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8/2/2019 Concrete EU Eurocode 2 p59
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Properties of Concretefor use in Eurocode 2How to optimise the engineering properties of concrete in
design to Eurocode 2
A cement and concrete industry publication
P.Bamforth BSc (Hons) PhD C Eng MICE
D.Chisholm BE (Hons) CPEng IntPE(NZ)
J.Gibbs BA MICT
T.Harrison BSc PhD C Eng FICT MICE
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Properties of concrete for usEurocode 2
Contents
Symbols ii1. Introduction 1
2. Assumptions underlying Eurocode 2 4
3. Compressive strength 5
4. Tensile strength 11
5. Bond strength 17
6. Modulus of elasticity 19
7. Tensile strain capacity 24
8. Creep 26
9. Shrinkage 30
10. Thermal expansion 35
11. Thermal conductivity 37
12. Specific heat 38
13 Fire resistance 39
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Symbols
c cover to reinforcement
cp
specific heat
cv
coefficient of variation
D thermal diffusivity
Ec
tangent modulus
Ecd
design value of modulus of elast
Ec,eff
effective modulus of elasticity o
Ecm
mean secant modulus of elastici
fbd
ultimate (design) bond stress
fcd
design compressive strength
fcd,fat
design fatigue strength
fck specified characteristic cylinder fck,c
confined characteristic compres
fck,cube
specified characteristic cube com
fcm
mean concrete cylinder compres
fcm,cube
mean concrete cube compressiv
fctd
design tensile strength
fctk
characteristic axial tensile streng
fctm mean axial tensile strengthfctm,sp
mean splitting tensile strength
fctm,fl
mean flexural tensile strength
fct,sp
tensile splitting strength
fcu
specified characteristic cube com
s coefficient for cement type used
sr,max
crack spacing
t time
coefficient applied to age functio
ccoefficient of thermal expansion
cc
coefficient for long-term and loa
strength
ct
coefficient for long-term and loa
(t) age function for strength
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c
thermal conductivity
density
p,eff
ratio of area of reinforcement to
f bar diameter
(, t0) creep coefficient at time t=
c
constant compressive stress app
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1. Introduction
In the design of concrete structures, engineers have t
concrete type(s) aimed at meeting the specific perfor
For instance where calculated deflections exceed serv
achieve lower deflections by increasing the class of co
of elasticity, rather than by resizing members.
With this flexibility goes the responsibility for ensuring
production and subsequent site operations will enabl
specified requirements in service.
Typically concrete is specified by compressive strengt
characteristic compressive strength required. However
concrete are used that are not normally part of the corelate to both structural integrity and serviceability. B
of concrete structures, Part 1-1 General rules and rules for
these properties which are generally assumed to be re
strength, expressed either as the characteristic or the
using expressions which include one or other of these
This publication covers the background to the use of
structured to provide guidance on:
the range of concrete properties required in the de
how each property is determined in BS EN 1992-1
how the property can be measured.
how the measured value may be used in design.
options for modifying the value of the property.
The guidance is intended to provide design engineers
concrete behaviour, so that they can optimise the us
in their design.
Section 3 of BS EN 1992-1-1 gives principles and rule
1.1 Scope
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BS EN 1992-1-1 (Eurocode 2: Design of concrete struc
design of concrete structures and in table 3.1 gives re
mechanical properties of concrete for use in design. T
number of assumptions and in general will be conser
values will be appropriate; however, in some circumst
limit the design possibilities. Engineers who wish to t
concrete construction may therefore wish to look at identify where changes may be cost-effective. This ma
to use higher-strength concrete, when serviceability c
the design process.1 As an example, if a higher value o
spans could be increased without increasing thicknes
also lead to lower shrinkage and creep values.
Designers may therefore wish to specify a value highe
particular property and this guide provides informatiodesigner should, however, seek assurance from the co
that the concrete required to achieve the specified va
see Section 1.2.
In addition to compressive strength, the following me
used in some design procedures, and guidance is prov
targeted values may be achieved for normal-weight c tensile and flexural strength
bond strength
modulus of elasticity
tensile strain capacity
creep.
Table 3.1 of BS EN 1992-1-1 provides values for the pr
characteristics of concrete for a range of strength class
Table A1.
I ddi i i l i h d iff
1.1.1 Mechanical properties
1 1 2 Other properties
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The achievement of ductility in a structure2 is not cove
of concrete structures, the formation of plastic hinges
reinforcement will continue to take the load while the
cl 3.2.4 gives provisions for using reinforcement with
will also improve the ductility of concrete, but this is
and BS EN 1992-1-1.
Where the specifier wishes to establish if a particular
in design, he should first consult with the concrete su
available. However, it may be necessary to request an
supply) where the relationship between this property a
strength can be established. Such testing can take som
timetabled.
If the property values from the test programme have s
allow for a degree of uncertainty by building in a mar
version from the property values to an equivalent com
specification should then either be based on the com
priate the types of materials that are expected to pro
alternatively it should be agreed with the producer ththe required property.
Most of the test methods for other properties listed i
higher within-test coefficient of variation than for com
initial testing should be designed to establish the pro
strength only, and compressive strength should rema
supply based on this relationship.
In circumstances in which specified properties may re
normal range of production, it is advisable for the spe
with the concrete producer. In particular, the followin
Additional lead time may be required for the proc
d l d i
1.2 Practical aspects of
supply
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2. Assumptions underlying
Importantly, Eurocode 2 assumes that design and co
be subject to adequate supervision and quality co
be carried out by personnel having the appropriat
use materials and products as specified.
meet the requirements for execution and workman
2008), Execution of concrete structures, and its co
It is also assumed that the structure will be used in ac
be adequately maintained.
In addition, BS EN 1990, Basis of structural design, imp
using limit state principles. Limit states are states beyfulfils the design intent.
Ultimate Limit States (ULS) are associated with
failure, for example, through flexural failure, shear f
Serviceability Limit States (SLS) correspond to c
service requirements are no longer met, for examp
cracking or stress.
In design, both limit states are checked (or verified) a
relevant design situations. ULS calculations always us
calculations almost always use mean values.
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3. Compressive strength
The only engineering property of concrete that is rou
compressive strength. This has a relationship to most
provides the basis for estimating these.
It is important that the design strength of a structure
durability, fire design or structural design requiremen
design stage. This will avoid having to recheck and/or
consequence of an increased strength requirement to
example, from which there could be implications. As
strength as a result of going to a higher class of concr
ratio will need to be increased for crack control purpo
In BS EN 206-1: Concrete Specification, performanc
pressive strength is expressed as a strength class. BS
compressive cylinder strength fck
(based on 2:1 cylinde
It also provides the basis for expressions in BS EN 199
properties (for example, tensile strength, E-value, cre
precise values may be derived when necessary from te
test standard.
While the specified 28-day characteristic strength is th
there are situations where it may be appropriate to u
an instance includes where the structure will not be l
and the concrete is of a type and in a situation where
develop significantly beyond 28 days.
In addition, it may be necessary to know the strength
transfer of pre-stress, or for removal of props.
In the UK the compressive strength is tested using cu
Com
3.1 Strength class
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The design compressive strength of concrete, fcd
, acco
fcd
= cc
fck
/c
where
fck
= characteristic cylinder compressive streng
c
= partial (safety) factor for concrete
cc
= a coefficient taking account of long-term e
(which is reduced under sustained load) and
the way the load is applied.
Expression (1) is equivalent to the term fcd
= 0.67fcu
/
represented as fck,cube
). In each case the material safety
recommends that cc
= 1.
However, cc
is an NDP and the UK National Annex t
cc
should be 0.85 for compression in flexure and axia
(for example, shear, torsion and web compression s
be taken conservatively as 0.85 for all phenomena. Th
consistent with that of BS 8110 as shown in Figure 1 f
3.3 Design strength
Fre
uency
q
Mean =fcm
Characteristic fck
Design
= 0.85 / 1.5
f
fcd
ck
CYLINDER strength
Mean fcm, c
=
0 10 20 30 40
fck /1.5
(
Compatibledesign strength
BS 8110
BS EN 1992-1-1 f c
Figure 1Compressive strength definitions to BS EN
1992-1-1 and BS 8110 for strength classC30/37.
EC2 3.15
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3.4 Confined concrete
Com
Confinement of concrete results in a modification of t
Confinement can be generated by links or cross-ties ad
stresses. This results in an increased effective compres
strains as outlined in BS EN 1992-1-1, Clause 3.1.9. Th
expressions:
fck,c
= fck
(1000 + 5.0 2
/fck
) for 2
0.05fck
fck,c
= fck
(1125 + 2.5 2/f
ck) for
2> 0.05f
ck
where
2
is the effective lateral stress due to confinem
Mechanical properties are used to check serviceability
always related to the mean compressive strength and
simplicity, the mean strength is assumed to be the ch
(cylinder), equivalent to plus 10MPa in terms of cube
nature of the relationships between the mechanical pr
strength, the use of a margin of 8MPa (cylinder) and 1
and there is no justification for using a lower margin.
The target mean strength, fcm
, is also the value used t
intended to take account of the normal variability tha
This margin of 8MPa for cylinders is consistent with a
deviation (SD) of about 5MPa:
fck
= fcm
1.64SD, where 1.64SD = 8
Therefore
SD = 8/1.64 5MPa
The margin is 10MPa for cubes, which is equivalent to
6MP Thi i ll i hi h bili fTable 1
3.5 Target mean strength
EC2 3.24
EC2 3.25
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Numerous types of cement are available and in gener
assumed that the cement type will not affect the 28-
However, the cement type has a significant effect on
and other properties, and the concrete supplier should
development data. Alternatively BS EN 1992-1-1 exp
are given below. Appendix A, Table A2 provides detail
cements and combinations.
While design is usually based on the 28-day strength
gives an expression for the development of the mean
with time at 20C as follows:
fcm
(t) = [cc
(t)] fcm
wherefcm
(t) is the mean compressive strength at age td
where
s is a coefficient which depends on cement type= 0.20 for cement of strength classes CEM 42.5R,
= 0.25 for cement of strength classes CEM 32.5R,
= 0.38 for cement of strength classes CEM 32.5N
(where Class R = high early strength; Class N = no
early strength).
Usually the cement class will not be known at the des
should be assumed unless the following alternatives Where ground granulated blastfurnace slag (ggbs)
bination or where fly ash (fa) exceeds 20%, class N
Where ggbs exceeds 65% or fa exceeds 35%, Clas
C i h b i d f E i (4)
3.6 Development of
compressive strength with
time
cc(t) = exp {s[1 (28)0.5
]} tEC2 3.2
EC2 3.1
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Com
CEM 42.5RCEM 52.5NCEM 52.5 (Class R)
CEM 32.5RCEM 42.5 (Class N
CEM 32.5 (Class S)
1 10 Age (days)
1.4
1.2
1.0
0.8
0.6
0.4
0.2
0.0
Proportionof
28
-day
compressivestrength
R
N
N
Figure 2Rate of compressive strength development at
20C for different cement strength classes.
In reality there is a wide range of strength developme
If the designer has information that shows that the con
more rapidly, this information could be used, for exam
BS EN 1992-1-1 notes that the estimated strength de
not be used retrospectively to justify a non-conformi
The strength obtained using standard test specimens
the actual compressive strength in the structure. This
including the process of manufacture and curing whic
small test specimens. BS EN 13791Assessment of in-s
and pre-cast concrete components requires that the m
0.85 times the strength of standard specimens. This f
factor m and should not be confused with cc which
The rate of strength development in the structure its
type of concrete (mainly cement type and conten
concrete placing temperature
bi
3.7 Strength in the
structure
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10 10100 1000
Age (days) Age
1.8 1.8
1.6 1.6
1.4 1.4
1.2 1.2
1.0 1.0
0.8 0.8
0.6 0.6
0.4 0.4
0.2 0.2
0.0 0.0
Proportionof
28-
daycubestrength
Proportionof
28-
daycubestrength
1.5 m blocks 300 mm walls
CEMI
CEMIIIA (50% ggbs)
CEMIIB-V (30% fly ash)
a) b)
cube
Figure 3Strength development measured from cores. Examples of long-term strength development are sho
by testing 1:1 cores extracted from both 1.5m cubes a
and values are expressed as a proportion of the 28-da
strength of the CEM I concrete only marginally excee
one year, concrete using CEM IIIA was more than 20%
was more than 40% higher, indicating the long-term
cement types provided conditions are sufficiently mocontinue.
Computer models based on maturity calculations are a
development if necessary. The producer can provide ba
type, class and content, and the adiabatic temperatu
model is being used. The models assume that there is
continue without interruption and this is a reasonablafter casting. The validity of this assumption for longe
assessed on a case-by-case basis.
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4. Tensile strength
In design, tensile strength is used in both serviceability
for example:
In general, considerations of cracking, shear, punc
The evaluation of the cracking moment for prestre
The design of reinforcement to control crack width
early-age thermal contraction.
Developing moment-curvature diagrams and in th
calculation of deflection, higher tensile strengths l
lower deflection.
The design of fibre-reinforced concrete.
It is also used in the design of unreinforced concre
pavements.
It should be noted that increasing the tensile strength
For example, in the case of early thermal cracking, hig
increased minimum steel ratio to accommodate the
when a crack occurs. In addition higher strength norm
binder content and hence higher temperature rise an
Tensile strength is commonly defined in one of three
splitting strength or flexural strength. Values derived
Table 2.
4.1 How tensile strength is
dealt with in BS EN 1992-1-1
Mix designation C12/16 C16/20 C20/25 C25/30 C30/37 C35/45 C40/50 C45/55 C50/60 C55/6
Mean axial tensilestrength fctm
1.6 1.9 2.2 2.6 2.9 3.2 3.5 3.8 4.1 4.2
Table 2Values of tensile strength in relation to
strength class.
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The design tensile strength of concrete, fctd
, according
fctd
= ct
fctk
0.05
/c
where
fctk
0.05
= characteristic tensile strength of concre
c
= partial (safety) factor for concrete = 1.5
ct
= coefficient taking account of long-term
is an NDP with a recommended value o
In BS EN 1992-1-1, the term tensile strength refers t
under concentric tensile loading.
For normal structural uses, the mean tensile strength,
by the expressions:
Strength classes C50/60 fctm
= 0.30 fck
(2/3)
Strength classes > C50/60 fctm
= 2.12 loge
[1
Note that for strength classes C50/60 fctm
is derive
strength classes > C50/60 the tensile strength is deri
The direct tensile strength is a value that is rarely det
European or International Standard. However, where
by the tensile splitting test in accordance with BS EN
the tensile strength to be calculated from the tensile
fct
= 0.90 fct,sp
When using this approach, tests should be on concre
pressive strength, as this will result in the best estima
4.1.1 Tensile strength used in
design
4.1.2 Tensile splitting strength
EC2 3.16
EC2 Table 3.1
EC2 3.3
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The flexural strength is the higher of:
fctm,fl
= (1.6 h/1000) fctm
where
h is the total member depth in mm
or fctm,fl
= fctm
Rearranging Expression (11), the fctm
may be estimated
on a 100 100mm prism in accordance with BS EN 1
fctm
= fctm,fl
/1.5
BS EN 1992-1-1 provides expressions for calculating te
fctm
(t) = [cc
(t)]fctm
where
cc
(t) is defined in Expression (5)
= 1 for t < 28 days
= 2/3 for t 28 days.
Hence up to 28 days the development of tensile streng
strength. However, beyond 28 days the tensile streng
extent as shown in Figure 4.
4.1.4 Effect of age
CEM 42.5RCEM 52.5N
1.4
1.2
strength
Figure 4Rate of tensile strength development at 20C
for different cement strength classes.
EC2 3.23
EC2 3.4
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When estimating development of tensile strength, fo
risk of early-age cracking and the requirement for crac
recommends that tests should be carried out, taking
conditions and the dimensions of the structural mem
itself may not reflect directly the exposure conditions
member, but it may be possible to test specimens wi
In Figure 5, which shows the development of tensile s
restrained movement, the upper two lines show the t
the lower of these lines (fb) reflecting the 0.7 reductio
lower two lines show the induced early-age contract
The upper of the two lines (2b) shows the additional
It can be seen that in addition to the risk of restraine
cracking from long-term drying shrinkage after ten ye
effect of temperature which can be significant is not
StrengthMPa
4.0
3.0
2.0
1.0
0
1
2
Days
Years
1 2 3 5 7 10 14 28 56 100
0.5
T
h
en
t
sile
sreng
t
Tensile
stre
ss
T
Sus
Contractio
n +cre
Contraction stress+
Age
Figure 5Development of tensile strength and tensile
stress from restrained movement.
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Figure 6Location of the weakest link in (a) the
flexural test, (b) the tensile splitting test,and (c) the direct tensile test.
(a) Flexural Test
Weakest link in unde
(c) Direct tensile strength
W
(b) Splitting test
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Because of high test variability of tensile testing, it is r
be based on the measurement of compressive streng
information on the relationship between tensile and
concrete for comparison with that given in BS EN 199
Where information on the development of tensile stre
is sought, the test method needs to be agreed and th
either the tensile splitting test BS EN 12390-6, or the fl
reference method is used. Due to testing variability, at
should be tested at each age. To compensate for the la
ded that the result is presented as a mean value, rath
Depending on what the data are required for, the con
should be either:
those that are expected to give the target mean cotest value is then taken as the corresponding mea
those that are expected to give the characteristic c
test value is then taken as the corresponding chara
Depending upon the specific requirements it may be
decrease the tensile strength. For example, to resist c
desirable, but if cracking is likely to occur then the mi
reduced for a lower tensile strength. Factors which ha
are as follows:
Compressive strength: in general the tensile streng
pressive strength.
The relative volumes of cement paste and aggregate
Coarse aggregate type: concrete containing high-qtends to have higher tensile strength than concret
crushed flint gravels in particular may result in a lo
with the glassy flint surfaces.
Aggregate size: the tensile strength tends to be hig
d t th i i t f d
4.3 Some testing practical
advice
4.4 Factors influencing
tensile strength
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5. Bond strength
In reinforcement design, BS EN 1992-1-1 covers only
Knowledge of the bond strength of reinforcement is r
To establish anchor and lap lengths.
To enable crack spacing and crack width to be calc
BS EN 1992-1-1 provides information on bond in rela
bond stress is given by the expression:
fbd = 2.25 12fctd
where
fbd
is the ultimate (design) bond stress
1
is a coefficient related to the quality of the
the bar during concreting
= 1.0 for condition of good bond
= 0.7 for all other cases and for bars in struc
2
is related to bar diameter
= 1.0 for f 40mm (NDP)
= (140 f)/100 for f> 40mm
fctd
is the design tensile strength defined as:
fctd
= ct fctk,0.05
/c
where
c is the partial safety factor for concrete = 1.5
ctis a coefficient taking account of long-term
unfavourable effects resulting from the way
5.1 How bond strength is
dealt with in BS EN 1992-1-1
EC2 8.2
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where
c is the cover to reinforcement
f is the bar diameter
p,eff
is the ratio of the area of reinforcement to t
The coefficients 3.4 and 0.425 are the UKs NDPs
k1
is a coefficient which takes account of the b
= 0.8 for high bond bars.
The coefficient k1
has replaced the ratio fct
/fb
(= 0.67)
crack spacing in BS 8007. Other more significant chan
BS 8007, most notably a reduction in the effective are
the steel, have led to the required area of reinforcemen
reduced.
Observations of early-age cracking suggest that the rrally applicable, with occasional crack widths in exces
would be unacceptable to adopt a significantly less ro
mended in CIRIA C6606 that the factor of 0.7 (BS EN
where it cannot be shown that good bond exists) sho
value to 0.8/0.7 = 1.14 until experience with applicat
indicates that a value of 0.8 is acceptable.
Bond testing is covered by BS EN 10080. The test req
involves four-point bending of a test beam which con
bar in the tensile zone. This has replaced the previous p
force and slip is measured and the bond strength is c
stress at which a particular magnitude of slip occurs.
The bond strength is determined by the characteristi
concrete as follows:
F d f d b h j d ib h d
5.3 Measuring bond
strength
5.4 Factors influencing
bond strength
Mo
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Mo
6. Modulus of elasticity
The value of the modulus of elasticity, E-value, chose
analysis with regard to stiffness of members. For exam
deflection often the controlling factor in slab des
moment analysis
requirements for prestressed elements column shortening under load
stresses due to restrained movements.
Such movements are also influenced by creep which
There are two types of elastic modulus. The static m
deformation of a cylinder under an applied load, usua
The dynamic modulus is determined by resonance m
ultrasonic pulse velocity (UPV). The two test procedu
value of the modulus. Static modulus is the value usu
The E-value is the ratio between stress (load/area) an
length/length). As concrete is not a truly elastic mate
and strain is not constant. Three E-value conventions
the secant modulus
the tangent modulus
the initial tangent modulus (see Figure 7).
6.1 Definitions
Tangent
modulusInitialtangentmodulus
Secant
Stress
Figure 7Diagrammatic stressstrain relationships for
concrete.11
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These are all measurements of the static modulus. Th
approximately equal to the dynamic modulus and, by
low stress levels. The most generally useful measure is
1992-1-1 it is the secant modulus, Ecm, that is used in
In design, the secant modulus, Ecm
(in GPa), is derived
fcm
(in MPa), from the expression:
Ecm
= 22 [fcm
/10]0.3 GPa
In Figure 8 moduli derived from Expression (17) are se
c = 0 to 0.4fcm with quartzite aggregates. For limestonis reduced by 10% and 30% respectively and for basa
6.2 How E-value is dealt
with in BS EN 1992-1-16.2.1 Use of E-value in design
60
50
40
30
20
10
0
C12/16
C16/20
C20/25
C25/30
C30/37
C35/45
C40/50
C45/55
C50/60
C5 5
Compressive strength c
Modulusof
ela
sticity(GP
a)
Figure 8Modulus of elasticity in relation to
compressive strength class and aggregatetype.
Although not explicitly stated in BS EN 1992-1-1, Claus
aggregates may also be applied to concretes with sili
assumes that the designer knows the aggregate to be
EC2 Table 3.1
Mo
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Mo
Poissons ratio is also used in elastic analysis and in a
taken as 0.2 for uncracked concrete and 0 for cracked
The variation of modulus of elasticity with time is est
Ecm(t) = [fcm(t)/fcm]0.3Ecm
where Ecm
(t) and fcm
(t) are the values at an age of tda
28 days. The rate of development of modulus of elastic
that modulus develops more rapidly than strength in
ficant growth beyond 28 days. In addition the cemen
This is not surprising as the usually stiffer aggregate c
of the concrete and is therefore the dominant factor.
6.2.2 Variation with age
CEM 42.5RCEM 52.5NCEM 52.5 (Class R)
CEM 32.5RCEM 42.5 (Class N)
CEM 32.5 (Class S)
1 10
Age (days)
1.4
1.2
1.0
0.8
0.6
0.4
0.2
0.0
Proportionof2
8-daymodulus
28
R
N
N
Figure 9Rate of development of modulus of elasticity
at 20C for different cement strength classes.
Work is in progress within the European Committee fo
6.3 Measuring the E-value
6.3.1 Test methods
EC2 3.5
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The initial tangent modulus may be determined in
1. By undertaking ultrasonic pulse velocity (UPV) me
EN 12504-4. However, there is no procedure for c
initial tangent modulus. The procedure is covered
that this procedure will be included in the UK Nati
2. Measuring the dynamic modulus by means of a varia
for measuring the dynamic modulus ( initial tange
As deflection forms part of the serviceability limit sta
so the concrete mix proportions used for testing shou
compressive strength.
Care is needed when selecting a test machine to use in calibration for cube testing may not be suitable for
tend to be with high-capacity machines (heavy plate
seating is not free to rotate. The indication of a probl
large differences between the three strain readings.
When a measured E-value is being used, the designer
partial safety factor of cE
, say 1.1 in place of the norm
A safety factor cE
less than 1.1 is not recommended d
with the measured value and variability of production
There are a number of factors to be considered:
Compressive strength. While a higher strength lea
there is no direct proportionality. For example, to necessary to increase the strength by at least thre
a cost-effective solution.
Aggregate E-value. The aggregate comprises abo
stiffer than the cement paste. Hence the E-value of
h E l f h Fi 10 h h
6.3.2 Guidance on E-value
testing
6.4 Factors influencing
modulus of elasticity
Mo
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60
55
50
45
40
35
30
25
20
15
10
M
od
ulu
so
fe
las
ticit
y(C
oncre
te
GP
a)
C12/16 C20/25 C30/37 C40/50 C50/60 C60
Strength class
Figure 10The relationship between strength class,
aggregate E-value (and specific gravity) andconcrete E-value.
Mo
Mineral additions. The presence of either fly ash
reduced elastic deformations provided the design
than 28 days at 20C and conditions are such that
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7. Tensile strain capacity
The tensile strain capacity, ctu
, is the maximum strain
without a continuous crack forming. It is used in the
CIRIA C6606 to assess the risk of early-age thermal cr
width.
Tensile strain capacity of concrete ctu
is not dealt with
comprehensive review of published data14 a simple lin
between ctu
and the ratio of the tensile strength fctm
t
in compression) as follows:
ctu
= [1.01(fctm
/Ecm
) 106] + 8.4 microstrain
Simplifying this expression to:
ctu
= fctm
/Ecm
was found to provide a lower bound value for use in d
of ctu have been derived from estimates given in BS E(Section 4) and elastic modulus (Section 6) for each s
gate types.
Values estimated from BS EN 1992-1-1 apply under c
take account of sustained loading during an early the
1. a creep coefficient, which increases the tensile stra
2. a coefficient to take account of reduced capacity u
The net effect on ctu
is an increase of 23%6. Results o
Figure 11. To assess cracking at later life, ctu
may be d
applying age factors to fctm
and Ecm
, that is:
7.1 How tensile strain
capacity is dealt with in
BS EN 1992-1-1
Ten
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Ten
140
120
100
80
60
40
20
0
Straincap
acity(microstrain)
C12/16
C16/20
C20/25
C25/30
C30/37
C35/45
C40/50
C45/55
C50/60
C 5
Compressive strength cla
Figure 11Early-age (three-day) tensile strain capacity
under sustained loading.
There is no standard test for measuring tensile strain
measuring tensile strain capacity ctu
is to subject pris
measure the strain up to failure.15 Direct measuremen
conditions within a test specimen that are similar to
cracking - for example, stress rig tests subject a dog-b
cycle. During heating the concrete is allowed to expa
contraction. When the concrete cracks, the release of
used to derive the strain at failure. This may be comp
temperature change and hence, with a knowledge of
expansion), the restrained thermal contraction require
calculated.
Direct measurement of ctu generally requires a large monitoring equipment. An alternative approach is to
tensile strength fctm
and elastic modulus Ecm
.14
7.2 Measuring tensile strain
capacity
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8. Creep
Creep is time-dependent deformation (strain) under
load-induced deformations such as shrinkage, swellin
Creep strain is typically two to four times the elastic s
needed for several reasons:
To estimate long-term deflections in beams and lowalls. This may be important, for example, in esta
when fixing rigid, brittle partitions to a concrete fr
To estimate prestress losses.
To estimate stress relaxation and redistribution ov
reducing the risk and/or extent of cracking. Creep
stresses induced by other restrained movements, fo
contraction; or by loading.
St
ra
in
Figure 12Time-dependent deformations in concrete
subjected to a sustained load - change instrain of a loaded and drying specimen.11
Generally, creep depends on ambient humidity, the d
composition of the concrete. It is also influenced by t
first loaded and on the duration and magnitude of th
8.1 How creep is dealt with
in BS EN 1992-1-1
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The creep coefficient (, t0) is determined by the f
Relative humidity for indoor conditions (RH = 5
(RH = 80%). More creep occurs under dryer condi
Element geometry defined by a notional thicknes
Strength class.
Age at loading which affects the stress/strength
Cement class Slow, Normal or Rapid strength ga
Stress/strength ratio at loading Expression (21ratio of 0.45 based on the characteristic cylinder st
the stress exceeds this value, micro-cracking will ca
sions are provided in BS EN 1992-1-1 for taking th
In order to develop creep curves showing the develop
mative) of BS EN 1992-1-1 provides an expression whic
element size, the strength class and the age at loadinshown in Figure 13 for two examples:
a 500 1000mm precast bridge beam using C35/
loaded at 28 days;
an internal floor slab (50% RH) using C30/37 load
About 50% of the ultimate creep occurs during the fi
first few years. The coefficient of variation using the a
to be 20%.
Elastic Strai
Creep stra
500 x 1000mm beam, extern
250mm slab, internal
4.0
3.5
3.0
2.5
2.0
1.5
1.0
0.5
l+
creepcoef
ficient
Figure 13Estimates of creep coefficients, .
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There is currently no European standard test for creep
series, but a test is being developed for repair products
and uses 40 40 160mm prisms which makes it un
Work has started on an ISO test (ISO/ DIS 1920-9) a
standard stage.
ASTM C 512 provides a method of measuring the total
of concrete. While some standard conditions are defin
varied to obtain information relevant to a specific pro
are cast, two used for strength testing, two used for c
loading to determine the changes of strain without lo
and to autogenous shrinkage. The applied load shall n
pressive strength at the time of loading. Readings are t
then again 26 hours later, and then at defined intervone year. A procedure is given for calculating the cree
According to Brooks,17 the equipment for the ASTM C
researchers tend to use smaller, less expensive equipm
8.2 Measurement of creep
8.2.1 Test methods
35
30
25
20
15
10
5
0
Ef
fec
tivemo
du
lus
500 x 1000m
250mm slab
0 1 2 3 4 5 6
Age (years)
C35/45C30/37
Elasticmodulus
Figure 14Estimates of effective modulus, Ec,eff.
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Achieving representative drying conditions. Drying
ratio and it is not normally practical to vary the sp
take a worse case, or test at a different relative hum
parts of the section.
Achieving a representative temperature. In the nor
of structures, the effect of temperature is relativel
sidered for specific applications.
Continuing the test for a sufficiently long period topolation for the life of the structure. Gilbert16 has rev
for the shape of the creep coefficient versus time c
useful expressions. He also concluded that the exp
creep from 28-day creep test data were not reliab
recommended. Testing of concretes for nuclear pr
months was acceptable, representing about half a
log timescale.
Expression (1) of ASTM C 512 should be used to calcu
deformation at, say, 30 years. The expression may als
coefficient (as opposed to assuming it, as in BS EN 19
deformation by the measured elastic strain.
Factors affecting creep, other than those already inclu
are as follows:
Aggregate volume. As creep takes place in the cem
of the aggregates will reduce creep.
The type of cement is important if the age of load
more rapidly will have higher strength at the age o
ratio and a lower creep. However, where the stressand the environment is one where the strength wi
develop more strength after loading will have a low
why under some circumstances concretes contain
or CEM III (blastfurnace cement) tend to have low
Th f i f i ifi l
8.3 Factors influencing
creep
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9. Shrinkage
For design purposes, shrinkage is a combination of au
shrinkage. While it is recognised that shrinkage may o
state, these deformations are not considered within t
Knowledge of shrinkage is important for several reaso If shrinkage is restrained, cracking may occur and t
reinforcement to limit crack widths.
In prestressed concrete, shrinkage will result in los
In asymmetrically reinforced concrete, deflections
Axially loaded columns or walls may be subject to
Creep may be increased with increased shrinkage.
Autogenous shrinkage, ca
, occurs during early hydr
consumption of water during hydration, the hydratio
than the unhydrated cement and water. Historically,
structural concrete was assumed to be of low magnit
ignored in design. However the tensile strain capacity
100 microstrain, see Section 7, hence, in relation to thconcrete, even this small strain may be significant. BS
autogenous shrinkage occurs in all structural concret
hardening, BS EN 1992-1-1 recommends that it shou
new concrete is cast against hardened concrete, i.e. i
cracking.
In high-strength concrete with a low w/c ratio, the auhigher and may exceed the drying shrinkage.
Drying shrinkage, cd
, is caused by the loss of water fr
Generally this loss of water is from the cement paste
the main loss of water and contribution to the drying
9.1 Types of shrinkage
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The ultimate autogenous shrinkage is calculated from
strength and is given by the expression:
ca
() = 2.5(fck
10) 106
and at time, tdays, the autogenous shrinkage is:
ca(t) = ca() [1 exp ( 0.2 t0.5)]
Design values of autogenous shrinkage estimated usi
shown against age in Figure 15.
9.2.1 Autogenous shrinkage
220
200
180
160
140
120
100
80
60
40
20
0
0 50 100 150 20Time (days)
Autogen
ous
shrinkage(microstrain)
Figure 15Autogenous shrinkage in relation to strength
class.
9 2 2 D i g h i k g
EC2 3.11 and 3.13
EC2 3.12
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Some typical values for indoor and outdoor exposure
BS EN 1992-1-1 for a range of notional thicknesses ar
While the procedures in BS EN 1992-1-1 take account
of aggregate type. There is no recognition of the high
when certain aggregate types are used. However, wh
expected that the shrinkage of the aggregates would
There is no specific European or international standard
shrinkage. Measurement is particularly difficult as it m
500
450
400
350
300
250
200
150
100
50
0
250
200
150
100
50
00.01 0.1 1 10 100 0.01 0.1
Time (years) Tim
Dryingshrinkage(micros
train)
Dryingshrinkage(microstrain)
6 months 30 yrs
150mm
225mm
300mm
500mm1000mm
b) OUTDOORa) INDOOR
Figure 16Drying shrinkage for (a) indoor and (b)
outdoor conditions using C30/37 in sectionsof varying notional thickness.
9.3 Measurement ofshrinkage
9.3.1 Autogenous shrinkage
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Any drying shrinkage test on concrete will give the to
combined drying shrinkage and residual autogenous sh
normal-strength classes (up to C40/50), the compone
would be expected to be small (< 20 microstrain) but f
autogenous shrinkage may dominate. Hence, for high
for the autogenous shrinkage (which takes place up t
reading is taken) should be added to the drying shrinka
value for use in design.
As drying shrinkage is related to the serviceability limi
used for testing this property should be those that ar
compressive strength. If the drying shrinkage test use
interest, the values obtained in the short-term test ca
BS EN 1992-1-1 and the basic (unrestrained by reinfo
calculated. By assuming proportional changes, it is alshrinkage at other relative humidities.
Work has started on an ISO test (ISO/DIS 1920-8). T
standard stage and is based on an Australian test pro
The AS 1012.13 test method for measuring drying shr
prisms that are 285mm long. After 24 hours in the m
lime-saturated water for seven days at 23 2C, aftespecimen is measured to an accuracy of 0.001mm (t
stored in a chamber at 23 2C and 50 4% relativ
length readings being taken at regular intervals in the
The rate of drying shrinkage is a function of the speci
typical shrinkage value after eight weeks drying is 750
The drying shrinkage of aggregates is measured on coIn the UK, in areas where aggregates with high drying
a drying shrinkage limit of 750 microstrain on the agg
requirement, but they would be expected to take any re
The drying shrinkage obtained by this test should not be
b i f ) d i h i k i f h
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Other factors which may affect autogenous shrinkag
The use of a small proportion of lightweight aggre
example, replacement of 6% of sand20 will mainta
reduce auto-genous shrinkage).
There is limited evidence (summarised in referenc
be affected by the use of mineral additions. Likely
using CEM I alone expressed as weight of addition o
increased by 10% for every 1% of silica fume reduced in direct proportion to the mass perc
increased by 8% for every 10% of ggbs.
It is not recommended that these changes are use
autogenous shrinkage is desirable it may be appro
these options.
Drying shrinkage is caused by the loss of water from t
from the aggregate. In addition to the parameters inclu
the following factors will influence drying shrinkage:
The relative volume of the cement paste and aggr
volume will reduce shrinkage. This may be achieve
aggregate size. Increasing the aggregate volume fr
shrinkage by about 20%.16
The relative stiffness of the cement paste and agg
shrinkage of the cement paste, so the higher the E
the shrinkage.
Use of aggregates with a low drying shrinkage.
Use of plasticising admixtures to achieve the requir
increasing the cement content will reduce drying s
Use of special admixtures that either reduce or co
9.4.2 Drying shrinkage
T
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10. Thermal expansion
The coefficient of thermal expansion, c, of concrete
produced in concrete subject to a unit change in tem
microstrain per degree centigrade (/C). Values are t
occurrence of thermal strain has a number of design
The need to provide joints to accommodate the m The provision of tolerances for elements attached t
panels.
Design of reinforcement to control crack widths w
restrained. This may be of particular concern at ea
from the cement and additions (see Section 14) m
to about 50C, and subsequent contraction on co
cracking.6
The Eurocode states that unless more accurate inform
thermal expansion may be taken as 10 microstrain/
this may not be a conservative value.
10.1 How the coefficient of
thermal expansion is dealt
with in BS EN 1992-1-1
Coarse aggregate/rock group Thermal expansRock S
Chert or flint 7.413.0 1
Quartzite 7.013.2 1
Sandstone 4.312.1 9
Marble 2.216.0 4
Siliceous limestone 3.69.7 8
Granite 1.811.9 8
Dolerite 4.58.5 A
Basalt 4.09.7 7
Limestone 1.811.7 4
Glacial gravel 9
Sintered fly ash (coarse and fine) 5
Table 3Coefficients of thermal expansion of coarse
aggregate and concrete5,20.
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While in design c
is assumed to be constant for a pa
with both age and moisture content. Semi-dry concr
of thermal expansion than saturated concrete.17 It is i
undertaken under conditions that reflect the service en
in relation to the value obtained.
In-house methods have to be used. Typically, measurin
specimen that is placed on roller bearings in a water tuntil there is equilibrium of temperature, and a set of le
then heated to, say, 80C and kept constant until this
the specimen depth. A second set of readings is taken
expansion calculated.
When testing for early-age values, this may be achiev
(commonly 1m3 with 100mm polystyrene insulation o
couples and strain gauges. Both temperature and stra
calculated during cooldown.6
The concrete mix proportions for the test should be t
target mean compressive strength.
As aggregate comprises about 70% of the concrete v
on the coefficient of thermal expansion as shown in T
Reducing paste volume will lead to a small reduction in
but this change is significantly less than that achieved
10.3 Factors influencing the
coefficient of thermal
expansion
The
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11. Thermal conductivity
The thermal conductivity of concrete, c, determines
transported through it and hence the rate of heat los
design it may be necessary when estimating temperat
in some specific situations as follows:
Predicting early-age temperature rise and differen Estimating temperature differentials under transie
storage vessels that are regularly filled and emptie
Thermal conductivity is not dealt with in BS EN 1992
The measurement of thermal conductivity is address
general method for testing the thermal performance
the test involves imposing a temperature gradient th
achieve moisture stability and specimens are general
obtained will therefore be more representative of theto be used in early-age analyses, the measured value
There are three principal factors influencing the therm
1. The aggregate type.
2. The aggregate volume aggregate has a higher the
and water.
3. The moisture content as concrete hydrates and
by water empties and the conductivity reduces.
Published values of thermal conductivity vary conside
11.1 How thermal
conductivity is dealt with inBS EN 1992-1-1
11.2 Measurement of
thermal conductivity
11.3 Factors influencing
thermal conductivity
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12. Specific heat
The specific heat of concrete, cp, is required in the de
(through the expression D =c/c
p) used in thermal
concrete may vary from 0.75 to 1.17kJ/kgC.22 This is a
that the temperature rise associated with a particular
by as much as 20% from a mean value of about 0.9
therefore, that a representative value is used in early-a
based on heat generation from the cement.
Specific heat is not dealt with in BS EN 1992-1-1.
Specific heat is generally measured using calorimetrybe predicted with a reasonable degree of accuracy usvalues for the individual constituents.
Two factors in particular influence the specific heat o1. The aggregate type. Aggregate constitutes the larg
specific heat for rocks ranges from 0.8 to 1.0kJ/kgmay result in a 15% difference for concrete.
2. The water content. Water has a specific heat that mix constituents. Dealing with the water content heat differs for free water (4.18kJ/kgC) and bound
Therefore to calculate the specific heat for concrete, bound water need to be known and this is determine
method is described in CIRIA C660
6
and values derivedthermal analysis are given in Figure 17 for concretes ww/c ratios. Late-life values may be 510% lower.
12.1 How specific heat is
dealt with in BS EN 1992-1-1
12.2 Measurement of
specific heat
12.3 Factors influencing
specific heat
1.0Figure 17
The relationship between cement content, w/cratio and early age specific heat of concrete
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13. Fire resistance
Concrete is non-combustible and does not support th
smoke, toxic gases or emissions when exposed to fire
load. Not surprisingly, the European Commission has
fire designation, namely A1.
Concrete has a slow rate of heat transfer which makes
compartments, and under typical fire conditions con
Structural fire design is dealt with in BS EN 1992-1-2.
The effects of fire on concrete are loss of strength of th
surface. Loss of strength of concrete starts as a result o
the effect is modest up to about 300C, being of the
300C the strength loss is much more severe and at
50%.23 Due to the slow heat transfer through concre
limited to the surface zone and the section retains m
with most types of concrete but the severity depends u
class and the moisture content. Sometimes explosive s
in vapour pressure as water turns into steam. Spallingconcrete as its ability to relieve the vapour pressure r
the integrity of the remaining reinforced concrete is u
BS EN 1992-1-2 provides three methods of determinin
tabulated data (for member analysis only); simplified
analysis or parts of structures); and advanced calcula
including global structural analysis). In special cases fi
levels and resistance are calculated, may be used.
Information on fire resistance is given in BS EN 1992
13.1 The effects of fire
13.2 How fire resistance is
dealt with in BS EN 1992-1-2
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High-strength concrete is dealt with separately in Sec
information presented for three strength classes definUK National Annex as follows:
Class 1 C55/67 and C60/75
Class 2 C70/85 and C80/95
Class 3 C90/105.
The effect of temperature on the compressive strength
No distinction is made for aggregate type. High-stren
adversely affected by temperature.
Compressive s
Calcareo
Silic
Tensilestrength
Temperature (
Relativestrength
1.0
0.9
0.8
0.7
0.6
0.5
0.4
0.3
0.2
0.1
00 200 400 600 800
Class 1C55/67 & C60/75
Relativestrength
0.8
Class 3C90/105
1.0
0.9
0.7
0.6
0.5
0.4
0.3
0 2
Siliceous aggregate
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There is a vast database of concrete fire testing over m
rating of concrete members is based. Historically, lab
structural members which could be tested; however,
been performed at facilities such as the Building Rese
Cardington. Criteria for fire testing are based on main
restricting transfer of heat and smoke.
In most normal situations, concrete can be considere
that further enhancement is not necessary. For a few
ment of the fire protection or resistance may be requ
as follows:
Use of limestone aggregates rather than siliceous
Use of lightweight aggregate concretes. When dry
but laboratory tests indicate possible poor perform
fire begins.23
Calcium aluminate cement has a higher resistance
types. While this cement is widely used for non-st
refractory linings, there is still debate over its suita
local provisions need to be followed.
Recognition that high-strength, low-permeability c
some situations, structural considerations overridemay be little practical scope for reducing concrete
BS EN 1992-1-2 recommends the option of using n
polypropylene fibres. The mechanism is believed t
absorbed in the cement matrix, providing voids for
caused by steam build-up. However, further resea
mechanism.23
Notwithstanding the above recommendations, it sho
normal approach is to improve the fire resistance of an
concrete itself. The most widely used approach is to in
to use render and plaster coatings. Where the loss of
ifi i l l f h b id
13.3 How fire resistance ismeasured
13.4 Improving the fire
resistance of concrete
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14. Adiabatic temperature
For the control of early-age thermal cracking, a limit
rature rise of concrete or on allowable temperature diff
Compliance may require either appropriate concrete se
initial testing of the proposed concrete and/or some
which requires information on the heat generation of
Full-scale trials are generally expensive and the contr
producer to undertake some initial testing of the conc
temperature rise, i.e. the temperature rise under perfe
this condition is difficult to achieve and the concrete
of the adiabatic temperature rise.
CIRIA C6606 provides temperature rise data for a rang
the cement content and type, and a simple numerica
ture rise and thermal gradients in walls. The model us
as a basis for temperature prediction.
The control of early-age thermal cracking is dealt with
design of liquid-retaining and containment structures.
BS EN 1992-1-1, Section 7.3 for the design of reinforce
conditions of conti-nuous edge restraint, i.e. a wall on
determined in part by the magnitude of the restrained
on temperature rise and fall in relation to the concret
range of concretes and element sizes.
There are numerous tests that may be used to measu
14.1 The need for adiabatic
temperature rise data
14.2 How early-age
temperature rise is dealt
with in BS EN 1992-3
14 3 Measuring the
Adiabati
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per unit weight of cement (kJ/kg) based on the mass
calorimeter. The specific heat of the mortar is about 1
obtained using the semi-adiabatic test are shown in F
combinations.25
When generating data to make predictions of temper
is to test concrete using constituents and proportions
representative of, the mix to be used in practice. Whi
design stage, it is advisable, where thermal cracking i
soon as the concrete mixes have been established. O
may be required and this provides an opportunity to
Under conditions where a high temperature rise is ex
with a high cement content, or when placing at high appropriate to provide information on temperature r
a cube, commonly 1m3, which is insulated on all face
polystyrene.
0 10 20 30 40 0 10 200 0
10 10
20 20
30 30
40 40
50 50
60 60
70 70
80 80
Temperaturerise( C)
Te
mp
eraturerise( C)
Time (hours) Time (ho
CEM I
20% fly ash
35% fly ash
50% fly ash
Figure 20Semi-adiabatic test results for concretes
containing (a) fly ash and (b) ggbs24 (bindercontent = 500kg/m3).
(a) flyash (b) ggbs
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If it is necessary to reduce the temperature rise in-sit
available6 as follows:
Cooling the aggregates by spraying with water or
Using ice to partially replace mix water.
Using liquid nitrogen to cool the mixed concrete.
Using cooling pipes in the element to remove hea
Using low-insulation formwork to permit rapid he
temperature gradients are not critical).
In addition to reducing early-age temperature rise, th
to reduce the risk of thermal cracking:6
Using aggregate with a low coefficient of thermal
Using aggregate which leads to a high tensile strai
Reducing restraint by planning pour sizes and sequ
Reducing restraint by introducing full- or partial-m
Using high-insulation formwork or surface insulati
sections when temperature gradients are critical.
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15. Durability
Design for durability uses a deemed-to-satisfy approa
proportions and cover provided for a variety of expos
constituent materials are also specified or their prope
dations for the UK are provided in BS 8500 Part 1 wh
Standard to BS EN 206-1, which is in turn referenced8500-1 gives recommendations for an intended wo
years. However the UK National Annex for Eurocode
working life of 120 years for Category 5 structures wh
engineering structures. It can be assumed that the BS
also suitable for an indicative design working life of 12
Corrosion of reinforcement occurs when the protecti
environment in concrete is lost, either as a result of ca
Exposure conditions are categorised as follows:
X0 no risk of reinforcement corrosion or attack
XC reinforcement corrosion induced by carbona
XD reinforcement corrosion induced by chloride
XS reinforcement corrosion induced by chlorides
For each of these environmental actions and levels of
values are given for maximum w/c ratio, minimum st
content. BS 8500-1 provides limits specific to the UK
that it allows a trade-off between concrete quality an
BS EN 8500-1 gives four levels of freezethaw exposu
ment is the recognised means for resisting freezetha
required, typically in the range 35.5%, with the highe
a smaller maximum aggregate size Also limits are pla
15.1 Preventing
reinforcement corrosion
15.2 Preventing freeze
thaw damage
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BS EN 206-1 defines only three levels of chemical att
groundwater (XA1 to XA3). The XA action is redefined
exposure classes limiting values and test methods rec
significantly from UK practice. BRE Special Digest 126 c
actions including those for mobile groundwater, acids
recommends this BRE approach. Recommendations i
Design Chemical (DC) classes which take account of th
acidity, the mobility of the groundwater and the hydroguidance on additional protective measures (APM) th
BS EN 206-1 deals with alkalisilica reaction through
constituent materials shall not contain harmful ingre
be detrimental to durability. BS 8500-2 requires the
minimise the risk of potentially damaging ASR. Follow
is deemed to satisfy this requirement.
In addition to the deemed-to-satisfy prescriptive app
performance-based design methods for durability. Su
appropriate under a range of circumstances including the working life significantly exceeds 50 years
the structure is special, requiring a low probabilit
the environmental actions are particularly aggress
In adopting the performance-based approach based o
are proven and representative of actual conditions, a
criteria. When analytical methods are used these sho
that are representative of actual conditions.
15.3 Preventing chemicalattack
15.4 Avoiding alkalisilica
reaction
15.5 Performance-based
design for durability
The use of re
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16. The use of recycled agg
The UK aggregate industry optimises the use of recy
wider aim of sustainable development.
BS EN 206-1 notes that it does not include provision
suitability may be established on the basis of the gen
European Technical Approval, or national standards o
their use in concrete conforming to BS EN 206-1.
BS 8500-2 permits the use of RA and RCA (recycled
to specific requirements of BS 8500 and which, when
aggregates, meet the requirements of BS EN 12620. Tlimited to strength classes C40/50 and to less aggr
carbonation and the lowest levels of freezethaw and
contains a full specification for RCA but not for RA as t
robust general specification for every possible type of
A particular feature of both RA and RCA is a lower sp
aggregates. Oven-dried values may typically be 2.02
typically in the range 2.32.8 for primary aggregates.
higher absorption and less stiffness. Properties of con
factors should therefore be considered when RA or RC
modulus, creep and shrinkage, which are all influence
deflections and creep deformations are of importance
be considered carefully. It should also be appreciated t
combination with primary aggregate and any effects
to the relative proportions of the materials used.
16.1 Requirements of
BS EN 206-1 and BS 8500
16.2 Properties influenced
by the use of Recycled
Aggregate and Recycled
Concrete Aggregate
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References
1. GILBERT, R. I. Design properties of materials changes pr
2. BEEBY, A. Why do we need ductility in reinforced concr
No. 5, pp. 2729.
3. HARRISON, T. A. Formwork striking times criteria, pred
CIRIA, 1995, Report 136, ISBN 0 86017 431 X.
4. THE CONCRETE SOCIETY. In situ strength of concrete a
core strength and the standard cube strength. Camberley
Society, 2004, Project Report No. 3.
5. HARRISON, T. A. Early-age thermal crack control in concr
edition, ISBN 0 86017 329.
6. BAMFORTH, P. B. Early-age thermal crack control in con
revision to CIRIA Report 91, ISBN 0 86017 660 6.
7. RYLE, R. The influence of test machines on cylinder splittiNo. 77.
8. SHERIFF, T. The control of ready-mixed concrete using the
DoE requirements. Institute of Concrete Technology, 197
9. DHIR, R. K., TITTLE, P. A. J. and McCARTHY, M. J. Role of
durability of concrete. University of Dundee, 2001, cont
(CC 1629)).
10. DAVIDSON, R. J. Report on an investigation into the varia
Taylor Woodrow, 1987, Report No. 014H/87/3241.11. NEVILLE, A. M. Properties of Concrete. Longman, 1995.
12. BAMFORTH, P. B., PRICE, W. F. and FLEISCHER, C. C. Th
nuclear power station structures. Nuclear Energy, 1997,
13. IDE, J. M. Comparison of statically and dynamically dete
Proceedings of the National Academy of Sciences, 1936,
14. TASDEMIR, M. A., LYDON, F. D. and BARR, B. I. G. The te
of Concrete Research, 1996, Vol. 48, No. 176, Sept., pp.
15. SWADDIWUDHIPONG, S., LU, H. R. and LEE, T. H. Prob
concrete. 3rd International Conference on Concrete under
Canada, 1820 June 2001 (eds N. Banthai, K. Satai and
pp. 16021609.
16. GILBERT, R. I. Time effects in concrete structures. Amste
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BS EN 1990, Eurocode: Basis of structural design (includi
BS EN 1992, Eurocode 2: Design of concrete structures
Part 1-1 General rules and rules for buildings (includ
Part 1-2 General rules Structural fire design (inclu
Part 3 Liquid retaining and containment structures
BS EN 196-8, Methods of testing cement. Heat of hydrat
BS EN 196-9, Methods of testing cement. Heat of hydrat
BS EN 197-1, Composition, specifications and conformity
BS EN 206-1, Concrete specification, performance, pro
BS EN 1367-4, Tests for thermal and weathering properti
shrinkage. BSI, 1998.
BS EN 1770, Products and systems for the protection and
BS EN 10080 Steel for the reinforcement of concrete: w
European and other
national standards
23. CATHER, R. Concrete and fire exposure. InAdvanced co(eds J. Newman and Ba. S. Choo). 2003, ISBN 0 7506 5
24. WADSO, J.An experimental comparison between isother
and solution calorimetry for the study of cement hydration
No.1534-01, Technical Report 533, Tekniikantie 12.
25. DHIR, R. K., PAINE, K. A. and ZHENG, L. Design data for
University of Dundee, 2006, Research Contract No. CTU
26. BUILDING RESEARCH ESTABLISHMENT. Concrete in agg
Special Digest 1.
27. BUILDING RESEARCH ESTABLISHMENT.Alkalisilica rea
1999, Digest 330.
28. THE CONCRETE SOCIETY.Alkalisilica reaction; minimis
Camberley, The Concrete Society, 1999, Technical Repo
29. BAMFORTH, P. B. The derivation of input data for mode
exposure trials. Magazine of Concrete Research, 1999, V
30. WALEED, N. and CANISIUS, T. D. G. Investigation of the
engineering properties of concrete. 2006, WRAP Aggreg
31. ALDER, A. J. J. and ROBERTS, C. P. The use of recycled co
Crowthorne, Transport Research Laboratory, 2005, TRL
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BS EN 13791,Assessment of insitu compressive strength icomponents. BSI, 2007.
BS 1881-209, Testing concrete: recommendations for the
elasticity. BSI, 1990.
BS 4449, Steel for reinforcement of concrete: weldable r
BS 8007, Code of practice for design of structures contain
BS 8110, Structural use of concrete. Code of practice for
BS 8500-1, Concrete complementary British Standard and guidance for the specifier. BSI, 2006.
BS 8500-2, Concrete complementary British Standard
constituent materials and concrete. BSI, 2006.
DD ENV 13670-1, Execution of concrete structures. Com
PD 6687, Background paper to the UK National Annexes
AASHTO, TP 60-00 Standard test method for coefficien
concrete. AASHTO, 2004.
AS 1012.13-1995, Methods of testing concrete determin
samples prepared in the field or in the laboratory. Standa
ASTM C 157/C, Standard test method for length change
concrete. ASTM, 2006.
ASTM C 512, Standard test method for creep of concrete
ISO/WD 1920-5, Testing concrete Part X: Determinatiosamples prepared in the field or in the laboratory(draft).
ISO/WD 1920-9, Testing concrete Part Y: Determinatio
compression (draft).
International standards
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Appendix ATable A1
Extract from BS EN 1992-1-1 - Table 3.1.
25/30
C30/37
C35/45
C40/50
C45/55C50/60
C55/67
C60/75
C70
/85
C80/95
C90/105
Analyticalrelation
5
30
35
40
45
50
55
60
70
80
90
0
37
45
50
55
60
67
75
85
95
105
3
38
43
48
53
58
63
68
78
88
98
fcm=
fck
+8
(MPa
)
6
2.9
3.2
3.5
3.8
4.1
4.2
4.4
4.6
4.8
5.0
fctm=
0.3
0xf
ck
(2/3) C50
/60
fctm=
2.1
2In
[1+
(fcm
/10
)]
>C5
0/60
8
2.0
2.2
2.5
2.7
2.9
3.0
3.1
3.2
3.4
3.5
fctk,0.
05
=0
.7xfc
tm
5 %
f i
l
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Table A2Nomenclature and composition for cements
and combination typesa.
Broad designationb Composition
CEM I Portland cement
SRPC Sulfate-resisting Portland cement
IIA Portland cement with 620% fly ashground granulated blastfurnace slaglimestone, or 610% silica fumec
IIB-S Portland cement with 2135% groungranulated blastfurnace slag
IIB-V Portland cement with 2535% fly as
IIB+SR Portland cement with 2535% fly as
IIIAd, e Portland cement with 3665%ground granulated blastfurnace slag
IIA+SRe Portland cement with 3665%ground granulated blastfurnace slag
with additional requirements thatenhance sulfate resistance
IIIBe, g Portland cement with 6680%ground granulated blastfurnace slag
IIIB+SRe Portland cement with 6680%ground granulated blastfurnace slagwith additional requirements thatenhance sulfate resistance
IVB-V Portland cement with 3655% fly as
Keya There are a number of cements and combinations not listed in this table that may
Special Digest 12 for the sulfate-resisting characteristics of other cements and com
b The use of these broad designations is sufficient for most applications. Where a m
required, select from the notations given in BS 85002: 2006, Table 1.
c When IIA or IIAD is specified, CEM I and silica fume may be combined in the con
2000, Cl. 5.2.5.2.3.
d Where IIIA is specified, IIIA+SR may be used.
e Inclusive of low early strength option (see BS EN 1974 and the L classes in BS 85
f +SR indicates additional restrictions related to sulfate resistance. See BS 85002
g Where IIIB is specified, IIIB+SR may be used.
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Table A3Standard methods for measurement of
physical properties.
Property Standard tests Co
Compressive strength,cylinders and cubes
BS EN 12390-3
Tensile splitting strength BS EN 12390-6
Flexural strength BS EN 12390-5
Direct tensile strength No standards
Bond strength BS EN 10080 Ben
Static modulus of electricity
(secant modulus)
Standard BS EN test
under development
Tensile strain capacity No standards Maydivid
Dynamic modulus of elasticity( initial tangent modulus)
BS EN 12504-4
BS 1881-209
Thisof ufor tmodthatNatmea
( in
Creep No standard EN test.ASTM C 512-02ISO/WD 1920-Y
MeaMea
Autogenous shrinkage No standards
Drying shrinkage of concrete No standard EN test.ASTM C 157/CISO/WD 1920-X
Drying shrinkage of aggregate BS EN 1367-4 Tho
meadryi
Autogenous shrinkage No standards
Coefficient of thermalexpansion
No standards
Thermal conductivity BS EN 12667
Specific heat No standards
Adiabatic heat BS EN 196-9
~
CI/Sfb
UDC624.012.4.001.63
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Properties of Concrete for use in Eurocode 2
This publication is aimed at providing both civil and structural
design engineers with a greater knowledge of concrete
behaviour. This will enable the optimal use of the material
aspects of concrete to be utilised in design. Guidance relates
to the use of concrete properties for design to Eurocode 2
and the corresponding UK National Annex.
In the design of concrete structures, engineers have the flexibility to
specify particular concrete type(s) to meet the specific performance
requirements for the project. For instance where calculated
deflections exceed serviceability limits, the designer can achieve
lower deflections by increasing the class of concrete and the
associated modulus of elasticity, rather than by resizing members.
This publication will assist in designing concrete structures taylor-
made for particular applications.
CCIP-029
Published January 2008
ISBN 978-1-904482-39-0
Price Group P
The Concrete Centre
Riverside House, 4 Meadows Business Park,
Station Approach, Blackwater, Camberley, Surrey, GU17 9AB
Tel: +44 (0)1276 606 800
www.concretecentre.com
Phil Bamforth spent his early career managing construction
consultancy and research for Taywood Engineering, and has a wide
experience in concrete technology and construction both in the
UK and abroad. Now in private consultancy, supporting design and
construction activities in concrete, he has written numerous papers
related to concrete material performance.
Derek Chisholm is project manager for technical publications at
The Concrete Centre and has a background in concrete materials
technology.
John Gibbs is technical advisor for the European Ready-Mixed
Concrete Organisation (ERMCO). He has spent most of his career in
the ready-mixed, quarrying and construction industries.
Tom Harrison is technical director of the British-Ready Mix
Concrete Association and in that capacity chaired the committee
that produced Guidance to the Engineering Properties of Concrete
from which this publication has developed.
Recommended