Fosroc Nitowrap GW
Unidirectional E-glass fabric that bonds into a high-strength FRP laminate for seismic retrofit, shear and flexural strengthening of concrete and masonry.
What is it?
A unidirectional woven E-glass fibre fabric (GFRP) that, once saturated with Fosroc’s structural epoxy, cures into a thin, high-tensile composite laminate bonded to the concrete surface.
Where is it used?
Columns, beams, slabs, shear walls, bridge piers and masonry that need extra load capacity, ductility or seismic resistance without adding meaningful dead load.
Why use it?
It lifts flexural and shear capacity, confines columns and upgrades structures for change-of-use or seismic codes at a lower material cost than carbon fibre.
How is it applied?
The prepared surface is primed, the dry fabric is placed along the direction of load and saturated with epoxy by the wet-layup method, then cured and (if exposed) top-coated.
About Fosroc Nitowrap GW
Fosroc Nitowrap GW is the glass fibre element of Fosroc’s Nitowrap externally bonded FRP strengthening range. It is a unidirectional woven E-glass fabric in which the structural fibres run in a single direction, so nearly all the tensile capacity is delivered along that axis. On its own the fabric is soft and drapable; its engineering value appears only after it is impregnated with a Fosroc structural epoxy on site, at which point fibre and resin work together as a composite laminate that is bonded to, and acts with, the parent concrete. Because the finished laminate is only a fraction of a millimetre thick per ply, the technique adds negligible dead load and almost no change in member size, which is why it has become a mainstream alternative to steel plate bonding and concrete jacketing.
In practice, engineers reach for Nitowrap GW when a structure has to carry more than it was designed for, has lost capacity through deterioration or damage, or needs to meet current seismic detailing. Wrapping a column in the hoop direction confines the concrete and improves ductility; bonding fabric to a beam soffit adds flexural steel-equivalent capacity; and U-wraps or side-bonded plies boost shear resistance. The glass version is chosen where the demand is real but moderate and budgets matter, since E-glass gives a genuine strength uplift at a materially lower cost than carbon fibre. For Delhi NCR and pan-India projects, Space Arc Engineering supplies the fabric together with the matching Fosroc resins and can carry out the application as an authorised applicator.
The technical insight
The mechanism is composite action. A dry glass fabric has high tensile strength in the fibre direction but no useful stiffness or shape on its own. When it is wet-laid into a Fosroc epoxy saturant, the resin wets each filament, locks the fibres in place and transfers stress between them and, critically, into the concrete substrate through the epoxy bond line. The cured laminate then behaves as an externally bonded reinforcement: as the concrete member deflects or the column dilates, load is shed into the far stiffer, far stronger fibres in tension. This is why substrate preparation governs the whole result. Fosroc calls for concrete that has been ground or shot-blasted to sound aggregate, is dry and dust-free, with a minimum tensile pull-off strength above 1.5 MPa, because the joint can only be as strong as the surface it grips. Unidirectional orientation is deliberate: the installer aligns the fibres with the principal tensile stress (hoop for confinement, longitudinal for flexure, or across the crack path for shear), so that the anisotropy of the fabric is turned into an advantage rather than a limitation.
Where it is used
- Hoop confinement of reinforced concrete columns to improve ductility and seismic performance
- Shear strengthening of RC beams and shear walls using U-wraps or side-bonded plies
- Flexural strengthening of slabs and beam soffits to carry increased loads
- Confinement of bridge piers and piles in elevated and marine-adjacent structures
- Seismic retrofit and upgrading of buildings to current code requirements
- Change-of-use strengthening where floors must take heavier live loads
- Restoring capacity to structurally damaged or deteriorated concrete members
- Strengthening of load-bearing masonry elements
Key advantages
- High tensile strength along the fibre direction (typically greater than 2000 MPa for the dry E-glass fibre)
- Adds strength and stiffness with negligible increase in dead load or member size
- More cost-efficient than carbon fibre where the strengthening demand is moderate
- Thin, low-build laminate that follows curved and irregular contours
- Non-corroding, chemically resistant reinforcement with long service life
- Non-intrusive, low-disruption installation with minimal downtime for the structure
- Can be applied by dry or wet layup and shaped on site to the member geometry
- Integrates into a complete Fosroc system with matched primer, saturant and topcoat
Limitations & considerations
- Strength is unidirectional; fibres must be aligned with the principal tensile stress or the uplift is lost
- Performance depends entirely on substrate quality, needing a pull-off strength above 1.5 MPa and a clean, dry surface
- Glass fibre has a lower modulus and lower ultimate strength than carbon fibre, so it is unsuited to the most demanding upgrades
- Cannot be applied in rain; high humidity above 85% RH extends cure time and monsoon work needs protective covering
- Epoxy resins are temperature-sensitive and require correct mixing, so quality depends on a trained applicator
- Atmospherically exposed laminates need a protective topcoat against UV and long-term weathering
Selection & best practice
Treat surface preparation as the load-bearing step, not a formality. Grind or shot-blast the concrete to expose clean, sound aggregate, remove all carbonated or weak material, round off sharp corners on columns so the fabric is not stressed over an edge, and confirm the surface is dry and dust-free. Verify tensile pull-off strength exceeds 1.5 MPa before wrapping. Apply the Fosroc epoxy primer, then place the fabric with the fibres oriented along the design tension direction and fully saturate it, working out air voids so the laminate is properly consolidated. Respect the epoxy’s mixing ratio, pot life and ambient conditions, and avoid application in rain or above 85% RH. Allow full cure before loading and, on exposed structures, finish with a protective topcoat. Because the design intent (number of plies, orientation and anchorage) comes from a structural engineer, the wrap should always be installed to a stamped strengthening scheme rather than by eye.
Specifications
| Product type | Unidirectional woven glass fibre FRP fabric (GFRP) |
| Fibre material | E-glass (electrical grade glass fibre) |
| Fibre orientation | Unidirectional (primary strength along the fibre direction) |
| Tensile strength (dry fibre) | Greater than 2000 MPa (typical) |
| Tensile modulus (dry fibre) | 70-80 GPa (typical) |
| Saturant / resin | Applied with Fosroc Nitowrap structural epoxy on site |
| Application method | Wet layup / dry wrap; hand lamination |
| Min. substrate pull-off strength | Greater than 1.5 MPa |
| Application constraint | Not to be applied in rain; humidity above 85% RH extends cure |
Industry use cases
Seismic retrofit
Column jacketing in the hoop direction to confine concrete and add ductility for buildings being brought up to current seismic detailing.
Commercial change-of-use
Flexural strengthening of slabs and beams when a floor is repurposed to carry heavier live loads, such as offices converted to storage or plant rooms.
Bridges and infrastructure
Confinement of piers and piles to restore or upgrade capacity in ageing or overloaded structures without full reconstruction.
Repair and rehabilitation
Re-establishing the lost capacity of concrete members degraded by corrosion, overloading or physical damage.
Heritage and masonry
Strengthening of load-bearing masonry where a thin, non-intrusive reinforcement is needed to preserve appearance and mass.
Frequently asked questions
What is the difference between Nitowrap GW and the carbon fibre Nitowrap products?
Can Nitowrap GW be used on its own?
How is the fabric bonded to the concrete?
What surface strength does the concrete need before wrapping?
Can it be applied during the monsoon?
Does Space Arc supply the full system and can you apply it?
How we position Fosroc Nitowrap GW
Nitowrap GW is the cost-efficient, glass fibre choice within Fosroc’s Nitowrap externally bonded FRP family. It is always used with the matched Fosroc epoxy system, so specify it alongside the Nitowrap primer, high-build epoxy saturant and, for exposed structures, the polyurethane protective topcoat that completes the wrap. Where the strengthening demand is high or stiffness is critical, step up to Fosroc’s carbon fibre Nitowrap laminate/fabric options instead of glass. Strengthening work rarely stands alone: pair the wrap with Fosroc’s Renderoc repair mortars to reinstate spalled or damaged concrete before wrapping, and with a Nitobond bonding aid where fresh repair concrete meets old. For clients standardising on other brands we carry, comparable FRP strengthening solutions are available from Sika (SikaWrap fabrics with Sikadur epoxies) and MC-Bauchemie, which our team can cross-reference on request.
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