Sika CarboDur S
Pultruded carbon-fibre laminate plates that add flexural capacity to concrete beams and slabs without adding weight, corrosion risk, or lost headroom.
What is it?
A factory-pultruded, unidirectional carbon-fibre reinforced polymer (CFRP) plate that is epoxy-bonded to the tension face of a structural member.
Where is it used?
Soffits of RC beams and slabs, bridge girders, transfer plates, parking decks and industrial frames that need more load capacity.
Why use it?
It restores or increases flexural strength on overloaded, damaged or repurposed structures, with no corrosion and almost no added dead load.
How is it applied?
The prepared concrete surface is primed, the plate is coated with Sikadur-30 adhesive, pressed on with a roller, and squeeze-out is tooled off.
About Sika CarboDur S
Sika CarboDur S is a pultruded carbon-fibre reinforced polymer plate used to strengthen existing concrete, and in some cases timber, masonry and steel members. Each plate is manufactured by drawing continuous unidirectional carbon fibres through a heated epoxy matrix, which produces a straight, dimensionally stable laminate with a very high proportion of aligned fibre. That geometry is what gives the plate its characteristic behaviour: enormous tensile capacity along its length, near-zero stretch under service loads, and a thickness of barely over a millimetre. In practical terms, a strip a few centimetres wide can do the work of a far heavier steel plate while adding negligible dead load to the member it is bonded to.
The plate is a bonded-on external reinforcement, so it never works in isolation. It is always installed as part of the Sika CarboDur system, in which the plate is adhered to a sound, prepared concrete surface with Sikadur-30, a thixotropic structural epoxy. Once the adhesive cures, the plate and the concrete act compositely, and the CFRP takes up the additional tensile stress that the original steel reinforcement alone cannot safely carry. For engineers and consultants in Delhi NCR and across India, it is a clean, low-disruption route to upgrading a structure that has been overloaded, damaged, corroded, or asked to carry a use it was never designed for, without the demolition, downtime and dead weight that section enlargement or steel plate bonding would involve.
The technical insight
The engineering logic behind CarboDur S is composite action through the bond line. When a reinforced concrete beam is loaded in bending, its soffit goes into tension, and that is exactly where the plate is bonded. Because the carbon fibres are all aligned along the plate and occupy more than two-thirds of its cross-section, the laminate has a very high elastic modulus (mean around 165 GPa, characteristic 150 GPa) and a mean tensile strength in the region of 3,100 MPa, comfortably several times the yield strength of ordinary reinforcing steel. Crucially, it stretches very little before it fails, breaking at a strain above 1.7 percent, so it starts sharing load as soon as the member deflects. The Sikadur-30 adhesive is the component that transfers shear between the concrete and the plate; get the surface preparation and adhesive thickness right and the two act as one section. Get them wrong and the failure mode shifts to premature debonding, which is why the bond and the concrete substrate strength, not the raw fibre strength, usually govern the design.
Where it is used
- Flexural strengthening of reinforced concrete beams and one-way / two-way slabs
- Soffit strengthening of bridge girders and deck slabs to raise live-load ratings
- Reinforcement of flat slabs and transfer plates where columns are removed or repositioned
- Upgrading parking-structure decks and ramps for higher axle or usage loads
- Strengthening industrial and warehouse frames before installing heavier plant or mezzanines
- Restoring capacity to members weakened by reinforcement corrosion, impact or overload
- Compensating for construction defects such as misplaced or deficient steel reinforcement
- Strengthening timber, masonry and steel elements as part of the CarboDur system
Key advantages
- Exceptional tensile strength and stiffness at a fraction of the weight of equivalent steel plate
- Completely non-corroding, so it suits marine, coastal, wastewater and de-iced structures
- Factory-pultruded to consistent dimensions and fibre content for predictable design values
- Barely over a millimetre thick, so headroom, clearances and floor levels are preserved
- Fast, low-disruption installation that keeps buildings and bridges partially in service
- Delivered in continuous rolls and cut to exact length on site, with almost no offcut waste
- Long, maintenance-free service life when correctly bonded and protected
- Backed by the proven CarboDur system with Sikadur-30 adhesive and design support
Limitations & considerations
- Strengthening is limited by the substrate: it needs sound concrete of adequate pull-off strength to bond to
- Effectiveness depends on correct surface preparation and adhesive application; poor workmanship leads to debonding
- Provides tensile reinforcement only, so it does not increase compression or, on its own, shear capacity
- Bare CFRP loses capacity in fire and must be protected where fire rating is required
- The unprotected epoxy and plate are sensitive to prolonged UV exposure and elevated temperatures near the glass transition point
- Design and installation must be carried out by trained specialists to approved calculations, not fitted ad hoc
Selection & best practice
Treat the plate as one part of a designed system, not a standalone product. Start with a structural assessment and a plate schedule from a competent engineer, then verify the concrete substrate: it should be sound, and pull-off tests should confirm adequate tensile strength before any bonding. Grind or grit-blast the soffit to remove laitance and expose aggregate, and clean the plate face with the recommended solvent immediately before bonding. Mix and apply Sikadur-30 to both the concrete and the plate, press the plate home with a rubber roller so adhesive squeezes out evenly along both edges, and tool off the excess. Keep the substrate and ambient temperatures within the adhesive’s working range and protect the fresh bond from disturbance, water and dust while it cures. Where fire rating, impact or UV exposure is a factor, over-clad or coat the installed plate. For column confinement, contours or shear wrapping, pair the plates with a fabric wrap system rather than forcing the plate to do a job it is not shaped for.
Specifications
| Product type | Pultruded unidirectional carbon-fibre reinforced polymer (CFRP) plate |
| Cross-sections (India range) | S512, S612, S812, S1012, S1213, S1512 (50–150 mm wide) |
| Plate thickness | 1.2 mm (1.3 mm on the 120 mm width) |
| Cross-sectional area | Approx. 60–180 mm² depending on plate size |
| Tensile E-modulus | Mean approx. 165 GPa; characteristic 150 GPa |
| Tensile strength | Mean approx. 3,100 MPa; characteristic approx. 2,800 MPa |
| Strain at break | Greater than 1.7 percent |
| Density | Approximately 1.6 g/cm³ |
| Bonding adhesive | Sikadur-30 structural epoxy (part of the CarboDur system) |
Industry use cases
Bridges & Infrastructure
Raising the live-load rating of ageing RC girders and deck slabs so heavier traffic can be carried without replacing the span.
Commercial & Retail Fit-out
Strengthening beams and slabs when openings are cut, columns are removed, or floors are re-purposed for heavier occupancy.
Parking & Podium Structures
Upgrading decks, ramps and transfer plates for higher vehicle loads while keeping clearances and levels unchanged.
Industrial & Warehousing
Reinforcing frames and floor slabs ahead of new machinery, racking or mezzanines that exceed the original design loads.
Repair & Rehabilitation
Restoring flexural capacity to members degraded by reinforcement corrosion, fire, impact or long-term overload.
Frequently asked questions
What exactly is Sika CarboDur S used for?
How is CarboDur S different from a carbon-fibre fabric wrap?
Which adhesive is used to bond the plate?
What plate sizes are available?
Does the concrete need to be in good condition first?
Can we self-install it, or do we need specialists?
How we position Sika CarboDur S
Sika CarboDur S is the plate of choice for straight flexural strengthening, and it is always specified with Sikadur-30 adhesive from the same system. Where the job calls for column confinement, shear strengthening, or wrapping around contours and corners, pair it with a fabric solution such as Sika Wrap rather than the rigid plate. For repairing and preparing the concrete substrate before bonding, our Sika MonoTop repair mortars and Sikadur crack-injection resins complete the sequence. Buyers who standardise on Fosroc for a project can achieve comparable strengthening through the Fosroc Nitowrap fabric range and Renderoc repair mortars, and our team will help match the right system to the structure, the loads and the specifier’s preference.
Fosroc Nitowrap CW — Choose the Fosroc Nitowrap CW fabric route when the member needs column confinement, shear wrapping, or strengthening around curves and corners where a rigid pultruded plate cannot conform, or when the project is standardised on Fosroc materials.
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