One of the most cost effective and least invasive ways for strengthening, rehabilitation or repairing reinforced concrete members is to use external carbon fiber reinforced polymer or CFRP.

The use of carbon fiber for strengthening new or existing concrete structures has become a widely used and common repair to rehabilitate infrastructure. What are the advantages of CFRP vs traditional strengthening methods?

The ultra thin profile of the reinforced composite can easily be installed around mechanical components that often prohibit traditional steel installations that are often invasive and heavy. Not only is carbon fiber 10x stronger than steel it's also significantly lighter. This is another distinct advantage when it comes to increasing the load capacity of structures without adding additional weight to it.

Carbon Fiber can greatly improve the flexural and shear capacity of deteriorated members extending their useful life. Commonly structural support beams are strengthened for rooftop HVAC installations using SRS-600UNI. Bidirectional & Unidirectional Carbon Fiber - These two distinctly different weaves each have their own advantages and are specific to the repair application. Understanding the characteristics and material properties of CFRP can open up a world of opportunities for structural strengthening.

What are the advantages of using heavier weight carbon fiber fabric for structural strengthening of concrete elements? SRS-660UNI contains 12,000 strands of carbon fiber per tow which gives it distinct advantages over lighter weight material. In many commercial, civil and industrial applications lamination time and the material cost are reduced considerably with a single layer of 600gram fabric which adds more strength and thickness to a structure than 3 layers of 3k 195g cloth.

Unidirectional Carbon Fiber fabric is best utilized for strengthening of concrete and masonry components where ultimate tensile strength is needed in one direction such as in the following applications;

•Bowing wall stabilization
•Reinforcement of broken corners
•Flexural strengthening
•Shear strengthening
•Increasing load capacity
•Confinement of structural elements

Crack repairs are one of the most common uses of bidirectional carbon fiber. From problematic cracks in poured walls to stair step cracks in block. CFRP provides unparalleled confinement strength over the crack to arrest all movement and prevent future failures. The ability to add this kind of strength to a crack repair has significant benefits. It can be used to remedy a problem injection or to simply reinforce a crack repair to provide peace of mind that it will not re-open. In addition to the strength properties provided by SRS-660BI, waterproofing capabilities are another benefit to its use.

CFRP or Carbon Fiber Reinforced Polymer - How do these two components work together? The SRS-1000 Structural Epoxy Adhesive, specifically formulated to saturate the carbon fiber fabric, penetrates deep into the pores of the concrete while providing a bond strength to the substrate of over 35,000lbs per foot.

Once the SRS-660 Bidirectional fabric is applied to the initial layer of epoxy, a composite strengthening system is formed. Each tow of fabric contains 12,000 filaments of carbon fiber to bridge the crack, forming a permanent bond while stopping the crack from ever reopening. Since the carbon fiber is 10x stronger than steel, and has little to no elongation, this type of repair application provides exceptional confinement strength to stop the spread of cracks in concrete.

Another common application for the SRS-660BI is the reinforcement of cracks related to corroded rebar. As the corrosion progresses it worsens the condition of the concrete around the reinforcing steel. One method to reinforce against these types of failures is to repair these areas with a bidirectional carbon fiber. This will not only provide confining strength over the repair, but will also help make up for any section loss in the corroded rebar.

Any time there are changes to a structural component such as a slab or a wall, consideration has to be made for any rebar or tensioning cables that have to be cut. In most cases CFRP can be used to transfer the stress around the opening and back to the initial tensile carrying components.

The two most popular places this is seen are in load bearing walls or structural slabs. In the case of a wall, typically the reinforcement would be needed on both sides of the wall as it will need to be strengthened as to not deflect in either direction.

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