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10/1/2013
1
Crack Control of Fibre Reinforced Concrete
Presenter Biography
• Dr. Izni Syahrizal bin Ibrahim
• Working in UTM since 1998
• Has been actively involved in the research of fibre reinforced concrete since 2008
• Published more than 30 technical papers in International journals and conference proceedings
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What is Fibre Reinforced Concrete?
Fibre Reinforced Concrete is concrete containing fibrous material which increases its structural integrity.
Contains short discrete fibres that are uniformly distributed and randomly oriented.
The concept of using randomly distributed fibres to reinforced concrete was pioneered in the USA.
Types of fibre: carbon fibre, steel fibre, glass fibre, synthetic fibre and natural fibre.
Types of Fibre
Carbon Fibre
Steel Fibre
Natural Fibre Glass Fibre
Synthetic
Fibre
What is Fibre Reinforced Concrete?
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Types of Steel Fibre
FLAT END
CRIMPED
STRAIGHT HOOKED
END
WAVY
TYPES OF STEEL FIBRE
The suitability of steel fibres depends on the required application
Application
1 Precast slab ready
to be assemble 2 Precast slab
installation
The main idea in this research is the use of steel fibre to replace BRC in the in-situ concrete floor slab
3 BRC fixing 4 Concrete topping
covered BRC
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Application
Utilization of steel fibres have somehow been accepted in the construction industry, but it is limited for light duty applications
Pavement
Car Park
Plastering
Shotcrete
Precast element
Why Steel Fibre?
With various types of steel fibres generated that differ in terms of size, shape and texture, this widens the scope of steel fibres itself, as fibres with different capabilities were found.
In most of the research, it is agreed that, an addition of randomly distributed steel fibres improve concrete characteristics in:
1. Delaying concrete
micro-cracks propagation
2. Restraining macro-cracks development
3. Enhancing concrete
ductility after formation of micro-cracks
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Why Steel Fibre?
Unreinforced Fibre reinforced
SFRC becomes common alternative in industrial flooring to prevent opening of micro cracks.
In concrete structures, crack growth due to loading and shrinkage occurs at fresh state.
Short steel fibre will function as a bridge by transferring tensile forces across the crack, hence, lower the stress concentration at the crack-end.
Why Steel Fibre?
Advantages in Replacing BRC with Steel Fibre
Reduce crack
propagation as soon as
microcracks appears
Reduce higher
dependency on foreign
workers
Increase the bearing
capacity of the slab
No problem with
concrete cover
Reduce slab thickness
Lapping in BRC
Replace BRC with SF
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Why Steel Fibre?
Shape Surface texture
Aspect ratio
Tensile Capacity
Grade of mechanical anchorage
Concrete strength
Water-cement
ratio
Factors influencing the
mechanical properties of SFRC
Related Works
Author(s) Type of
Steel Fibre
Asp
ect
Rat
io,
L/D
Vo
lum
e Fr
acti
on
, vf Specimen Size (mm)
General Regression Models for prediction of fct and ft Splitting
Tensile Test Flexural
Test
A. R. Khaloo et. al.
Hooked-End 58 0.5-1.5 150 300 cyl. 150 150 500
B. W. Xu et. al.
Straight Crimped
Hooked-End
55-80 0.5-2.0 150 300 cyl. 150 150 500
I. S. Ibrahim et. al.
Hooked-End 80 0.5-1.25
150 300 cyl. 100 100 500
J. Gao et. al. Rectangular 46 58 70
0.6-2.0 100 100
100 cube
100 100 400
J. Thomas et. al.
Hooked-End 55 0.5-1.5 150 300 cyl. 100 100 500
M. Ramli et. al.
Hooked-End 54 0.25-2.0
100 200 cyl. 100 100 500
P.S. Song et. al.
Hooked-End 64 0.5-2.0 150 300 cyl. 100 100 530
S. Yazici et. al.
Hooked-End
45 65 80
0.5-1.5 150 150
150 cube
100 100 600
21 ffcu BVAVff
B
cufAf )(
B
cufAf )(
DLBVVAff ffplain /1
CRIRIfBfAf cucu
2
ff CVBVAf
2
ffcu BVAVff
fCVDLBAf )/(
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Standard Reference
• ACI 544.1R-96
• ACI 544.3R-08
• ACI 544.4R-08
• ASTM C1116/C1116M
• JCI-SF
• RILEM TC 162-TDF
SFRC
• BS EN12350-2: 2009 – Slump
• BS EN12390-2: 2009 – Curing
• BS EN12390-3: 2009 – fcu
• BS EN12390-5: 2009 – ft • BS EN12390-6: 2009 – fct
Mechanical properties
Scope of Work
1. Hooked-end type steel fibre was used. The types of steel fibres were HE0.75/60 (SF60), HE0.75/50 (SF50), and HE0.55/33 (SF33).
2. The concrete strength fixed at C40.
3. The size of specimens for the material properties investigations were: Cube of 150 mm 150 mm 150 mm Cylinder of 150 mm diameter 300 mm height Prism of 150 mm 150 mm 750 mm length
4. Floor slab: 350 mm width 500 mm length 75 mm height
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Scope of Work
Research Methodology
Data sources were collected by carrying out experimental work at the Structure & Material Laboratory, Facuty of Civil Engineering, Universiti Teknologi Malaysia, Skudai, Johor
Steel Fibre Supplier
SF60 Oriental Housetop Sdn. Bhd.
SF50 Manufacturer X Sdn. Bhd.
SF33 Manufacturer X Sdn. Bhd.
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Research Methodology
Properties SF60 SF50 SF33
Appearance
Length, L (mm) 60 50 33
Diameter, D (mm)
0.75 0.75 0.55
Aspect ratio, L/D
80 67 60
Density (kg/m3) 7860 7860 7860
Tensile strength (MPa)
1100 1200 1250
Research Findings
0
10
20
30
40
50
60
0.00 0.25 0.50 0.75 1.00 1.25 1.50 1.75 2.00
SF60
SF50
SF33
Slu
mp
(m
m)
Volume Fraction, vf (%)
Max slump
Min slump
Workability test: Slump at fresh state
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Research Findings
Compression test: Design strength of 40 N/mm2
0
5
10
15
20
25
30
35
40
45
50
0.00 0.25 0.50 0.75 1.00 1.25 1.50 1.75 2.00
SF60
SF50
SF33
Cu
be
Co
mp
ress
ive
Stre
ngt
h, f c
u (N
/mm
2 )
Volume Fraction, vf (%)
Design strength
Research Findings
Compression test: Design strength of 40 N/mm2
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Research Findings
Splitting tensile test
0.00
1.00
2.00
3.00
4.00
5.00
6.00
7.00
8.00
0.00 0.25 0.50 0.75 1.00 1.25 1.50 1.75 2.00
SF60
SF50
SF33
Volume Fraction, vf (%)
Split
tin
g Te
nsi
le S
tren
gth
, f c
t (N
/mm
2 )
Research Findings
Splitting tensile test
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Research Findings
Flexural test
0.00
2.00
4.00
6.00
8.00
10.00
12.00
0.00 0.25 0.50 0.75 1.00 1.25 1.50 1.75 2.00
SF60
SF50
SF33
Volume Fraction, vf (%)
Flex
ura
l Str
engt
h, f t
(N/m
m2 )
Research Findings
Flexural test
0
20
40
60
80
0 1 2 3 4
Deflection,mm
Control mix
Load
,kN
0
20
40
60
80
0 1 2 3 4
Deflection,mm
HE0.75/60_0.50%
Load
,kN
0
20
40
60
80
0 1 2 3 4
Deflection,mm
HE0/75/60_1.00%
Load
,kN
0
20
40
60
80
0 1 2 3 4Deflection,mm
HE0.75/60_1.50%
Load
,kN
0
20
40
60
80
0 1 2 3 4
Deflection,mm
Load
,kN
HE0.75/60_2.00%
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Research Findings
Flexural test
SFRC Performance
Performance of SFRC can be estimated using the law of mixtures Contributed by three components:
(i) Concrete matrix, fc Vc (ii) Steel fibres, ff Vf (iii) Interaction between concrete-steel fibres, fc ff
𝒇𝑺𝑭𝑹𝑪 = 𝒇𝒄𝑽𝒄 + 𝒇𝒇𝑽𝒇 + 𝒇𝒄𝒇𝒇
where: fc is the concrete stress, ff is the fibre stress, Vc is the concrete volume fraction and Vf is the fibre volume fraction
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SFRC Performance
)/(001.0019.0127.22
DLVfVff fcufcuct
)/(001.0016.0278.22
DLVfVff fcufcut
)/(2
DLVCfVBfAf fcufcuSFRC
In general term:
Bending and Shear Test
First crack At failure
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Bending and Shear Test
0
40
80
120
160
200
0 2 4 6 8
Ap
plie
d L
oad
(kN
)
Mid-span Deflection (mm)
0-S1 0.25-S1 0.50-S2 0.75-S2 1.0-S1
Pcal = 174 kN
Bending and Shear Test
Failure Mode 1 Failure Mode 2
