Journal of Engineering and Development, Vol. 14, No.

2, June (2010) ISSN 1813-7822

The Effect Of Steel Fiber On The Deflection Of Self

Compacted Reinforced Concrete One Way Slab With And
Without Repairing

Dr.Ali Sabah AL-Amili Dr. Saad Khalaf Mohaisen Asst. Lect. Zena Waleed Abass
Civil Engineering Department, College of Engineering
Al- Mustansirya University, Baghdad, Iraq

Abstract:
The effect of steel fiber on the deflection of self- compacted slab with and with out
repairing was investigated experimentally in this study. Three specimens were used in this
study and six tests were taken. All specimens were tested under two point loads to found the
deflection of the slabs with and without repairing.

The results showed that, when used (0.2-0.5%Vf) steel fiber added to concrete the
deflection of the slabs decreases from (46% t0 43%) than slabs without fiber under the
same loads, since the steel fiber increased the tensile capacity for concrete. The results also
showed that the load capacity can be increased after repairing as compared with before
repairing to (5.3%, 9.6% and 17.6%)for slabs with (0,0.2 and 0.5% Vf)steel fiber
respectively. On the other hand the results was checked with finite elements method by
using sophisticated finite element programme (ANSYS) and it found that the result was
acceptable the difference was not more than 9%.

:‫الخالصـــــــــة‬
‫يدرس عملياددتأعحددالايعر اامدديعر ل ددحديع ددىعر ذريددرعميداعكوددرعر م اددتثعر قدلقييخاددتعر لهدديذتع مددرع ع ددرعح ديخ ددتع‬
‫يمدخهدثالعح نداعل لدتعللدتاتع دىعر م ادتثع قدرع‬.‫درسطتع ط تع هخطايتع دىعر ذريدرعحتمدجعميداعسدطخعر م ادتع درسدطتعر‬
‫للدددددداتعفحدددددتوعكذ ددددداىعر اع مدددددرعر خ ديدددددتع رع تدددددتلثع دددددرعر خ ديدددددتعكخ دددددمخعمدددددر عر اذد دددددتثعسدددددختعكذد دددددتثالعععععععععععععععععععععععع‬
‫جلاععفاهعر حلتاتعحخخميعملياتأع خهياطعدلياىع خهت ياىعمياعر م اتثعإليجت علهمتعر اورع دجد ع عمرمع جدد عر خ ديدتع‬
‫)عإ داعر قدلقييدجعر لي ددأعكدافعر اودرعكدثعر م ادتثع‬% 2‫ال‬0-2‫ال‬0(‫العأظ يثعر حختئجعرلهع إضتكتعلهمتعدجلاهع ىعر ااميع‬
‫فعر اامديعينيدرع دىع ت دتع‬.‫)ع تسلتع ت م اتع ر فعكاميعحذجعحالايعلاد عر دلدتاعر لهديطتلعا د ع‬% 64-%64(‫ي رع ىع‬
‫عخلتعحمعر خذ اقعكا تع حت وخ تال حظ ديع‬KFRC‫سخا ت اتع إل حعر خ ريعر لاقعر ذنمع ىع مرعشيرئخع‬.‫ر ورعر قدلقييجعال عحذلارعر طت تعر‬
‫)ع حهبعر اامديعر لضدت ع‬%6.‫ال‬4‫ع‬،6‫ال‬4‫عع‬،‫ع‬0‫ال‬4(‫ر حختئجعأيضتعرلهع ت تعر م اتثع ألدلتاعين ر عع رعح ديخ تعحن ر ع حهمتع‬
‫)عمياعر خدر ثععع ع ىعج تعأنيىعحمعحر اقعر حختئجع ععايي تعر حت يعر لذر ةع تسخ لتاع يلدت جعندتأع‬%2‫ال‬0،‫ع‬2‫ال‬0‫ع‬،2(
‫ع عفثعلهمتع مد تع ألغيرضعر لياتع دعع‬6%‫عحخجت زع‬.‫نخ ع‬.‫(عع ع رع جرعأفعر حختئجع مد تع علهمتعر‬ANSYS7.0)
.‫يرمتةعظي عر خجتسب‬

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Journal of Engineering and Development, Vol. 14, No. 2, June (2010) ISSN 1813-7822

1-Introduction:
Steel fibers are used instead of ordinary steel reinforcement or in addition to reinforcing
bars. Both under service and ultimate loading conditions, the fiber reinforcement is subjected
to resist tensile forces (1).

Steel fiber reinforced concrete is concrete containing fibrous material which increases
its structural integrity. It contains short discrete fibers that are uniformly distributed and
randomly oriented. The addition of steel fibers to concrete changes its mechanical properties.
Depending on the type and amount of fibers an increase in ductility and better cracking
behavior can be achieved (2). Fibers are usually used in concrete to control plastic shrinkage
cracking and drying shrinkage cracking. They also lower the permeability of concrete and
thus reduce bleeding of water. The amount of fibers added to a concrete mix is measured as a
percentage of the total volume of the composite (concrete and fibers) termed volume fraction
(Vf). Vf typically ranges from (0.1-3%). Aspect ratio (L/d) is calculated by dividing fiber
length (L) by its diameter (d). Increase in the aspect ratio of the fiber usually segments the
flexural strength and toughness of the matrix. However, fibers which are too long tend to ball
in the mix and create workability problems.

Steel fibers are manufactured in different types: hooked, undulated or flat, according to
the construction project (3)

2- Self-compacted concrete:
Self- compacted concrete was developed around 1988 in Japan, to improve the
durability of concrete structures. The early stage deteriorations of concrete structures are
results of the manual placing and the inadequate consolidation. Therefore, the need for
development of concrete with high fluidity and no segregation was felt. For several years, the
problem of the durability of concrete structures has been a major problem posed to engineers.
To make durable concrete structures, sufficient compaction is required. Compaction for
conventional concrete is done by vibrating. Over vibration can easily cause segregation. If
steel is not properly surrounded by concrete it leads to durability problems. The answer to the
problem may be a type of concrete which can get compacted in to every corner of formwork
and gap between steel, purely by means of its own weight and without the need for
compaction. The SSC concept can be stated as the concrete that meets special performance
and uniformity requirements that cannot always be obtained by using conventional
ingredients, normal mixing procedure and curing practices(4).

Its important to test whether the concrete is self-compactable or not and also to evaluate
deformability or viscosity for estimating proper mix proportioning if the concrete dose not
have sufficient self- compact actability.

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Journal of Engineering and Development, Vol. 14, No. 2, June (2010) ISSN 1813-7822

The existing procedures for self- compacting characteristics are those, which measure
height different points under free flow and also resistance against blocking. There is some test
to show whether the concrete is self- compacted or not these test are (5):

1- Slump flow Test for measuring flow ability.

2- V- Fannel Test.

3- U-Type Test.

4- L- Box Test.

5- Fill Box Test.

6- Ring Combination Test.

7- GTM segregation test.

8- Orimet\J-ring combination Test.

In our study,the V-Fannel, U-Type and L-box tests were used to found the content of
our mixtures.

2-1 Mix design:

Self- compatibility can be largely effected by the characteristics of materials and the mix
proportion. A rational mix design method for SCC using a variety of materials is necessary.
The mixed design as proposed is (6):

A- Coarse aggregate content is fixed at 50% of the solid volume,

B- Fine aggregate content is fixed at 40% of the mortar volume,

C- Water powder ratio in volume is assumed as 0.9 to 1.0 depending on

the properties of the powder,

D- Super plasticizer dosage and the final water- powder ratio are determined so as to ensure
compatibility.

The mix design is shown in Table (1).

3- Experimental work:

In this study, the effect of steel fiber on the deflection of self- compacted concrete slab
was studied using slab specimens with dimensions of (600x250 mm) with thickness of 70mm.
The slabs were reinforced with steel bars in two directions (in short direction ø4@145mmc/c)
and (in long direction ø4@115mmc/c)as shown in Figure (1).

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Journal of Engineering and Development, Vol. 14, No. 2, June (2010) ISSN 1813-7822

Three slabs were tested:

1/ Self- compacted concrete slab without steel fiber (SL1).

2/ Self- compacted concrete slab with {0.2% Vf} steel fiber added to

concrete mix (SL2).

3/ Self- compacted concrete slab with {0.5%Vf} steel fiber added to

concrete mix (SL3).

The slabs were repaired with a plate of dimensions (250*250) with 0.5mm thickness,
when the cracks were appeared on the surface of the slabs. The repairing plate was fixed on
the surface of the slab by epoxy as shown in Figure (2).

Table (1) Mix design used for self- compacted fiber reinforced concrete slab

Used materials Amount content

cement 550 Kg/m3

Coarse aggregate 832 Kg/m3

Fine aggregate 825 Kg/m3

Water/ cement ratio 0.21

Super plasticizer %from

weight of cement content
9.5%

Nine concrete cubes were tested to found the compressive strength for three slabs and
the average values for these cubes for slabs (SL1 to SL3) are shown in table (2) for twenty
eight days curing.

In all mixes, the cement was Ordinary Portland cement, Type I, which was
manufactured by United Company Cement factory/Iraq. Al-Ekhaider natural sand of
(4.75mm) maximum size was used as fine aggregate. while the coarse aggregate was crushed
gravel with max size of (19mm). The properties of the steel fibers added to concrete are listed
in table (3) while the properties of steel reinforcement and steel plate are listed in table (4) .
Twenty four hours after pouring, the slabs were stripped out from moulds and cured in water
containers for twenty eight days. Then the slabs were removed from the water containers and
then tested in a compression machine under two point loads as shown in Figure (3).

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Journal of Engineering and Development, Vol. 14, No. 2, June (2010) ISSN 1813-7822

The two point loads were applied gradually until the cracks were appeared. The slabs
(i.e. SL1 to SL3 ) were repaired with a repairing plate after the cracks were appeared on the
surface of the slabs and then the slabs were retained back to the compression machine and the
loads applied gradually until the slabs was failure. The gage of the machine was read the
deflection of the slab with every applied load.

Table (2) Compression strength of SCC tested slabs

No. of slab %Vf steel fiber Compression

content Strength Mpa

SL1 0% 34.85

SL2 0.2% 35.1

SL3 0.5% 37.7

Table (3) Properties of Steel Fiber

Property Specifications

Density 7860kg/m3

Ultimate strength 1130Mpa

Modulus of elasticity 200x103Mpa

Strain at proportion limit 5650x10-6

Average length 250mm

Normal diameter 0.4mm

Aspect ratio(L\d) 625

Table (4) Properties of Steel Reinforcement and Steel plate used for repairing
Name of Steel Dimensions Yield strength Modulus of Poisson's ratio
Part (mm) elasticity Mpa
(Mpa)

Steel Bar Diam ø4 420 200x103 0.3

Reinforcement

Repairing Plate 250x250x0.5 250 200x103 0.3

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Journal of Engineering and Development, Vol. 14, No. 2, June (2010) ISSN 1813-7822

10mm

70mm 250mm

600mm

Diam.4@145mm C/c Diam.4@115mmC/c

Fig. (1) Tested slab's dimensions and reinforcement.

600mm

250mm

Repairing plate (250x250mm)

Fig.(2) Tested slab with repairing plate

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Journal of Engineering and Development, Vol. 14, No. 2, June (2010) ISSN 1813-7822

P P

20cm 20cm 20cm

7cm

50cm

60cm

Fig.(3) Two point loads applied on the tested slabs with and without repairing
plate

4-Theioritical Work:

4-1 Finite Element Software:

A successful analysis of an engineering problem needs the existence of an efficient code

translation of the existing solution algorithm to be used by a digital computer. Finite element
solutions are good examples of the fact due to the required target memories and tedious
computations. For the present work purposes, it is sufficient to use a general pre-made
programme, since neither special circumstances are met nor special aims are to be
accomplished. On the other hand tables (5) represent the primary mesh for the case study in
this paper.

4-2 ANSYS 7.0:

In this work, the commercial program ANSYS 7.0 (7) is used to accomplish the finite
element solution. ANSYS 7.0 is an interactive finite element programme for the analysis of
linear and nonlinear structural systems.

Static and dynamic analyses are achieved by a combination of one, two and three-
dimensional elements. ANSYS 7.0 programme is capable of performing finite element
analysis using about 100 elements.

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4-3 Adopted Elements (7):

The present study adopts several elements to simulate the reinforced slab and repaired
slab as follows:

A- Solid 65 (Three- Dimensional Reinforced Concrete Element) :

This is used for the three- dimensional modeling of solids with or without reinforcing
bars (rebar). The solid is capable of cracking in tension and crushing in compression in
concrete applications, the solid capability of the element may be used to model the concrete
while the rebar capability is available for modelling reinforcement behaviour as shown in Fig
(4).(This element will be use for concrete and reinforced concrete parts).

P
O
5 6 4
M N
Z (reba
2
L r) Y 3
Z
X  1 K
I Y
J
X

Fig.4 Solid65 three-dimensional reinforced concrete element

B- Shell 43:
This is well suited to model linear warped, moderately- thick shell structures. The
element has six degrees of freedom at each node: translation in the nodal x , y , z directions
and rotations about the nodal x , y , z axes as shown in Fig. (5). The deformation shapes are
linear in both in-plan directions. This element will be use for steel plat using for repairing
parts).

Z L
Y
6
1 5
I X
 2
3 K
Z
4
J
Y

Fig.5 Shell 43 plastic large- strain element

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Journal of Engineering and Development, Vol. 14, No. 2, June (2010) ISSN 1813-7822

C- Contact 52 (Point-to- Point Contact):

This represents two surfaces which may maintain or break physical contact and may
slide relative to each other. The element is capable of supporting only compression in the
direction normal to the surfaces ad shear (coulomb friction) in the tangential direction. The
element has three degree of freedom at each node: translations in the node x , y , z directions
as shown in Fig.(6). This element will be use representing the interface between concrete and
reinforced concrete and the plate using in repairing parts (point to point contact element).

Z
J
X GA
Z
P
Y

Z
Y

Y
X
Z

Y Z

X
Y
X
X

Fig. 6 Contact 52 (3D) point-to-point contact element.

Table (5) Numbers of elements at primary mesh (Per one layer)

Numbers of elements per

Element type Location of element
one layer

Solid 65 Concrete and reinforced concrete part 150000

Shell43 Steel plat using for repairing 62500

Interface between concrete and plat

Contact52 10336
(point to point)

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Journal of Engineering and Development, Vol. 14, No. 2, June (2010) ISSN 1813-7822

5- Discussion of the Results and Conclusions:

The ultimate strength in flexure could vary considerably depending up on the volume
fraction of fiber, length and bond characteristics of the fiber and the ultimate strength of the
fibers. Depending up on the contributions of these influencing factors, the ultimate strength of
FRC could be either smaller or larger than its first cracking strength.

35.00

30.00

25.00
Load (KN)

20.00
slab before and after repairing

slab SL3
15.00 slab SL2
slab SL1
slab SL2 with rep.
10.00
slab SL1 with rep.
slab SL3 with rep.

5.00

0.00

0.00 0.50 1.00 1.50 2.00 2.50 3.00 3.50 4.00

Deflection(mm)

Fig. (7 ): Load-deflection curve before and after repairing.

35.00

30.00

25.00
Load (KN)

20.00

slabs before rep. (test and program)

15.00
slab SL3 (test)
slab SL3 (program)
10.00 slab SL2 (test)
slab SL2 (program)
slab SL1 (test)
5.00
slab SL1 (program)

0.00

0.00 0.50 1.00 1.50 2.00 2.50 3.00 3.50 4.00

Deflection (mm)

Fig(8) Load- deflection curve for slabs before repairing (Test and Programs)

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Journal of Engineering and Development, Vol. 14, No. 2, June (2010) ISSN 1813-7822

30.00

25.00

20.00

Load (KN)

15.00
slabs after rep. (tests and program)

slab SL3 (test)

slab SL3 (program)
10.00
slab SL2 (test)
slab SL2 (program)
slab SL1 (test)
5.00
slab SL1 (program)

0.00

0.00 0.50 1.00 1.50 2.00 2.50

Deflection (mm)

Fig(9) Load- deflection curve for slabs after repairing (Test and Programs)

The load deflection curves for slabs shown in Fig.(7) were nearly linear up to {11kN}.
The strengthening mechanism in this portion of the behavior involves a transfer of stress from
the matrix to the fibers by interfacial shear. The imposed stress is sheared between the matrix
and the fibers until the matrix cracks at which was termed as "first cracking strength". After
the first cracks stage the repairing plates were fixed on surface of the slabs as shown in Fig
(2) , the slabs were retained back to the testing machine and the two point loads were applied
on the surface of slabs gradually.

With increasing loads, the fibers tends to gradually pull out from the matrix leading to a
nonlinear load- deflection response until the ultimate flexural load capacity for slabs(sl2, sl3)
were reached. This point is termed as "peak strength". A post peak descending portion
following the peak strength until complete failure of the composite. The load – deflection
response in this portion of behavior and the degree at which loss in strength is encountered
with increasing deformation is an important indication of the ability of the fiber composite to
absorb large amount of energy before failure and is a characteristic that distinguishes fiber-
reinforced concrete from plain concrete.

This characteristic is referred to as "toughness". From the load-deflection curve shown

in Fig. (7 ), it is shown that:

1- when used 0.2% S.F. in slab (SL2), the load capacity in this slab increased by (8.8%) than
(SL1), while deflection decreased to (46%). The deflection in slab (SL3) when 0.5% S.F.
used, decreased to (43%) than slab(SL1) for the same load failure. .

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Journal of Engineering and Development, Vol. 14, No. 2, June (2010) ISSN 1813-7822

2- The patterns given the same behaviors after repairing, since the deflection decrease in slab
(SL2) by (45.4% ) than SL1 after repairing in both slabs, and load capacity in slab (SL3)
increased to (12.5% ) than (SL1) after repairing in both slabs, while the deflection
decreased to ( 38.6% ) for the same load.

3- The results are shown that the steel fiber increase the load capacity and decrease the
deflection. Since, the steel fiber increased the tensile capacity for concrete.

4- The repairing for slabs (SL1 to SL3) shown the load capacity can be increased after
repairing as compared with before repairing to (5.8%) in slab (SL1), (9.6%) in slab (SL2)
and (17.6%) in slab (SL3).

5- The behaviors of all cases of slabs in the initial loads in load –deflection curves shown in
Fig. (7) until (11 KN) , is same, after that each slab behavior depended on its properties
from steel fiber ratio.

6- From Fig (8) and Fig (9) , the results of deflections of various slabs samples is checked
with the results of finite elements with differences less than 9%. The difference in results
is due to the differences in adopting of material properties and structural supports fixing at
experimental and theoretical representations of samples.

Photos of The Experimental Work

Fig. (10) The Machine That To Be Used In The Work And The Tested Repairing
Slab (Structural Libratory In College Of Engineering In Al- Mustansirya
University)

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Journal of Engineering and Development, Vol. 14, No. 2, June (2010) ISSN 1813-7822

Fig (11) The Machine Applied Load On The Slab (Structural Libratory In College
Of Engineering In Al- Mustansirya University)

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Journal of Engineering and Development, Vol. 14, No. 2, June (2010) ISSN 1813-7822

Fig (12) Deflected Slab

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Journal of Engineering and Development, Vol. 14, No. 2, June (2010) ISSN 1813-7822

Fig (13) Slab with Repairing Plat

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Journal of Engineering and Development, Vol. 14, No. 2, June (2010) ISSN 1813-7822

5- References:
1- Dr.Volker Henke, and Dr. Horst Folkner, "Steel Fiber Reinforced Concrete From Research
to Standards ", Concrete Structures Journal, Vol.6, No.4, May 2005 pp 394-414.

2- Tan, Kiang H. , saha and Mithun Kumar,"Ten- Year Study on Steel Fiber Reinforced
concrete Beams Under Sustained loads", ACI Structural Journal, Vol.91,No.4, May2005,
pp384-393.

3- Banthia, N. and Torttier, " Concrete Reinforced With Deformed Steel Fiber, Part: Bond-
Slip Mechanisms" ACI Materials Journal, Vol.91,No.5,September- October 1994, pp435-
446.

4- P. Kumar, " Self- Compacting Concrete: Methods of Testing and Design" Journal of
Advanced Concrete Technology, Vol.86,February 2006 ,pp.145-149.

5- Hajime O. Kamura and Masahiro Ouchi, " Self- Compacting Concrete" Journal of
Advanced Concrete Technology, Vol.1,No.1 ,April 2003, pp.5-15.

6- Jacob ,Hansen and Tomny Baek, " Self- Compacting Concrete Based on White Portland
Cement" Concrete Plant International World Wide, February 2006, pp.84-93.

7- Swanson Analysis Systems, Ansys- Engineering Analysis . Theoretical Manual (for Ansys
Revision 4.4), Swanson Analysis Systems, 1989.

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