Sika Sikadur-300 IN
The two-part epoxy impregnating resin that saturates SikaWrap fabrics and turns them into load-bearing FRP laminates on site.
What is it?
A two-part, moisture-tolerant epoxy impregnating and laminating resin engineered to saturate SikaWrap carbon and glass fabrics for wet-layup FRP strengthening.
Where is it used?
On beams, slabs, columns and joints during structural retrofit, seismic upgrade and capacity restoration of RCC and masonry members.
Why use it?
It fully wets out the fabric and bonds it to concrete so the composite acts as external reinforcement, adding flexural, shear and confinement capacity without heavy sections.
How is it applied?
Mixed Part A to Part B at 100:35 by weight, then applied by roller as a primer/saturant coat, the fabric is pressed in, and a second coat closes the layup.
About Sika Sikadur-300 IN
Sikadur-300 IN is the resin half of the SikaWrap strengthening system, the component that actually converts a dry sheet of carbon or glass fabric into a structural fibre-reinforced polymer laminate. It is a two-part epoxy: Part A resin and Part B hardener, blended at 100:35 by weight. On its own it is an adhesive and impregnation medium; combined with SikaWrap fabric it forms a composite that carries tension across cracks, confines columns and restores lost capacity in members that can no longer be economically enlarged. For Indian retrofit contractors, it is the material that makes non-intrusive strengthening possible where jacketing or steel plating would be too heavy, too slow, or too disruptive to occupied structures.
What sets it apart in the field is its tolerance of real site conditions. Concrete in India is rarely bone-dry when a strengthening crew arrives, and Sikadur-300 IN is formulated to wet, cure and bond in the presence of moisture on the substrate. It also carries a generous pot life, roughly 50 minutes per 100 g at +30°C, which matters on a hot Delhi or coastal afternoon when a shorter-lived epoxy would gel in the pot before the fabric is fully impregnated. That combination of moisture tolerance and workable open time is why specifiers reach for it on live bridges, industrial frames and heritage retrofits alike.
The technical insight
The mechanism is composite action. The dry fabric supplies the fibres, which are extremely strong in tension but useless unstressed and unbonded. Sikadur-300 IN is the matrix: as it saturates the weave it fills every interstice, transfers shear between adjacent filaments, and forms a continuous adhesive bond to the prepared concrete. Once cured, load applied to the member is transmitted through the concrete-to-resin interface, into the resin matrix, and finally into the fibres, which mobilise their full tensile strength. Because the epoxy also protects the fibres from abrasion and alkalinity, the laminate behaves as a durable external reinforcement rather than a surface patch. The resin’s own tensile strength of around 45 N/mm² at 7 days, and a tensile adhesion to concrete of about 4 N/mm² that fails in the concrete rather than at the bond line, confirm that the weak link is the substrate, not the resin, which is exactly what a designer wants from a bonded FRP system.
Where it is used
- Wet-layup FRP strengthening of reinforced-concrete beams, slabs, columns and walls
- Flexural strengthening of beams and slabs where added tensile capacity is required
- Shear strengthening of beams and short columns using bonded fabric
- Column confinement to raise axial capacity and ductility
- Seismic retrofit and ductility upgrade of frames, joints and piers
- Capacity restoration of members degraded by corrosion, overload or deterioration
- Strengthening of masonry and chimney/silo shells with wrapped fabric
- Retrofitting bridge girders, pier caps and industrial support structures
Key advantages
- Moisture-tolerant before, during and after cure, suiting damp Indian substrates
- Long pot life of about 50 minutes per 100 g at +30°C for comfortable working in the heat
- High-strength, high-modulus matrix that develops full composite action with SikaWrap fabric
- Tensile adhesion to concrete that fails in the parent concrete, confirming a sound bond
- Simple 100:35 by-weight mix ratio, supplied pre-batched to avoid dosing error
- Applied by roller with standard hand tools, no heavy plant or hot works needed
- Adds strength with negligible added weight and section, ideal for occupied structures
- Part of a fully engineered SikaWrap system with published design data
Limitations & considerations
- It is an impregnation resin only, it must be paired with SikaWrap fabric to form a structural laminate
- Ambient and substrate temperature should sit within roughly +15°C to +40°C for correct cure
- Bond depends entirely on surface preparation, weak or laitance-covered concrete will not develop full adhesion
- Pot life shortens sharply as temperature rises, so mixed quantities must be planned to the crew’s pace
- Being epoxy, the cured laminate needs UV protection, such as a topcoat, on atmospherically exposed faces
- FRP strengthening must be designed and detailed by a competent engineer, it is not a general-purpose repair mortar
Selection & best practice
Success with Sikadur-300 IN is decided at the substrate. Prepare the concrete to a sound, clean, roughened profile, remove laitance and loose material, and make good any spalls or unevenness so the fabric can lie flat without bridging voids. Work within the recommended +15°C to +40°C window and check that the substrate is sound even if damp. Mix Part A and Part B thoroughly at 100:35 by weight, using the pre-batched pack where possible, and only mix what the crew can consume within the pot life at site temperature. Apply a first saturant coat, lay the SikaWrap fabric into the wet resin, and roll firmly along the fibre direction to expel air and drive resin fully through the weave, then apply the closing coat. Plan consumption around 0.4 to 1.0 kg/m² depending on fabric type and substrate roughness, and protect exposed laminates with an appropriate topcoat once cured.
Specifications
| Product type | Two-part epoxy impregnating and laminating resin |
| Base chemistry | Epoxy resin (Part A) with hardener (Part B) |
| Mixing ratio | Part A : Part B = 100 : 35 by weight |
| Consumption | Approx. 0.4 to 1.0 kg/m² (varies with fabric and substrate roughness) |
| Tensile strength | Approx. 45 N/mm² at 7 days |
| Tensile adhesion to concrete | Approx. 4 N/mm² with concrete failure (7 days at +30°C) |
| Pot life | Approx. 50 minutes per 100 g at +30°C |
| Application temperature | Approx. +15°C to +40°C |
| Packaging | 5.4 kg pre-batched (Part A 4.0 kg + Part B 1.4 kg) |
Industry use cases
Bridges & infrastructure
Flexural and shear strengthening of girders, pier caps and deck soffits to carry revised or increased traffic loads without demolition.
Commercial & residential buildings
Restoring beams and slabs weakened by corrosion, overload or a change of use, with minimal loss of headroom or floor space.
Seismic retrofit
Column confinement and joint wrapping to add ductility and axial capacity in frames being upgraded to current seismic codes.
Industrial plants
Strengthening support frames, foundations and equipment plinths subjected to raised loads, vibration or process-related deterioration.
Water & marine structures
Wrapping tanks, chimneys and coastal members where moisture tolerance during application is essential to a durable bond.
Frequently asked questions
Is Sikadur-300 IN used on its own?
What is the mixing ratio and does it need weighing on site?
How much resin will I need per square metre?
Can it be applied to damp concrete?
How long do I have to work after mixing?
Does the finished laminate need any protection?
How we position Sika Sikadur-300 IN
Sikadur-300 IN is the resin at the heart of Sika’s SikaWrap FRP strengthening system, so it is specified alongside SikaWrap carbon and glass fabrics rather than in isolation, and finished with a Sika protective topcoat where the laminate is exposed. Where a designer prefers a plate-bonding or near-surface-mounted approach instead of wet-layup wrapping, the Sikadur structural adhesive range is the natural companion within the same brand family. Across our other lines, contractors carrying out full rehabilitation schemes often pair FRP strengthening with a micro-concrete or repair mortar to reinstate section first, and Space Arc can supply both the Sika strengthening system and compatible repair and protection products to complete the specification.
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