Performance of Steel Fiber under Fire and Impact Loading (Piti Sukontasukkul)

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

http://en.wikipedia.org/wiki/Halomethane

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


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%


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%


PEFRC

I5 I10 I20


Cross-section after 800oC

Synthetic FRC Steel FRC


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

)


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)


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



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



S2 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



R100/S3 Scabbing + Spalling pass Scabbing pass

R50/S4 Scabbing + Spalling 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.

Performance of Steel Fiber under Fire and Impact Loading (Piti Sukontasukkul)

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