Effect of fiber types on creep behavior of concrete

Prévia do material em texto

Construction and Building Materials 105 (2016) 416–422
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Construction and Building Materials
journal homepage: www.elsevier .com/locate /conbui ldmat
Effect of fiber types on creep behavior of concrete
http://dx.doi.org/10.1016/j.conbuildmat.2015.12.149
0950-0618/� 2015 Elsevier Ltd. All rights reserved.
⇑ Corresponding author.
E-mail address: zhaoqingxin@ysu.edu.cn (Q. Zhao).
Qingxin Zhao a,⇑, Junchao Yu b, Guoqing Geng c, Jinyang Jiang d, Xiaochen Liu a
aKey Laboratory of Mechanical Reliability for Heavy Equipments and Large Structures of Hebei Province, Yanshan University, Qinhuangdao, China
bHebei Research Institute of Construction & Geotechnical Investigation Co., Ltd., Shijiazhuang, China
cDepartment of Civil and Environmental Engineering, University of California, Berkeley, USA
d Jiangsu Key Laboratory for Construction Materials, Southeast University, Nanjing, China
h i g h l i g h t s
� We examined the creep of concretes with several typical fibers.
� The elastic modulus of fibers is the significant factor influencing concrete creep.
� Fibers with elastic modulus much higher than plain concrete can restrict creep.
� The creep behavior of FRC has a clear correlation with its 28 days elastic modulus.
a r t i c l e i n f o
Article history:
Received 17 August 2015
Received in revised form 26 November 2015
Accepted 22 December 2015
Available online 28 December 2015
Keywords:
Fiber reinforced concrete (FRC)
Creep
Elastic modulus
a b s t r a c t
In this paper, the effect of fiber types such as steel fiber, polyvinyl alcohol (PVA) fiber, polypropylene (PP)
fiber and basalt fiber, on the creep of concrete after one-year-loading was studied and the principle of
fiber’s effect on concrete creep was analyzed. The elastic modulus of fibers is shown to be the most sig-
nificant factor influencing concrete creep. Fibers with elastic modulus much higher than plain concrete
can clearly restrict creep, while fibers with lower elastic modulus have the opposite effect. For example,
2% volumetric blending of steel fiber reduces specific creep by 25.1%, compared with plain concrete, while
0.9 kg/m3 mass blending of PVA fibers increases it by 19.9%. The internal defects introduced by fiber addi-
tion, i.e., the fiber-concrete interfacial zone and non-uniform fiber distribution, weakens its creep resis-
tance. There is a clear correlation between the 28 days elastic modulus of fiber reinforced concrete (FRC)
and its long-term creep behavior, indicating that they are influenced by similar factors. Larger elastic
modulus at 28 days tends to yield less specific creep at 1 year.
� 2015 Elsevier Ltd. All rights reserved.
1. Introduction
Nowadays, increasing the use of supplementary cementitious
materials in concrete is a common approach to reduce carbon
emissions. Supplementary cementitious materials, such as ground
granulated blast-furnace slag and fly ash, as well as fiber and poly-
mer modification, have been widely used in concrete to improve its
workability and long-term performance [1–3]. Fiber reinforced
concrete is also widely used in many civil engineering applications
(e.g. industrial pavements, tunnel linings, marine structures,
earthquake-resistant structures, etc) [4]. With fiber addition, plain
concrete can be transformed from brittle into a pseudo-ductile
material, thus improving the resistance to crack formation and
propagation [5,6], impact toughness [7] as well as ductility [8].
Steel fibers are mainly used for crack control when ductile con-
struction is required [9]. Low volume fractions of steel fiber are
efficient in various applications, such as concrete slabs, tunnel lin-
ings and other concrete constructions [10,11]. Volume proportion
of 0.1% glass and polypropylene fibers is sufficient for plastic and
drying shrinkage cracking control [12,13]. Commonly used fibers,
for example steel fiber, polypropylene (PP) fiber, polyvinyl alcohol
(PVA) fiber and basalt fiber influence the creep behavior of con-
crete, which has important effect on concrete long-term deforma-
tion performance. Several authors have found out that fibers could
reduce creep and shrinkage [14,15]. Previous researches are
reported on the creep ability of various fibers reinforced concrete
(FRC). Mangat [16,17] and Zhang [18] concluded that the mixing
of steel fibers in concrete could decrease concrete creep. A model
was built to predict creep of steel fiber reinforced concrete (SFRC).
Chem [19] studied the influence of temperature and humidity on
the deformation performance of SFRC and discovered that steel
fiber can reduce the shrinkage and creep of cement-based material,
and lower the effect of temperature on concrete creep as well.
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Table 1
Chemical compositions and specific surface area of cement and fly ash.
Materials Chemical compositions (%) Specific surface area (m2 kg�1)
CaO SiO2 Al2O3 Fe2O3 MgO Na2O K2O MnO TiO2 P2O5 SO3 LOI*
Cement 63.7 20.3 4.83 3.25 3.28 0.03 1.28 0.12 0.33 0.12 2.67 3.26 350
Fly ash 7.50 49.1 32.5 4.78 0.80 0.51 1.88 0.08 1.49 0.23 0.58 1.60 390
* LOI = loss on ignition.
Q. Zhao et al. / Construction and Building Materials 105 (2016) 416–422 417
However in practical project, the increase of water–cement ratio,
in the hope of improving FRC’s workability, would increase its
creep. The creep of concrete would be increased by 20–40% when
adding PP fiber, but with the addition of silica fume the increase
of creep was only 5–10% [20]. All the studies above showed that
various kinds of fibers would have influences on concrete creep,
but few of them had deep analysis on the influencing mechanisms
of fibers on concrete creep. The loading term of experiments on
some of those papers was relatively short. In this paper, creep
behavior of FRC with four typical fibers and common dosages
was investigated. Total loading term was extended to one year,
and the mechanism of fibers’ influence on concrete creep was
analyzed.
2. Experimental
2.1. Materials
The cementing materials used in the experiment were the Portland cement and
fly ash, whose chemical component and specific surface area are shown in Table 1.
Continuous grading crushed limestone with the particle sizes of 5–25 mm and an
apparent density of 2780 kg/m3 was used as coarse aggregate. River sand with a
fineness modulus of 2.9 was selected as fine aggregate. A naphthalene water redu-
cer with a water-reducing rate of 30% was employed to guarantee fluidity and water
retention. The fibers used in the experiment included steel fiber, PP fiber, PVA fiber
and basalt fiber, whose physical and mechanical properties index are shown in
Table 2.
2.2. Experimental method
The water–cement ratio of plain concrete, named F0, was 0.45 and its substitu-
tional dosage of fly ash was w.t. 30% with respect to cement. The fiber volume frac-
tions of SFRC were 1%, 2% and 3%, with indexes of S1, S2 and S3. The fiber dosage of
polypropylene fiber reinforced concrete (PPFRC), named PP, was 0.9 kg/m3. The
fiber dosage of polyvinyl alcohol fiber reinforced concrete (PVAFRC), named PVA,
Table 2
Physical and mechanical properties of fibers.
Fiber Filament
diameter
(lm)
Length
(mm)
Tensile
strength
(MPa)
Density
(kg/m3)
Tensile
modulus
Ef (GPa)
Steel fiber 1000 50 800 7850 200
PP fiber 48 19 620 910 4.5
PVA fiber 15 12 1532 1280 30.7
Basalt fiber 15 18 4150–4800 2650 100
Table 3
Mix proportion and prism strength of concrete.
Sample
No.
Mix proportion/(kg/m3) fc/MPa
Cement Fly
ash
Water River
sand
Crushed
stone
Fiber
F0 273 117 175 695 1135 0 37.5
S1 273 117 175 695 1135 78.5 36.2
S2 273 117 175 695 1135 157 38.0
S3 273 117 175 695 1135 235.5 37.5
PP 273 117 175 695 1135 0.9 35.8
PVA 273 117 175695 1135 0.9 35.3
B 273 117 175 695 1135 1.5 38.0
was 0.9 kg/m3. The fiber dosage of basalt fiber reinforced concrete (BFRC), named
B, was 1.5 kg/m3. The specific mix proportions are in Table 3. Compared to the plain
concrete F0, 30 extra seconds of mixing time was applied to FRC, and its slump was
controlled within (100 ± 10) mm. To determine the ultimate strength, sample
dimension 100 mm � 100 mm � 300 mm was applied. To test the elastic modulus,
shrinkage and creep, sample size 100 mm � 100 mm � 400 mm was used. The
specimens were cured at 20 ± 1 �C and relative humidity (RH)P 95% for 28 days
before creep experiment.
Concrete specimens with fiber were prepared with the mixture proportion in
Table 3 and were removed into the saturated calcium hydroxide to be cured to
the ages of 28 days. The interface microstructure of the interfacial zone of fibers
was investigated by SEM secondary electron imaging according to the method
described in the reference [21].
The concretes for testing shrinkage and creep had same sample size and cured
under the same environment. After concrete reach its curing age of 28 days, its
prism strength fc (as shown in Table 3) was tested according to the method
described in the reference [3] and 40% of fc was used as control load. According
to ASTM C512 [22], the experiment used spring creep loading device, and the con-
crete creep was tested by electrometric method which is a way to measure the
strain of components with resistance strain gauge, as well as the concrete shrink-
age. For the entire duration of the curing process as well as during the testing,
the environment was kept constant at (20 ± 2) �C and the humidity was controlled
at (60 ± 5)%. After loading for 1 day, 3 days, 7 days, 14 days, 28 days, 45 days,
60 days, 90 days, 120 days, 150 days, 180 days, 270 days and 365 days, the shrink-
age and creep of concrete were measured.
3. Analysis of the experimental result
The specific creep Ct is used to evaluate the creep ability of con-
crete in this paper. The calculation formula of Ct is shown as for-
mula (1):
Ct ¼ ðect � etÞ=r ð1Þ
where Ct is the specific creep at the age of loading for t days; ect is
the measured creep strain at the age of loading for t days; et is
the shrinkage strain of concrete of the same age with creep strain
and r is the loading stress.
3.1. The influence of steel fiber on creep of concrete
Evolutions of specific creeps of plain and SFRCs following the
increasing ages are shown in Fig. 1. The 1 year specific creeps of
the concretes are shown in Fig. 2. From Figs. 1 and 2, the specific
creep of all the SFRCs are less than that of plain concrete and the
reduction percentages are 10.1%, 25.1%, 15.5%. Steel fiber can
decrease the concrete creep while overdosage (from 2% to 3%)
might decrease the creep-resistance.
3.2. The influence of various fibers on creep of concrete
The specific creep curves of concrete with different fibers within
1a loading age are shown in Fig. 3. In Fig. 4, the 1 year specific
creep of various concrete is provided. The influence of different
fibers to the concrete creep ability varies. Compared with the 1a
specific creep of plain concrete, that of concrete with PP fiber is
slightly larger, that of concrete with PVA fiber is 19.9% up and that
of concrete with basalt fiber is 8.8% off while that of concrete with
steel fiber 10.1% off.
0 50 100 150 200 250 300 350 400
0
10
20
30
40
Ages after loading/d
F0
 S1
 S2
 S3Sp
ec
ifi
c 
cr
ee
p 
/×
10
-6
/M
Pa
-1
Fig. 1. Specific creep curves of plain concrete and steel fiber reinforced concrete.
F0 S1 S2 S3
0
10
20
30
40
Sample No.
Sp
ec
ifi
c 
cr
ee
p
/×
10
-6
/M
Pa
-1
Fig. 2. Specific creep of plain concrete and steel fiber reinforced concrete after one-
year-loading.
0 50 100 150 200 250 300 350 400
0
10
20
30
40
Sp
ec
ifi
c 
cr
ee
p 
/×
10
-6
/M
Pa
-1
Ages after loading/d
 F0
 S1
 PP
 PVA
 B
Fig. 3. Specific creep curves of plain concrete and concrete with different fibers.
F0 S1 PP PVA B
20
25
30
35
40
Sp
ec
ifi
c 
cr
ee
p
/×
10
-6
/M
Pa
-1
Sample No.
Fig. 4. Specific creep of plain concrete and concrete with different fibers after one-
year-loading.
S B F0 PP PVA
0
4
8
0.8
1.0
1.2
1.4
R
el
at
iv
e 
va
lu
e 
of
 sp
ec
ifi
c 
cr
ee
p 
R
el
at
iv
e 
va
lu
e 
of
 E
f
Sample No.
 Elastic modulus of fiber 
 Specific creep of concrete 
Fig. 5. Relative value of specific creep of concrete after one-year-loading and tensile
modulus of different fibers.
418 Q. Zhao et al. / Construction and Building Materials 105 (2016) 416–422
4. Influencing mechanism of fibers on concrete creep
4.1. The effect of the elastic modulus of fiber on the concrete creep
The relationship between the 1a specific creep of different FRC
and the elastic modulus of the added fiber Ef is shown in Fig. 5, dis-
played as specific values with respect to the elastic modulus of
concrete F0 (measured as 33.2 GPa). It follows the trend that when
the elastic modulus of fiber is much larger than that of plain con-
crete F0, its relative 1a specific creep is smaller than that of F0
and its ability to resist creep increases. However, when the elastic
modulus of the fiber is smaller than or the same with that of plain
concrete F0, the adding of fiber is a disadvantage to concrete to
resist creep.
The stress loading level of concrete in this experiment is 40%.
The strength of concrete will increase with the loading age and
therefore the real loading level drops slightly. In general, concrete
is at a relatively low stress level and are free from large cracks.
Fibers of different elastic modulus have different influence on the
deformation performance of concrete after load. Stiffer fibers can
better pin the microcracks of concrete and release the concentra-
tion of stress at the tip of the cracks. This increases the propagation
resistance of the cracks and limits the further deformation of the
concrete. Fibers with low elastic modulus can only expend energy
and increase concrete’s ductility by their relatively strong defor-
mation ability when the expansion of the concrete cracks is rela-
tively large. However they cannot improve the long-time
deformation of concrete under a low stress level. In a word, fibers
with elastic modulus larger than that of plain concrete can reduce
the deformation of concrete but fibers with low elastic modulus
can’t help with reducing creep. The experiment results in this
paper prove this theory.
What needs to be pointed out is that the elastic modulus of PP
fiber and PVA fiber are both lower than that of plain concrete, and
their 1a specific creep values are both smaller than that of plain
concrete. This satisfies the influence law of the elastic modulus
of fibers on concrete creep. But it can be seen from Fig. 5 that
the elastic modulus of PVA fiber is larger than that of PP fiber,
but the relationship between the resistance to creep of those FRC
is on the opposite, which indicates that the specific creep of FRC
is influenced by not only the elastic modulus of fiber.
Q. Zhao et al. / Construction and Building Materials 105 (2016) 416–422 419
4.2. The effect of concrete internal defects on the creep
Fibers increase the water pass ways inside concrete, and they
also increase the internal defects of concrete [23]. Loading state
causes the transportation and exudation of gel adsorbed water,
and then increases creep of concrete. The internal defects intro-
duced by fiber addition can be described in the following two ways.
One is the distribution characteristic of fibers. According to past
research, the inhomogeneous distribution of fibers will increase
the internal defects of concrete, which will cause weakness to var-
ious performances of concrete with no exception to concrete creep.
Fig. 6 shows the distribution characteristics of different FRC. It can
be concluded that compared with two other SFRCs, the fiber distri-
bution of S3 shows obvious characteristic of inhomogeneous,
which is of greatdisadvantage to the reduction of concrete creep,
verified by the creep value when steel addition increases from 2%
to 3%.
Another internal defect is the micro defect of concrete, espe-
cially at the fiber-concrete interface, due to the ‘‘wall-effect”
[24,25]. Fig. 7 is the SEM image of the interfacial zone of fibers with
cementitious matrix. It can be discovered that basalt fiber and steel
S1 S2
Fig. 6. Fiber distribution feature images of d
(a) BFRC (b) PP
(d) SFR
Fig. 7. Combination of vario
fiber bond better with concrete, however the bonding of the other
two organic fibers are not as dense, which increases the micro
defect of the interface. The creep experiment shows exactly the
same result that the two organic FRC resist creep poorer than the
other concrete. Besides, between the two organic fibers, the bond-
ing of PP fiber with concrete is worse, leading to less resistance to
creep. The comparison of the interfacial bonding of different fibers
with concrete better explains the result of creep experiment.
To verify the correlation between fiber-concrete interface and
the creep resistance, this paper calculates the area of the interfaces
of single specimen of various FRC according to relevant technical
parameters of fiber. The results are shown in Table 4.
Among the fibers, PVA fiber and PP fiber are both organic. Their
shape and size are at the same magnitude order and their volume
dosages are both relatively small. The elastic moduli of the two
organic fibers are both smaller than plain concrete. They are both
of disadvantages to the resistance of concrete creep. However,
the experiment shows that the difference between their weaken-
ing effect to the resistance of concrete creep are large and it has
been mentioned above that the creep law of the two fibers are
not determined by the elastic modulus of fibers.
S3
ifferent steel fiber reinforced concretes.
FRC (c) PVAFRC 
C 
us fibers with concrete.
Table 4
Fiber properties and area of interface layer in each concrete sample.
Sample
No.
Fiber volume
fraction (%)
Quantity
of fibers
Total
length/m
Area of interface
layer/m2
S1 1.000 1019 50.96 0.160
PP 0.099 115121 2187.30 0.330
PVA 0.070 1326964 15923.57 0.750
B 0.057 712165 12818.97 0.604
Table 6
The relative values of specific creep of all concrete after one-year-loading, prism
compressive strength and 28-day elastic modulus of all concrete.
Sample
No.
Specific
creep
Elastic modulus of
concrete at 28 days
Prism compressive strength
of concrete at 28 days
F0 1.00 1.00 1.00
S1 0.90 1.04 0.97
PP 1.02 0.99 0.95
PVA 1.21 0.95 0.94
B 0.91 1.03 1.01
S B F0 PP PVA
0.90
0.95
1.00
1.05
1.10
0.8
0.9
1.0
1.1
1.2
R
el
at
iv
e 
va
lu
e 
of
 sp
ec
ifi
c 
cr
ee
p 
R
el
at
iv
e 
va
lu
e 
of
 f c
Sample No
 Prism compressive strength at 28th day 
 Specific creep of concrete 
Fig. 8. Relative value of specific creep after one-year-loading and prism compres-
sive strength of concrete at 28 days.
1.05
1.10
1.1
1.2
ifi
c 
cr
ee
p 
 E
 Elastic modulus of concrete at 28th day 
 Specific creep of concrete 
420 Q. Zhao et al. / Construction and Building Materials 105 (2016) 416–422
It is discovered that the area of PVAFRC is the largest, which is
much larger than that of PPFRC. When considering the influence of
interface layer on increasing creep, PVA fiber has the worst effect
on concrete’s resistance of creep. This is in accordance with the
result of the experiment, which shows that the 1a specific creep
of PVAFRC is the largest of all and its ability to resist creep is the
worst. The above analysis shows that the conclusion of the increas-
ing of interface layer increases the concrete creep also works for
organic fibers. And it also explains that the difference in the ability
to creep of PVAFRC and PPFRC and their relationship.
In a word, the influence of fiber on the ability to restrict con-
crete creep is mainly shown in two ways: one is the influence of
elastic modulus, whose basic law is that fibers with elastic modu-
lus larger than that of plain concrete have the ability to resist con-
crete creep, and vice versa; the other is that the increased internal
defects caused by fibers will decrease concrete’s ability to resist
creep deformation.
5. Relationship between various parameters of FRCs and their
creep abilities
The analysis of the creep mechanism of FRC above shows that
fibers influence the creep of FRC by the elastic modulus and the
increasing of internal defects. And both of the two ways will reflect
on some of the macro nature of concrete such as its compressive
strength and elastic modulus and so on. So, it is necessary to study
the relationship between the macro nature of the concrete and its
creep ability, especially the elastic modulus of concrete. This paper
carries out the study below based on that.
5.1. Relationship between the parameters of FRC and their creep ability
The 28-day elastic modulus and compressive strength and the
elastic modulus of relevant fibers of different concretes are shown
in Table 5. All data are ratioed with respect to that of the plain con-
crete F0 without fiber.
Taking the creep, 28-day elastic modulus and compressive
strength of plain concrete as the unit 1, the relative values of speci-
fic creep of all concrete after one-year-loading, prism compressive
strength and 28-day elastic modulus of all concrete are shown in
Table 6.
The relationship between 28-day prism compressive strength fc
and the 1a specific creep of different groups of concrete is shown in
Fig. 8, from which we can conclude that the fc and 1a specific creep
Table 5
Prism compressive strength and elastic modulus of concrete at 28 days and tensile
modulus of fiber.
Sample
No.
Tensile
modulus of
fiber/GPa
Elastic modulus
of concrete at
28 days/GPa
Prism compressive
strength of concrete
at 28 days/MPa
F0 – 33.2 37.5
S1 200 34.5 36.2
PP 4.5 32.8 35.8
PVA 30.7 31.7 35.3
B 100 34.2 38.0
of concrete is probably correlated. The 1a specific creep of concrete
increase with the decrease of fc except for some individual concrete
(S1) and the ability to resist creep deformation of concrete
decreases accordingly. As for S1, its strength is lower than that of
plain concrete but its 1a specific creep is relatively large.
The relationship between the 28-day elastic modulus Ec and the
1a specific creep of the concretes are shown in Fig. 9. It can be seen
that Ec and 1a specific creep of the concrete are of good correlation,
which express in that the 1a specific creep gradually increases with
the decrease of the 28-day elastic modulus of the concrete and
concrete’s ability to resist creep deformation gradually decreases
with that. Recall that in Fig. 5, the relationship between 1a specific
creep and fibers’ elastic modulus Ef has already been discussed.
5.2. Relation between concrete parameters and their creep behavior
It can be seen from the above analysis that the 28-day elastic
modulus and compressive strength of the concrete and the elastic
S B F0 PP PVA
0.90
0.95
1.00
0.8
0.9
1.0
R
el
at
iv
e 
va
lu
e 
of
 sp
ec
R
el
at
iv
e 
va
lu
e 
of
Sample No.
Fig. 9. Relative value of specific creep after one-year-loading and elastic modulus of
concrete at 28 days.
(a) The 1a specific creep of concrete (b) Ec
(c) fc (d) Ef
Fig. 10. P–P plots of different parameters and specific creep of concrete after one-year-loading.
Q. Zhao et al. / Construction and Building Materials 105 (2016) 416–422 421
modulus of its relative fiber all have some regularity with the 1a
specific creep of the concrete.
Use the method of data statistics analysis to compare the rela-
tivity of the concrete parameters and its 1a specific creep. First,
the SPSS 16.0 software was used to analyze relative parameters
in normally distributed way and draw their P–P diagram in
Fig. 10. It can be shown that all the points in the diagram are close
to the strict line, which proves that the data basically goes with
normal distribution. Then, under the conditionof confidence level
a = 0.01, the Pearson simplified relative parameter q of the 1a
specific creep of concrete with its fc, Ec and Ef are calculated. The
calculation result is shown in Table 7.
By comparing the relative parameters q of 1a specific creep
with the concrete parameters in Table 7, it can be analyzed clearly
that the relative parameter of concrete’s 1a specific creep with the
Table 7
Correlation coefficient between different parameters and specific creep of concrete
after one-year-loading.
Parameters Prism compressive
strength of concrete
at 28th day
Elastic modulus
of concrete at
28th day
Elastic
modulus
of fiber
Sig. 0.235 0.004 0.223
Correlation coefficient q �0.650 �0.977 �0.662
elastic modulus of its 28-day elastic modulus is q = �0.997, Sig.
= 0.004. The result is clear and negative relativity can be drawn.
The relative parameters of concrete’s 1a specific creep with the
other two parameters are �0.650 and �0.662, which cannot pass
the experiment. It can be concluded by the analysis of the above
data and Fig. 10 that the 28-day elastic moduli of concrete are in
negative relationship with its 1a specific creep. Compared with
plain concrete, the higher the FRC’s 28 days elastic modulus, the
smaller its specific creep, and vice versa.
It is mentioned above that the creep of FRC is affected by multi-
ple perspectives of fiber. For FRC, all the influences can be reflected
in the 28-day elastic modulus of concrete, which is an indicator of
concrete’s ability to resist deformation after the mixing of fiber.
Based on that, it is possible to predict the long time creep ability
by comparing 28-day elastic modulus of FRC and plain concrete.
6. Conclusions
The influences of various types of fibers on FRC’s creep behavior
were studied. The mechanism of fiber’s influence on concrete from
both the elastic modulus of fiber and the internal defects of con-
crete was analyzed. The correlations between the physical param-
eters of FRC and its 1a specific creep were also studied. Several
conclusions can be drawn as follows:
422 Q. Zhao et al. / Construction and Building Materials 105 (2016) 416–422
(1) Fibers with elastic modulus far higher than plain concrete
can resist concrete creep. However, that with elasticmodulus
lower than that of plain concrete tends to weaken concrete’s
interface structure and therefore increase its creep.
(2) After addingfibers into concrete, the increased internal defect
of concrete will decrease its ability to resist creep. These
defects include non-uniform distribution of fibers and
defected interface between fibers and cementitious matrix.
(3) The creep of FRC depends on various factors, and the 28-day
elastic modulus of FRC is an indicator at macro scale. There is
a high negative correlation between 28-day elastic modulus
and 1a specific creep. Compared with plain concrete, the
higher 28-day elastic modulus of FRC, the lower its long-
term specific creep, and vice versa. Based on this, it is possi-
ble to predict the creep behavior of FRC by comparing its 28-
day elastic modulus with that of plain concrete.
Acknowledgements
Financial support from the Project 2015CB655100 supported by
China National 973 Plan, Project 51078322 supported by National
Natural Science Foundation of China (NSFC) and the Project
51578477 supported by National Natural Science Foundation of
China (NSFC) is gratefully acknowledged.
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	Effect of fiber types on creep behavior of concrete
	1 Introduction
	2 Experimental
	2.1 Materials
	2.2 Experimental method
	3 Analysis of the experimental result
	3.1 The influence of steel fiber on creep of concrete
	3.2 The influence of various fibers on creep of concrete
	4 Influencing mechanism of fibers on concrete creep
	4.1 The effect of the elastic modulus of fiber on the concrete creep
	4.2 The effect of concrete internal defects on the creep
	5 Relationship between various parameters of FRCs and their creep abilities
	5.1 Relationship between the parameters of FRC and their creep ability
	5.2 Relation between concrete parameters and their creep behavior
	6 Conclusions
	Acknowledgements
	References