D. KOCÁB et al.: EXPERIMENTAL ANALYSIS OF THE INFLUENCE OF CONCRETE ...
657–665
EXPERIMENTAL ANALYSIS OF THE INFLUENCE OF CONCRETE
CURING ON THE DEVELOPMENT OF ITS ELASTIC MODULUS
OVER TIME
EKSPERIMENTALNA ANALIZA VPLIVA UTRJEVANJA BETONA
NA RAZVOJ MODULA ELASTI^NOSTI V DALJ[EM ^ASOVNEM
OBDOBJU
Dalibor Kocáb, Monika Králíková, Petr Cikrle, Petr Misák,
Barbara Kucharczyková
Brno University of Technology, Faculty of Civil Engineering, Veveøí 95, 602 00 Brno, Czech Republic
kralikova.m@fce.vutbr.cz
Prejem rokopisa – received: 2016-08-08; sprejem za objavo – accepted for publication: 2016-12-13
doi:10.17222/mit.2016.248
The modulus of elasticity is one of the most important properties of concrete, especially during structural analyses of buildings.
It is, among others, an important parameter in the calculation of the concrete-element deflection or during the design of pre- or
post-tensioned structures. The modulus of elasticity is not a specific number. It is a property with a high variability of the final
values, which depend on the concrete composition (together with other factors). Some of the significant factors, which influence
the final value of the elastic modulus of concrete, are also the means and quality of its curing, especially at the early stage of its
setting and hardening. Apart from maintaining the temperature within the correct limits, it is important to focus on the moisture
content of concrete while it is being cured. The purpose of the experiment described herein was to determine the development of
the dynamic as well as static modulus of elasticity for structural concrete while using different curing methods. The experiment
used four series of beam specimens with nominal dimensions of 100 × 100 × 400 mm made from air-entrained and non-air-en-
trained concretes of the C 30/37 strength class. A half of the specimens in each series aged in laboratory conditions and the
other half was stored under water. Based on the evaluation of the experimental measurements, it can be said that the manner of
storage has a significant influence on the development and final values of the static and dynamic modulus of elasticity.
Keywords: concrete, curing, modulus of elasticity, compressive strength
Ena od najpomembnej{ih lastnosti betona je modul elasti~nosti. Njegovo poznavanje je {e posebej pomembno za strukturno
analizo stavb. To je, med drugim, pomemben parameter pri izra~unu deformacij betonskih elementov pred ali med oblikovanjem
prednapetih struktur. Modul elasti~nosti ni specifi~na {tevilka; je lastnost z zelo razli~nimi kon~nimi vrednostmi, ki so odvisne
od sestave betona (skupaj z drugimi dejavniki). Pogoji njegovega utrjevanja so zelo pomembni. Vplivajo na kon~no velikost
elasti~nega modula betona, zlasti v zgodnji (za~etni) fazi utrjevanja. Razen ohranjanja temperature v pravilnih mejah, se je
pomembno osredoto~iti na vsebnost vlage v betonu, medtem, ko se le-ta utrjuje. Namen opisanega preizkusa je bil dolo~iti tako
razvoj dinami~nega kot tudi stati~nega modula elasti~nosti konstrukcijskega betona, z uporabo razli~nih metod utrjevanja. V
preizkusu so bile uporabljene {tiri serije preizku{ancev v obliki nosilcev z nazivnimi dimenzijami 100 mm × 100 mm × 400
mm, izdelanih iz zra~no tretiranih in netretiranih betonov iz trdnostnega razreda C 30/37 (N/mm2). Polovica vzorcev v vsaki
seriji je bila starana v laboratorijskih pogojih, druga polovica pa je bila shranjena v vodi. Na podlagi vrednotenja eksperi-
mentalnih meritev, lahko re~emo, da na~in shranjevanja pomembno vpliva na razvoj in kon~ne vrednosti stati~nega in
dinami~nega modula elasti~nosti.
Klju~ne besede: beton, utjevanje, modul elasti~nosti, tla~na trdnost
1 INTRODUCTION
The recent development in civil engineering has been
the cause of concrete being subject to far stricter require-
ments than several decades ago.1,2 The compressive
strength is no longer the single governing parameter in
the design of concrete structures. Attention is paid to
other properties, which affect mainly the deformation of
the structural element in question and the knowledge of
their real values is more frequently sought and required.
Next to the very frequently discussed durability,3,4 these
properties include mainly deformation properties, among
which the most important is considered to be the
modulus of elasticity.5–8 The modulus of elasticity is one
of the most important physical properties, which charac-
terise a material. This applies to concrete as well,
especially when it comes to the structural calculations of
the structures sensitive to deformation.6,7,9
The development of new kinds of concrete, such as
self-compacting concrete (SCC), high-strength concrete
(HSC), ultra-high performance concrete (UHPC) or
freshly compressed concrete (FCC) pushes the boun-
daries of their material characteristics and properties and
thus also their usability in civil engineering.10–13 The
compressive strength can be significantly improved with
a simple addition of state-of-the-art admixtures and
additives; however, an improvement in the modulus of
elasticity is much harder to guarantee. This fact is visible
in a very interesting comparison of the relationship
between the compressive strength and the modulus of
elasticity as proposed by EC214 and the relationships
described in other sources.2
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UDK 620.16:666.97.035:67.017 ISSN 1580-2949
Original scientific article/Izvirni znanstveni ~lanek MTAEC9, 51(4)657(2017)
The concrete modulus of elasticity is not a con-
stant15–18; on the contrary, it is a property with a result
variability, which depends mainly on the composition of
the concrete in question. The resulting value of the
elastic modulus is influenced mainly by the type, frac-
tion and amount of coarse aggregate, while a decisive
factor is often the ratio of the coarse aggregate to the
total volume of cement paste. The value is also affected
by the type of admixtures, especially the air-entraining
ones, their content or the resulting w/c ratio.5,9,16,19 The
curing of concrete, especially during the setting and
early hardening, is another significant factor. Apart from
maintaining the correct thermal conditions during the
concrete manufacture, placement and curing, it is also
necessary to pay attention to the moisture conditions
after the concrete has been placed and while it ages.20,21
Especially during placements at high ambient tempe-
ratures, it is necessary to cure the concrete carefully for
the first few hours or even days in order to prevent rapid
water evaporation from the concrete’s surface, which can
result in the formation of microcracks not only on the
surface but anywhere inside it as well.
A lack of water, especially at an early age, has a criti-
cal impact on the overall advancement of hydration,
which is further reflected in rapid shrinkage; this is
typically the first cause of the microcracks forming
inside of a concrete element’s structure.22,23 These micro-
cracks further influence the development of physico-me-
chanical properties of the concrete throughout its ageing
and can greatly affect the durability of the whole con-
crete structure. It was demonstrated that curing time (not
only the curing method) also substantially influences the
resulting values of the concrete’s material properties.24,25
The composition, the water content, the curing method
and the time are interlinked throughout the whole dura-
tion of the concrete ageing and can be considered as
influential factors, which affect the final value of its
modulus of elasticity.21
Another aspect, which is reflected in the final value
of the modulus of elasticity, is the choice of the test
method for its determination. The methods commonly
used in civil engineering are the dynamic ones, e.g., the
ultrasonic-pulse velocity test, resonance or impact-echo
method6,26, and the static methods, such as the compres-
sive-strength test, flexural-strength test or modified-com-
pact-tension test (MCT).15,27–29 The result of the dynamic
tests is the initial tangent modulus of elasticity16 and it
reaches higher values than the elastic modulus obtained
with the static tests. The fact of the matter is that during
static tests, the loading and unloading reduce the sub-
sequent creep, which causes a change in the steepness of
the stress-strain curve. The static modulus of elasticity is
thus often called the secant and its values are lower.16
The resulting values of the modulus of elasticity ob-
tained by means of each of the dynamic methods are not
identical and this fact applies to the values obtained with
the static methods as well. Apart from the choice of
method, the final result is also influenced by the shape
and slenderness ratio of the specimen used (beam9 vs.
cylinder15) or its size.6 The issue of the modulus of elas-
ticity of concrete is, therefore, still open and topical.
One of the key factors described above is the method
of curing after concrete has been placed in a formwork.
Not only the method and quality of curing have an effect,
the curing time does as well. The longer and more inten-
sively concrete is cured, the higher is the chance of im-
provement in its properties, including the modulus of
elasticity. For this reason, the authors of this paper fo-
cused on a detailed analysis of the influences the method
and time of concrete curing have on its modulus of elas-
ticity.
2 EXPERIMENTAL PART
The purpose of the experiment described herein was
to determine the development of the elastic modulus of
concrete (this particular one was designed for the con-
struction of bridges) cured under different conditions.
Half of the specimens were immersed in water and the
other half was stored in standard laboratory conditions
with no direct contact with liquid water. The goal was to
analyse the influence of the method and the time of
curing on the development of the concrete’s elastic mo-
dulus and its final value. Apart from the static modulus
of elasticity, the concrete was tested for the dynamic mo-
dulus as well. Two non-destructive methods were used
for this purpose.
2.1 Test method
The experiment used the ultrasonic-pulse velocity
test and the resonance method for the determination of
the dynamic modulus of elasticity. The static modulus of
elasticity was determined by means of subjecting the
specimens to a cyclic compressive stress.
2.1.1 Ultrasonic-pulse velocity test
The principle of the ultrasonic-pulse velocity test is
the repeated releasing of ultrasonic impulses into the
sample and measuring the time T required for them to
travel through, which is then used for determining the
velocity of ultrasonic-wave propagation vL through the
concrete. This velocity is, to some extent, a matter of
consensus as the real distance the ultrasonic-pulse travels
is not precisely known (i.e., the velocity is calculated
with the measured time and the length of a specimen). In
the end, the dynamic modulus of elasticity is calculated
using Equation (1):
E D v
kcu L
= ⋅ ⋅ ⋅ −2 2
61 10 (1)
where Ecu is the dynamic modulus of elasticity in MPa,
D is the material’s bulk density in kg/m3, vL is the ultra-
sonic-pulse velocity in m/s and k is the dimensionality
coefficient.
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The dimensionality coefficient k equals 1 for a one-
dimensional environment and in the cases of two- and
three-dimensional environments, it depends on the value
of Poisson’s ratio μ, which can be determined by means
of the resonance method (as was done in the experiment
described here).
The velocity of the ultrasonic-wave propagation was
measured using 82 kHz transducers. The time, for which
the ultrasonic pulse travelled through each specimen was
measured longitudinally in three positions, as illustrated
by Figure 1. The ultrasonic-wave velocity was calcu-
lated for each position and the average of the results was
used as the velocity vL in the calculation of the elastic
modulus according to Equation (1). High-plasticity mod-
elling clay was used to ensure a sufficient acoustic
coupling between the transducers and the specimens.
Prior to the measurement of each specimen, the testing
instrument was calibrated using a calibration rod.
2.1.2 Resonance method
Every solid object vibrates upon a mechanical im-
pulse, which can manifest itself in several ways.
The dynamic material properties of a body with regular
geometry are evaluated using the natural frequencies of
longitudinal vibration fL, flexural vibration ff and tor-
sional vibration ft. Using the measured natural freq-
uencies, the dynamic moduli of elasticity EcrL of the
material under tension and compression (longitudinal
vibration) can be calculated according to Equation (2):
E L f DcrL L= ⋅ ⋅4
2 2 (2)
where EcrL is the dynamic compressive modulus of elas-
ticity in MPa, L is the specimen length in m, fL is the
natural frequency of longitudinal vibration in kHz and D
is the material’s bulk density in kg/m3, while Ecrf (from
flexural vibration) is obtained using Equation (3):
E c L f D
icrf f
= ⋅ ⋅ ⋅ ⋅0 0789
1
1
4 2
2. (3)
where Ecrf is the dynamic compressive modulus of elas-
ticity in MPa, c1 is the correction coefficient, L is the
specimen length in m, ff is the natural frequency of
flexural vibration in kHz, D is the material’s bulk
density in kg/m3 and i is the cross-sectional radius of
gyration of a specimen in m.
Each specimen was placed onto a soft pad and vi-
brated by a mechanical impulse produced by an impact
hammer as seen in Figure 2. The natural frequencies of
longitudinal fL, flexural ff and torsional vibration ft were
determined by means of an oscilloscope with an acoustic
emission (AE) sensor.
2.1.3 Method for the static modulus of elasticity
The principle of the test for determining the static
modulus of elasticity is cyclic loading of a specimen
while recording its longitudinal deformation. The speci-
men is first stressed with 0.5 MPa, after which the load is
gradually increased to one third of the expected value of
the compressive strength. The relative deformation at the
corresponding stress is recorded and the modulus of elas-
ticity is calculated with Equation (4):
Ec
a b
a b
= =
−
−




 

 
(4)
where Ec is the static compressive modulus of elasticity
in MPa, 
a is the upper loading stress in MPa, i.e., 1/3·fc,

b is the basic loading stress in MPa, i.e., 0.5 MPa, a is
the average deformation at the upper loading stress and
b is the average deformation at the basic loading stress.
In this experiment, the relative deformation was cal-
culated from the deformations measured using mechani-
cal strain gauges of 200 mm in length. Each specimen
was always loaded with two preloading cycles and one
reloading cycle, from which the value of the static mo-
dulus of elasticity was calculated using Equation (4).
The expected 28- and 90-day compressive strengths of
the specimens were determined from their cube com-
pressive strength and from the measured dynamic
properties. At the ages of 365 d and 730 d, the expected
beam compressive strength of the concrete was deter-
mined only from the measured values of the dynamic
moduli of elasticity.
After the test of the static modulus of elasticity Ec,
the 28-day beam strength of one specimen was deter-
mined in order to verify the chosen upper loading stress

a. The remaining specimens were left for the tests of the
elastic moduli carried out at later ages. The same
procedure was also performed at the ages of 90 d and
365 d. Thus, the static modulus of elasticity was per-
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Figure 2: Diagram of the test arrangement for determining the reso-
nance (natural) frequencies of a specimen; IH (impact hammer) indi-
cates the place of the mechanical impulse, S is the position of the AE
sensor, L is the measurement of longitudinal vibration, f is the mea-
surement of flexural vibration and t is the measurement of torsional
vibration
Figure 1: Diagram showing the arrangement for the test determining
the time of the ultrasonic-wave passage through a specimen; the ar-
rows indicate the positions, at which the measurement was performed;
R is the receiver, T is the transmitter
formed repeatedly with some of the specimens at diffe-
rent ages. However, it must be noted that the test beam
was always loaded only up to 1/3 of its maximum
compressive strength and thus Ec was only tested in
terms of elastic deformations. The total maximum num-
ber of the loading cycles per specimen was 12. This is a
low number and with the multiple means of loading, it
does not influence the final value of the static modulus of
elasticity.16
2.2 Material
Four series of beam- and cube-shaped specimens
were made for the experiment. The dimensions of the
beams were 100 × 100 × 400 mm and the cubes were
150 mm in size. All the specimens were made from a
concrete of the C 30/37 strength class taken from the
agitator trucks present at the construction site of the
bridge on Hradecká Street in Brno (Czech Republic).
Table 1 lists the concretes used for making each series,
their production dates and the parts of the bridge being
built when the samples were taken.
Table 1: Specimens, type of concrete, production date
Series Concreteformula
Concrete
ID
Concrete
type
Date of
casting
Part of
bridge
1 A A air-en-trained
17 March
2009 abutment
2 B B air-en-trained
1 May
2009
deck
beams
3 C C-1 not air-en-trained
23 May
2009
deck slab
(span 1)
4 C C-2 not air-en-trained
30 May
2009
deck slab
(span 2)
Table 2: Concrete compositions
Component
kg / 1 m3 of FC
Concrete
A
Concrete
B
Concrete
C
Cement CEM I 42.5 R
(Mokrá) 400 400 400
Aggregate 0–4 mm (Ledce) 700 700 700
Aggregate 8–16 mm
(Olbramovice) 669 669 669
Aggregate 11–22 mm
(Lomni~ka) 284 284 284
Water 172 172 172
Air-entraining admixture
(Sika Aer200) 0.60 0.30 -
Plasticiser (Sika ViscoCrete
5-800 multimix) 2.40 2.40 2.40
The first series of the specimens was made during the
construction of the bridge abutment. The second series
was made during the casting of deck beams, the third
specimen series was made when the deck slab of the
bridge’s span 1 was being cast and the fourth series of
the specimens was made during the casting of the deck
slab of span 2. Table 2 shows the composition of each
concrete. Concrete A was taken from two agitator trucks;
all the other concretes were sampled from three trucks.
Fresh-concrete (FC) properties were always determined
prior to the moulding of the specimens; their values are
shown in Table 3.
Table 3: Fresh-concrete properties (the air content was not determined
for concrete C as it was not air-entrained)
Concrete Agitatortruck
Slump test
(mm)
Air content
(%)
Bulk density
(kg/m3)
A
1 130 4.5 2 240
2 120 4.2 2 270
B
1 120 3.7 2 290
2 120 4.1 2 280
3 110 3.3 2 320
C-1
1 140 - 2 330
2 140 - 2 320
3 110 - 2 340
C-2
1 160 - 2 330
2 150 - 2 340
3 150 - 2 330
Table 4: Division of the test beams from individual agitator trucks
(mixes) into test sets
Concrete A Concrete B Concrete C-1 Concrete C-2
Speci-
men Mix
Speci-
men Mix
Speci-
men Mix
Speci-
men Mix
A/N1 1 B/N1 1 C-1/N1 1 C-2/N1 1
A/N2 1 B/N2 2 C-1/N2 2 C-2/N2 2
A/N3 2 B/N3 3 C-1/N3 3 C-2/N3 3
A/N4 1 B/N4 1 C-1/N4 1 C-2/N4 1
A/N5 1 B/N5 2 C-1/N5 2 C-2/N5 2
A/N6 2 B/N6 3 C-1/N6 3 C-2/N6 2
A/S1 1 B/S1 1 C-1/S1 1 C-2/S1 1
A/S2 1 B/S2 2 C-1/S2 2 C-2/S2 2
A/S3 2 B/S3 3 C-1/S3 3 C-2/S3 3
A/S4 1 B/S4 1 C-1/S4 1 C-2/S4 1
A/S5 1 B/S5 2 C-1/S5 2 C-2/S5 2
A/S6 2 B/S6 3 C-1/S6 3 C-2/S6 2
All the specimens from each construction day were
placed onto a flat surface at the construction site, covered
with moist geotextile, sprinkled with water and then cov-
ered with PE foil to prevent drying. After three days of
curing, the current batch of the specimen was transported
to the laboratory at the Institute of Building Testing at
the BUT Faculty of Civil Engineering where they were
demoulded. The beams of each series were then divided
into two groups of six. The specimens from the first
group were marked as N1–N6 and were immersed in wa-
ter. The beam specimens from the second group were
marked as S1–S6 and were stored in a normal laboratory
environment with no additional water curing. The speci-
mens with the N identification (stored in water at
20±3 °C) represented the concrete that was being cured
for the entire period. The specimens bearing the S identi-
fication (stored in normal laboratory conditions, at an
ambient temperature of 20±3 °C, a relative humidity of
50±10 %) represented the concrete, the curing of which
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ended three days after it was cast. The assumption was
that the way the specimens were stored at the construc-
tion site during the first three days was to simulate the
concrete being thoroughly cured in the structure. The
specimens made from the samples taken from each agita-
tor truck were uniformly divided into individual sets (Ta-
ble 4).
Apart from the beams, 150-mm cube specimens were
also made for the purposes of determining the concretes’
compressive strengths. Similarly to the beams, the cubes
from each concrete were divided into two groups – N
(cured under water) and S (uncured). The compressive
strength was determined at the ages of 28 d and 90 d; Ta-
ble 5 shows the results.
Table 5: Cube compressive strength at the age of 28 d and 90 d in
MPa; each value represents the average of three specimens
Age 28 days 90 days
Concrete Curing Averagevalue
Sample’s
standard
deviation
Average
value
Sample’s
standard
deviation
A
N 41.0 0.57 45.6 0.25
S 41.5 2.06 41.2 2.55
B
N 46.4 3.12 48.1 8.70
S 50.3 1.68 52.0 4.16
C-1
N 51.7 3.44 60.5 1.56
S 52.4 1.55 57.7 2.19
C-2
N 49.2 3.80 58.1 1.26
S 50.5 0.55 54.2 3.59
The dynamic modulus of elasticity of the beams in
every series was determined by means of the ultra-
sonic-pulse velocity test (Ecu) as well as the resonance
test (ErcL from the natural frequency of the longitudinal
vibration and Ercf from the natural frequency of the flex-
ural vibration) at the ages of (3, 7, 28, 90, 365 and 730)
d. The beams were also tested for the value of their static
compressive modulus of elasticity Ec at the ages of (28,
90, 365 and 730) d.
3 RESULTS AND DISCUSSION
The dynamic modulus of elasticity of the 3-day-old
concrete of all the series was tested after demoulding,
i.e., before placing specimens N1–N6 in water and be-
fore placing specimens S1–S6 under laboratory condi-
tions with no contact with liquid water. For this reason,
the values of both sets (N and S) of all the series are al-
most identical. However, four days later, i.e., at the age
of 7 d, a positive influence of curing the concrete under
water is clearly visible. The dynamic modulus of elas-
ticity for the cured sets N increased more rapidly com-
pared to the uncured sets S. The concretes stored in
laboratory conditions were not protected against drying
in any way. In fact, massive water evaporation was
permitted by the design. A drop in the relative humidity
in the concrete pore structure influences cement hydr-
ation30 and simultaneously affects the mechanical
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Figure 4: Diagram of the progress of the average values of elastic
moduli for concrete B; the error bars indicate sample standard devia-
tions; a) set of cured specimens N; b) set of uncured specimens S
Figure 3: Diagram of the progress of the average values of elastic
moduli for concrete A; the error bars indicate sample standard devia-
tions; a) set of cured specimens N; b) set of uncured specimens S
properties of the concrete body.20 This explains different
increases in the dynamic elastic moduli of the cured and
uncured concretes. The trend is clearly visible on all the
concretes before the age of 28 d. The concrete stored in
water saw a substantially steeper increase in the observed
dynamic properties as opposed to the concrete stored in
the air; Figures 3–6.
Apart from the dynamic moduli of elasticity Ecu, EcrL
and Ecrf, the static modulus of elasticity Ec was also
determined at the age of 28 d. The cured concrete of all
the series reached higher values of the static modulus of
elasticity than the uncured concrete. However, the dif-
ferences between the average values of 28-day elastic
moduli of the individual test sets are not particularly
significant. The influence of curing was of the greatest
magnitude for the air-entrained concrete A, where the
difference between the values of the static elastic
modulus of the cured and uncured concrete was 12.8 %;
Table 6. The data was compared and the conclusions
were drawn using an analysis of variance (ANOVA) at a
significance level of 0.05.
There is a very interesting difference in the behaviour
of the cured and uncured concretes at the age of 28 d and
90 d. While the concrete stored under water still shows
an increase in the dynamic and static modulus of elastic-
ity, the case of the uncured concrete is different. The av-
erage 28-day values of both the static and dynamic
modulus of elasticity of the uncured concrete begin to
stagnate and subsequently even decrease. At the age of
90 d, the dynamic values of the uncured concrete S
dropped approximately to the values of the 7-day
uncured concrete of all the series. Comparing the results
of the 90-day dynamic elastic moduli of uncured con-
crete S with the results for cured concrete N at the age of
7 d, the values of concrete S are lower for all the series
(Table 6).
The fact that the uncured concrete S saw no continu-
ous increase in the observed properties (in comparison
with cured concrete N) can be explained with the lack of
water necessary for the cement to fully hydrate.20,30 The
rapid water evaporation from the surface of the concrete
specimens affects the progress and the magnitude of
concrete shrinkage. The stress created as a result of
volume changes in the concrete at its early age can lead
to the appearance of microscopic defects in the internal
structure of the concrete, which further affects the devel-
opment of its mechanical properties. A similar stagnation
in the material properties of the uncured concrete com-
pared with a cured one was also published by the authors
of papers24,25, where the parameter observed was the
compressive strength. Insufficient concrete curing was
also reflected in the final values of the elastic modulus at
the later ages of the concrete.
The dynamic moduli of elasticity of uncured concrete
S at the ages of 365 d and 730 d reach lower values than
those determined for the same concrete at the age 3 d
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Figure 6: Diagram of the progress of the average values of elastic
moduli for concrete C-2; the error bars indicate sample standard devi-
ations; a) set of cured specimens N; b) set of uncured specimens S
Figure 5: Diagram of the progress of the average values of elastic
moduli for concrete C-1; the error bars indicate sample standard devi-
ations; a) set of cured specimens N; b) set of uncured specimens S
(Table 6). The only exception is concrete C-2, for which
these values are at the same level. The reason for this
decrease is probably a change in the internal structure of
the concrete manifesting itself as micro-defects. It was
found that concrete drying causes its shrinkage, due to
which microcracks and microscopic defects form in its
internal structure.31 These microcracks further change
the mechanical properties of the concrete and damage its
quality, modulus of elasticity and durability.31–33
The issue of removing concrete from direct contact
with liquid water and the magnitude of shrinkage caused
by doing this are documented in references22,23,31,34. The
difference in the behaviour of the cured and uncured
concrete is better and more conclusively reflected in the
results of dynamic tests, which react to damage to the in-
ternal structure with a much greater sensitivity than static
compressive tests. Table 6 shows the differences bet-
ween the average values of both static and dynamic
moduli of elasticity; it shows the difference, in percent,
between the elastic moduli of cured concrete N and
uncured concrete S at the ages of 28 d and 730 d.
The dynamic elastic moduli determined by means of
the ultrasonic-pulse velocity test (Ecu) showed results
similar to those obtained with the resonance method (EcrL
and Ecrf); (Figures 3–6). Thus, the modulus of elasticity
measured with the ultrasonic-pulse velocity test (Ecu)
was chosen to represent the dynamic elastic moduli for
the overall evaluation of the behaviour of cured and un-
cured concretes as shown in Table 6. Figure 7 displays a
diagram constructed from the data. For the sake of clar-
ity, the diagram includes only two series of specimens –
the air-entrained concrete of series 1 (concrete A) and
the non-air-entrained concrete of series 4 (concrete C-2).
Concerning the air-entrained concretes A and B, the
differences between the 730-day dynamic moduli of
elasticity Ecu for the cured and uncured concretes are
36.5 % and 30.9 %. The differences between the static
moduli of elasticity Ec are 30.5 % and 24.9 %. The non-
air-entrained concrete C again shows a greater difference
in the dynamic modulus of elasticity at the age of 730 d
(26.7 % and 29.0 %), compared with the static modulus
of elasticity (19.9 and 19.8 %). In summary, the air-en-
trained concretes saw a greater decrease in the observed
parameters.
4 CONCLUSIONS
The experiment results show a positive influence,
which the curing method has on the concrete’s resulting
modulus of elasticity. The concrete cured under water
D. KOCÁB et al.: EXPERIMENTAL ANALYSIS OF THE INFLUENCE OF CONCRETE ...
Materiali in tehnologije / Materials and technology 51 (2017) 4, 657–665 663
MATERIALI IN TEHNOLOGIJE/MATERIALS AND TECHNOLOGY (1967–2017) – 50 LET/50 YEARS
Table 6: Average values of the static modulus of elasticity Ec and the dynamic modulus of elasticity Ecu determined by means of the
ultrasonic-pulse velocity test; at the ages of 28 d and 730 d, a percentage difference between the elastic moduli of the cured and uncured concrete
is calculated
Concrete
Type of
elastic
modulus
Set
Age (days) Difference at
the age of
28 d (%)
Difference at
the age of
730 d (%)3 7 28 90 365 730
A
Ec
N - - 25 800 28 400 29 600 29 500
12.8 30.5
S - - 22 500 22 200 20 200 20 500
Ecu
N 25 700 30 800 35 300 36 400 37 600 37 800
16.7 36.5
S 25 600 28 000 29 400 27 500 24 400 24 000
B
Ec
N - - 29 200 29 700 33 000 33 700
2.4 24.9
S - - 28 500 27 200 25 100 25 300
Ecu
N 30 800 34 700 37 700 40 100 41 400 42 100
9.5 30.9
S 32 400 33 500 34 100 33 000 28 900 29 100
C-1
Ec
N - - 31 200 33 000 34 600 35 100
4.5 19.9
S - - 29 800 29 200 28 600 28 100
Ecu
N 33 900 37 200 40 000 42 300 43 300 43 400
14.3 26.7
S 33 100 33 800 34 300 34 000 32 300 31 800
C-2
Ec
N - - 30 600 33 300 35 300 35 300
5.9 19.8
S - - 28 800 28 800 28 300 28 300
Ecu
N 31 900 36 700 40 700 43 400 44 700 45 500
13.8 29.0
S 32 100 34 200 35 100 35 200 32 300 32 300
Figure 7: Diagram showing the influence of concrete curing on its dy-
namic modulus of elasticity Ecu including the difference between the
resulting values
sees an increase in the value of both dynamic and static
modulus of elasticity over time. This trend continues at
much later ages as well (an age of 90 d or more). On the
other hand, the modulus of elasticity of the uncured con-
crete exposed to air demonstrably increases only during
the first 28 d and reaches lower values than the concrete
that was water cured. Between the ages of 28 d and 90 d,
the dynamic modulus of elasticity of the uncured con-
crete stagnates and begins to decrease. It was found that
the value of the static modulus of elasticity of the un-
cured concrete determined at the age of 730 d was lower
than the value measured at the age of 28 d. In fact, the
730-day value of the dynamic modulus of elasticity of
the uncured concrete was lower than the value measured
at the age of 3 d. The decrease in the properties of the
uncured concrete was significant. All the series of the
tested concretes exhibited a similar trend in the develop-
ment of the values of the elastic modulus over time for
the cured as well as uncured concrete.
Acknowledgement
This paper has been worked under the project No.
LO1408 "AdMaS UP - Advanced Materials, Structures
and Technologies", supported by the Ministry of Educa-
tion, Youth and Sports under the "National Sustainability
Programme I".
5 REFERENCES
1 H. S. Abdelgader, A. S. Elbaden, A. Diouri, N. Khachani, M. A.
Talbi, Concreting method that produce high modulus of elasticity,
MATEC Web of Conferences, (2014) 11, doi:10.1051/matecconf/
20141103012
2 C. H. Tsai, D. S. Hsu, Diagnosis of Reinforced Concrete Structural
Damage Base on Displacement Time History Using the
Back-Propagation Neural Network Technique, Journal of Computing
in Civil Engineering, 16 (2002) 1, 49–58, doi:10.1061/(ASCE)0887-
3801(2002)16:1(49)
3 T. Komarkova, M. Kralikova, P. Kovacs, Application of computed to-
mography in comparison with the standardized methods for deter-
mining the permeability of cement-composite structures, Mater.
Tehnol., 49 (2015) 4, 587–595, doi:10.17222/mit.2014.194
4 L. Pazdera, L. Topolar, J. Smutny, K. Timcakova, Nondestructive
Testing of Advanced Concrete Structure during Lifetime, Advances
in Materials Science and Engineering, 1–5 (2015),
doi:10.1155/2015/286469
5 H. Yýldýrým, O. Sengul, Modulus of elasticity of substandard and
normal concretes, Construction and Building Materials, 25 (2011) 4,
1645–1652, doi:10.1016/j.conbuildmat.2010.10.009
6 B. Lee, S. H. Kee, T. Oh, Y. Y. Kim, Effect of Cylinder Size on the
Modulus of Elasticity and Compressive Strength of Concrete from
Static and Dynamic Tests, Advances in Materials Science and Engi-
neering, 1–12 (2015), doi:10.1155/2015/580638
7 R. V. Silva, R. Vasco, J. De Brito, R. K. Dhir, Establishing a relation-
ship between modulus of elasticity and compressive strength of recy-
cled aggregate concrete, Journal of Cleaner Production, 112 (2016),
2171–2186, doi:10.1016/j.jclepro.2015.10.064.
8 M. Zhang, A. P. Jivkov, Micromechanical modelling of deformation
and fracture of hydrating cement paste using X-ray computed tomog-
raphy characterisation, Composites Part B: Engineering, 88 (2016),
64–72, doi:10.1016/j.compositesb.2015.11.007
9 Y. Zhou, J. Gao, Z. Sun, W. Qu, A fundamental study on compres-
sive strength, static and dynamic elastic moduli of young concrete,
Construction and Building Materials, 98 (2015), 137–145,
doi:10.1016/j.conbuildmat.2015.08.110
10 J. S. Park, Y. Kim, J. R. Cho, S. J. Jeon, Early-Age Strength of Ul-
tra-High Performance Concrete in Various Curing Conditions, Mate-
rials, 8 (2015) 8, 5537–5553, doi:10.3390/ma8085261
11 M. Dehestani, I. M. Nikbin, S. Asadollahi, Effects of specimen shape
and size on the compressive strength of self-consolidating concrete
(SCC), Construction and Building Materials, 66 (2014), 685–691,
doi: 10.1016/j.conbuildmat.2014.06.008
12 C. K. Ma, A. Awang, W. Omar, Flexural ductility design of confined
high-strength concrete columns: Theoretical modelling, Measure-
ment, 78 (2016), 42–48, doi:10.1016/j.measurement.2015.09.039
13 M. Nematzadeh, M. Naghipour, Compressive strength and modulus
of elasticity of freshly compressed concrete, Construction and Build-
ing Materials, 34 (2012), 476–485, doi:10.1016/j.conbuildmat.
2012.02.055
14 EN 1992-1-1, Eurocode 2: Design of concrete structures – Part 1-1:
General rules and rules for buildings, 1 Brussels, Belgium: Comité
Européen de Normalisation (CEN), 2008
15 M. Shariq, J. Prasad, H. Abbas, Effect of GGBFS on age dependent
static modulus of elasticity of concrete, Construction and Building
Materials, 41 (2013), 411–418, doi:10.1016/j.conbuildmat.2012.
12.035
16 A. Neville, J. Brooks, Concrete technology, 2nd ed., Harlow, Eng-
land, Prentice Hall, 2010
17 J. Newman, B. S. Choo, Advanced concrete technology: Concrete
properties, 1st edition, Amsterdam, Elsevier, 2003
18 A. Neville, Properties of concrete, 5th ed., New York, Pearson, 2011
19 N. Kockal, Validity and reliability of estimated modulus of elasticity
of cementitious materials, IOP Conference Series: Materials Science
and Engineering, 103 (2015), doi:10.1088/1757-899X/103/1/012024
20 B. Liu, W. Lv, L. Li, P Li, Effect of moisture content on static com-
pressive elasticity modulus of concrete, Construction and Building
Materials, 69 (2014), 133–142, doi:10.1016/j.conbuildmat.2014.
06.094
21 S. N. Shoukry, G. W. William, B. Downie, M. Y. Riad, Effect of
moisture and temperature on the mechanical properties of concrete,
Construction and Building Materials, 25 (2011) 2, 688–696,
doi:10.1016/j.conbuildmat.2010.07.020
22 M. Maslehuddin, M. Ibrahim, M. Shameem, M. R. Ali, M. H.
Al-Mehthel, Effect of curing methods on shrinkage and corrosion
resistance of concrete, Construction and Building Materials, 41
(2013), 634–641, doi:10.1016/j.conbuildmat.2012.12.064
23 A. S. Al-Gahtani, Effect of curing methods on the properties of plain
and blended cement concretes, Construction and Building Materials,
24 (2010) 3, 308–314, doi:10.1016/j.conbuildmat.2009.08.036
24 M. Uddin, M. Jameel, H. Sobuz, M. Islam, N. Hasan, Experimental
study on strength gaining characteristics of concrete using Portland
Composite Cement, KSCE Journal of Civil Engineering, 17 (2013) 4,
789-796, doi:10.1007/s12205-013-0236-x
25 B. Ozer, M. H. Ozkul, The influence of initial water curing on the
strength development of ordinary portland and pozzolanic cement
concretes, Cement and Concrete Research, 34 (2004) 1, 13–18,
doi:10.1016/S0008-8846(03)00185-6
26 X. Lu, Q. Sun, W. Feng, J. Tian, Evaluation of dynamic modulus of
elasticity of concrete using impact-echo method, Construction and
Building Materials, 47 (2013), 231–239, doi:10.1016/j.conbuildmat.
2013.04.043
27 H. Simonova, I. Havlikova, P. Danek, The effect of a superplasticizer
admixture on the mechanical fracture parameters of concrete, Mater.
Tehnol., 49 (2015) 3, 417-421, doi:10.17222/mit.2014.114
28 T. Holusova, S. Seitl, A. Fernández-Canteli, Numerical Simulation of
Modified Compact Tension Test Depicting of Experimental Measure-
ment by ARAMIS, Key Engineering Materials, 627 (2014),
277–280, doi:10.4028/www.scientific.net/KEM.627.277
D. KOCÁB et al.: EXPERIMENTAL ANALYSIS OF THE INFLUENCE OF CONCRETE ...
664 Materiali in tehnologije / Materials and technology 51 (2017) 4, 657–665
MATERIALI IN TEHNOLOGIJE/MATERIALS AND TECHNOLOGY (1967–2017) – 50 LET/50 YEARS
29 Ý. B. Topçu, Alternative estimation of the modulus of elasticity for
dam concrete, Cement and Concrete Research, 35 (2005) 11,
2199–2202, doi:10.1016/j.cemconres.2004.08.010
30 J. Newman, J. B. Choo, Advanced concrete technology: Concrete
properties, 1st edition, Amsterdam: Elsevier, 2003
31 Y. Wei, W. Guo, X. Zheng, Integrated shrinkage, relative humidity,
strength development, and cracking potential of internally cured con-
crete exposed to different drying conditions, Drying Technology, 34
(2015) 7, 741–752, doi:10.1080/07373937.2015.1072549
32 G. De Schutter, Hydration and temperature development of concrete
made with blast-furnace slag cement, Cement and Concrete Re-
search, 29 (1999) 1, 143–149, doi:10.1016/S0008-8846(98)00229-4
33 G. De Schutter, L. Taerwe, General hydration model for portland ce-
ment and blast furnace slag cement, Cement and Concrete Research,
25 (1995) 3, 593–604, doi:10.1016/0008-8846(95)00048-H
34 S. H. Alsayed, M. A. Amjad, Effect of curing conditions on strength,
porosity, absorptivity, and shrinkage of concrete in hot and dry cli-
mate, Cement and Concrete Research, 24 (1994) 7, 1390–1398,
doi:10.1016/0008-8846(94)90124-4
D. KOCÁB et al.: EXPERIMENTAL ANALYSIS OF THE INFLUENCE OF CONCRETE ...
Materiali in tehnologije / Materials and technology 51 (2017) 4, 657–665 665
MATERIALI IN TEHNOLOGIJE/MATERIALS AND TECHNOLOGY (1967–2017) – 50 LET/50 YEARS