Sika Sikadur-55 SLV IN
A solvent-free, super low-viscosity two-part epoxy that penetrates and structurally re-bonds fine cracks in concrete, masonry and stone by gravity or low-pressure injection.
What is it?
A two-component, 100% solids, moisture-tolerant epoxy resin with super low viscosity (~350 cps at 25 C), used as a crack healer, penetrating sealer and injection binder for fine, non-moving cracks.
Where is it used?
Structural crack repair in concrete, masonry, stone and hydraulic structures, on horizontal or vertical faces, by gravity feed or single-pump low-pressure injection.
Why use it?
Its very low viscosity lets it travel deep into hairline cracks that thicker resins cannot reach, restoring monolithic load transfer with high mechanical and bond strength.
How is it applied?
Mix Part A:B at 7:2 by weight, then gravity-pond over horizontal cracks or inject through ports set at ~25 cm spacing, working bottom-up on vertical cracks.
About Sika Sikadur-55 SLV IN
Sikadur-55 SLV IN is Sika’s India-specification super low-viscosity crack repair epoxy, and it earns its place on a repair site because of one property above all others: it flows. Where a standard injection grout stalls at the mouth of a fine crack, this resin keeps moving, working its way through hairline fissures and re-establishing the structural continuity that the crack broke. It is a two-component, 100% solids, solvent-free system that conforms to ASTM C881 (Type I and IV, Grade 1, Class C, except for gel time), so specifiers can reference a recognised standard rather than a marketing claim. Because it is moisture-tolerant, it bonds in both dry and slightly damp cracks, which matters on real Indian sites where a substrate is rarely bone-dry.
On the ground it behaves as a genuinely multipurpose product. Contractors use it three ways: gravity-fed into horizontal cracks in slabs and decks, low-pressure injected into vertical and horizontal cracks in columns, beams and walls, and blended with filler as an epoxy mortar binder for patch repair on interior horizontal surfaces. It comes pre-batched (Part A 0.7 kg plus Part B 0.2 kg, in sets of four 0.9 kg units), which removes on-site dosing guesswork and keeps the 7:2 ratio right every time. For consultants and PMC engineers signing off structural repairs on bridges, flyovers, plants and buildings, that combination of a low-viscosity flow, standard compliance and controlled mixing is what makes it a dependable specification.
The technical insight
The whole value of Sikadur-55 SLV IN rests on capillary flow. A crack is essentially a very thin capillary channel, and the depth to which a resin can travel into it before gelling is governed by its viscosity and surface tension. At roughly 350 cps at 25 C (and about 700 cps at the cooler 15 C), this resin sits at the low end of what an injectable epoxy can be while still carrying real structural strength, so it wicks into narrow openings that a 1,000 cps-plus grout would simply bridge over at the surface. Once inside, the two-component epoxy cross-links into a rigid, shrinkage-free solid that keys mechanically to both crack faces. The result is a repaired section that transfers load across the old crack line rather than around it, with neat-resin compressive strength reaching around 90 N/mm2 at 28 days and tensile adhesion of 10 N/mm2 or more after moist curing. The moisture tolerance comes from a hardener chemistry that still cures and bonds against a damp surface, which is why it holds in cracks that are dry or slightly damp but not actively leaking. The trade-off is short working time: pot life is only about 24 minutes at 25 C, so the flow advantage has to be used quickly before the resin thickens toward gel.
Where it is used
- Low-pressure injection of fine structural cracks in reinforced concrete columns, beams and slabs
- Gravity feed of hairline cracks in horizontal concrete decks, floors and bridge decks
- Crack repair in load-bearing brick and stone masonry
- Structural crack healing in precast elements and industrial building frames
- Epoxy binder for site-batched epoxy mortar patching and overlay on interior horizontal surfaces
- Sealing and re-bonding of cracks in hydraulic structures such as water tanks and channels
- Crack rehabilitation in flyovers, viaducts and elevated corridors
- Penetrating seal of cracked slabs against water, chloride and mild chemical ingress
Key advantages
- Super low viscosity (~350 cps at 25 C) for deep penetration into very fine cracks
- Solvent-free, 100% solids formulation with shrinkage-free hardening
- Moisture-tolerant, bonds in both dry and slightly damp cracks
- High mechanical strength, neat-resin compressive up to ~90 N/mm2 at 28 days
- Strong tensile adhesion of 10 N/mm2 or more, giving concrete-failure bonds
- Conforms to ASTM C881 (Type I & IV, Grade 1, Class C) for specification confidence
- Pre-batched A and B packs keep the 7:2 mix ratio accurate on site
- Injectable with simple single-component pumps, and doubles as an epoxy mortar binder
Limitations & considerations
- Not for actively water-leaking cracks under hydrostatic pressure; stop the flow with polyurethane injection first
- Short pot life of around 24 minutes at 25 C, so mix only what can be placed quickly
- Only for static, non-dynamic cracks; not suitable for moving or expansion cracks
- Maximum injectable crack width is about 5 mm; consult Sika for wider cracks
- Requires substrate and ambient temperature between +15 C and +45 C to cure correctly
- Rigid after cure and not UV-stable, so it is a structural repair, not a decorative or exposed finish
Selection & best practice
Success with this resin is mostly about preparation and speed. Clean the crack of dust, laitance, oil and loose material by mechanical means and blow it out with compressed air; the substrate should be sound and free of standing water, though slight dampness is acceptable. Weigh Part A and Part B at 7:2 by weight and mix for three minutes at low speed (400 to 500 rpm) until the colour is uniform, avoiding air entrainment, and only batch what you can use inside the ~24 minute pot life at 25 C. For gravity feed, pond the resin over horizontal cracks and let it draw in, sealing the underside with Sikadur-31 IN where accessible to stop leakage. For injection, set ports at roughly 25 cm centres, seal the crack line between ports, and work vertical cracks from the bottom up, moving to the next port as resin oozes out. Keep both substrate and air between +15 C and +45 C, and remember the concrete should be at least 21 to 28 days old. On critical structural work, run a trial and verify penetration by core testing.
Specifications
| Product type | Two-component, 100% solids, solvent-free epoxy crack healer / injection resin |
| Standard | Conforms to ASTM C881, Type I & IV, Grade 1, Class C (except gel time) |
| Mixing ratio | Part A : Part B = 7 : 2 by weight |
| Mixed viscosity | ~350 cps at +25 C; ~700 cps at +15 C (ASTM D1084) |
| Density (mixed) | 1.15 +/- 0.05 kg/L at +25 C (EN ISO 2811-1) |
| Pot life | ~24 minutes at +25 C; ~75 minutes at +15 C (100 g mass) |
| Compressive strength (neat resin) | Up to ~90 N/mm2 at 28 days, +25 C (ASTM D695) |
| Tensile adhesion strength | >= 10 N/mm2 at 14 days moist cure (ASTM C882) |
| Packaging | Pre-batched 0.9 kg units x 4 sets (Part A 0.7 kg + Part B 0.2 kg) |
Industry use cases
Bridges & Flyovers
Re-bonding fine flexural and shrinkage cracks in decks, girders and piers to restore load transfer without removing sound concrete.
Commercial & High-Rise Buildings
Repairing hairline cracks in RC columns, beams and shear walls flagged during structural audits and repair contracts.
Industrial Plants & Power Stations
Sealing cracks in machine foundations, floors and structural frames exposed to vibration-induced static cracking.
Water-Retaining & Hydraulic Structures
Injecting cracks in tanks, channels and sumps as an epoxy binder, provided the crack is not actively leaking during application.
Heritage & Masonry Repair
Consolidating cracked stone and brick masonry where a low-viscosity resin can travel through fine, irregular fissures.
Frequently asked questions
Can Sikadur-55 SLV IN seal a crack that is actively leaking water?
What is the finest and widest crack it can handle?
How is it mixed and how long do I have to work it?
Is it just for injection, or can it do more?
Which standard does it comply with?
What pack size does it come in and how should it be stored?
How we position Sika Sikadur-55 SLV IN
Within the Sika repair family, Sikadur-55 SLV IN is the low-viscosity crack injection and healing resin; where a job needs a thicker, gap-filling epoxy to seal ports or bond larger cracks, pair it with Sikadur-31 IN epoxy mortar, and for anchoring or doweling use Sikadur AnchorFix. If the crack is live and leaking, move to a Sika polyurethane injection resin to arrest the water before epoxy re-bonding. Across our other brands, MC-Bauchemie and Dr. Fixit offer comparable epoxy injection systems where a specifier is standardised on those ranges. Our team can help match the resin to the exact crack width, moisture state and structural role.
Fosroc Nitofill LV — Choose Nitofill LV when the project or repair specification is standardised on Fosroc; it is a comparable low-viscosity two-part epoxy injection resin for structural crack re-bonding, though its P3 injectability targets cracks from about 0.3 mm rather than the finest hairline openings.
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