CARBON FIBERS AND THEIR APPLICATION IN CIVIL ENGINEERING 5 from 7

CFRP chimney liners been in service up to 20 years have proven CFRP survival at high tempera- true, resistance to chemicals, structural reliability, low life-cycle cost, and low maintenance.

Beam, Column and Slab strengthening is another very important application of Carbon Fiber composites’ In flexural reinforced concrete members, the addition of carbon fibers improves the modulus of rupture (bending strength).

Also, there is evidence that carbon fibers can be effective replacements for shear steel stirrups commonly used in RCC beams and other structural elements such as shear keys and

corbels.

Two techniques can be adopted to strengthen the beams. First one is to paste CFRP plates to the bottom (generally the tension face) of a beam.

This increases the strength of beam, deflection capacity of beam and stiffness(load required to make unit deflection).

Alternatively, CFRP strips can be pasted in ‘U’ shape around the sides and bottom of a beam, resulting in higher shear resistance.

Columns in building can be wrapped with CFRP for achieving higher strength’ The technique works by restraining the Lateral expansion of the column.

Slabs may be strengthened by pasting CFRP strips at their bottom (tension face).

This will result in better performance, since the tensile resistance of slabs is supplementedby the tensile strength of CFRP In the case of beams and slabs, the effectiveness of CFRP strengthening depends on the performance of the resin chosen for bonding.

Pre-stressing carbon fiber reinforced polymers

By means of pre-stressing capacity, the stiffness of strengthened structures can be improved greatly for the sake of delaying the onset of cracking, reducing the deflection, relieving the strain in internal reinforcement, etc.

In the early stage of CFRP pre-stressing technique, CFRP plate was often chosen as pre- stressing material to strengthen the structures owing to its fixed shape, but this fixed shape