Reinforcement of concrete beams with carbon fiber

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This post is going to show a reinforcement method for structural element, that is replacing the traditional methods.

In many cases is necessary to reinforce a concrete structure, some causes are:

  • Increase of design loads.
  • Change in construction use (from residential to public use).
  • Steel reinforcement corrosion.

The traditional reinforcement methods in many cases are too invasive, like for example section regrowth. This post proposes other method, the reinforcement using carbon fiber, that can appear to be more expensive but due to the easiness, low amount of material and easy application, can be the best and cheapest option.

Carbon fiber sheets are applied directly on the clean concrete surface, so with this methods aren´t necessary special execution tools.

The use of this method is very useful for reinforcement of concrete beams for bending and shear, and for columns.

This material has a tensile strength of 2500 N/mm2, what means 5 times more than steel B-500. This can give an idea of the great potential of this material.

The recommended maximum deflection is 0,60 %, with this deflection the design tensile strength is 1000 N/mm2, twice than steel, so to compensate 2cm2 of B-500 steel, 1cm2 of carbon fiber is required.

Two standard fibers used are:

  • 50 mm width x 1,2 mm depth = 60 mm2. What corresponds to 120 mm2 of steel B-500 that is approximately like use one rebar Ø12.
  • 80 mm width x 1,2 mm depth = 96 mm2. What corresponds to 192 mm2 of steel B-500 that is approximately like use one rebar Ø16.

As explained at the beginning of the article, the main advantage of this method is the easy application, it is only necessary to adhere the carbon fiber sheet on the surface. It is fast, easy and do not alter the existing structure.


Bending reinforcement               Shear reinforcement

Another advantage of the carbon fiber reinforcement is the durability:

  • No corrosion.
  • Resistance to any kind of environment (industrial or marine).
  • High fatigue strength

In conclusion, this method in many cases is the best option to achieve and efficient reinforcement of your structure, and can be more efficient than the traditional methods used. It will only be required to clean the concrete surface and you can apply the reinforcement directly.