Fiber-Reinforced Concrete for Bridge

Structures

H. Celik Ozyildirim, Ph.D., P.E.

Mary Sharifiasl, MECE

Virginia Concrete Conference, 2019

Outline

• Goal: longevity

• Deterioration mechanisms

• Protective measures

• Fiber-reinforced concrete (FRC)

• Field Applications of FRC

• Conclusions

2

Goal is Longevity! Build to Last!

Innovations in concretes and reinforcement

have enabled:

• Improved durability

• Low environmental impact

• Cost-effectiveness

• Minimal inconvenience to traveling public

• Improved safety

3

Pantheon

CONCRETE IS DURABLE!

Roman concrete, 2,000 years old! 4

Year 1,002,019

Cast: 2,006 Cast: 2019

Design and Build it right! Keep it dry!

5

Infiltration into Concrete

• Deterioration because of water

and solutions penetrating through

poor quality concrete and cracks:

Freezing and thawing

Alkali-aggregate reactions

Sulfate attack

Corrosion: if reinforced

6

Freezing and Thawing Damage

Saturated, non-air entrained

7

Alkali-Silica Reactions

Water is necessary.

8

Sulfate Attack

Sulfate solution penetration

9

Corrosion

• Corrosion is a major distress in reinforced

concrete structures exposed to the environment.

10

Improvements in Concrete

• Low Permeability

– Supplementary cementitious material (SCM)

– Low water-cementitious materials ratio

• Low shrinkage

– Low paste content, shrinkage reducing

admixture (SRA)

• Crack resistant: (reduce amount and width)

– Fibers

• Abrasion resistant

• Good construction practices

– Proper consolidation and curing

11

Improvements in Reinforcement

• Corrosion-resistant conventional reinforcement

– Stainless steel (SS), MMFX2, etc.

• Corrosion-resistant and corrosion-free

prestressed reinforcement

– Carbon Fiber Reinforced Polymer (CFRP)

and SS

12

CFRP Reinforcement

13

CFRP is corrosion-free.

Cracks

Charlie Robson

Former VDOT State Materials Engineer

There are two kinds of concrete:

• One cracked

• One about to crack

Cracks

• Occur when tensile stresses exceed the tensile

strength of concrete

• Causes:

Volumetric changes: moisture and

temperature

Chemical reactions

Loading

15

Crack Control – FRC

• Synthetic fibers in low amounts, 1.5 lb/yd3

(0.1%) are used to minimize plastic shrinkage.

• Larger amounts of fibers up to 2% needed for

crack control in hardened concrete. The goal is

to keep crack width less than 0.1 mm. Such

tight cracks resist infiltration of water and

solutions.

Crack Control – FRC

• FRC: fiber-reinforced concrete

– Improve tensile strength

– Increase ductility

– Control cracking

• Special FRC

ECC: engineered cementitious composite

VHPC: very high-performance concrete

UHPC: ultra high-performance concrete

17

Flexural Test - FRC

18

0

1000

2000

3000

4000

5000

6000

0 0.05 0.1 0.15

Load

(lb

f)

Deflection (in)

No fiber

Deflection Hardening

Deflection Softening

19

Early Work with FRC - Lexington

0 0.01 0.02 0.03 0.04 0.05 0.06 0.07 0.08

Lo

ad

(lb

f)

Deflection (in)

Residual strength

15 lb/yd3

9 lb/yd3

9 lb/yd3 PP+PE 3500

3000

2500

2000

1500

100

500

Lexington – FRC 2000

Lexington Crack Survey - FRC

Crack Control Fiber

Total Length (ft) 151 59

Average Width (mm) 0.53 0.29

After 5 years

ECC – 2013 on

• Shear Keys

– Winchester

– Surry

• Closure Pours

– I-64 Bridge over Dunlap Creek

• Culvert Repair

22

PVA

7-d comp str > 4,000 psi

ECC Mixtures

23 First crack flexural strength at 7 days: 667 psi

Max flexural strength at 7 days: 1,140 psi

24

ECC

• Bendable concrete, tight cracks <0.1 mm

25

Deflection

Tight cracks (<0.1 mm)

ECC

Route 645 Bridge: Shear Keys ECC

26

Route 645 - Shear Keys - 2013

ECC with PVA fibers UHPC

Non-shrink grout

After 3 months, only ECC did not leak

27

ECC – Culvert Repairs – 2017, 2018

28

29

Trailer Pump

Finished Repair with ECC

30

I-64 Dunlap Creek Bridges: 2014, 2015

31

Link Slab (Closure Pour)

32

Fiber Reinforcements – I-64

33

PVA

Steel

PP

Tight Cracks

34

VHPC work at Bristol - 2018

• The mix had high flow rates but was sticky

35

36

VHPC in Block-outs

28-d compressive strength > 11,500 psi

VHPC work at Sperryville - 2019

37

VHPC work at Sperryville - 2019

38

39

UHPC - Route 624 - 2007

28-d compressive strength > 30,000 psi

with steam curing

40

UHPC - Steel Fibers

Brass coated steel fibers; L = 14 mm, diameter = 0.185 mm

UHPC Mixture

42

UHPC Beams

Plant had twin shaft mixer

43

Flexural Strength

4-in-thick beams at 2 months

0

2000

4000

6000

8000

10000

12000

14000

16000

0 0.05 0.1 0.15 0.2 0.25

Lo

ad

(lb

f)

Deflection (in)

First crack strength: 1,510psi

Max strength: 2,650 psi

44

UHPC - Tight Cracks

1-in-thick beam

New UHPC - 2019

45

Planetary mixer

28-d compressive strength > 17,000 psi

Flexural Strength – New UHPC

46

0

2000

4000

6000

8000

10000

12000

14000

16000

18000

20000

0 0.02 0.04 0.06 0.08 0.1 0.12 0.14

Lo

ad

(lb

f)

Deflection (in)

7 days

28 days

First crack strength: 1,790psi

Max strength: 3,340 psi

First crack strength: 1,435 psi

Max strength: 2,570 psi

Conclusion

• Fibers provide residual strength after cracking,

which limits the size and length of cracks and

can be used in shear keys, closure pours, block-

outs, and culvert repairs.

• The level of residual strength depends on the

type and amount of fibers.

• High residual strengths that exhibit strain and

deflection hardening limit cracks widths below

0.1 mm.

47

Acknowledgements

• FHWA

• VDOT CO

• VDOT Districts

• VTRC

• Industry

48

Thank You.