About Sika SikaWrap Hex-230 C

SikaWrap Hex-230 C is Sika’s workhorse carbon fibre fabric for structural strengthening, and it is the material specifiers reach for when an existing member has to do more than it was originally designed for. The fabric is unidirectional, meaning almost all of the carbon runs in one direction (the warp), so the full tensile capacity is delivered exactly along the line of stress the engineer wants to reinforce. On its own the fabric is only a dry cloth of black carbon filaments held in shape by a light thermoplastic weft; it becomes a load-bearing element only once it is impregnated on site with a Sikadur epoxy such as Sikadur-330. That two-part combination, fabric plus resin, is what forms the carbon fibre reinforced polymer (CFRP) that bonds to and works with the parent concrete.

For engineers and contractors across Delhi NCR and the rest of India, the appeal is practical. A CFRP wrap adds enormous tensile strength while adding almost no thickness and almost no weight, so it does not steal headroom, does not change the way loads travel to the foundations, and does not need heavy lifting equipment to install. It suits the situations Indian building stock throws up constantly, an old slab asked to carry a new use, a column that needs confinement before a seismic reassessment, a bridge girder facing heavier traffic, or a member damaged by corrosion or impact. Space Arc Engineering supplies SikaWrap Hex-230 C together with its companion Sikadur resins and handles application through trained crews, so the system is delivered as a designed solution rather than a loose roll of cloth.

The technical insight

The mechanism is straightforward composite action. Carbon fibre is extraordinarily strong in tension, with a dry-fibre tensile strength around 3,793 MPa and a modulus near 234 GPa, but it is a bundle of loose filaments with no stiffness of its own until it is set in a matrix. The Sikadur epoxy does three jobs at once: it wets out and locks every filament so they share load evenly, it glues the whole laminate to the concrete so strain transfers from the member into the fibres, and it protects the carbon from the environment. Because the fabric is unidirectional and only about 0.128 mm of actual fibre thick per ply, the engineer can align that thin, immensely strong sheet precisely where tensile demand is highest, on the soffit of a beam for flexure, wrapped around a column for confinement, or diagonally for shear, and add plies to reach the calculated capacity. The fabric strains to roughly 1.5 percent at failure, and design is always governed by a debonding or strain limit rather than by the raw fibre strength, which is why the manufacturer publishes design values well below the ultimate. It is a strengthening system, not a repair mortar, so the concrete underneath must already be sound and prepared to a proper pull-off strength before any fibre goes on.

Where it is used

• Flexural strengthening of RC beams by bonding fabric to the tension soffit
• Shear strengthening of beams using U-wraps or side-bonded strips
• Confinement wrapping of columns to raise axial and ductility capacity
• Flexural strengthening of one-way and two-way RC slabs
• Strengthening of bridge girders and decks for increased traffic loading
• Seismic retrofit and ductility upgrade of columns and joints
• Strengthening of masonry walls, chimneys and silos
• Restoring capacity to members weakened by corrosion, impact or fire

Key advantages

• Very high tensile strength in the fibre direction, around 3,793 MPa dry-fibre
• Adds almost no dead load or section thickness to the strengthened member
• Non-corrosive and alkali resistant, unlike bonded steel plate
• Flexible dry fabric wraps tightly around columns, curves and complex shapes
• Fast, low-disruption installation that returns the structure to service quickly
• Can be used for flexure, shear or confinement from the same fabric
• Backed by international approval (ICC ESR-3288, IBC 2015 compliance)
• Long service life once encapsulated in Sikadur epoxy

Limitations & considerations

• Not a standalone product, it must be laminated with a Sikadur epoxy to work
• Design must be carried out and certified by a qualified structural engineer
• Substrate must be sound and mechanically prepared to a verified pull-off strength
• Carbon fibre must be isolated from steel to avoid galvanic corrosion
• The cured laminate is a vapour barrier, so it is unsuitable where concrete faces freeze-thaw while saturated
• Untreated CFRP loses strength in fire and usually needs a separate fire-protection coating

Selection & best practice

Specifications

Industry use cases

How we position Sika SikaWrap Hex-230 C

Within the Sika family, SikaWrap Hex-230 C is the standard-modulus carbon fabric and is almost always specified with its designed partner resins, Sikadur-330 for the dry lay-up and priming, or Sikadur-300 for saturated wet lay-up; where a stiffer, higher-modulus wrap is called for, Sika offers heavier carbon grades in the same family. For anchoring the ends of a wrap into adjacent members, SikaWrap FX anchorage cords with Sikadur-330 complete the system. Space Arc also supplies the genuine equivalent from the Fosroc range for specifiers standardised on that brand, and for cases where a jacket rather than a bonded wrap is preferred we can advise on micro-concrete and repair-mortar routes instead. The right choice depends on the design intent, so we scope the strengthening scheme with the consulting engineer before recommending a specific fabric and resin combination.

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