Mark Shaw, Technical Manager for Refurbishment at Sika Limited

What is Carbon Fibre Reinforced Plastic (CFRP)? A not-so uncommon question, as keyword research reveals an average 50 such online enquiries are made each month.

 

CFRP is seen as a safer, cost-effective and environmentally-friendly alternative to steel in shear, flexural and axial loading enhancement when increasing the existing load carrying capacity of all types of structures. Buildings, bridges, marine structures and structural elements such as beams, columns, slabs, walls…CFRP can be used to provide long-term structural strength for numerous applications when bonded on the surface of reinforced concrete, steel, masonry, cast iron and timber.

 

Its benefits include:

  • Excellent resistance to corrosion and chemical effects
  • CFRP increases a structure’s lifetime
  • Proven global track record
  • Increased strength to weight ratio compared to steel
  • Minimal visual impact owing to the thickness

The Sika carbon fibre system comes in two forms: prefabricated (carbon fibre plates and rods and epoxy structural adhesive; a special post-tensioned system is also available) and wet lay -up sheet systems: carbon fibre structural fabrics and epoxy laminating resin.

 

Prefabricated systems represent 80% of the current applications in Europe as they are usually considered a safer system. As well as requiring less-restrictive measures in relation to the unevenness of a concrete surface, a prefabricated system offers a higher degree of efficiency during the installation process. The ultimate strength of CFRP is likely to be at least five times the ultimate strength of steel for the same cross-sectional area.

The disadvantages of CFRP are few. A CFRP composite plate is more expensive than its steel counterpart of the equivalent load capacity. However, CFRP’s easy application helps reduce onsite costs, whilst its durability negates the need for costly maintenance caused by steel-based corrosion. It therefore retains its long-term cost-effectivness.  

 

Having established CFRP’s properties and uses, what is its market availability? Sika provides a range of structural strengthening solutions and integrated systems to suit almost any project and site requirement. Sika structural strengthening systems have been tested extensively internally and externally under many different conditions to ensure long-term performance in different environments for:

  • Sustainable – less reliance of other less sustainable materials such as steel, aluminium and titanium
  • Long-term fatigue resistance
  • Artificial ageing
  • Exposure in most environments
  • Installation under dynamic load
  • Installation in cold temperatures

Sika® Carbodur®

The Sika® Carbodur® System is one of the most established and proven carbon fibre-reinforced polymer (CFRP) based structural strengthening prefabricated plate solutions in the world. It consists of Sika Carbodur® CFRP plates and rods, plus the structural epoxy resin-based adhesive Sikadur®-30. This simple and reliable, high-performance system is easy to apply and provides outstanding long-term durability. It is the ideal externally-bonded flexural strengthening solution for concrete, steel, timber, masonry and cast iron structures.

Sika® CarboShear®

The range also includes the Sika CarboShear® System, a unique solution for external shear strengthening of beams. Its L-shaped CFRP profiles, which are bonded onto a beam  with Sikadur®-30  structural epoxy resin-based adhesive, significantly increasing the capacity of reinforced concrete-beams to highly-effective and efficient shear strengthening.

Other benefits include:

  • Easy and fast installation
  • Pre-prepared end section to provide excellent anchorage
  • Low thickness, easy to overcoat
  • Available in different dimensions  

SikaWrap®

For structural column confinement, strengthening of weaker concrete, masonry, natural stone and timber structures; the SikaWrap® Fabric Strengthening System offers outstanding performance when applied to irregularly-shaped structures and substrates to enable enhanced load-carrying capacity or ductility.

The above are just a few examples of the virtually tailor-made solutions Sika provides for the repair, refurbishment and improvement-by-strengthening of existing buildings and civil engineering structures. As well as its superb product range and integrated systems to suit almost every project and site requirement, Sika provides exemplary customer advice, support to their design and detailing software (available from their website), contractor training, practical installation, successful completion on site and guarantees.

 

Its expertise is based on experience on large and small strengthening projects all over the world. Strong and flexible, CFRP is a 21st century cost-effective solution to the age-old challenge of keeping our structures safe and operational.