Sika SikaWrap-300 C NW
A unidirectional carbon fibre fabric that adds flexural, shear and confinement capacity to concrete, masonry and timber without adding meaningful dead load.
What is it?
A 300 g/m2 class unidirectional (0 degree) carbon fibre fabric, stitched non-woven, used as external bonded reinforcement in the Sika strengthening system.
Where is it used?
Beams, columns, slabs, walls, chimneys, silos and masonry that need extra load capacity or seismic confinement.
Why use it?
Very high tensile strength at negligible weight, so members gain capacity without new dead load or altered geometry.
How is it applied?
Bonded to a prepared substrate by wet lay-up with Sikadur-300 or dry lay-up with Sikadur-330 epoxy, fibres running along the load direction.
About Sika SikaWrap-300 C NW
SikaWrap-300 C NW is a unidirectional carbon fibre fabric supplied as part of Sika’s externally bonded reinforcement (EBR) system. The load-carrying fibres are aligned in a single 0 degree direction and held in place by a light non-woven stitching, which is what the NW in the name refers to. Because virtually all the mass is structural carbon, the fabric behaves almost purely along its length, letting a designer place strength exactly where a member is deficient. Cured onto concrete, masonry, brickwork or timber with a Sikadur epoxy, it forms a thin composite laminate that shares tension with the parent element and lifts its flexural, shear or axial capacity.
For engineers and contractors in India, the appeal is practical. A strengthening scheme that once meant steel plates, jacketing or added sections can often be replaced by a few millimetres of bonded fabric that adds almost no dead load and needs no heavy lifting gear. Space Arc Engineering supplies SikaWrap-300 C NW as an authorised Sika distributor and applicator across Delhi NCR and Pan-India, alongside the matching Sikadur resins and primers so the system is specified and installed as one compatible package rather than mixed brands.
The technical insight
The mechanism is straightforward once you picture where the load goes. Carbon fibre is extremely stiff and strong in tension but does nothing useful in compression or across its width, so the fabric is engineered as a one-way material: roughly 99 percent black carbon warp fibres carrying load, with about 1 percent white heat-set thermoplastic weft simply holding the tows straight and evenly spaced until the resin locks them. The dry fibre develops around 4,000 N/mm2 tensile strength at a modulus near 230,000 N/mm2, yet elongates only about 1.7 percent at break, which is why it is treated as an elastic reinforcement that stays effective right up to failure. When impregnated with Sikadur epoxy and cured, the fabric and resin act as a single laminate with a design thickness of 0.167 mm, giving roughly 167 mm2 of effective cross section per metre of width and characteristic laminate strengths of about 3,200 N/mm2. Bond is everything: the epoxy transfers stress by shear from the concrete into the fibres, so the substrate must offer at least 1.0 N/mm2 pull-off strength for the system to reach its rated performance.
Where it is used
- Flexural strengthening of reinforced concrete beams and slabs where extra sagging or hogging capacity is required
- Shear strengthening of beams and short columns by U-wrapping or full wrapping across the member
- Seismic confinement of columns to raise ductility and axial capacity in retrofit projects
- Upgrading of masonry and brick walls for improved in-plane and out-of-plane seismic behaviour
- Compensating for corroded, missing or under-provided steel reinforcement in ageing structures
- Increasing load rating of structures facing a change of use, added floors or heavier machinery
- Repair and durability upgrades on chimneys, silos, water tanks, piles and soffits
- Strengthening of timber elements as part of a designed composite scheme
Key advantages
- Very high tensile strength (around 4,000 N/mm2 dry fibre) at negligible added dead load
- Unidirectional layout lets the designer place capacity precisely along the load path
- Thin bonded laminate does not change member size, headroom or architectural lines
- Flexible fabric wraps tight radii and irregular shapes such as columns, piles and chimneys
- Fast to install compared with steel jacketing, with no welding, cutting or heavy plant
- Corrosion-free carbon avoids the long-term rusting problems of bonded steel plates
- Backed by recognised design guidance including ACI 440.2R and Concrete Society TR55
- Full Sika system compatibility when paired with matched Sikadur primers and resins
Limitations & considerations
- Performance depends entirely on substrate quality; concrete must give at least 1.0 N/mm2 pull-off bond
- Purely unidirectional, so it strengthens only along the fibre direction and needs correct orientation
- Requires a qualified structural engineer to size layers and detail anchorage; it is not a DIY repair
- Carbon fabric needs UV and, where fire matters, cementitious or protective over-coating for durability
- System components must not be interchanged; only Sikadur resins are validated with this fabric
- Epoxy cure is temperature-sensitive, so hot-weather Indian sites need planning around working times
Selection & best practice
Success hinges on preparation and staying inside the Sika system. Grind or grit-blast the concrete to a sound, laitance-free, open-textured surface, make good any spalls, and round off sharp corners to at least a 20-25 mm radius before wrapping columns so the fabric is not cut by an edge. Confirm the substrate gives a minimum 1.0 N/mm2 pull-off strength. Cut the fabric with proper shears or a sharp knife and never fold it, as kinks permanently weaken the fibres. For dry lay-up, prime and laminate with Sikadur-330 (about 1.0-1.5 kg/m2 including primer for the first layer, then 0.8 kg/m2 per further layer); for wet lay-up use Sikadur-300 (primer 0.4-0.6 kg/m2, fabric layers around 0.6 kg/m2). Consolidate each ply with a ribbed roller to remove air and fully wet out the fibres, keep layers aligned to the design direction, and respect the epoxy pot life in warm conditions. Where the wrap is exposed, over-coat for UV protection, for example with Sikagard-550 W Elastic.
Specifications
| Fibre orientation | 0 degree, unidirectional |
| Construction | Stitched, non-woven; warp 99% black carbon, weft ~1% heat-set thermoplastic |
| Mass per area | 304 g/m2 (carbon fibres only), tolerance +/- 10 g/m2 |
| Dry fibre tensile strength | 4,000 N/mm2 (ISO 10618) |
| Dry fibre modulus of elasticity | 230,000 N/mm2 (ISO 10618) |
| Dry fibre elongation at break | 1.7% (ISO 10618) |
| Design nominal thickness | 0.167 mm (167 mm2 cross section per m width) |
| Laminate tensile strength | ~3,500 N/mm2 average / 3,200 N/mm2 characteristic |
| Minimum substrate pull-off strength | 1.0 N/mm2 |
Industry use cases
Commercial and IT parks
Beams and slabs strengthened to carry added services, mezzanines or heavier fit-outs during refurbishment without recasting members.
Bridges and infrastructure
Girders and pier caps upgraded for increased traffic loading or to correct deficient reinforcement, using externally bonded fabric per ACI 440 guidance.
Seismic retrofit
RC columns and masonry walls confined and wrapped to improve ductility and meet current seismic codes in earthquake-prone zones.
Industrial plants
Silos, chimneys, pile caps and machine foundations reinforced to handle raised process loads or to arrest deterioration.
Heritage and residential repair
Ageing concrete and brick structures upgraded discreetly, adding capacity without altering the visible geometry of the building.
Frequently asked questions
What does the NW in SikaWrap-300 C NW mean?
Which resins do I use with it?
How much resin will I need per square metre?
Can I design a strengthening scheme myself?
Does the substrate need any minimum strength?
Do I need to protect the wrap after installation?
How we position Sika SikaWrap-300 C NW
SikaWrap-300 C NW sits in the mid-strength band of the Sika carbon fabric range and is best specified as a complete system with Sikadur-330 (dry lay-up) or Sikadur-300 (wet lay-up) resins, finished where exposed with Sikagard-550 W Elastic. Where a project calls for a pre-cured, factory-controlled laminate instead of a wet-applied fabric, look at Sika CarboDur plates bonded with Sikadur-30 as a stiffer alternative for straight tension members. Across our other brands, Space Arc also supplies competing CFRP wrap systems from Fosroc and MC-Bauchemie, so specifiers who standardise on a particular house can be matched to an equivalent grade. For substrate repair ahead of wrapping, pair it with a structural repair mortar such as Sika MonoTop before bonding the fabric.
Fosroc Nitowrap EP(CF) — A genuine equivalent unidirectional CFRP wrap (CF300 grade matches this 300 g/m2 class), worth choosing when a project is standardised on the Fosroc Nitowrap system and its matched Nitowrap primer, saturant and UV topcoat.
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Authorised distribution, technical advice & professional application across Delhi NCR and Pan-India.