16 April 2018
As CSC Services commence work installing a carbon fibre strengthening system to a structural beam at Hartlepool Power Station, Mark Lemon, CSC Services’ Managing Director takes a brief look at the process and its uses.
Following the identification of concrete spalling, the reinstatement of a structural beam within the Reactor Building of the Power Station is required. To improve the durability of the structure and prevent further degradation the refurbishment work will include the installation of carbon fibre plates and carbon fibre wrap.
Carbon fibre has very high tensile strength and is also very lightweight. When bonded to the exterior of a concrete column, beam, or slab, it can add significant strength without adding weight that would increase the load on foundations and other structural members.
Carbon Fibre Plates
Carbon fibre plates can be used to improve, increase or repair the performance and resistance of concrete structures. Strategically placed, strengthening plates can be bonded to concrete elements to provide significant increases in carrying capacity and stiffness.
Carbon fibre plates, or sheets as they are sometimes referred to are made from carbon fabric and epoxy resins. They are available in thicknesses from 1.4mm to 40mm and there are various products on the market. In addition to excellent durability and high strength, carbon fibre plates are none corroding. They have a low system thickness and are available for unlimited lengths with no joints required.
Carbon fibre plates are often used when a structural system has been changed by the removal of walls or columns, or to repair design or construction defects such as insufficient reinforcement or structural depth. Carbon fibre plates can increase load carrying capacity of floor slabs, beams and bridge sections; be used to stabilise vibrating structures or provide support for the installation of heavy machinery.
In this case the carbon fibre plates will be used to improve the durability of the structure. They will improve fatigue resistance, and reduce stress in the steel reinforcement, preventing further cracking.
Carbon fibre rods are also available depending on the requirements of the strengthening system. Manufactured using unidirectional carbon fibres, carbon fibre rods are available in a range of diameters.
Carbon Fibre Wrapping
To complete the reinforcing system, carbon fibre wrapping of the structural beam will be undertaken. Woven unidirectional carbon fibre fabric will be wrapped around the beam in a series of over-lapping layers to further strengthen the reinforced concrete.
A mix of usually carbon or glass fibre fabrics, and an epoxy resin, wrapping systems are custom designed for each project and application.
Where there is an element of corrosion in the structure, carbon fibre wrapping can be used to both weather-proof corrosion and structurally re-enforce the structure. The impervious material will protect a structure from moisture intrusion and further corrosion, reducing the need for ongoing maintenance work.
Carbon fibre strengthening can be a cost effective, clean and un-intrusive solution to a common structural problem. It isn’t suitable for every strengthening project and you should always get advice from a specialist contractor about the best method to use. Please contact CSC Services on 0191 410 3444 for further information about carbon fibre strengthening.
Thanks to Sika for providing images.