• Designing for the Future with Composites

C-Grid™ Reinforcement: Innovative Composites Solution for Eliminating Corrosion in Concrete

Construction and Repair

John Carson Executive Director-AltusGroup, Inc

Designing for the Future with Composites

Topics

• Basic introduction to Carbon Fiber Grids

• Mechanical and Physical Characteristics

• Common Applications of Carbon Fiber Grids

and Successful Projects

• Construction Use Considerations

• Conclusions

What are carbon grids?IN GENERAL:

• Carbon grids are an FRP (Fiber reinforced polymer) product form

• Combination of carbon fibers + epoxy resin

• Alternative to traditional steel reinforcement (WWM) used in concrete and masonry

SPECIFICALLY:

• Non-woven, carbon/epoxy FRP composite structures

• NOT geotech fabrics/membranes!• Typically 0/90 fiber orientations

• 2-dimensional reinforcements (thin)

• NOT FRP grating!• Continuous and flexible - delivered on rolls

and in specific sizes and sheeted goods

Grid Manufacturing• Carbon grids are made in a high speed

continuous process that:

• Aligns carbon fibers in a 0/90 configuration

• Impregnates the fiber with epoxy resin

• Repeatable, consistent high quality product

• High volume capacity

• Testing (every roll)

• Weight

• Tensile- Minimum Average Tensile Values(MARV’s):

• Why? Thin small cross sectional area.

• Strength is the property being sold

Carbon Grid Types

Grids are… Engineered to provide the right amount of strength in each direction.

Bi-directional or unidirectional.

Incorporate the right amount of carbon fiber needed for cost effectiveness

• Designing for the Future with Composites

CARBON FIBER GRID Material Characteristics

7

FRP Constituent Materials

0

100

200

300

400

500

600

700

0.000 0.010 0.020 0.030 0.040 0.050 0.060

Tensile Strain (in./in.)

Ten

sile

Str

ess

(ks

i)

Carbon

Aramid

Glass

Note: Fiber properties depicted

Comparison of the Tensile Strength of the Fibers

Grid Properties – Tensile Strength

0

100

200

300

400

500

600

700

0.000 0.010 0.020 0.030 0.040 0.050 0.060

Strain (in/in)

Stre

ss (

ksi)

Carbon Fiber

Gr 270 PT Strand

Gr 60 Rebar

Carbon grids are linear elastic materials

(they do not yield)

9

Material Properties of FRPs

0.5

0.6

0.7

0.8

0.9

1

0 2000 4000 6000 8000 10000

Hours of Exposure

Str

en

gth

Re

ten

tio

n

Carbon/Epoxy

E-glass/Epoxy

Note: Data from CALTRANS test program for 100 °F at 100% RH exposure

Effects of Environmental Exposure

In general, carbon fibers

are more resistant to a

wider range of chemical

environments than

fiberglass or aramid

Grid Properties Flexural Behavior

Example

• Carbon grid reinforced slab

• 4.75” thick

• 4-pt bending

0

500

1000

1500

2000

2500

3000

0 0.1 0.2 0.3 0.4 0.5 0.6

Deflection (in)

Load

(Lb

s)

Flexural behavior of grid reinforced members exhibits “ductile” behavior

Carbon Grid Properties

• Tensile strength depends on size and

spacing of carbon strands

• Tensile modulus is similar to steel

Material Properties of FRPs

Fatigue Behavior

• Resistance of a material to repeated loadings

Sustained Load

• Unique property to FRP materials

• Resistance of a material to support sustained loads over a period of time

• Not to be confused with creep

Carbon fibers, in general, exhibit better fatigue and sustained load performance than glass or aramid fibers.

Percent Max Load vs. log(Number of Fatigue Cycles)**EX Panel Flexure

y = -0.0284x + 1.022

R2 = 0.834

0%

20%

40%

60%

80%

100%

120%

0 1 2 3 4 5 6 7

log(# of Fatigue Cycles)%

Max

Loa

d (M

ax =

127

2 lb

s.)

How does Carbon Fiber Grid Compare to WWM?

• Carbon grids do not corrode.

• They are not ductile

• Carbon grids have similar stiffness (modulus) to steel

• Carbon grids are comparable to

– Lighter weight welded wire fabric

(W1.4, W2, W2.5)

– #3 bars @ 12”

– #4 bars @ 18”

• Carbon grids are mostly used as:

– Temperature/shrinkage reinforcement

– Light structural reinforcement (secondary)

– Non-corrosive reinforcement where corrosion resistance and weight are a

primary concern

Common CFRP Grid Uses?

• Precast concrete

– Insulated sandwich wall panels

– Architectural panels and cladding

– Double tees (floor/roof)

– Piles

• Concrete décor and retail items

• Cast in place, Pervious, Tunnel Lining

• Concrete repair

– Shotcrete

– Overlays and Topping slabs

– Ferro cement

– Timber repair (strengthening)

How are they used?

• Typically carbon grids are used inside concrete as reinforcement

• May be externally bonded with cementitious or polymer materials (e.g. polyurea, polymer modified concrete admixtures)

• Carbon grids resist only tension forces as a concrete reinforcement

• May be used alone or together with traditional reinforcing materials

So, why use Carbon grids?• Carbon grids may offer performance and use advantages that can

outweigh higher material cost. (Durability, longterm performance, R-Value etc).

FACT: Carbon grids cost more than traditional commodity construction material they replace (like concrete and steel)

• Cost benefits can be deeply rooted and systematic

• Flexible grids are easy to handle and place

• Supplied in rolls, easy to ship and handle versus WWM

• Lays flat

• Easy to cut/trim, position and install

• Provide possible Labor Savings and process automation potential

In general, Novel FRP materials must offer an initial cost benefit! (This is true

for carbon grids as well)

• Designing for the Future with Composites

CARBON FIBER GRIDS INPRECAST CONCRETE STRUCTURES

Carbon Grids & Precast Concrete

Carbon fiber grids are used as…

• Flexural reinforcement

• Double tees

• Architectural cladding

• Floating marine structures,planking

• Sound and MSE walls

• Shear connectors

• Insulated concrete sandwich wall panels

• Architectural cladding

• Shear and confinement reinforcement

• Piling

Pre-topped Double Tees

• Requires less concrete cover…thinner flanges are possible

• Up to 12% lighter than traditional product

Precast Double Tees

Benefits

• Corrosion resistance → durability , eliminates post

application sealer need

• Thinner top flanges → lighter structures

• Lower substructure and foundation costs

• Lower erection costs

• Lower operating/maintenance costs

• Elimination of WWF (labor savings)Carbon grid is the primary flange

reinforcement!

Double Tee - Load vs. Deflection – Conc.

LoadLoad vs Deflection T-Beam2, 02/13/04

0

1000

2000

3000

4000

5000

6000

7000

8000

9000

0.000 0.500 1.000 1.500 2.000 2.500

Deflection (in.)

Load

(lb

s.)

Doubletee Projects

Precast Insulated Wall Panel

Carbon fiber grid shear connectors…

• Connect concrete wythes together

• Provide composite action between wythes

• Contribute to higher R-Values as a low thermal conductivity connector

Exterior

Interior

Carbon Fiber Shear Connector

Wythe Reinforcement

Pilaster

Typical Cross Section

Sandwich Wall Panels

Insulated Sandwich Wall Panel Projects

Cold Storage Distribution Facility

Architectural Panels:

Carbon Fiber Grid is used in precast panel face as flexural reinforcement in addition to shear truss reinforcement

1. Corrosion resistance of carbon grids leads to less concrete cover required…………

2. Less concrete cover leads to lighter weight panels……..

3. Lighter weight panels lead to…

� Lower foundation costs

� Larger pieces

� Lower shipping costs

� Lower erection costs and increased speed of erection

A more expensive material leads to lower initial costs

Architectural Panels

End Product Benefits

• Thinner wythes → 50 - 67% lighter façade panels

• Reduction in superstructure and foundation

requirements → lower iniQal construcQon costs

• Corrosion resistance → durability

• Lower erection costs

• Higher R-values

• Excellent crack control

Carbon Grids & Precast ConcreteArchitectural Panels

ASTM E119 Fire Test

ASTM E119 Hose Stream Test

FL Missile Impact Test

Architectural Cladding Projects

Symphony House

Philadelphia, PA USA

(20 stories)

Architectural Cladding

The HeldrichNew Brunswick, NJ USA

Precast Piles

• Designing for the Future with Composites

CARBON FIBER GRIDS IN

REPAIR, SHOTCRETE,

OVERLAYS

AND DÉCOR CONCRETE

Oregon Inlet Bridge

Span repaired with CFRP Grids

Concrete RepairsOregon Inlet Bridge

Shotcrete RepairsOuter Banks, NC USA

Access Bridge Topping Slab

• CHS Terminal (Myrtle Grove, LA)

• 4-span access bridge

• Simply-supported spans

• Side-by-side pre-stressed T-beams

topped with a 4” overlay

• Relatively good condition

Access Bridge Topping Slab

Repair Strategy

• Use carbon fiber sheets to strengthen the underside T-beams for flexure and shear

• Use a 2” carbon grid reinforced topping slab to strengthen the cantilever flanges

• Initial concept was to use a thicker steel reinforced topping slab which would have added an excessive amount of dead load which the structure couldn’t support

Access Bridge Topping SlabCHS TerminalMyrtle Grove, LA

Access Bridge Topping Slab

CHS TerminalMyrtle Grove, LA

Tunnel & Lining

Timber / Pile Rehab

Pervious Concrete• Carbon fiber grid is the only economical non-

corrosive high strength reinforcement suitable

for pervious concrete.

Parking Garage Deck RepairsNorthhampton Garage, Easton PA

Stamped Concrete Slab-on-GradeFive Bridge Inn,Rehoboth, MA

Pool Decking

Balconies and Slabs

Midtown Miami IIBalconies

Miami, FL US

Hydronic Radiant Heat Floor Slab

Japan

MSE and Soundwalls

• Designing for the Future with Composites

Construction Considerations when using Carbon Fiber Grids

Construction ConsiderationsGrid Placement Techniques

• Place between lifts of

concrete (works well with

SCC, precast, and

ferrocement)

• Place on appropriate

chairs/bolsters/concrete

accessory products for the

depth of concrete required

• Segment cast to avoid heavy

surface/foot traffic

• Embed into concrete surface

using appropriate installation

methodology.

Construction Considerations

Concrete Mixes

• Extensive experience with SCC (self consolidating concrete) – works well!

• Stiff mixes (low slump) may require more vibration to consolidate concrete around grids

• Larger aggregate mixes require larger opening grids

Grid Properties – Splice Length

• Splice length varies

from grid to grid for

proper development

• Depends on

tow/strand size

• Typically ranges from

2 - 4 opening overlap

• Designing for the Future with Composites

Concluding Thoughts on Carbon Fiber Grid Reinforcing

Carbon Fiber Grids Enable Sustainable

Design• Carbon grids are durable

– Structures last longer

– Lower maintenance and repair costs

– Lower life cycle costs

• Carbon grids do not corrode

– Less cover concrete is required

– Less concrete is needed

• Carbon fiber grids can contribute to more thermally efficient

structures in wall panels and cladding

STEEL CARBON GRID

12 Months in a Brine solution

Sustainable Precast Design with CarbonLeads to…….

• Reduced gravity load and seismic loads on structure

• Less steel or concrete used in superstructure

• Less steel and concrete used in foundation

• Lighter precast leads to enhanced sustainability of the other structural systems of the building and Co2 Footprint reduction

• Less fuel used to…

• ship precast members

• erect precast members

• Delivers highly sustainable building designs!

Summary• Carbon grids are a viable method for reinforcing and strengthening

concrete structures

• Carbon grids must effectively compete with traditional materials on an installed cost and system basis

• Carbon grids, like other FRPs, are not a panacea for all applications…they must make sense to be specified and used

• Carbon grids are highly successful commercial examples of a CFRP material accepted by the civil/construction industry

• The future looks very bright for Carbon Fiber Grids!

• Designing for the Future with Composites

2011 Construction, Corrosion & Infrastructure Conference

Designing for the Future with Composites

Thank You!Jcarson@altusprecast.com

www.chomarat.comwww.carbongrid.com

864.314.3486

Brine Tank Shotcrete Lining• PCS/Allan (Saskatoon, SK)

– Existing steel brine tank lined with concrete

– Corrosion of WWF necessitated repairs

– Carbon grids used to reinforce a spray-applied cement

– Carbon grids anchored to substrate

Brine Tank Shotcrete LiningPCS/AllanSaskatoon, SK

Industrial Floor Overlay• Dial Corporation (Burlington, IA)

– Food processing plant (floors cleaned daily with aggressive

chemicals

– Elevated slab consisting of concrete and acid brick

– Acid brick kept in place and topped with 2” of concrete

– Carbon grid used to reinforce topping and provide additional

crack/corrosion control

Industrial Floor Overlay

Dial CorporationBurlington, IA

Naumburg Bandshell

Ferrocement

Repair strategy• Remove existing roof and make minor repairs to substrate

• Install waterproofing membrane

• Cast ribs and place foam blocks between ribs for enhanced structural

integrity

• Build up fibrocement shell in 4 lifts

• Used 3 layers of carbon grid in 0/45/0 sequence between lifts

Ferrocement

Central Park BandshellNew York, NY

Ferrocement

Central Park BandshellNew York, NY

Commercial Concrete Décor