Performance of Steel Fiber Reinforced Concrete under High Temperature and Impact Load from Direct Fire Weapon
Assc. Prof. Dr. Piti Sukontasukkul
King Mongkut University of Technology-North Bangkok
Thailand Concrete Association
Presentation Topic
Performance of SFRC subjected to high temperature
• Concrete under high temperature
• SFRC under high temperature
• Steel fiber vs. Other fibers
Performance of SFRC under impact loading
• Structure under attack
• Material behavior under impact loading
• Performance of SFRC under impact loading
Performance of SFRC under High Temperature
General Knowledge
To Stop Fire
• Turning off the gas supply, which removes the fuel source;
• Covering the flame completely, which remove the oxygen in the air and displaces it CO2;
• Application of water, which removes heat from the fire faster than the fire can produce it
• Application of a retardant chemical such as Halon to the flame, which retards the chemical reaction itself until the rate of combustion is too slow to maintain the chain reaction. Credit -
http://en.wikipedia.org/wiki/Fire
Temperature by Flame
Appearance
Temperatures of flames by appearance
Red
Just visible: 525 °C (980 °F)
Dull: 700 °C (1,300 °F)
Cherry, dull: 800 °C (1,500 °F)
Cherry, full: 900 °C (1,700 °F)
Cherry, clear: 1,000 °C
(1,800 °F)
Orange
Deep: 1,100 °C (2,000 °F)
Clear: 1,200 °C (2,200 °F)
White
Whitish: 1,300 °C (2,400 °F)
Bright: 1,400 °C (2,600 °F)
Dazzling: 1,500 °C (2,700 °F)
Credit - http://en.wikipedia.org/wiki/Fire
Behavior of Concrete Subjected to High Temperature
Pore pressure rises
Increasing compression stress at the heated surfaces
Internal cracking between agg. and paste
Cracking and spalling between paste and rebar.
Strength drop ?????
Expansion under Thermal Difference
Expansion of RC. Structure under High Temp. include
Expansion of aggregates
Expansion of cement paste
Expansion of rebar
Thermal Expansion Coefficient
Cement paste
11-16 x 10-6 /oC
Coarse aggregate
0.9-12 x 10-6/oC
Steel
11-12 x 10-6 /oC
Temperature Change vs. Strain
Type of Thermal Cracking and Spalling
Violent Spalling,
• Appear at the very beginning of the exposure.
• A separation of small pieces from the cross section, during energy release. They form popping off pieces with a certain speed, and a cracking sound.
Progressive Gradual Spalling,
• After long period of exposure, loss of strength due to internal crack and deterioration of cement paste cause this kind of spalling.
Corner Spalling
• The type of spalling that occurs when a corner of concrete breaks off due to the restrained expansion or the difference in TEC of paste and rebar.
Explosive Spalling,
• This occurs when there is a thermal gradients in the cross-section (one side of structure expose to high temperature while the other side does not).
http://www.promat-tunnel.com/en/concrete-spalling-effect-standard-fire-tests.aspx
Plain Concrete vs. SFRC subjected to Fire
Plain Concrete
• Unequal expansions of cement paste and aggregates cause cracking and spalling to occur.
• At temperature lower 200oC, the expansions are still small, in many cases the strength is found to remain unchanged or may be increased slightly.
• At temperature higher than 200oC, the strength begins to drop.
SFRC
• The cracks are restrained by fibers, this reduce the process of disintegration and maintain the ability of concrete to sustain load.
• Similar results are found at temperature lower than 200oC, increasing in strength and toughness is found.
• At temperature higher than 200oC, both strength and toughness are found to decrease but still higher than plain concrete
Compressive Strength
Mahasneh, B, The Effect of Addition of Fiber Reinforcement on Fire Resistant Composite Concrete Material, J. Applied Sci., 5 (2): 373-379, 2005
Tensile Strength
Mahasneh, B, The Effect of Addition of Fiber Reinforcement on Fire Resistant Composite Concrete Material, J. Applied Sci., 5 (2): 373-379, 2005
EXPERIMENTS AT KMUTNB:- FLEXURAL PERFORMANCE OF FRC SUBJECTED TO FIRE
Flexural Toughness ASTM C1018
10.5δ
FIRSTCRACK
LOAD
DEFLECTION0 0'
δ
3δ 5.5δ
A
B
C
D
E
F
G
H
10.5δ
FIRSTCRACK
LOAD
DEFLECTION0 0'
δ
3δ 5.5δ
A
B
C
D
E
F
G
H
Flexural Toughness
• = Area under the curve up to elastic limit (OAB)
• 3 = Area under the curve up to 3 time of (OACD)
• 5.5 = Area under the curve up to 5.5 times of (OAEF)
• 10.5 = Area under the curve up to 10.5 times of (OAGH)
Toughness Indexes
• I5 = Area OACD / Area OAB
• I10 = Area OAEF / Area OAB
• I20 = Area OAGH / Area OAB
Standard Fire Test ASTM E119-98
Sukontasukkul, P., and Pomchiengpin, W., Post-Crack (or Post Peak) Flexural Reponse and Toughness of FRC after Exposure to Elavated Temperature, Journal of Construction and Building Material (JCBM), Vol. 24, 2010, pp. 1967-1974.
Flexural Response of PC vs. SFRC
Plain Concrete
SFRC (@Bekeart HE Steel Fiber)
0
5
10
15
20
25
30
0 2 4 6 8
Load
(kN
)
Deflection (mm)
0.5%SFRC
Room Temp800oC
600oC
400oC
0
5
10
15
20
25
30
0 2 4 6 8
Load
(kN
)
Deflection (mm)
1.0%SFRC
Room Temp
800oC
600oC
400oC
0
5
10
15
20
25
30
0 0.2 0.4 0.6 0.8 1
Load
(kN
)
Deflection (mm)
Room Temp
400oC
800oC
600oC
Plain Concrete
Sukontasukkul, P., and Pomchiengpin, W., Post-Crack (or Post Peak) Flexural Reponse and Toughness of FRC after Exposure to Elavated Temperature, Journal of Construction and Building Material (JCBM), Vol. 24, 2010, pp. 1967-1974.
Toughness Indexes of SFRC
-
5.0
10.0
15.0
20.0
25.0
0.5% 1.0% 0.5% 1.0% 0.5% 1.0% 0.5% 1.0%
Room Temp 400 C 600 C 800 C
SFRC
I5 I10 I20
Before subjecting to Fire
After subjecting to Fire (800oC) Sukontasukkul, P., and Pomchiengpin, W., Post-Crack (or Post Peak) Flexural Reponse and Toughness of FRC after Exposure to Elavated Temperature, Journal of Construction and Building Material (JCBM), Vol. 24, 2010, pp. 1967-1974.
Steel Fiber vs. Synthetic Fibers
0
5
10
15
20
25
30
0 2 4 6 8
Loa
d (k
N)
Deflection (mm)
1.0%PPFRC
Room Temp800oC
600oC
400oC
0
5
10
15
20
25
30
0 2 4 6 8
Load
(kN
)
Deflection (mm)
0.5%PPFRC
800oC
600oC
400oC
Room Temp
0
5
10
15
20
25
30
0 2 4 6 8
Load
(kN
)
Deflection (mm)
1.0%PE/PP FRC
800oC
600oC
400oC
Room Temp
0
5
10
15
20
25
30
0 2 4 6 8
Load
(kN
)
Deflection (mm)
0.5%PE/PP FRC
800oC
600oC
400oCRoom Temp
PPRC (@Bekeart PP Fiber) PP/PE Fiber (@Strux Fiber)
Flexural Toughness Synthetic Fibers
-
5.0
10.0
15.0
20.0
25.0
30.0
0.5% 1.0% 0.5% 1.0% 0.5% 1.0% 0.5% 1.0%
Room Temp 400 C 600 C 800 C
PPFRC
I5 I10 I20
-
5.0
10.0
15.0
20.0
25.0
0.5% 1.0% 0.5% 1.0% 0.5% 1.0% 0.5% 1.0%
Room Temp 400 C 600 C 800 C
PEFRC
I5 I10 I20
Sukontasukkul, P., and Pomchiengpin, W., Post-Crack (or Post Peak) Flexural Reponse and Toughness of FRC after Exposure to Elavated Temperature, Journal of Construction and Building Material (JCBM), Vol. 24, 2010, pp. 1967-1974.
Cross-section after 800oC
Synthetic FRC Steel FRC
Sukontasukkul, P., and Pomchiengpin, W., Post-Crack (or Post Peak) Flexural Reponse and Toughness of FRC after Exposure to Elavated Temperature, Journal of Construction and Building Material (JCBM), Vol. 24, 2010, pp. 1967-1974.
Ultrasound Test
Room 400 C 600 C 800 C
Plain 4,795 4,445 4,132 3,257
PEFRC-0.5 4,683 4,383 4,260 2,922
PEFRC-1.0 4,718 4,295 3,590 2,866
PPFRC-0.5 4,667 4,357 3,702 2,883
PPFRC-1.0 4,728 4,122 3,620 2,808
SFRC-0.5 4,683 4,525 3,815 2,990
SFRC-1.0 4,667 4,277 3,687 2,972
2,500
3,000
3,500
4,000
4,500
5,000 P
uls
e V
elo
city
(m/s
)
Sukontasukkul, P., and Pomchiengpin, W., Post-Crack (or Post Peak) Flexural Reponse and Toughness of FRC after Exposure to Elavated Temperature, Journal of Construction and Building Material (JCBM), Vol. 24, 2010, pp. 1967-1974.
Conclusion
Steel fibers exhibit the ability to improve the fire resistance of concrete as seen by the ability the maintain strength and toughness after subjection to high elevated temperature.
Steel fiber’s ability to bridge across the cracks that occurred during exposure to fire play an important role on this matter.
Concrete Under High Rate of Loading
Concrete may sometime be required to withstand dynamic loads due to impact, or explosion.
Under high rate of loading, the strength of concrete increases with the increasing loading rate.
Large cracks are typically found.
Cracks are forced to propagate through aggregates.
-
10
20
30
40
50
60
70
80
90
- 0.005 0.010 0.015 0.020 0.025 0.030
Strain
Str
es
s (
MP
a)
Static loading
Impact loading (250mm)
Impact loading (500mm)
SFRC under Impact Loading
Mechanical Properties: strength increases, toughness increases and bond strength increases
Under high rate of loading, fibers are forced to pullout at faster rate, thus cause the increase in mechanical properties.
Multiple cracks with less severity are often found.
-
10
20
30
40
50
60
70
80
90
- 0.005 0.010 0.015 0.020 0.025 0.030
Strain
Str
es
s (
MP
a)
Static loading
Impact loading (250mm)
Impact loading (500mm)
Structures Being Hit by Bullets
Three Scenarios
• Penetrated Bullets: When the bullets hit the wall and penetrate through. They injure people or damage properties
• Un-penetrated Bullets: when the bullets hit the wall, but do not penetrate, instead turning into flying debris (broken concrete pieces and ricocheted bullets). The debris injure people and damage properties.
• Panicking: People get panic, running around, stumbling and get hurt.
Typical Failure Patterns of Bulletproof Panel
Penetration Perforation
Scabbing Spalling
Global Local
Flexure
In the case of impact loading by bullet which leading to penetration, the specimen response is usually dominated by the local response of the small zone at the contact area
Main Ideas of Bulletproof Panel
Requirement for bulletproof panel:
• Penetration or perforation must not occurs.
In order to achieve that:
• Improve impact resistance by increasing strength and energy absorption ability of the panel.
• Anticipating energy dissipation by using soft medium into the panel.
http://www.examiner.com/article/ethics-panel-ruling-keeps-jobsohio-bullet-proof-on-kasich-board-biz-deals
Two Types of Panel
SFRC Panel
•Fiber: Hooked End steel fiber (©Dramix Bekeart), Addition rate: 2%-4%
•Thickness: 3 cm.
•Category: Improve impact resistance using steel fiber.
Double layer: SFRC and Rubberized Concrete
•Fiber: Hooked End steel fiber (©Dramix Bekeart) , Addition rate: 2%-4%
•Crumb rubber: Commercial type, Size: passing seive No. 6.
•Panel Thickness: 3 cm. Varied Thickness between layer from 0.5:2.5, 1.0:2.0 and 1.5:1.5
•Category:
•Adding energy dissipation medium (rubberized concrete),
• Increase impact resistance using steel fiber
T1
T2
Rubberized Concrete
Steel Fiber Reinforced Concrete
Two Types of Bullet
Manufacturer Load Mass Velocity Energy Expansion Penetration PC TSC
Winchester FMJ 7.5 g (115 gr) 352 m/s 462 J 9.1 mm 620 mm 41 mL 174 mL
Remington FMJ 15 g (230 gr) 255 m/s 483 J 11 mm 690 mm 70.3 mL 150 mL
Failure Patterns PC vs. SFRC Panel
Plain concrete Panel
SFRC Panel
Front Back
29 . 43 .
Failure Patterns : Double Layer Panel
Typical Failure Patterns Partially Energy Dissipation
Ideal Failure Patterns Full Energy Dissipation
Passing Requirement 9 mm 11 mm
Type Failure Type Classification Failure Type Classification
R25 Perforation not pass Perforation not pass
R50 Perforation not pass Perforation not pass
R75 Perforation not pass Perforation not pass
S2 Scabbing pass Scabbing pass
S3 Scabbing pass Scabbing pass
S4 Scabbing pass Scabbing pass
R50/S2 Scabbing pass Scabbing pass
R75/S2 Scabbing + Spalling pass Scabbing + Spalling pass
R100/S2 Scabbing + Spalling pass Scabbing + Spalling pass
R50/S3 Scabbing pass Scabbing pass
R75/S3 Scabbing pass Scabbing pass
R100/S3 Scabbing + Spalling pass Scabbing pass
R50/S4 Scabbing + Spalling pass Scabbing pass
R75/S4 Scabbing pass Scabbing pass
R100/S4 Scabbing pass Scabbing pass
A-R75/S2 Scabbing + Spalling pass Scabbing + Perforation not pass
B-R75/S2 Scabbing + Spalling pass Scabbing + Perforation not pass
A-R75/S3 Scabbing + Perforation not pass Scabbing + Perforation not pass
B-R75/S3 Scabbing + Perforation not pass Scabbing + Perforation not pass
Typical Acceleration Res. SFRC (9 mm)
Typical Acceleration Res. Double Layer (9 mm Bul.)
Comparison Single Layer Plate Double Layer Plate
Responding time: Slower in Double layer plate
Acceleration Value: Lower in Double layer plate
Center Acc. vs. Rubber content Double-layer plate
1,053.38
785.21
579.81
819.33
759.05
526.22
864.41
602.97
389.40
735.98
432.51
353.43
-
200.00
400.00
600.00
800.00
1,000.00
1,200.00
SFRC2% SFRC3% SFRC4%
Acc
eler
atio
n (m
2 /s)
0% Crumb Rubber
50% CR (0.5/2.5)
75%CR (0.5/2.5)
100%CR (0.5/2.5)
Bullet Type vs. Center Acceleration
81
9.3
3
75
9.0
5
52
6.2
2
86
4.4
1
60
2.9
7
38
9.4
0
73
5.9
8
43
2.5
1
35
3.4
3
62
8.4
2
55
4.8
4
45
1.3
4
73
8.4
5
50
6.4
7
45
2.3
1
64
8.2
2
35
5.2
8
54
6.5
2
-
100.00
200.00
300.00
400.00
500.00
600.00
700.00
800.00
900.00
1,000.00
50
R2
S (0
.5/2
.5)
50
R3
S (0
.5/2
.5)
50
R4
S (0
.5/2
.5)
75
R2
S (0
.5/2
.5)
75
R3
S (0
.5/2
.5)
75
R4
S (0
.5/2
.5)
10
0R
2S
(0.5
/2.5
)
10
0R
3S
(0.5
/2.5
)
10
0R
4S
(0.5
/2.5
)
Acc
ele
rati
on
(m
2/s
)
9 mm.
11 mm.
Displacement (9 mm.) SFRC 2% SFRC 3%
50RS2 50RS3
Conclusions
Steel fiber reinforced concrete exhibit superior impact resistance as seen by the test results that no perforation occur in the SFRC panels.
Crumb rubber used in this study has shown it ability to enhance the efficiency of the bulletproof SFRC panels.
The results are successfully shown that the rubberized concrete layer is able to act as a cushion layer and dissipate the impact energy from the bullet test as seen by the decreasing values of acceleration, displacement and D/W ratios.
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