What is carbon fibre reinforced polymers (CFRP)?
Carbon fibre is one of the materials that has assisted the building and repair sectors, it is also known as graphite fibre or carbon graphite. It is a type of high-performance fibre used in civil engineering.
It has increasingly become a go-to option as a lightweight, extraordinarily strong reinforcement with a high load-bearing capacity when combined with other materials to create a composite.
Carbon fibre provides high versatility. Wide temperature tolerance, low thermal expansion, strong tensile strength, outstanding chemical resistance, and adaptability for various circumstances. Additionally, carbon fibre is lighter than steel while providing up to five times the strength, has a higher elastic modulus than glass fibres, and has higher fatigue strength.
Due to its high strength-to-weight ratio, resistance to corrosion, and simplicity of installation, carbon fibre has been utilised extensively in recent years to repair and reinforce concrete structures.
Why carbon fiber reinforced polymers (CFRP) strengthening material needs to be fire-proofed?
CFRP-strengthened reinforced concrete structures have very poor fire protection. When concrete structures are reinforced and repaired with CFRP, the ambient temperature shouldn’t consistently exceed 60 C. One the one hand, epoxy is the most common type of glue used to adhere carbon fibre sheets. The adhesives break down or soften when the temperature rises over the glass transition temperature (Tg), which eliminates the shear tension between the fibres and keeps them from buckling. On the other hand, CFRP will plainly oxidise under aerobic conditions when the temperature is higher than 400 C, and the combustion would generate hazardous smoke.
It is discovered that a CFRP-strengthened structure cannot easily meet the fire resistance standards in the absence of any fire prevention measures. Therefore, adopting sensible precautions to increase the fire resistance of CFRP- strengthened reinforced concrete structures is crucial
What are the types of fire-proofing materials available in the market?
Following reinforcement, the buildings’ required fire protection grades should be achieved using fire-resistant materials and associated treatment techniques. When reinforced structures are placed in other special environments, efficient protection materials should be chosen based on the specific situation. Currently, thick fire-retardant coating, ultra-thin fire- retardant coating, fire prevention board, and ordinary cement mortar are the main fire protection materials utilised in CFRP-strengthened reinforced concrete structures.
- Thick fire-retardant coating – Thick fire-retardant coatings work by using the good thermal insulation of high-efficiency insulation materials that are already present in the coatings and the heat absorption effect of additives to prevent and consume fire heat from reaching the surface of the substrate, thereby reducing the substrate’s critical temperature. In addition to its apparent benefits in terms of fire resistance, thick fire retardant coatings also have the advantages of being water-borne, inexpensive, and weather resistant.
- Ultra-thin fire-retardant coating – A light porous carbonised foam layer is created when the coating expands and foams during firing, effectively preventing heat from transferring to the substrate. In an experiment, it was discovered that reinforced beams with ultra-thin fire-retardant coatings for fire protection initially had wider cracks in the coating, which slowly filled as the foaming thickness increased. In comparison to thick fireproof coating, ultra-thin fireproof coating exhibits lower fire resistance. In addition to the wire mesh between coatings and CFRP, a small amount of quartz sand should be sprayed outside to improve the adhesion between coatings and CFRP.
- Fire prevention board – It is made mostly of inorganic materials, to which different modified materials are then added following a certain process. This type of board exhibits good dimensional stability and fire insulation performance while retaining some strength in a fire.
- Cement mortar – The surface of the reinforcement components will be coated or sprayed with cement mortar. Mortar made of cement is not fire-resistant. Under the circumstance of a low fire-proof limit, it is suggested that regular cement mortar can also be employed as a fire-proof protective method for strengthening concrete beams. CFRP should be protected against early shedding by being set between cement mortar and U-shaped steel wire mesh. To reinforce the steel wire mesh, expansion screws should be installed at the top of the beam on both sides.
Therefore, Structural Repairs (M) Sdn Bhd, a qualified contractor that can assess the issue for you first before recommending the best course of action to you.
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