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• 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 [email protected]
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