Why Carbon Fiber Works and Its Various Applications

Written by Steve Maxwell of BaileyLineRoad.com

Carbon fiber is an up-and-coming material that combines great tensile strength with light weight, and that’s why you’re seeing it used in everything from aircraft construction to tennis rackets.  Carbon fiber is also revolutionizing the repair of cracked and failing structural concrete, especially in above-ground, foundation and basement situations.  In this application the light weight of carbon fiber is not a particular advantage, but strength certainly is.  If you want the strongest, most reliable, easiest-to-apply concrete fix, carbon fiber delivers.  Rhino Carbon Fiber is currently the most widely available option for industrial and commercial applications.  Check out the six most common repair situations described in this blog, and see why carbon fiber is the best way to make things right.  It’s actually stronger than the surrounding concrete and far stronger than any fix involving metal straps and bolts.  Why?  Besides the fact that carbon fiber is 10 times stronger than steel, it also doesn’t rely on point-load anchoring.  A carbon fiber repair is anchored across the entire repair zone continuously by epoxy adhesive, side-stepping the problem of steel reinforcement tearing away from bolts and fasteners anchored here and there, as necessary with traditional methods.

How It Works

Bring the area around the repair zone back to bare concrete by grinding or scraping as needed, then apply catalyzed epoxy to the surface.  While this is still wet, apply carbon fiber fabric to the repair zone, and then apply more liquid epoxy over the carbon fiber, saturating the fabric and encasing it.  A paint roller works well for this.  When the epoxy has hardened, the repair is complete.  The effectiveness comes down to the remarkable tensile strength of carbon fiber and its continuous anchoring on the surface.

The tensile strength of carbon fiber is outstanding, especially when it’s encased in a hardened layer of epoxy resin.  Rhino Carbon Fiber repair fabric ranges from 63,000 to 122,000 pounds per square inch, depending on the type.  Carbon fiber made for concrete repair also comes in the form of “stitches”.  Unlike the cloth configuration of carbon fiber fabric, carbon fiber stitches are made to inset into slots cut into concrete across cracks.  Each stitch can resist a tensile pulling force of 2900 pounds, and includes enlarged ends that allow each stitch to anchor firmly below the wall surface, embedded in epoxy.  

Carbon Fiber Repair Scenario #1: 

Typical Basement Wall Cracks

This is one of the most common applications for the carbon fiber system, and it delivers results that are easier to complete than other methods and much stronger.  And unlike steel reinforcement, a carbon fiber repair also adds no significant thickness to the wall.  The wall can be covered and finished after repair just like other, non-cracked areas.

Carbon Fiber Repair Scenario #2:

 Bowed Basement Walls

When soil pressure pushes foundation walls inward, it’s one of the most challenging repair situations ever because there’s so much pressure involved.  Another source of challenge is that this pressure is continuous.  When inward deflection of the wall has not progressed beyond 2 inches of inward movement over an 8-foot high wall, the situation can be stabilized using long bands of carbon fiber fabric extending from top to bottom.  In addition to encasing and bonding the carbon fiber with epoxy, this system also uses mechanical anchors at the top and bottom ends of the carbon fiber bands, making the most of the high tensile strength of the material.  Once again, even with the use of metal anchoring hardware, the results of bowed wall repair are flat, with nothing significant extending out beyond the inner face of the wall.

Carbon Fiber Repair Scenario #3: 

Outside Corner Wall Repairs

This is another application where carbon fiber banding is used with great success, but this time the bands are typically applied horizontally, not vertically, as with a bowed wall repair.  In the case of corner repairs, epoxy anchoring alone is enough to do the job.

Carbon Fiber Repair Scenario #4: 

Beam and Column Repair

Exterior concrete beams and columns can fail from overloading, but also from spalling due to freeze-thaw cycles that cause concrete to crumble in cold climates.  The carbon fiber system can be used indoors or outside, providing surface protection as well as additional strength.  All repairs involving structural beams and columns must be completed following an engineer’s assessment and approval.  The carbon fiber fabric itself is not harmed by UV rays, but the epoxy coating needs to be protected with paint.  Even something as simple as exterior latex primer and paint works well in this application.

Carbon Fiber Repair Scenario #5:

Concrete Deck Repair

Spalling and deterioration of the underside of concrete floor decks is common because of water infiltration, and it’s difficult to repair properly using conventional methods because of the overhead working orientation.  Carbon fiber is easy to install properly, even when used overhead.  Brush or roll on a layer of epoxy, then press the fabric into the liquid and roll on another layer.  One big advantage of carbon fiber repair for the underside of decks is appearance.  Where conventional patching never looks as professional as most repair contractors want, carbon fiber looks heavy-duty and inspires confidence in clients. 

Carbon Fiber Repair Scenario #6: 

Retaining Wall Repair 

This is another situation involving a lot of continuous pressure, and it is why bowed and failing concrete retaining walls are a common sight.  Carbon fiber applied in the same way as on the outer face of a bowed basement wall is an excellent option for stabilizing cracked and failing retaining walls.  For maximum strength, retaining wall repairs need mechanical anchoring top and bottom, plus the usual epoxy anchoring.

There are many other applications where carbon fiber offers superior results compared with conventional repair methods, including new applications being developed all the time.  Strength, simplicity and durability are the hallmarks of the system, and it does what no other anchoring system can do as well.

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About the Author

Steve Maxwell is founder and publisher of BaileyLineRoad.com with 30 years experience explaining building technology for professional audiences. Visit rhinocarbonfiber.com for more information about carbon fiber structural repair systems.