Designing for the Future with Composites

Transcription

1 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 Designing for the Future with Composites

2 Topics Basic introduction to Carbon Fiber Grids Mechanical and Physical Characteristics Common Applications of Carbon Fiber Grids and Successful Projects Construction Use Considerations Conclusions

3 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

4 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

5 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

6 CARBON FIBER GRID Material Characteristics Designing for the Future with Composites

7 FRP Constituent Materials Comparison of the Tensile Strength of the Fibers 700 Tensile Stress (ksi) Carbon Aramid Glass Tensile Strain (in./in.) Note: Fiber properties depicted 7

8 Grid Properties Tensile Strength 700 Stress (ksi) Carbon Fiber Gr 270 PT Strand Gr 60 Rebar Strain (in/in) Carbon grids are linear elastic materials (they do not yield)

9 Material Properties of FRPs Effects of Environmental Exposure Carbon/Epoxy In general, carbon fibers are more resistant to a wider range of chemical environments than fiberglass or aramid Strength Retention E-glass/Epoxy Hours of Exposure 9 Note: Data from CALTRANS test program for 100 F at 100% RH exposure

10 Grid Properties Flexural Behavior Example Carbon grid reinforced slab 4.75 thick 4-pt bending Load (Lbs) Deflection (in) Flexural behavior of grid reinforced members exhibits ductile behavior

11 Carbon Grid Properties Tensile strength depends on size and spacing of carbon strands Tensile modulus is similar to steel

12 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. % Max Load (Max = 1272 lbs.) 120% 100% Percent Max Load vs. log(number of Fatigue Cycles)* *EX Panel Flexure 80% 60% 40% 20% y = x R 2 = % log(# of Fatigue Cycles)

13 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 12 #4 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

14 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)

15 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

16 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 initialcost benefit! (This is true for carbon grids as well)

17 CARBON FIBER GRIDS IN PRECAST CONCRETE STRUCTURES Designing for the Future with Composites

18 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

19 Pre-topped Double Tees Requires less concrete cover thinner flanges are possible Up to 12% lighter than traditional product

20 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!

21 Double Tee -Load vs. Deflection Conc. Load Load vs Deflection T-Beam2, 02/13/ Load (lbs.) Deflection (in.)

22 DoubleteeProjects

23 Precast Insulated Wall Panel Wythe Reinforcement Exterior Interior Pilaster Typical Cross Section Carbon Fiber Shear Connector 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

24 Sandwich Wall Panels

25 Insulated Sandwich Wall Panel Projects Cold Storage Distribution Facility

26 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

27 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

28 Carbon Grids & Precast Concrete Architectural Panels ASTM E119 Fire Test ASTM E119 Hose Stream Test FL Missile Impact Test

29 Architectural Cladding Projects Symphony House Philadelphia, PA USA (20 stories)

30 Architectural Cladding The Heldrich New Brunswick, NJ USA

31 Precast Piles

32 CARBON FIBER GRIDS IN REPAIR, SHOTCRETE, OVERLAYS AND DÉCOR CONCRETE Designing for the Future with Composites

33 Span repaired with CFRP Grids Oregon Inlet Bridge

34 Oregon Inlet Bridge Shotcrete Repairs Outer Banks, NC USA Concrete Repairs

35 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

36 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

37 CHS Terminal Myrtle Grove, LA Access Bridge Topping Slab

38 Access Bridge Topping Slab CHS Terminal Myrtle Grove, LA

39 Tunnel & Lining

40 Timber / Pile Rehab

41 Pervious Concrete Carbon fiber grid is the only economical noncorrosive high strength reinforcement suitable for pervious concrete.

42 Parking Garage Deck Repairs Northhampton Garage, Easton PA

43 Stamped Concrete Slab-on-Grade Five Bridge Inn, Rehoboth, MA

44 Pool Decking

45 Balconies and Slabs Midtown Miami II Balconies Miami, FL US Hydronic Radiant Heat Floor Slab Japan

46 MSE and Soundwalls

47 Construction Considerations when using Carbon Fiber Grids Designing for the Future with Composites

48 Grid Placement Techniques Construction Considerations 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.

49 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

50 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

51 Concluding Thoughts on Carbon Fiber Grid Reinforcing Designing for the Future with Composites

52 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 STEEL CARBON GRID 12 Months in a Brine solution Carbon fiber grids can contribute to more thermally efficient structures in wall panels and cladding

53 Sustainable Precast Design with Carbon Leads 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!

54 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!

55 Thank You! Construction, Corrosion & Infrastructure Conference Designing for the Future with Composites Designing for the Future with Composites

56 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

57 PCS/Allan Saskatoon, SK Brine Tank Shotcrete Lining

58 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

59 Industrial Floor Overlay Dial Corporation Burlington, IA

60 Naumburg Bandshell

61 Repair strategy Ferrocement 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

62 Central Park Bandshell New York, NY Ferrocement

63 Central Park Bandshell New York, NY Ferrocement

64 Commercial Concrete Décor