The costs to facilitate the rehabilitation or retrofit of existing structures can be significantly less than what would be required for demolition and reconstruction. However, existing methods of rehabilitation and retrofit using traditional materials such as steel and concrete are showing signs of inadequacy. Rehabilitation applications using fibre composite materials are showing promising results as long-term solutions. In earthquake prone areas the structural performance of steel reinforced civil structures can be improved by wrapping existing concrete columns in CFRP to increase ductility and improve earthquake response . Studies have shown that CFRP used in some seismic retrofit projects are less expensive than the traditional steel jackets. Fibre composites are demonstrating the potential to save owners significant amounts of money in the maintenance and repair of buildings and infrastructure with potential savings of between 30 and 40 percent expected over traditional materials.

Fibre composites are a two-phase material in which one phase reinforces the other. High strength fibres are used as the primary means of carrying load and a matrix material binds the fibres into a cohesive structural unit. The combination of fibres and resin produces a bulk material with strength and stiffness approaching that of the fibres and chemical resistance dictated by the resin. Composites are particularly useful in rehabilitation and retrofit projects due to their strength-to-weight and stiffness-to-weight ratios, chemical resistance, manufacturing versatility and superior adhesion.

The most common fibre composite materials used for rehabilitation and retrofit projects are epoxy resins and carbon or glass fibres. The epoxy resin system is provided in a two parts which must be combined in exact amounts to ensure correct properties of the hardened resin. Once mixed the resin has around 30 minutes of working time (depending on the constituents) before it begins to harden. Carbon fibres or glass fibres are often used in these projects in the form of strips of either dry cloth or pre-made laminates which can be bonded to the structure after the damaged area has been prepared.

Dear Debasish,

You provided useful info about the the composites; however my question was about another issue. I would really appreciate it if you can share with us any info or experience you may have related to my question.

Thanks 👍

The durability and service life of external CFRP composites; whether in beams or columns depends on its purpose and service life. This is because CFRP composites has different qualities (material properties) and different orientation of attachment depending on purpose. For example, a CFRP retrofitted structure may perform well more than 50 years if there was no such things happen which may cause damage or deterioration of the composites. However, CFRP may be out of work if structures exposed to such stress/loading frequently and if it's poorly installed.

So your question's answer is too relative as there's no conclusive answer for sure. But if you are just looking for a run out of the mill answer, I must say if CFRP composites are installed adequately with engineering knowledge, it will perform well - no question about that.

Dear Imros,

Thank you for your answer! Defnitly the service life will be longer depending on the configuration of the composites, i.e. in columns they will last longer than beams because they are wrapped around the column with an overlap, also U wrapping may be stronger thab straight application at the bottom of the beam, also the use of anchorage system increases the efficiency and service life.

However, the answer to my question cannot be just a prediction, we all known it will perform well, but for how long? Such info needs experience with CFRP repair projects whether from actual repair projects or long term lab specimens.

We have been using this material for enhancement of life of many aged concrete structures like buildings, foundations and bridges. It's working fine for last five years. In the recent past we have recommended to many of our clients and they are satisfied.