined by adding all the widths of the cracks that
intersect with a measuring line placed along a cracked area of the structure and then
dividing it by the length of the measuring line.
3.10 Structural risk:
a measure for the seriousness of the consequences relating to the possible
presence of ASR.


3.11 Control strategy:
the strategic choice of the period in which and level at which a
structure will be maintained by performing control measures.
3.12 Control measure:
the package of measures that are to be taken immediately and in the
future to keep a structure in a prearranged condition or to achieve a predetermined
situation.


4 Classification
4.1 Inspection and study classes
The class of inspection and/or nature and scale of the study to be performed must be
agreed upon in advance by reporting a class as stated below. It is possible to agree on
several different classes at the same time (see table 1).
Explanation
Examples of control measures are reinforcing the structure or measures to delay or
p
revent the progress of the damage mechanism, such as limitation of the moisture
load.
Explanation
The structural risk is determined by analysing the reinforcement configuration and
the consequences of the damage observed for aspects such as safety and functioning.
Explanation
Well-known reactive components are opal, chalcedony, moganite, cristo
b
alite,
tridymite, cryptocrystalline quartz, (porous) flintstone (silex / chert / flint), impure
sandstone (grey wacke, siltstone), siliceous limestone and certain types of volcanic
rock due to the glass that is present in it.
CUR - Recommendation 102


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Class I Exploratory inspection
The purpose of this inspection is to find out whether ASR is present in the structure or
whether the cracks that were observed are more likely to have a different cause.

Class II Technical study
The purpose of this study is to confirm that ASR is indeed present, as well as to obtain
an initial indication of the seriousness of the damage. Among other things, this is done
by establishing whether a relatively low uniaxial tensile strength is present.

Class III Targeted study
The purpose of this study is to gather more information in a targeted manner, to be able
to determine reliable material properties on the basis of this, among other things, for the
structural assessment calculation and the specification of control measures.

Class IV Structural study
The purpose of this study is to obtain an insight into the structural safety of the
structure. The structural study is divided into:
Class IVA Manual inspection of transverse forces in representative cross-sections,
either with or without basic calculation software.
Class IVB Numerical inspection of transverse forces in representative cross-sections.
Class IVC Structural assessment of the entire structure.

A representative cross-section is the cross-section in which the modified mechanical
properties of the concrete have the greatest effect on the load-bearing capacity and the
structural safety of the entire structure.



Figure 1 shows the relationship between the various components. The various studies
are specified in more detail in 5.2 to 5.5.
The diagram in Figure 1 will only have to be followed if the structural risk is “medium”
or “high”, see 7.3.1.
Explanation
To assess the structural safety calculation models are used that are only valid for
certain structures, see 8. The determination of representative cross-sections requires
a good structural understanding and can therefore best be left to an experienced
structural engineer.
Explanation
The tests described in this Recommendation serve as a supplement to the inspection
and test methods in CUR Recommendation 72, “Inspection and testing of concrete
structures”, and describe tests that are related to ASR in more detail. In certain cases
it is recommended to ascertain whether it is desirable to perform an inspection or
study according to CUR Recommendation 72 at the same time, supplementary to a
study according to this Recommendation.
CUR - Recommendation 102


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Figure 1 Flow chart for inspection and studies
Explanation of flow chart
In the flow chart used the various study classes are described in a mutual context.
Generally speaking, an increasing amount of information is obtained from top to
bottom in the flow chart, whereby the study effort also increases. Please note that a
step-by-step approach was chosen, whereby different levels of study are performed
in succession. In some situations the additional costs and nuisance (traffic measures)
may be such, that it will be better to decide to take all the sam
p
les in advance, in
anticipation of a possible targeted study in the laboratory. With regard to this, it is
im
p
ortant to have a clear image of the desired results of the study in advance. The
studies mentioned will only be useful in practice if the structural risk is “medium” or
“high”.
Y
Y
Y
Y
Y
N N
N
N
N
N
Class I
ex
p
lorator
y
ins
p
ection
Class II
technical stud
y
Class III
targeted study
Class IV
structural stud
y
ASR
p
ossible

ASR
Indication of low
tensile stren
g
th
Safety now
g
uaranteed
Report
Report
Report
Report with
safety
measures
Possibly further
study into cause of
cracks
Low tensile
strength
Report
CUR - Recommendation 102


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4.2 Reporting
Based on their contents, reports are divided into:

Class A Reporting of data.
Class B Reporting of data and measures to be taken.
Class C Reporting of data and control measures to be taken.

For the contents of the reports, please refer to chapter 9.


4.3 Specification of study and reporting, data
In order to determine which study is required and which type of report is to be prepared,
at least the following must be agreed:
a. the type of inspection or study, based on the classification in 4.1;
• for an exploratory inspection it must also be agreed whether the pattern of cracks
is to be recorded in accordance with 7.1;
• for a technical study it must also be agreed whether impregnated cores are to be
assessed;
• for a targeted study it must also be agreed whether the reinforcement
configuration is to be determined;
b. the method and contents of the required report, based on the classification in 4.2.

Prior to an inspection or study of a concrete structure at least the following data must be
available:
• the definition of the problem relating to the inspection or the study;
• the location of the structure to be studied;
• the nature and type of the structure;
• the shape and size of the structure;
• the age of the structure and, where available, the design life;
• the component or components of the structure to be studied;
• whether any previous studies have been performed on these components or the
structure;
• the accessibility of the structure as a whole and of the most important structural
components at which the study is aimed;
• the possibilities of closing-off the building site as well as the need to take traffic
measures.

If a structural study is prescribed the following must also be agreed:
• whether the (original) design calculations, verification calculations and reinforce-
ment drawings are available;
• the number of representative cross-sections that must be tested (see 5.5).

If any control measures are to be specified, the client should provide information about
the control strategy that applies to the concrete structure in question.
Explanation
Please note that a link exists between the type of study and the possible reports. For
example, an inspection according to class 1 will provide insufficient data to prepare
a report according to class C.
This Recommendation is aimed at identifying ASR and the consequences of it. If
ASR cannot be identified as a cause or the only cause of the cracks observed, it is
advisable to have these cracks and the consequences of them assessed further by an
expert. It may also be useful for maintenance purposes to obtain information about
other defects and shortcomings in the structure. For the recording of a study different
to one concerning ASR, please refer to the various inspection classes that are stated
in CUR Recommendation 72.
CUR - Recommendation 102


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5 Nature and scale of the study
5.1 General information
In this chapter the inspection and studies stated in 4.1, which may either be performed
separately or together, are described in more detail.
When prescribing a particular study or a combination of studies the intended objective
must be clear, for example, merely determining whether ASR is present or, for example,
answering the question of whether the structural safety is still guaranteed. Table 1
indicates which study is required to obtain a particular result.

Table 1 Overview of relevant questions and studies required
Scale of study at least
Exploratory
inspection
Technical study
Targeted study
Structural study

Question
See 5.2
See 5.3
See 5.4
See 5.5
Could ASR have occurred?

To be performed



Could the mechanical properties
have been affected in a negative
manner?

To be performed
To be performed

Has ASR currently led to a
structurally unsafe situation?

To be performed
To be performed
To be performed
5.2 Exploratory inspection
5.2.1
Contents of inspection
For each component to be studied, an exploratory inspection must at least consist of the
following:
• Establishing whether a crazed pattern of cracks is present, which is the case if the
cracks are more or less perpendicular to each other. The crazing may exhibit a
preferred direction, for example, due to the forces in the structure.
• Establishing whether the crazing is uniform over the entire surface or whether there
are areas with limited crazing and areas with a large amount of crazing.
• Identifying other cracks and crack patterns, whereby at least the following is recorded:
the shape of the cracks, the crack distance, the crack width and an estimate of the
cumulative crack width.
If this has been agreed, the crack pattern should also be recorded in accordance with 7.1.

The following must also be recorded for the structure that contains the component to be
assessed:
• Any visually identifiable expansion and deformation of the structure, for example,
the structure being out of centre at joint interfaces, lopsidedness of bearings as well
as unusual curvature, lopsidedness or shifting of faces.
Explanation
The reliability of statements relating to the damage, the consequences and the
measures to be taken is determined for a large part by the study. For example, an
exploratory inspection provides an insufficient basis for specifying control measures.
Table 1 shows which studies are considered to be required at the least to be able to
make a particular statement.
If any previous studies were performed on the structure, either with regard to ASR or
other types of damage, it will be useful to provide this information as well.
Depending on the nature and scale of the previous study it may be decided to limit
the study described in this Recommendation.
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• Any environmental factors relating to the moisture load, for example, for car decks
the possibility of loads exerted as a result of de-icing salts and excessive forms of
moisture load as a result of the design and/or inadequate drainage of the structure.
• Any secretion of alkali-silica gel present or the spalling of pieces of concrete for
reasons other than reinforcement corrosion.
• The presence of a coating or signs of concrete repairs performed previously. In
particular, the possibility must be taken into account here that a coating may hide
previous damage by ASR that was repaired.


5.2.2
Performance method
Where agreed, the pattern of cracks must be recorded in accordance with 7.1 in at least
three locations where the most severe form of crazing is visible.


5.3 Technical study
5.3.1
Contents of study
The technical study must at least consist of:
• Removing drilling cores for polarisation and fluorescence microscopy (PFM test)
and to determine the mechanical properties.
• Recording the relative cumulative crack width according to 7.2 in at least 3 locations
with a crazed pattern of cracks.
• An analysis of the structure on the basis of information provided, see 7.3.1,
including any exploratory inspections performed.
• A verification of the tensile strength of the cores measured against the designed
tensile strength and the low tensile strength criterion according to 7.5.2.


5.3.2
Performance method
For the technical study a sufficient number of cores with the correct length must be
drilled out of the structure or structural components in order to perform the test of the
mechanical properties and for the presence of ASR. The diameter of the drilling cores
must be around 75 mm. The length of the drilling cores is derived from the property that
is to be determined.

Explanation
Depending on the size of the object, it may be decided to have the pattern of cracks
recorded in a greater or smaller number of locations. For possible testing of the
uniaxial tensile strength perpendicular to the span, in other words, in the plane of the
element, it is recommended that at least three cores be drilled. To establish the
necessity of a test of the uniaxial tensile strength in the plane of the element, please
refer to 8.3.1.
Explanation
It may be useful to draw and record the pattern of cracks in order to monitor possible
developments.
Explanation
To recognise damage patterns that may be related to ASR, please refer to the “ASR”
picture-book, a publication of the Public Works Service of the Directorate-General
for Public Works and Water Management, which can be accessed via
www.bouwdienst.nl.
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The number of cores required and the length of the cores is:
• at least 6 to determine the uniaxial tensile strength according to 7.5, their length
must be equal to twice the diameter of the core;
• at least 3 to determine the compression strength according to 7.6, their length must
at least be equal to the diameter of the core.
The drilling locations of the cores must be spread out over the “bad areas”, but not on a
crack and preferably in representative cross-sections in terms of transverse force.

In addition to the cores stated, it may be necessary to collect additional sample material
for a PFM test. These cores must have a length of at least 100 mm and should
preferably be drilled on a crack. The core must also include the outside surface.

All drilled cores must be assessed visually for signs of ASR. At least one core
containing material suitable for the PFM test according to 7.4 must be selected from the
available sample material.


5.4 Targeted study
5.4.1
Contents of study
The targeted mechanical study must at least consist of drilling cores for mechanical
testing. Where agreed, the reinforcement configuration must also be determined.
5.4.2
Performance method
Drilling cores

The locations where drilling cores are to be removed for the structural test must be
determined by an experienced concrete maintenance expert with a structural
understanding, or else in consultation with the structural engineer who is responsible for
the more detailed structural study. The cores should basically be removed from areas in
which transverse forces are present.



Explanation
Please note that the areas in which the transverse force is normative are particularly
interesting; more so than areas in which it is at its maximum.
Explanation
Additional cores are required for PFM testing, as a sufficient number of cores must
be available to test the mechanical properties. It cannot be excluded that additional
material is obtained when drilling cores for mechanical testing before the number of
cores with the correct length stated is collected. This material could be used for PFM
testing. A drilling core can be used for more than one purpose, provided that its
length is sufficient.
Please note that a core with a greater diameter, for example, 100 mm, and a length of
more than 300 mm may provide more information when this core is fully
impregnated compared to the minimum dimensions prescribed. This is simply
because more material will then be available.
By impregnating cores with a fluorescent resin a greater insight is obtained into the
cause and the severity of the cracks that are present. The presence of ASR is often
shown with PFM, but it is difficult to ascertain whether ASR really is the primary
cause of the cracks that are present due to the limited dimensions of the test piece. A
better insight is obtained by impregnating entire cores.
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A sufficient number of cores must be drilled from each area designated for the test. The
diameter of the drilling cores must be around 75 mm. The number of cores must be:
• at least 3 to determine the uniaxial tensile strength according to 7.5, their length
must at least be equal to twice the diameter of the core;
• at least 3 to determine the compression strength according to 7.6, their length must
at least be equal to the diameter.

The cores for the uniaxial tensile strength and compression strength test should
preferably be taken from one and the same location to prevent weakening as much as
possible, for example, by drilling a core with a length of at least 250 mm and then
cutting it into sections.
If cores were already drilled before in the cross-section in question as part of a technical
study in accordance with 5.3, the compression strength and uniaxial tensile strength of
these were determined and if these results are available, the number of cores may be
reduced in accordance with the number of tests performed before.
5.4.3
Establishing the reinforcement configuration
It must be ascertained whether the configuration of the (outside) reinforcement matches
the reinforcement pattern stated on the drawing. In at least two locations per structural
component the diameter of the reinforcement present and the type of reinforcement
must be determined by means of destructive testing. If the reinforcement configuration
differs this must be discussed with a structural engineer.

If drawings are unavailable the scale of the study into the reinforcement configuration
must be such that an image is created of the main reinforcement present in the structural
component to be assessed that is sufficiently reliable to allow a verification calculation
to be performed on the basis of it.


5.5 Structural study
5.5.1
General information
Regardless of the type of structural study (IVA, IVB or IVC) at least the following
aspects must be considered:
• cracks as a result of ASR;
• deformation of the structure by ASR;
• the compressive and tensile strength present with special attention for uniaxial
tensile strength;
• the variation in the uniaxial tensile strength and possibly other mechanical properties
for each cross-section observed and between the various individual cross-sections
observed.
Explanation
To be able to determine the diameter the surrounding reinforcement will have to be
cleared away sufficiently. The type of reinforcement can be derived from the profile
of the rebar. In consultation, the number of locations where destructive testing is to
b
e performed may be limited. The purpose of establishing the reinforcement
configuration is to obtain an impression of whether the structure was built in
accordance with the drawings. If this is not the case, a structurally unsafe situation
may also be present even without ASR. It is therefore advisable to assess the
consequences of a differing reinforcement configuration first.
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5.5.2
Contents of study
A structural class IVA study at least includes:
• A verification calculation of the transverse force on the agreed cross-sections,
performed either manually or with basic computer software. Here the design
calculation with regard to the distribution of forces in the structure may be used if it
is available and usable.

A structural class IVB study at least includes:
• A numerical calculation of the shear stress present in the agreed cross-sections. In
this case the modelling of the structure must be performed using shell elements.

A structural class IVC study at least includes:
• An assessment of the transverse force stated under IVA and IVB.
• A test of the entire structure, taking into account the material properties that were
derived from the test results in accordance with chapter 8.

A study according to classes IVA, IVB or IVC does not require a test of the bending
moment capacity.



For the assessment method, please refer to chapter 8.
6 Sample-taking
6.1 General information
When removing drilling cores the drilling through structural reinforcement present must
be prevented as much as possible. To achieve this at least the outside reinforcement
must be located in advance using a concrete cover meter.
Prestressed reinforcement must not be drilled through.

The load-bearing capacity of the structure must not be affected substantially by the
sample-taking. If this is a possibility, the number of drilling cores to be removed must
be agreed in advance.

For each core the following must be recorded:
• The location of the core by indicating the position of the centre of the drilling core on a
drawing or relative to recognisable parts of the structure with an accuracy of 0.1 m.
• Visually recognisable aspects of the removed core that may be a sign of ASR and
that provide information about the condition of the concrete, for example, the
presence of reaction edges around coarse aggregate, stained drying, the presence of
gel, cracks, a layered structure, honeycombing, construction joints, etc.
• Visually recognisable aspects of the concrete surrounding the core, for example,
extensive cracking, weathering, moist patches, etc.
• Whether anything unusual has occurred while drilling, for example, breakage while
drilling.
Explanation
Practical tests on severely damaged structural parts and theoretical studies have
shown that the failure moment does not differ from that of a structural part not
affected by ASR. The tension in the reinforcement must be allowed to build up
gradually. The ends of the bars must be located in the zero points of the moments or
the reinforcement must include hooks or bends that can transfer the force in the
reinforcement to the concrete. The practical tests were performed on beams cut from
sheets with severe horizontal cracks, whereby the uniaxial tensile strength in a
direction perpendicular to the sheet plane had dropped to 1/7 of the expected value
for the tensile strength based on a splitting test.
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6.2 Marking and drilling
The location and orientation of the core in the structural component to be tested must be
indicated clearly on both the core and in a drawing or sketch of the structure in question.
The following must be indicated on the core with a permanent marker:
• An orientation cross on the top face, whereby the axes match the span direction of
the component and the transverse direction of the component, respectively. Both
directions must be recognisable by different colours or a pattern of lines.
• Which side of the core was in the original structural surface.
• An unambiguous number of the core.
The drilling core must be drilled and removed with care. The occurrence of undesirable
effects such as cracks, which may adversely affect both the observations during the
PFM test and the values measured during the mechanical study, must be prevented.


6.3 Treatment of drilled cores
After removing and assessing the core it must be handled and stored as follows:
• Clean the core immediately after removing it using a minimum amount of water to
remove any attached material.
• A unique sample number must be applied additionally or again.
• Wrap the core in an uncoloured, hand-wrung cloth and wrap it in self-adhesive film
to prevent drying-out and damage during transport.
• Place each of the cores in one piece with a diameter-length ratio of 1:2 or more
slender and cores that already consist of various fragments in a tightly fitting,
durable plastic tube for transport.
• Short, compact whole cores may be transported after wrapping them in cloth and
film.
• The number of the drilling core must be printed on the wrapping.
• The cores must be placed in the means of transport or in additional packaging in
such a way that they cannot be damaged during the journey to the laboratory.
6.4 Repairing drilled holes
Unless agreed differently, drilled holes must be sealed using a cement-based low-
shrinkage mortar in accordance with CUR Recommendation 54, application class RC2,
environmental class 3.
Holes in asphalt must be sealed with liquid asphalt.
Ancillary materials, such as formwork, must be stripped from the mortar after
hardening. Drilled holes, etc. must be sealed.
7 Measuring and assessment methods
7.1 Crack pattern, crazing
Crazing must be recorded by marking the cracks on a measuring square, preferably with
edges of 1 metre in length. The orientation of the measuring square should preferably
match the orientation of the pattern of cracks.
7.2 Cumulative crack width
The relative cumulative crack width ε
ASR
must be determined as follows:
• draw two orthogonal lines within the measuring square;
• measure the crack width w
i
of all the cracks n that cross the line in question. The
crack width must be measured perpendicularly to the crack;
• measure the angle α
i
between crack i and the edge in question;
Explanation
It is recommended to attach the drilling installation to the structure in a fixed
position and prevent wobbling of the core drill.
CUR - Recommendation 102


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15
• adjust the crack width w
i
to the direction of the measuring edge according to w
i
/cos
α
I
(Figure 2);
• for each measuring line add the corrected crack widths and divide them by length l
of the relevant measuring line, as a result of which the relative cumulative crack
width ε
ASR
is obtained:

l
w
n
i
i
i
ASR

=
=1
cosα
ε


in which:
ε
ASR
is the relative cumulative crack width in mm/m;
l is the length of the measuring line when determining ε
ASR
, in m;

w
i
is the crack width of crack i in mm;
α
i
is the angle between measuring line and crack i when determining ε
ASR
.




Figure 2 Principle of measuring Figure 3 Detail of measuring the crack
the relative cumulative

width and angular correction
crack width ε
ASR


Instead of the previous procedure, it will also be sufficient to estimate the value of ε
ASR

for the exploratory inspection. This can be done simply by counting the number of
cracks n that cross a measuring line with length l. Following this the average crack
width w
average
can be estimated or roughly measured. Then the relative cumulative crack
width ε
ASR
can be calculated as follows:

l
wn
average
ASR




in which:
ε
ASR
is the relative cumulative crack width in mm/m
l is the length of the measuring line when determining ε
ASR
, in m

n is the number of cracks
w
average
is the average crack width in mm

The cumulative crack width that is determined must be classified in a class on the basis
of table 2.
CUR - Recommendation 102


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Table 2 Classification based on relative cumulative crack width
Relative cumulative crack width
Class
0 mm/m
< 0.6 mm/m
0.6 mm/m to 1.0 mm/m
1.0 mm/m to 1.5 mm/m
1.5 mm/m to 2.5 mm/m
≥ 2.5 mm/m
none
very little
little
limited
significant
very significant
7.3 Assessment of data and structure
7.3.1
Assessment of data
The assessment of the available data must at least consist of the following, see table 3:
• Determining the high-risk components with regard to ASR based on the
reinforcement configuration.
• Determining high-risk components with regard to safety and the functioning of the
concrete structure.
• A classification of the risk of ASR for a structure (structural risk).

Aspects that must at least be weighed when determining high-risk components with
regard to safety and functioning are:
• The feeling or perception of safety.
• The risk of significant consequential damage and/or loss of function as a result of
continued expansion, for example, the jamming of moving parts.
• The (economic) damage, both direct and indirect, as well as the amount of human,
emotional and/or social suffering if the structure fails entirely or partially.

Table 3 Structural risk derived from reinforcement configuration and the conse-
quences for safety and functioning
Consequences for safety and
functioning
Reinforcement
configuration
Notes on reinforcement configuration
Major
Minor
High-quality 3D
reinforcement, see Figure
4, for example
The concrete is enclosed on all sides. ASR expansion is
slightly tensioning the reinforcement. This limits the
consequences.
Watch out for detachment of the prestress and
delamination in the plane of the prestress.

Structural risk

= medium
Structural risk

= low
3D reinforcement with
moderate anchoring
Watch out for detachment of lap joints due to the ASR
expansion.


Structural risk

= medium

Structural risk

= low
2D reinforcement with good
or moderate anchoring or
no reinforcement, Figure 5.
ASR expansion concentrated in 1 direction. In this
direction the tensile strength drops. Layers may form in
the concrete. The ASR may cause transverse force or
shearing problems.

Structural risk

= high
Structural risk

= medium








Figure 4 Cross-section of beam, column Figure 5 Cross-section of plate, wall
CUR - Recommendation 102


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17
7.3.2
Assessment of structure
When assessing the structure watch out for signs that may indicate ASR. Special
attention must be paid here to aspects such as:
• (Restrained) deformation of components.
• Indications of possible failure.
When indications of possible failure are found for critical components of the structure,
measures must be taken immediately.


7.4 Polarisation and fluorescence microscopy (PFM)
7.4.1
Procedure
For each PFM study the drilling core with a length of at least 100 mm must be
impregnated as a whole in vacuum with a UV-fluorescent epoxy resin prepared in
accordance with Appendix A.
After the epoxy resin has fully hardened the impregnated core must be cut lengthwise in
two pieces and both halves must be petrographically tested for cracks and other relevant
signs (of damage) as stated in 7.4.2.
An impregnated thin section must be prepared from at least one of the two halves
according to the method described in Appendix B. The thickness of the thin section
must be (20 ± 1) µm and the surface area must be at least 30 mm x 45 mm.
7.4.2
Aspects to be established
The combined data of the assessment of the impregnated core and the thin section must
at least establish the following:
• whether any cracks are present or not, assessed for various scale sizes, as well as the
excessive presence of these;
• whether any potentially reactive components with regard to ASR are present and
whether these components actually show signs of a reaction;
• the bonding of the cement matrix to the aggregate;
• the number of aggregate grains affected in the overall concrete (level of ASR);
• a qualitative impression of the amount of gel that is present;
• the lithological composition of the entire aggregate, regardless of any ASR-sensitive
behaviour assumed or observed;
• the possible type of cement, an indication of the water-cement ratio and the level of
hydration;
• whether, on the basis of observation, ASR could be the primary cause of any cracks
observed and whether the ASR observed is more than would be expected for a
material without a reactive aggregate.
Explanation
Due to the reinforcement configuration or an irregular moisture load ASR expansion
may occur irregularly in the concrete. As a result of this deformations may occur,
resulting in tensions that were not taken into account during the design, for example,
as a result of eccentricity in columns.
Deformation by ASR can be prevented by the surroundings of the components
affected by ASR. As a result of this tensions may occur in the affected component
and the neighbouring component. These tensions were often not taken into account
during the design and in some cases they may result in damage to one component or
both components.
Indications of possible failure are large cracks and deformation. Other indications
are: detachment of lap joints, buckling of components or, if cracks are present,
mutual shifting of the crack planes.
For the observations mentioned above no “generally decisive criterion” can be
defined. Which measures are to be taken depends on the specific structure.
CUR - Recommendation 102


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7.4.3
Microscope requirements
The assessment of the thin sections must be performed using a stereo microscope with a
magnification factor of around 50 to 80. To assess a thin section the petrographic
polarisation microscope must have a blue-light fluorescence system.


7.5 Uniaxial tensile strength
7.5.1
Determination of the uniaxial tensile strength
The uniaxial tensile strength must be determined for cylinders with a diameter of 75
mm and a length of 150 mm. Both ends of the cylinder must be flattened in a plane-
parallel fashion, perpendicularly to the axis of the core. The required smoothness is 0.1
mm per 100 mm.
Steel tie plates with a diameter equal to the diameter of the core must be attached to the
ends by glueing them on.
The test pieces must be conditioned at 20°C and 98% R.H. for at least 2 periods of 24
hours.

After sufficient hardening the test pieces must be pulled from the glue in a tensile
testing machine tester. Their capacity must not be more than 5x the expected tensile
strength. It must be possible to read the load with an accuracy of 1%. The load must be
increased gradually at a rate of (0.05 ± 0.01) N/mm
2
per second.

The tensile strength must be calculated with an accuracy of 0.1 N/mm
2
using:

A
F
ct
f =


in which:
f
ct
is the tensile strength in N/mm
2

F is the force at failure in N
A

is the surface area of the core in mm
2


If failure occurs directly underneath the pulling head the measurement will be invalid.
7.5.2
Verification of uniaxial tensile strength measured
It must be determined whether the uniaxial tensile strength measured is much lower
than the strength assumed during design. This will be the case if the following applies:

ƒ
bm,ref
< 0,7 ּ (1,00 + 0,05 ƒ’
’c,design
)

in which:
f
bm,ref
is the average uniaxial tensile strength based on test pieces in accordance
with 7.5.1, in N/mm
2
;
ƒ’
cc,design
is the average cube compressive strength used during design, in N/mm
2
;
0.7 is the conversion factor to convert the splitting tensile strength into uniaxial
tensile strength.
Explanation
For the best possible results the following characteristics are recommended for the
fluorescence filters:
• A so-called “band-pass” excitation filter for blue light with a wavelength range
of 450 to 490 nm.
• An emission filter for green light for a wavelength of 515 nm or more.
• A frequency splitter (beam splitter) that is centred around a wavelength of 510
nm.
CUR - Recommendation 102


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19

7.6 Compression strength
The compression strength of cylinders (diameter equal to height) must be determined in
accordance with CUR Recommendation 74. The lowest value measured, using at least 6
cylinders, is the value for the characteristic compression strength present.
8 Structural analysis
8.1 Analysis principles
a. Regardless of the type of structural study (IVA, IVB or IVC) it must be established
whether one of the following may be the case due to the deformation of the
structure:
• changes to the distribution of internal forces;
• changes to the eccentricity of normal forces;
• additional external loads to the structure due to kinematical restraint of swelling
deformation, for example, a bridge deck that rubs against abutment.
If the deflections in the structure are smaller than the allowable deflection according
to NEN 6702 or if the eccentricities are smaller than 30% of the eccentricity to be
taken into account according to 7.3.4 of NEN 6720 the changes mentioned above
will not require further structural consideration.
b. The structural analysis must be based on NEN 6702, NEN 6720 or NEN-EN 206-1
with the accompanying NEN 8005 and, for bridges and similar structures, NEN
6723.
c. Contrary to the standards and regulations mentioned above, the material strengths
derived from the test results using the method described in this chapter must be
used.
8.2 Deflection verification
For a structural analysis of the structure in accordance with this Recommendation no
verification of bending is required, see the explanation of 5.5.2.
8.3 Verification of shear forces
8.3.1
Principles
a. The verification of shear forces and the calculation of the calculation value of the
resulting shear stress must be performed in accordance with 8.2.1 and 8.2.2 of NEN
6720:1995, respectively.
b. To calculate the design value of shear stress the calculation methods in 8.3.2 must be
used. If c has been met the calculation methods in 8.3.3 may also be used, whereby
the more favourable result may be used.
c. The calculation methods in 8.3.3 may only be used if the conditions stated in it are
met.
d. For the design value of shear stress τ
1
no value greater than the upper limit accor-
ding to 8.3.4 may be taken into account, regardless of the value calculated in 8.3.2 or
8.3.3.
Explanation:
For the calculations in this Recommendation it was assumed that ASR causes a
significant reduction in the uniaxial tensile strength perpendicular to the plane of the
element, which was also established in the experiments on which the calculation
methods are based (see explanation 5.5.2).
It may happen that the uniaxial tensile strength is relatively low, both in the plane of
the element and perpendicular to it, even without ASR. In that case the calculation
methods included in 8.3.3 may not be used.
If a low uniaxial tensile strength is measured compared to the original compressive
strength, it is strongly recommended to complete the flow chart in figure 1 to
determine the structural safety or to determine which control measures to take.
CUR - Recommendation 102


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8.3.2
Design value of shear stress according to NEN 6720, based on average tensile strength
The calculation value for the tensile strength f
b
must be determined from:

m
refbm
ldb
f
f
γ
λ
,
1,1=


n
nff
ebmrefbm
75,0
)(
,,
−=


in which:
λ
ld
is the factor for calculating the long-term tensile strength of the concrete =
0.9;
ƒ
bm,ref
is the average uniaxial tensile strength based on test pieces, in N/mm
2
;
γ
m
is the partial material factor (= 1.35);
ƒ
bm;e
: is the average uniaxial tensile strength, determined in a direction
perpendicular to the axis of the structural component, of n test pieces, in
N/mm
2
;
n is the number of test pieces (at least 3).

The calculated value for f
b
must be entered in formula 8.2.3.1 of NEN 6720.


8.3.3
Design value of shear stress based on experimental research
The following calculation methods, determined from experimental research, may only
be applied if:
• it concerns plate-shaped structures (plates, walls) with a thickness of at least 400
mm;
• a bidirectional reinforcement (in one plane) is used in these plates;
• the damage by ASR has resulted in delamination parallel to the plane of the plate;
• this has resulted in “anisotropy” of the uniaxial tensile strength.
Explanation
As the uniaxial tensile strength is taken as the basis for determining the calculation
value rather than the splitting tensile strength a correction factor of 1.1 applies.
The value of 0.75 is obtained by multiplying 1.64, corresponding with a “95%
reliability interval”, with a mandatory standard deviation of 0.45 N/mm
2
.
Explanation
The Recommendation contains provisions that differ from NEN 6720 with regard to
the calculation principles and the determination of material properties. In NEN 6720
the tensile strength of concrete is considered equal to the splitting tensile strength.
For concrete damaged by ASR this will result in values for the tensile strength that
are too high. As a result, the uniaxial tensile strength is not derived from the
compression strength, but is determined on the basis of cores drilled from the
(affected) concrete.
8.3.2 states how the calculation value for the uniaxial tensile strength should be
determined. This value can then be entered in the formula in 8.2.3.1 of NEN 6720.
This calculation method provides a rather conservative estimate for the transverse
force capacity for concrete that is severely affected by ASR.
A less conservative value for the design value of shear stress is usually the value that
is obtained from a calculation according to 8.3.3 of this Recommendation. This
calculation method is based on the results of a study into the transverse force
capacity of a number of beams that were cut from fly-overs, which were severely
affected by ASR, and it therefore only applies to situations that are comparable to
t
his.
CUR - Recommendation 102


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21
If these conditions are met the calculation value for the design value of shear stress τ
1

may also be calculated from:

mmld
γ
τ
λ
τ
/6,0
,11
=


in which:
0.6 is a coefficient used for determining the characteristic lower limit of the
design value of shear stress from the average ultimate design value of shear
stress τ
1,m
;

λ
ld
is a factor for calculating the long-term tensile strength of the concrete (=
0.9);
τ
1,m
is the average ultimate design value of shear stress, in N/mm
2
;
γ
m
is the material factor (= 1.5).

The effect of any transverse force reinforcement that may be present must not be taken
into account. If the calculated value is more favourable than the value calculated
according to 8.3.2, the calculated value may be used, taking into account the maximum
value stated in 8.3.4.

The average ultimate value of shear stress τ
1,m
must be calculated with the formula:

)'.(
90,,0,,1 bmdctrefct
dS
I
m
ff στ +=


in which:
I is the second moment of area of the cross-section that is assumed to be
uncracked, in mm
4

d is the effective depth, in mm
S is the largest value for the first moment of area of the cross-section, in mm
3

σ‘
bmd
is the average concrete compressive stress in the cross-section due to the
normal force generated by the prestress load and the other loads on the
structure (+σ‘
bmd
for pressure; -σ‘
bmd
for tension), in N/mm
2
;
ƒ
ct,0,ref
= ƒ
bm,ref
: the average uniaxial tensile strength of n test pieces. The tensile
strength must be determined in a direction perpendicular to the axis of the
structural component, in N/mm
2
;

)'05,01(
,,0,90,measuredccrefctct
fff +⋅=
, in N/mm
2


in which:
ƒ’
cc, measured
is the measured average cube compressive strength, in N/mm
2
.


8.3.4
Upper limit of the design value of shear stress
The maximum value to be used for τ
1
is

τ ω
λ1 0
3
0 4=,f k k
b h

1
not smaller than 0.4 f
b
)
Explanation
The material factor γ
m
of 1.5 is a rather safe value due to model uncertainties (as the
formulas are based on a limited number of experiments). In the formula for f
ct,spl
it is
tacitly assumed that the value of 1 is a fixed value. This is not actually the case. The
value is subject to scatter and the formula too is an approximation of reality, based
on the best line that can be fit through a large number of test results.
CUR - Recommendation 102


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For an explanation of k
λ
, k
h
and ω
0
and the values to be used for these, please refer to
8.2.3.1 of NEN 6720. The value for f
b
must be calculated from the characteristic
concrete compression strength as stated in 6.1.2 of NEN 6720. However, a value of 0.9
can be used for the long-term strength.
8.3.5
Special load combinations
For special load combinations the factor for the long-term effect (λ
ld
= 1.0) is no longer
used and γ
m
can be reduced to
- γ
m
= 1.1 for a calculation according to 8.3.2;
- γ
m
= 1.25 for a calculation according to 8.3.3;
- γ
m
= 1.0 for the calculation of the upper limit according to 8.3.4.
8.4 Punch and torsion
The values calculated for the design value of shear stress may not be used for the
verification of punch and torsion.


9 Reporting
9.1 Class A
A written report according to class A should at least include:
• the definition of the problem;
• a description of the structure in question;
• a description of the study performed and the measurements, including the test
method;
• an indication of the measuring locations;
• the results of the visual inspection;
• a description of the cracks found and the classification of the cumulative crack width
(crazed pattern, etc.);
• the results of any measurements performed and laboratory testing;
• the results of the calculations performed.
9.2 Class B
A written report according to class B should include the points stated in 9.1, with the
addition of:
• a discussion of the results;
• the consequences of the findings and results for the component assessed or the
structure;
• any measures or actions to be taken immediately.

And more specifically for the various studies:
• Technical study: a statement whether ASR is present;
the classification of the relative cumulative crack width ε
ASR
;
a statement whether a relatively low uniaxial tensile strength
determined in accordance with 7.5.2 is present.
• Targeted study: a statement whether the results show that a further structural
study is required.
• Structural study: a statement whether the structure can still be considered safe.
9.3 Class C
A report according to class C should at least include the points stated in 9.2, with the
addition of possible control measures, see 9.4.
Explanation
The effects of structurally deleterious ASR on punch and torsion are still not
sufficiently known.
CUR - Recommendation 102


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23
9.4 Control strategy and control measures
9.4.1
Data required for control measures
The client must indicate what the control strategy is for the structure in question. At
least the following must be recorded here:
• the planned period in which the client wishes to continue using the structure;
• the minimally required state of repair of the structure, for example, whether damage
to preservations on concrete is allowed or not, or the presence of concrete damage;
• the loads and/or traffic class the structure must be able to absorb.

For the specification of a control plan at least the following data must be available and
must have been verified:
• the control strategy;
• the exposure conditions of the various structural components;
• the current damage.
9.4.2
Specification of control measures
Which control measures are to be taken depends on many factors and they may
therefore differ for each structure. As an indication, Table 4 provides an overview of
possible control measures depending on the risk classification according to Table 3, the
presence of a relatively low uniaxial tensile strength and the level at which cracks are
present.


Explanation of table 4
V Sealing against moisture; targeted drying of the concrete
More damage is usually observed in locations where moisture transport is high
compared to locations where a structure is fully submerged. Where possible,
one measure may therefore be aimed at limiting moisture transport through
(ASR) cracks. Puddles must be prevented from remaining directly on the
concrete.
Targeted drying of the concrete can be achieved by draining moisture correctly,
keeping moisture out of wet faces and allowing drying on “dry” faces. It is
pointless to “wrap up” a structure completely, as any moisture present will not
be able to get out. Here a role is played by the fact that structures “with their
base in the water” easily absorb moisture through the cracked concrete. In this
case wrapping-up the concrete will increase the wetness of the structure.

M Monitoring
Cracks can be monitored in a number of ways:
• The easiest way is to monitor the development of cracks in the structure. In
some cases it will be sufficient to visit the structure periodically.
• Periodically marking the cracks in the same location (see also 7.1) and
copying these cracks to a sheet of Perspex, whereby crack widths are
measured and stated. It is advisable to use the same person for this each
time, as the width of a crack changes starting at the surface and the edges of
cracks are not always clear-cut. This means that different people may
interpret things differently.
• Monitoring the cumulative crack width as described in 7.2.
Several measuring techniques (wire recorders) are available for monitoring
expansion in concrete. In this case it must be taken into account that expansion
is always related to temperature and, to a limited degree, moisture.
Moisture can be measured in various ways. Moisture can be measured
indirectly based on the relative humidity of the concrete. The electric
alternating-current resistance and the electric impedance of the concrete are
also moisture indicators.
CUR - Recommendation 102


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Table 4 Selection table for control measures. The table only provides an initial
indication for possible measures; these require further consideration for
each situation
Necessary measure(s)
Optional measures
Risk classification
of the structure
Relatively low
tensile strength
indication *)
Level of crack
formation
(indicative)
V
M
VF
C

V
M
VF
C
Low
Yes
< 1 mm/m
1




2
4



Yes
> 1 mm/m
2
4

5

4
1
1
1

No
< 1 mm/m





2
3



No
> 1 mm/m
1
4

3

4

1
1
Medium
Yes
< 1 mm/m
2
6
2


4

1
2

Yes
> 1 mm/m
6
6
2
4



2
1

No
< 1 mm/m
2
4
1


2
2
1
2

No
> 1 mm/m
5
4
2
4

1
2

1
High
Yes
< 1 mm/m
5
4
4





2

Yes
> 1 mm/m
6
4
5
4




2

No
< 1 mm/m
6
5
2




2
2

No
> 1 mm/m
6
6
3
4



1
2
*) obtained from 7.5.2, as the number of options may be limited based on the results if a structural
study has already been performed.

Table 4 indicates the importance of the measures using the numbers 1 to 6. The number 6 indicates
that the measures are highly recommended, the number 1 indicates that the measures are
considered to be the least urgent. If a cell is empty this means that the measure will not be useful.
The ratio of the numbers for necessary and optional measures provides an indication as to whether
it is better to choose the necessary or optional measure.

These moisture measurements are often related to temperature. It is therefore
recommended to determine both parameters at the same time. By measuring the
moisture content periodically it can be established whether the structure is
drying up.

VF Measures for guaranteeing safety and functioning
When considering measures for guaranteeing safety and functioning, they must
always be tuned to the specific situation. The Recommendation provides a
number of guides for this in Table 4. However, these are not exhaustive.
Examples of measures to guarantee safety / functioning are limiting the load or
applying a local reinforcement or support. If structural damage is about to
occur due to jamming of a structure, room for expansion may be created.

C Limiting the risk of reinforcement corrosion
If a structure damaged by ASR is cracked, reinforcement corrosion may occur
b
y penetration of chlorides and carbonation in these cracks. Depending on the
local situation, measures may be taken to seal the concrete from chlorides. One
option is to inject cracks. This will be required especially if a changeable wet-
dry situation is present with enough moisture.
CUR - Recommendation 102


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25
Titles of standards and CUR Recommendations stated

NEN 6702:2001 Technical principles for engineering structures. TGB
1990. Loads and deformations.

NEN 6720:1995 Concrete regulations. Structural requirements and cal-
culation methods (VBC 1995), incl. amendment A3:2004.

NEN 6723:1995 Concrete regulations. Bridges. Structural requirements
and calculation methods (VBB 1995), incl. amendment
A1:2003

NEN 8005:2004 Dutch specification of NEN-EN 206-1. Concrete, part 1.
Specification, performance, production and conformity.

NEN-EN 206-1:2001 Concrete; part 1. Specification, performance, production
and conformity.

CUR Recommendation 54 Concrete repair using manually applied or poured cement-
based mortar.

CUR Recommendation 72 Inspection and testing of concrete structures.

CUR Recommendation 74 Studying of concrete structures – Studying of compres-
sion strength.

CUR Recommendation 89 Measures to prevent damage to concrete by alkali-silica
reaction ASR.

Dutch standards are publications by Stichting Nederlands Normalisatie-instituut,
Vlinderweg 6, Postbus 5059, 2600 GB Delft. Orders can be placed at NEN, sales and
information hotline, tel. +31 (0)15 2690391.






CUR - Recommendation 102


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Appendix A Preparation of fluorescent epoxy
A1 Introduction
This appendix describes the preparation of fluorescent epoxy for the impregnation of
sample material.
A2 Composition
For the preparation of fluorescent epoxy the following substances and materials are
required:
• a fluorescent dye, namely finely ground powder of Hudson Yellow, for example,
EpoDye produced by Struers or equivalent;
• epoxy resin, for example, BY 158 by Ciba Geigy, or equivalent;
• epoxy hardener, for example, HY 2996 by Ciba Geigy, or equivalent;
• materials required: fume cupboard, plastic beaker, wooden spatula, bucket/tray of
cold water, magnetic stirrer, balances with a variety of weighing ranges.

A3 Safety
If the instructions and safety regulations of the manufacturer are not strictly observed
the handling of epoxy resin may be harmful to a person’s health. Epoxy resin must
therefore only be handled in a fume cupboard.
A4 Procedures
A4.1 Adding dye to the resin
Carefully add one weight percent of dye to a weighed quantity of epoxy resin in a
sealable container; also add a stirring magnet. Be careful with the dye, as it may even
contaminate the laboratory if a slight draught is present.

Seal the container and firmly mix the contents by hand. Place the glass on a magnetic
stirrer and leave it to stir for at least two days. Firmly shake the glass again by hand at
least once every 24 hours. Remove the stirring magnet with a steel pin after stirring and
clean it thoroughly.

The hardener and the coloured resin must be stored in the dark in a ventilated location
or in a fume cupboard.
A4.2 Mixing the two components
The coloured resin must be mixed with the hardener according to the instructions of the
manufacturer. Table A1 provides the current mixing ratio for products by Ciba Geigy.
Place a plastic beaker on a balance and add the required amount of coloured resin to it
first, then add the correct amount of hardener.


Explanation
Hudson Yellow is also known as Brilliant Yellow and by the trade name Epodye; it
is a fluorescent dye that lights up as light yellowish green under filtered blue light
with a wavelength of around 476 nm when viewed through an LWP 515 emission
filter.
Explanation
The final amount of coloured resin in the glass may contain a few lumps of undis-
solved fluorescent dye. To prevent false-
p
ositive fluorescence this contaminated
amount of resin must not be used for the impregnation of slices.
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Table A1 Mixing ratio by weight (g) for Ciba Geigy products
Coloured resin
BY 158
Hardener
HY 2996
Coloured resin + hardener
40
80
120
200
12
24
36
60
52
104
156
260
Start stirring the mixture immediately with a wooden spatula; stir in a circular motion
and in figures of eight in both a horizontal and vertical direction. Regularly scrape the
sides and bottom of the beaker. Stir vigorously for two whole minutes.
In addition to other problems, incomplete mixing may result in insufficient hardening.
The mixed epoxy must be used for impregnation within 30 minutes of mixing.

The hardening of the epoxy generates heat. Keep any epoxy that has not (yet) been used
in plastic beakers that are placed in cold water to prevent the epoxy from boiling. Make
sure that no water is added to the epoxy. After hardening (the next day) the excess
epoxy can be removed as regular waste.
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Appendix B Preparation of thin sections
B1 Introduction
These instructions describe the procedure for the preparation of thin sections for the
PFM test.
B2 Materials required
The following materials are required for the preparation of thin sections:
• diamond cutter with water cooling and a fully straight cutting blade that does not
vibrate;
• suitable diamond cutting (and lapping) equipment with water cooling;
• support slide matted on one side to be used as a reference for plane-parallel
treatment when impregnating and also as external “glued-on” reinforcement for
fragile samples;
• sample slide with one matted side;
• covering slide;
• UV-hardening glue;
• UV lamp;
• polarisation microscope;
• micrometer (optional);
• soft brush, or better yet, a clean ultrasonic cleaning bath to clear the sample of
cutting and grinding sludge;
• soft brush, or better yet, an electrostatic brush to clean the slide and the samples
before glueing;
• acetone and/or alcohol;
• soft paper, for example, cleaning paper for optical lenses;
• siphon or spray bottle of alcohol (60% V/V).
B3 Procedures
B3.1 General information
The slices are prepared as follows:
• select a location for a slice in the drilling core that was cut in half;
• cut a piece of at least 30 x 40 x 10 mm
3
from the selected section of the impregnated
sample;
• never reduce the amount of surface cut off; this will affect the representative
character of the sample;
• glue the section that was cut off to the support slide using a thin and even layer of
Loctite 330 or a similar alternative;
• cut off the sample parallel to the support slide so that a thickness of 2 to 5 mm is
obtained;
• grind the surface parallel to the support slide with a fine-grained diamond so that a
smooth and even surface is formed;
• glue a sample slide to the final surface;
• cut off any excess material;
• grind the surface further with increasingly fine diamond to a thickness of (20 ± 1)
µm;
• print the sample number on the finished slice.

A number of procedures are described in more detail below.
B3.2 Sample number
It is of essential importance that the unique sample number remains linked to the
samples at all times. This is why samples must be placed and processed in a logical
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order. Any residue that is cut off must be kept with the sample during all practical
procedures. Reattach the sample code to the treated sample as quickly as possible.
B3.3 Cutting with a diamond wheel
The following applies to cutting with a diamond wheel:
1. Use the thinnest possible diamond wheel.
2. Cut with the diamond wheel using an even pressure that is as low as possible and
always use water cooling (for some special applications, for example, for water-
soluble substances, cooling with alcohol is recommended). A sharp diamond cutter
will cut through the material almost without pressure.
3. If the cutting is too slow the diamond wheel may be worn-out or it may require
sharpening or needs to be replaced.. It may be that the wrong type of diamond wheel
is mounted to the cutter.
4. Diamond wheels require inspection and maintenance, and they must be replaced
where required:
• Where required, sharpen the wheel by cutting a soft material, for example, a
brick.
• Use a magnifying glass to check whether the outer layer is still covered in
diamond grains.
• Replace the diamond wheel if it is worn-out or if any wobbling, vibration or
shocking occurs, as this may damage the sample.
B3.4 Grinding
The grinding procedure largely depends on the equipment used. For good results the
following general points must be taken into account:
• Grinding is to be performed with a gradually decreasing grain size.
• Grinding with a particular grain size will not be finished until all the scratches from
the previous, coarser treatment (grinding or cutting) are removed.
• Prevent grains or particles from breaking free from the surface, especially along the
edges of the sample, by making sure that the sample is fully impregnated.
• After each grinding round, check the surface under an angled beam of light
(floodlight) for completely even grinding results, in other words, a flat surface
without ridges.
• Clear the surface of grinding waste after every treatment and then moisturise the
surface with alcohol by spraying, then dry it off with soft paper in a single swipe.
• The preparation may never dry up during the entire treatment. Water may leave
circles of microscopically small crystals, may contribute to artificial carbonation of
the cement paste and has a negative effect on the UV-hardening glue.
• The final surface quality must be sufficient for an unambiguous identification of
components and microstructural characteristics.
B3.5 Glueing-on the sample slide and the covering slide
It has been shown that the procedure below results in good and even glueing:
• Apply a diagonal cross of glue to the impregnated and finished sample surface (to
prevent air bubbles from becoming trapped).
• Place the slide at the centre of the sample.

Only for the sample slide:
• leave the layer of glue to even out by itself for 5 minutes and recentre the slide;
• hold the sample and the slide together for 10 minutes using a force that is evenly
distributed over the surface;
• expose the sample to UV light for 20 minutes.

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Only for the covering slide:
• leave the glue to even out by itself for 5 minutes;
• remove any excess glue from the edges of the covering slide with a pipe cleaner,
recentre the slide;
• place the sample under UV light for around 1 minute;
• carefully remove any excess glue with a Stanley knife and acetone or alcohol;
• place the sample under UV light for around 10 minutes;
• clean all surfaces with acetone or alcohol.
B3.6 Checking the thickness
The thickness of the thin section is checked with the polarisation microscope. The
correct thickness of around 20 µm is determined based on the white or light-grey
birefringent colour of quartz For some automatic grinding equipment the thickness can
also be measured with a micrometer, whereby the thickness of the UV-hardening glue
must be taken into account.
B4 Storing impregnated fluorescent thin sections
The fluorescent power of the thin sections is reduced noticeably if they are exposed to
strong light for a prolonged period of time. This is why thin sections must be stored in
the dark.
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It should be pointed out that this CUR Recommendation reflects the state of the art at
the moment of publication. Any suggestions for experiences with the use of this
Recommendation will be gratefully received by CURNET. CUR Recommendations are
evaluated three years after publication and are updated if necessary. This will be
reported in the press.

Copyright
All rights reserved. No part of this publication may be reproduced, stored in a retrieval
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It is allowed, in accordance with article 15a Netherlands Copyright Act 1912, to quote
data from this publication in order to use this in articles, essays and books, provided that
the source of the quotation, and, insofar as this has been published, the name of the
author, are clearly mentioned. “© CUR-Recommendation 102 “Inspection and
assessment of concrete structures in which the presence of ASR is suspected or has been
established”, April 2008, Gouda, The Netherlands.”

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Gouda, April 2008
The Board of CURNET

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