Sika SikaWrap-450 C
A high-strength unidirectional carbon fibre fabric for externally bonded FRP strengthening of concrete, masonry and timber members.
What is it?
A unidirectional woven carbon fibre fabric that is saturated on site with an epoxy resin to form a thin, high-strength FRP laminate bonded to the structure.
Where is it used?
On the tension face of beams and slabs, wrapped around columns and piers, and across walls, chimneys and silos where flexural, shear or seismic capacity has to be raised.
Why use it?
It adds substantial tensile strength with almost no added dead load or section size, so members can be upgraded without demolition or heavy new steel.
How is it applied?
The prepared substrate is primed, the fabric is cut to length, saturated with Sikadur epoxy (dry or wet lay-up) and rolled onto the surface until the resin fully impregnates the fibres.
About Sika SikaWrap-450 C
SikaWrap-450 C is Sika’s mid-weight unidirectional carbon fibre fabric, made for externally bonded reinforcement (EBR) of existing structures. All of the load-carrying fibres run in a single direction, held straight and evenly spaced by a fine thermoplastic weft that is heat-set during weaving. That construction lets the engineer orient the full strength of the carbon exactly along the line of the tensile or shear demand, whether that is along the span of a beam, around the hoop of a column, or diagonally across a shear zone. In service the fabric becomes part of a composite: once impregnated with epoxy and cured, the fibres and resin act together as a stiff, thin laminate only a fraction of a millimetre thick that is chemically and mechanically bonded to the parent concrete.
For contractors and consultants across India, the appeal is practical. A retrofit that would otherwise mean new steel plates, section enlargement or partial demolition can instead be handled with a fabric roll, a primer and a saturating resin, installed by hand in a fraction of the time and with negligible weight added to the structure. Because it is corrosion-proof and can follow curved or irregular profiles, SikaWrap-450 C suits both new-code upgrades and the repair of members already showing distress. Space Arc Engineering supplies the fabric together with the matching Sikadur resins and on-site guidance so the specified laminate is what actually gets built.
The technical insight
The strengthening mechanism is composite action through the bond line. Carbon fibre is extraordinarily strong and stiff in tension, roughly 4,000 N/mm² tensile strength and about 230,000 N/mm² elastic modulus, but on its own it is a loose, directional fabric with no shape. The epoxy saturant (Sikadur-330 for dry lay-up or Sikadur-300 for wet) does two jobs at once: it wets out and locks the individual filaments into a solid laminate, and it forms the adhesive bond to the concrete. Because the cured laminate is far stiffer than the concrete around it, once the member deflects and the tension face tries to elongate, the shear stress transferred across the epoxy interface pulls the carbon into action and it carries load the original section could not. The single fibre direction matters here: strength exists only along the fibres, so orientation is a design decision, not a detail. The governing limit is almost never the fibre, it is the bond, which is why a sound, roughened substrate with a minimum tensile (pull-off) strength of about 1.0 N/mm² is a non-negotiable precondition for the system to develop its rated capacity.
Where it is used
- Flexural strengthening of RC beams and slabs by bonding the fabric to the tension face along the span
- Shear strengthening of beams with vertical or inclined wraps across the web
- Seismic confinement and ductility upgrade of columns and piers using hoop-direction wrapping
- Retrofitting members to carry increased dead or live loads after a change of use
- Repair and reinstatement of structures weakened by corrosion, overload or impact damage
- Strengthening of masonry, brickwork and timber elements and load-bearing walls
- Confinement and refurbishment of chimneys, silos, towers and circular sections
- Substitute for external steel plate bonding where weight, corrosion or access rule steel out
Key advantages
- Very high tensile strength along the fibre direction with an extremely low self-weight
- Adds almost no thickness or dead load, so member size and foundations are unaffected
- Completely non-corroding, unlike bonded steel plate, which suits aggressive and damp environments
- Flexible dry fabric conforms to curved, angular and irregular surfaces
- Fibre orientation can be aligned precisely to the flexural, shear or confinement demand
- Fast, largely manual installation means shorter downtime and quicker return to service
- Compatible with both dry and wet lay-up using matched Sikadur epoxy resins
- Part of a documented Sika EBR system with published design and mechanical data
Limitations & considerations
- Strength is unidirectional; the fabric carries almost nothing across the fibre direction, so orientation must be engineered
- Performance depends entirely on the bond, and the substrate must reach roughly 1.0 N/mm2 pull-off strength before application
- Carbon is elastic to failure with about 1.7% elongation and little warning, so design must respect strain limits
- Being organic-resin based, the cured laminate needs fire protection or a protective overlay for fire-rated members
- Correct surface preparation, resin mixing and roller consolidation are critical; workmanship faults show up as poor bond
- Should be installed by trained applicators within the resin’s temperature and pot-life window.
Selection & best practice
Treat the substrate as the load-bearing partner. Grind or blast the concrete to expose sound aggregate, make good spalls and honeycombing, round off sharp arrises to at least a 20 mm radius where the fabric turns a corner, and confirm a minimum pull-off strength of about 1.0 N/mm² before starting. Prime and apply the matched Sikadur resin at the correct rate, keeping first-layer resin demand in the region of 0.8 to 1.2 kg/m² so the fibres are fully wetted out without starving or flooding the laminate. Lay the fabric with the fibres precisely in the design direction, then roll firmly along the fibres to drive out air and pull resin through the weave until the fabric turns uniformly dark. Overlap ends generously in the fibre direction as specified, respect resin pot life and the 5 to 35 degrees C working range, and protect the cured wrap with a top-coat or render where fire, UV or mechanical exposure demands it. Store the rolls flat and sealed in dry conditions, out of direct sun.
Specifications
| Fabric type | Unidirectional woven carbon fibre fabric, heat-set thermoplastic weft |
| Fibre orientation | 0 degree (unidirectional, longitudinal) |
| Dry fibre density | 1.82 g/cm3 |
| Dry fabric thickness | 0.255 mm |
| Dry fibre tensile strength | approx. 4,000 N/mm2 |
| Tensile E-modulus | approx. 230,000 N/mm2 |
| Elongation at break | approx. 1.7% |
| Saturating resin | Sikadur-330 (dry lay-up) or Sikadur-300 (wet lay-up) |
| Min. substrate tensile strength | 1.0 N/mm2 (pull-off) |
Industry use cases
Bridges & flyovers
Flexural and shear upgrading of RC girders and deck slabs to carry revised traffic loads without widening the section or adding steel.
Commercial & residential retrofit
Strengthening beams and slabs for a change of use, added floors or new heavy equipment where headroom and dead load are constrained.
Seismic rehabilitation
Hoop-direction wrapping of columns and piers to add confinement and ductility for compliance with current seismic codes.
Industrial structures
Confinement and repair of chimneys, silos and towers, and reinstatement of members degraded by corrosion or process loads.
Heritage & masonry
Discreet, low-weight strengthening of masonry walls and timber members where intrusive steelwork is undesirable.
Frequently asked questions
What resin is used with SikaWrap-450 C?
How much resin is needed per square metre?
Can it strengthen both for bending and for shear?
How is it different from steel plate bonding?
What surface condition does the concrete need?
Does the finished wrap need fire protection?
How we position Sika SikaWrap-450 C
SikaWrap-450 C sits in the middle of Sika’s FRP fabric range and is always specified with the matching Sikadur saturating resins (Sikadur-330 for dry lay-up, Sikadur-300 for wet lay-up) and a suitable primer, so treat it as a system rather than a single product. Where a design calls for a lighter or heavier areal weight, or a higher-modulus fibre, other SikaWrap grades cover those cases. For teams standardised on a single supplier, Space Arc also carries the equivalent Fosroc Nitowrap carbon fibre system and its Nitowrap epoxy saturants, which serve the same strengthening role. Speak to our technical team about the specified laminate, layer count and resin schedule before ordering.
Fosroc Nitowrap CW — Choose the Fosroc Nitowrap CW carbon fibre system when the project is already standardised on Fosroc products or their Nitowrap primer and saturant resins are being used for the rest of the strengthening scope.
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