Sika SikaWrap-301 C
High-strength unidirectional carbon fibre fabric for externally bonded flexural, shear and column-confinement strengthening of concrete, masonry and timber.
What is it?
A 304 g/m2 unidirectional woven carbon fibre (CFRP) fabric that is saturated in epoxy on site to form an externally bonded reinforcement laminate.
Where is it used?
Beams, slab soffits, columns, bridge girders, chimneys, silos and masonry walls that need added tensile, shear or confinement capacity without heavy jacketing.
Why use it?
Adds substantial tensile strength at negligible dead weight, installs fast with no cutting or welding, and does not corrode like bonded steel plate.
How is it applied?
Applied by hand lay-up into wet Sikadur epoxy over a primed, ground substrate; fibres are aligned to the direction of stress and rolled through to remove voids.
About Sika SikaWrap-301 C
SikaWrap-301 C is Sika’s high-strength, unidirectional carbon fibre fabric for externally bonded structural strengthening. The fabric carries its load-bearing carbon filaments in a single direction (the warp), while a fine thermo-welded weft holds the sheet dimensionally stable so it can be handled, cut and wrapped around real-world geometry without the fibres distorting. Once impregnated with a matched Sikadur epoxy on site, the dry fabric and resin cure into a stiff, thin CFRP laminate that is bonded to the concrete and works alongside the existing reinforcement. Because the composite is only a fraction of a millimetre thick per ply, it adds strength almost invisibly and without the mass, formwork or corrosion problems of steel plate or RC jacketing.
In practice this makes it a go-to solution when a structure has to carry more than it was designed for, or when deterioration and cracking have eaten into its capacity. Consultants specify it to lift the flexural and shear capacity of beams and slabs, to confine columns for higher axial load and ductility, and to bring older buildings and bridges up to current seismic demand. For a distributor-and-applicator like Space Arc across Delhi NCR and Pan-India, its appeal is practical: it reaches confined soffits and column heads that plate bonding cannot, the whole system is lightweight enough to be carried up scaffolding by hand, and structures can be returned to service quickly once the epoxy has cured.
The technical insight
The strengthening works because carbon fibre is extraordinarily strong and stiff in tension along its length, and SikaWrap-301 C places every one of those filaments in one direction so nothing is wasted. On its own the dry fabric is limp and cannot transfer load; the engineering happens when it is saturated in epoxy. The Sikadur resin does two jobs at once. It glues the laminate to the concrete so that strain in the member is transferred into the fibres, and it binds the thousands of individual filaments together so they share load as one sheet rather than pulling apart. The result is a bonded CFRP layer with a fibre tensile strength near 3,800 N/mm2 and an E-modulus around 230,000 N/mm2 that only reaches about 1.5% strain at rupture. That high stiffness matters: the fabric picks up tensile stress at very small deflections, so it engages before the concrete cracks widen, restrains crack growth, and adds capacity while the member is still serviceable. Correct fibre orientation is therefore everything. Fibres aligned to the span resist bending, fibres wrapped around the section resist shear and confine the core; get the direction wrong and the reinforcement contributes almost nothing.
Where it is used
- Flexural strengthening of RCC beams and one-way / two-way slab soffits where sagging capacity is deficient
- Shear strengthening of beams by U-wrapping or full wrapping across the web
- Column confinement to increase axial load capacity and ductility for seismic retrofit
- Seismic upgrading of frames, joints and shear walls to meet revised code demand
- Repair and capacity restoration of members damaged by corrosion, overload or fire
- Strengthening of bridge and flyover girders, decks and pier caps
- Wrapping of chimneys, silos, water tanks and circular sections
- Strengthening of masonry walls, arches and timber members on heritage and older structures
Key advantages
- Very high tensile strength (approx. 3,800 N/mm2) and stiffness in the fibre direction from a laminate only ~0.167 mm thick per ply
- Adds negligible dead load to the structure, unlike steel plate or concrete jacketing
- Completely non-corrosive, so it suits marine, industrial and buried-service environments
- Flexible dry fabric conforms to columns, curved sections and confined soffits that rigid plates cannot follow
- Fast, dry installation with no welding, hot works, drilling or heavy lifting equipment
- Thermo-welded weft keeps fibres straight and the sheet dimensionally stable during cutting and wrapping
- Wide 1200 mm roll covers large areas with fewer overlaps and joints
- Proven system when used with matched Sikadur epoxies, backed by Sika design support and international test data
Limitations & considerations
- Performance depends entirely on the matched Sikadur epoxy and on substrate preparation; the dry fabric has no strength by itself
- Bond is only as good as the concrete surface, which must be sound, ground, dust-free and repaired before application
- Being unidirectional, it strengthens only along the fibre axis, so ply orientation and layout must follow the engineer’s design
- Sensitive to elevated temperature and fire; an external protective or fire-rated coating is usually required for exposed applications
- Requires a dry substrate and controlled ambient conditions, and epoxy pot life shortens in Indian summer heat
- Skilled, trained applicators are essential; poor saturation, wrinkles or trapped air sharply reduce the effective capacity
Selection & best practice
Treat the wrap and the resin as one system and never substitute either. Start by having the strengthening designed by a competent engineer so the number of plies, their direction and lap lengths are defined before anything is ordered. On site, prepare the concrete first: repair spalls and honeycombing, grind back to a sound, roughened surface, round off sharp column corners to at least a 20 mm radius so the fibres are not cut on the arris, and remove all dust and laitance. Prime and level the surface with the specified Sikadur, then work the fabric into the wet resin in the design direction, saturating fully and rolling through with a ribbed roller so no air is trapped and the fibres wet out completely. Respect overlap lengths in the fibre direction, keep the work within the epoxy’s pot life (plan for shorter working times in hot weather), and protect the fresh laminate from rain, dust and traffic until cured. For any exposed or fire-critical location, over-coat the cured CFRP with a protective or fire-rated finish. Because installation quality governs the result, this is work for trained FRP applicators, not general labour.
Specifications
| Fabric type | Unidirectional woven carbon fibre fabric (CFRP) |
| Areal weight | 304 g/m2 |
| Dry fibre thickness | 0.167 mm per ply |
| Fibre tensile strength | approx. 3,800 N/mm2 |
| Fibre tensile E-modulus | approx. 230,000 N/mm2 |
| Elongation at break | approx. 1.5% |
| Fibre orientation | 0 degrees (unidirectional); thermo-welded weft for stability |
| Roll size | 1200 mm wide x 50 m long |
| Saturating resin | Sikadur-330 (dry lay-up) or Sikadur-300 with Sikadur-330 primer (wet lay-up) |
Industry use cases
Bridges & Infrastructure
Restoring and uprating girders, decks and pier caps carrying heavier modern traffic loads without demolition or lane closure over-runs.
Commercial & Residential Buildings
Strengthening beams and slabs for change of use or added floors, and confining columns during seismic retrofit of existing structures.
Industrial Plants
Reinforcing chimneys, silos, pipe racks and equipment foundations subject to increased loading or corrosion-driven loss of section.
Water & Marine
Rehabilitating tanks, reservoirs and jetty elements where non-corrosive strengthening is essential in wet and chloride-rich exposure.
Heritage & Older Structures
Discreetly upgrading masonry arches, walls and timber members where added mass and visible steelwork are unacceptable.
Frequently asked questions
What tensile strength and thickness does SikaWrap-301 C provide?
Which epoxy resin should be used with it?
Can it be applied to columns and curved surfaces?
How is it different from steel plate bonding?
Does the concrete need special preparation?
Can any contractor install it?
How we position Sika SikaWrap-301 C
SikaWrap-301 C sits in Sika’s externally bonded FRP strengthening range and should always be specified with its matched Sikadur epoxies: Sikadur-330 for dry lay-up or Sikadur-300 plus a Sikadur-330 primer for wet lay-up. Where a project needs higher stiffness or a heavier fabric, Sika’s wider SikaWrap family (including higher-modulus and glass variants such as SikaWrap-300 C and glass SikaWrap grades) offers alternatives within the same system. For carbon-plate rather than fabric strengthening of long soffits, the pre-cured Sika CarboDur laminates are the natural companion. Across our other brands, Space Arc also supplies equivalent carbon fibre wrap systems from Fosroc and MC-Bauchemie for specifiers who standardise on those houses; the choice usually comes down to approved-vendor lists and available design support rather than raw performance. Whichever system is chosen, it should be paired with the correct primer, saturant and surface repair mortar so the strengthening performs as designed.
Fosroc Nitowrap CW — A specifier standardised on Fosroc, or on a project with a Fosroc-approved vendor list, may prefer Nitowrap CW as a directly equivalent unidirectional carbon fibre wrap used with the Nitowrap 30 primer and Nitowrap 410 saturant system.
Related Structural Strengthening products
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