Fosroc Nitofill SL
A self-levelling, low-viscosity epoxy injection resin that seeps into fine horizontal cracks in slabs and floors, then cures to a rigid, load-transferring bond.
What is it?
A two-part, solvent-free low-viscosity epoxy resin from Fosroc’s Nitofill crack-injection family, formulated to self-level into fine cracks in flat concrete.
Where is it used?
Dormant hairline-to-medium cracks in floor slabs, industrial floors, basement rafts, water-retaining structures and other broadly horizontal concrete surfaces.
Why use it?
It penetrates cracks from about 0.3 mm and cures to a high-strength solid (around 93 N/mm2 compressive), restoring monolithic load transfer and sealing the crack against water.
How is it applied?
Poured or gravity-fed into surface-mounted ports along the crack, or low-pressure injected, after the crack line is surface-sealed to stop drainage.
About Fosroc Nitofill SL
Fosroc Nitofill SL is the self-levelling grade in the Nitofill crack-injection range, aimed squarely at the cracks that engineers meet most often on horizontal work: shrinkage and settlement lines in ground-floor slabs, warehouse floors, podium decks, basement rafts and the soffits of water-retaining structures. It is a two-component, solvent-free epoxy supplied as a base resin and a hardener that are proportioned and mixed on site. Once combined, the material stays deliberately thin and fluid, so on a flat surface it finds its own way into the crack under little more than its own weight, reaching fissures from roughly 0.3 mm wide before it begins to cure.
What separates a self-levelling epoxy from a general-purpose sealant is intent. Nitofill SL is not designed to flex; it is designed to knit a dormant crack back together. As it cures it develops high compressive and tensile strength and bonds tenaciously to both dry and damp crack faces, so the repaired section behaves close to monolithic concrete again rather than as two pieces held loosely across a filled gap. That makes it a structural repair material first and a waterproofing measure second, the seal being a useful by-product of a full-depth, well-bonded fill. For actively moving joints or live cracks a flexible sealant is the correct choice instead, and we will say so on a live project.
The technical insight
The performance comes down to viscosity, wetting and cross-link density. Because the mixed resin is very low in viscosity, capillary action and gravity draw it deep into narrow cracks that a thicker paste would simply bridge at the mouth, leaving the core unfilled. The epoxy chemistry then wets and chemically keys to the calcium-silicate crack faces even when they are damp, which is why Fosroc rates the Nitofill injection resins for adhesion on dry or wet concrete rather than demanding a bone-dry substrate. On cure the resin builds a dense, highly cross-linked network that carries load in shear across the crack plane; independent slant-shear testing under EN 1504-5 records a bond strength above 2.0 N/mm2 with failure occurring in the parent concrete rather than at the glue line, which is the definition of a monolithic repair. With compressive strength in the region of 93 N/mm2 and tensile strength around 47 N/mm2, the cured resin comfortably out-performs the surrounding concrete, so the crack ceases to be the weak plane. Pot life is short, roughly 20 to 25 minutes at 20 degrees C, because that same reactivity that gives fast strength gain also limits working time, and warm Indian site temperatures shorten it further.
Where it is used
- Injecting dormant shrinkage and settlement cracks in ground-floor and suspended slabs
- Sealing and rebonding fine cracks in industrial and warehouse floors before overlays or coatings
- Restoring monolithic action in basement rafts, podium decks and cast-in-situ floors
- Crack repair in the base and soffit of water-retaining structures such as tanks, sumps and reservoirs
- Rebonding hairline cracks in reinforced concrete beams and slabs where the crack line is broadly horizontal
- Full-depth filling of construction and cold joints that have opened as fine cracks
- Re-establishing load transfer across cracks that would otherwise let water track to the reinforcement
- Pre-treatment of cracked substrates ahead of flooring, membrane or protective-coating systems
Key advantages
- Low viscosity and self-levelling flow reach fine cracks from about 0.3 mm without high injection pressure
- Solvent-free, low-odour formulation suited to enclosed basements, tanks and occupied buildings
- Bonds to both dry and damp concrete, so work can proceed without waiting for a perfectly dry substrate
- Cures to a rigid, high-strength solid (around 93 N/mm2 compressive) that restores structural continuity
- Slant-shear bond above 2.0 N/mm2 with monolithic failure, confirming a repair stronger than the parent concrete
- Good resistance to most chemicals, acids, alkalis, water and frost once cured
- Complies with the EN 1504-5 standard for concrete injection products, giving specifiers a recognised benchmark
- Doubles as a waterproofing seal by filling the crack full-depth rather than only at the surface
Limitations & considerations
- Rigid when cured, so it is not suitable for actively moving or live cracks that need a flexible sealant
- Best suited to broadly horizontal surfaces where the resin can self-level; vertical and overhead cracks are better served by a higher-viscosity grade
- Short pot life of roughly 20-25 minutes at 20 degrees C, and shorter still in hot weather, so only mix what can be placed quickly
- Cure slows markedly below 15 degrees C and effectively stops near 5 degrees C, delaying strength gain in cold conditions
- Requires the crack line to be surface-sealed and fitted with ports first, otherwise the thin resin drains out before it cures
- Two-component product that demands correct on-site proportioning and thorough mixing to reach its rated strengths
Selection & best practice
Start by identifying whether the crack is genuinely dormant; Nitofill SL is a structural rebonding resin, not a movement accommodator. Clean the crack of dust, laitance and loose material, then fix injection ports or nipples along its length and surface-seal the crack line between them with a fast-setting epoxy paste so the low-viscosity resin cannot bleed away. Mix the full base and hardener packs together in the supplied ratio for at least two minutes until uniform, and mix only what your team can place inside the pot life, since warm weather cuts that window sharply. On flat work the resin can be gravity-fed into the ports and allowed to self-level into the crack; where fuller penetration is needed, low-pressure injection helps. Work port to port so you can see resin arriving at the next nipple, confirming the crack is filling. Keep the substrate between roughly 15 and 35 degrees C during placement and cure; below 15 degrees C strength gain slows and near 5 degrees C it halts. Once cured, remove ports and dress back the surface seal. Our applicators handle diagnosis, port layout and injection as a package across Delhi NCR and pan-India.
Specifications
| Type | Two-component, solvent-free low-viscosity epoxy injection resin |
| Crack width range | From approx. 0.3 mm up to around 9 mm |
| Compressive strength | Approx. 93 N/mm2 (at 7 days, 20 degrees C) |
| Tensile strength | Approx. 47 N/mm2 (at 7 days, 20 degrees C) |
| Adhesion (slant shear, EN 1504-5) | >2.0 N/mm2, monolithic (parent-concrete) failure |
| Non-volatile content | >95% |
| Glass transition temperature | >40 degrees C |
| Pot life | Approx. 20-25 minutes at 20 degrees C |
| Standard | EN 1504-5 (concrete injection products) |
Industry use cases
Industrial & warehouse floors
Rebonding shrinkage and load-induced cracks in slab-on-grade floors before installing overlays, screeds or protective coatings, so the crack does not telegraph through the new surface.
Basements & podium decks
Sealing fine cracks in rafts and suspended slabs to cut off water paths to reinforcement while restoring monolithic load transfer in the structure.
Water-retaining structures
Full-depth filling of dormant cracks in the floors and soffits of tanks, sumps and reservoirs where a low-viscosity resin that bonds to damp concrete is essential.
Commercial & residential RCC
Repairing settlement and thermal cracks in ground-floor slabs and suspended floors of buildings, re-establishing a continuous, watertight concrete section.
Infrastructure repair
Rebonding cracks in horizontal RCC elements such as deck slabs and culvert bases as part of a structured rehabilitation scheme.
Frequently asked questions
Is Nitofill SL an epoxy or a polyurethane?
How fine a crack can it fill?
Can I use it on an actively moving crack?
Does the concrete have to be completely dry first?
How strong is the finished repair?
How long do I have to work with the mixed material?
How we position Fosroc Nitofill SL
Within the Fosroc Nitofill crack-injection family, Nitofill SL is the self-levelling grade for horizontal work; its sibling Nitofill LV is the general low-viscosity injection resin for vertical and overhead cracks where you need to hold pressure, and Nitofill TH is the thixotropic grade for wide or open-ended cracks and for surface-sealing the crack line before injection. Where a repaired section also needs a fairing coat or reprofiling, the Fosroc Renderoc range of repair mortars pairs naturally with this injection work. Beyond Fosroc, our Sika (Sikadur injection resins) and Dr. Fixit lines cover comparable structural crack-repair needs, and our team will match the exact grade to the crack orientation, width and movement on your project rather than defaulting to a single product.
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