Sika SikaWrap-451 C IN
A 450 g/m2 unidirectional carbon fibre fabric that bonds to concrete, masonry and timber to add flexural, shear and confinement capacity without adding dead load.
What is it?
A high-strength unidirectional carbon fibre fabric, weighing 450 g/m2, that is saturated on site with epoxy resin to form an externally bonded FRP laminate for structural strengthening.
Where is it used?
Reinforced concrete beams, columns, slabs and soffits, plus masonry, brickwork and timber members needing extra flexural, shear or axial capacity.
Why use it?
It restores or increases load capacity, adds seismic ductility and lets a member be upgraded in place, with almost no added weight or loss of headroom.
How is it applied?
The prepared substrate is primed and saturated with Sikadur-330 IN, the dry fabric is laid into the resin along the load direction, then rolled through to fully wet out and remove air.
About Sika SikaWrap-451 C IN
SikaWrap-451 C IN is the India-grade version of Sika’s high-strength carbon fibre wrap, made for engineers who need to add capacity to an existing structure rather than demolish and rebuild it. The fabric is unidirectional: nearly all the load-carrying carbon filaments run in one direction (the warp, at 0 degrees), held in place by a light heat-set glass weft that keeps the roll stable and easy to handle on site. Because the fibres are aligned, the installer can orient the wrap exactly along the tension path of a beam or around the girth of a column, putting the strength precisely where the design calls for it.
On its own the dry fabric does very little; the performance comes from the composite. Once the fabric is saturated with Sikadur-330 IN epoxy and cured against a sound substrate, the carbon and resin act as a single externally bonded laminate that shares load with the parent concrete. The result is a thin, corrosion-immune layer, only about 0.25 mm of fibre thickness per ply, that carries very high tensile force yet adds negligible section and weight. This is why FRP strengthening has largely replaced steel plate bonding for retrofits: no bolts, no heavy jacketing, and no long shutdown of the structure.
The technical insight
The mechanism is externally bonded reinforcement working in tension. Concrete is strong in compression but weak in tension, so a beam fails on its tension face and a column loses capacity as it dilates under axial and seismic load. SikaWrap-451 C IN adds a carbon laminate exactly where that tension develops. The dry carbon fibres carry a tensile strength near 4,900 N/mm2 at a modulus of about 250,000 N/mm2, with elongation at break around 2.1 percent, meaning the fabric stays stiff and takes up load at very small strains, before the concrete can crack further. The epoxy does two jobs: it wets out every filament so the bundle acts together, and it transfers shear from the concrete surface into the fibres through the bond line. That bond is the design-critical link, which is why Sika specifies a minimum substrate tensile strength of 1.0 N/mm2 (or as the strengthening design requires). Wrapped fully around a column, the fabric adds passive confinement: as the concrete tries to expand under load, the hoop-oriented carbon restrains it, raising both strength and ductility, which is the property seismic retrofits depend on.
Where it is used
- Flexural strengthening of RC beams and slabs by bonding the wrap along the tension soffit
- Shear strengthening of beams with U-wraps or full wraps on the web
- Seismic confinement of columns to boost axial capacity and ductility
- Restoring capacity to members with corroded, insufficient or missing steel reinforcement
- Upgrading structures for higher live loads after a change of use or added storeys
- Strengthening masonry, brickwork and timber elements alongside concrete
- Rehabilitation of bridge girders, piers and industrial support members
- Repair of members cracked or damaged by overload, impact or fire
Key advantages
- Very high tensile strength (about 4,900 N/mm2 dry fibre) in a laminate only ~0.25 mm thick per ply
- Unidirectional layout lets you aim the strength precisely along the tension or hoop path
- Adds capacity with almost no extra dead load and no loss of clear headroom
- Carbon fibre does not corrode, suiting marine, coastal and aggressive environments
- Flexible dry fabric conforms to beams, round and square columns, soffits and curved surfaces
- Installed by hand with a matched Sika resin, so no welding, bolting or heavy plant
- Multiple plies can be built up where the design demands more strengthening
- Fast, low-disruption retrofit that can keep a structure largely in service
Limitations & considerations
- It is a structural product and must be designed by a qualified engineer, not applied to a rule of thumb
- Performance depends on bond, so the substrate must reach at least 1.0 N/mm2 tensile strength and be properly prepared
- Carbon fibre offers little fire resistance on its own and usually needs a protective or fire-rated overlay
- Full cure and load transfer rely on correct epoxy mixing, wet-out and site temperature control
- Being unidirectional, it strengthens only along the fibre axis; biaxial demands need extra plies or a different fabric
- Not a waterproofing or a cosmetic finish; a separate protective coating is normally specified over it
Selection & best practice
Treat the substrate as the foundation of the whole system. Grind or grit-blast the concrete to sound aggregate, round off sharp arrises (especially on columns, where a minimum corner radius prevents the fibre from being cut), repair spalls and honeycombing, and confirm the pull-off strength meets the 1.0 N/mm2 minimum before any resin goes down. Prime and saturate with Sikadur-330 IN at the specified consumption: roughly 0.8 to 1.2 kg/m2 for the first layer and 0.5 to 0.8 kg/m2 for each further layer. Lay the fabric strictly along the design fibre direction, then roll firmly in the fibre direction to fully wet out the carbon and drive out entrapped air, which is the most common cause of weak spots. Respect lap lengths, keep within the epoxy’s pot life and application temperature window, and protect the finished laminate with a suitable coating for UV and fire.
Specifications
| Fabric type | Unidirectional woven carbon fibre fabric (dry application) |
| Fibre orientation | 0 degrees (warp), heat-set glass weft |
| Areal weight | 450 g/m2 +/- 23 g/m2 (carbon fibres only) |
| Fibre thickness | 0.250 mm (based on fibre content) |
| Dry fibre tensile strength | 4,900 N/mm2 (ISO 10618) |
| Tensile E-modulus | 250,000 N/mm2 (ISO 10618) |
| Elongation at break | 2.1% (ISO 10618) |
| Saturating resin | Sikadur-330 IN epoxy |
| Roll size | 500 mm wide x >= 50 m long, 1 roll per box |
Industry use cases
Bridges & Infrastructure
Upgrading girders, piers and deck soffits to carry heavier traffic loads or to correct deficient reinforcement without closing the crossing.
Commercial & Residential Buildings
Strengthening beams, columns and slabs when a floor changes use, extra storeys are added or the original design is found under-reinforced.
Seismic Retrofit
Confining columns to add ductility and axial capacity so existing frames meet current seismic code demands.
Industrial Plants
Rehabilitating overloaded or fatigue-damaged support beams, pipe racks and equipment foundations while the plant stays in service.
Marine & Coastal Structures
Strengthening members in chloride-rich environments where carbon fibre’s immunity to corrosion is a decisive advantage over steel.
Frequently asked questions
What resin is used with SikaWrap-451 C IN?
How much resin will I need per square metre?
How strong is the fabric?
Can it be used to strengthen columns for earthquakes?
What condition does the concrete need to be in?
How is it supplied and does Space Arc apply it?
How we position Sika SikaWrap-451 C IN
SikaWrap-451 C IN sits in the mid-to-heavy range of Sika’s dry carbon fabric family. Where a design needs a lighter wrap, SikaWrap-230 C or -300 C are the lower-areal-weight options; SikaWrap-450 C is the closely related sibling. It always pairs with Sikadur-330 IN saturating resin, and where a pre-cured plate suits the geometry better than a fabric, the Sika CarboDur laminate strip range is the alternative. Across brands, Space Arc also supplies Fosroc’s Nitowrap carbon fibre system for teams standardised on that specification, so we can match the wrap to the consultant’s approved product list rather than the other way round.
Fosroc Nitowrap CF — Specify the Fosroc CFRP system when the consultant’s design or approved-vendor list is built around Nitowrap rather than SikaWrap, so the fabric and its epoxy come from one qualified supply chain.
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