CFRP Strengthening

Carbon Fibre Reinforced Polymer (CFRP) composites have been used for structural strengthening in the United Kingdom for almost 30 years. During this period, acceptance of CFRP composites as a mainstream construction material has grown, and so has the number of completed CFRP strengthening projects completed by The Gunite Group nationally. Carbon fibre is used to strengthen beams and columns adding capacity to carry load, typical applications include bridge cross beams and columns and beams within high rise buildings.

As a result, the use of CFRP for strengthening and retrofit is gaining more popularity among design professionals over conventional strengthening techniques, such as installation of supplemental structural steel work.

Applied to reinforced concrete structures for flexure, CFRP typically has a large impact on strength (doubling or more the strength of the section is not uncommon), but only a moderate increase in stiffness (perhaps a 10% increase).

This is because the material used in this application is typically very strong (e.g., 3000 MPa ultimate tensile strength, more than 10 times mild steel) but not particularly stiff (150 to 250 GPa, a little less than steel, is typical). As a consequence, only small cross-sectional areas of the material are used. Small areas of very high strength but moderate stiffness material will significantly increase strength, but not stiffness.

The two most common systems we apply at Gunite are carbon plate and carbon fibre wrap.

Plate bonding is where the composite plates, which are usually carbon fibre reinforced, are manufactured off site, and then bonded to the structure using epoxy adhesive.

CFRP wrap where the dry fibre fabric is rolled into the wet resin on the structures surface.

CFRP strengthening of existing structures can involve complex evaluation, design, and detailing processes, requiring a good understanding of the existing structural conditions along with the materials used to repair the structure prior to CFRP installation.

The Gunite Group can offer bespoke evaluation and design of your CFRP solution.

Should you wish to receive more information on the potential use of CFRP with your planned project please contact our head office where one of our technical team will be happy to assist.