Fosroc Nitofill PU25 LV
Two-component, low-viscosity elastic polyurethane injection resin for permanently sealing cracks, fissures and joints in concrete, walls, floors and sewers — performs on both wet and dry cracks.
What is it?
A two-component, low-viscosity polyurethane injection resin from Fosroc that cures into a tough yet elastic seal inside cracks, fissures and joints in concrete and masonry.
Where is it used?
Pressure-injected into cracked structural concrete, retaining walls, floor slabs, basements, water tanks, sewers and wet joints across building, infrastructure and water-retaining projects.
Why use it?
It stays permanently flexible after curing, bonds to damp concrete and metal without a primer, does not shrink, and is solvent- and phthalate-free — making it suited to live or moving cracks where a rigid epoxy could re-crack.
How is it applied?
The two components are metered, mixed and injected through surface-mounted packers or ports into the prepared crack using a single- or twin-feed injection pump until refusal.
About Fosroc Nitofill PU25 LV
Fosroc Nitofill PU25 LV is a two-component polyurethane resin engineered for the injection sealing of cracks, fissures and construction joints in concrete and masonry. Unlike Fosroc’s water-reactive PU foaming grouts (the PU 1F / PU130 / PU150 family), which expand on contact with water to chase down active leaks, PU25 LV is a slow-reacting, low-viscosity liquid resin in which the two components cure with each other to form a void-filling, elastic solid. Because the cure does not depend on water and produces no foam, the injected resin fills the crack with a dense, flexible body rather than a cellular foam — giving a cleaner, more durable seal in cracks that have stopped actively gushing but still need to be sealed against water and movement.
The low viscosity is the defining feature. A thin resin can penetrate hairline and fine cracks under modest injection pressure, travelling deep into the crack network and wetting both faces before it gels. This makes PU25 LV well suited to fine cracks in dense concrete where a thicker grout would simply not enter. Once cured, the resin remains elastic — it does not dry out, does not shrink, does not swell in contact with water and is not corrosive to embedded steel or metal fixings. That combination of penetration plus permanent flexibility is what separates it from a structural epoxy, which is rigid and intended to monolithically re-bond a crack rather than accommodate ongoing movement.
For Indian construction conditions, this product solves a recurring site problem: cracks that are damp. Substrates in basements, water tanks, STP/sewer structures, podiums and below-grade walls are rarely bone-dry, and many epoxy injection resins are compromised by moisture on the crack face. PU25 LV is formulated to perform on both wet and dry cracks and to bond to concrete and metal without a separate primer, which removes a step and a failure mode from site work. It is positioned as a sealing and waterproofing tool rather than a load-restoring structural repair, and Space Arc Engineering supplies it to applicators across Delhi NCR and Pan-India alongside the surface packers, injection pumps and surface-sealing pastes needed to deploy it correctly.
The technical insight
The engineering logic of Nitofill PU25 LV sits between two extremes in the crack-repair toolkit. A rigid epoxy (such as Fosroc Nitofill LV/EPLV) chemically welds a crack and restores structural continuity, but it has effectively zero elasticity — if the crack continues to move thermally or under load, the repair simply cracks again, often beside the original line. At the other end, water-reactive PU foams (Nitofill PU 1F / PU130 / PU150) expand aggressively to stop water under head, but the resulting foam is a leak-stopping barrier, not a clean structural fill, and its volume change can be hard to control. PU25 LV occupies the middle ground: a solvent-free, two-part PU that reacts slowly and predictably with itself (not with water), so the installer controls gel time and the resin keeps flowing into fine cracks before it sets. The slow, self-curing reaction is what gives the cured resin its elastic, void-filling character — it fills rather than foams, and it flexes rather than fractures. Because cure is not moisture-triggered, performance is consistent whether the crack is damp or dry; because the resin is phthalate- and solvent-free with no shrinkage, the seal does not pull away from the crack walls as it ages. The practical takeaway for a specifier: choose PU25 LV when the crack is fine, possibly damp, and likely to keep moving slightly, and when the goal is a durable elastic water seal rather than restoration of structural strength.
Where it is used
- Pressure injection of fine cracks and fissures in structural concrete elements such as columns, beams, slabs and walls
- Sealing damp or wet cracks in basement walls, retaining walls and below-grade structures
- Waterproofing repair of cracks in water tanks, reservoirs, swimming pools and water-retaining structures
- Sealing cracks and joints in sewers, STPs, manholes and wastewater concrete structures
- Filling construction and movement-prone joints in floors and slabs where a flexible seal is required
- Re-sealing cracks subject to slight ongoing thermal or live-load movement where rigid epoxy would re-fracture
- Crack sealing in tunnels, culverts and infrastructure concrete exposed to moisture
Key advantages
- Low viscosity penetrates fine and hairline cracks that thicker grouts cannot enter
- Cures to a permanently elastic solid that accommodates slight ongoing crack movement
- Performs on both wet and dry cracks — cure does not depend on moisture
- Excellent adhesion to concrete and metal without a separate primer, simplifying site work
- No volume shrinkage on cure, so the seal stays bonded to the crack walls
- Does not swell in contact with water, does not dry out, and is non-corrosive to embedded steel and metal
- Solvent-free and phthalate-free, improving site safety and lower odour in enclosed spaces
- Two-component self-reacting system gives controllable, predictable gel and cure
Limitations & considerations
- Not a structural repair — it seals and flexes but does not restore load-bearing strength to a crack the way a rigid epoxy does
- Requires injection equipment (packers/ports and an injection pump) and trained applicators; it is not a brush- or trowel-applied product
- Best suited to cracks that are no longer actively gushing under pressure — fast, high-head water ingress is better arrested first with a water-reactive PU foam
- Crack faces and bond surfaces must be sound; injection into dusty, loose or contaminated cracks reduces adhesion
- Surface ports and a surface-sealing paste are normally needed to contain the resin during injection
- Country-specific numeric data (exact viscosity, mix ratio, pot life, pack sizes) should be confirmed against the current regional Fosroc technical data sheet before specification
Selection & best practice
Begin by routing and cleaning the crack to remove dust, laitance and loose material, then fix surface injection packers or ports along the crack at spacing suited to the crack width and element thickness, and seal the crack face between ports with a fast-setting surface-sealing paste so the resin is contained. Meter and thoroughly mix the two components in the correct ratio (confirm the exact ratio and gel time from the current regional Fosroc TDS), and inject through a single- or twin-feed pump starting at the lowest port, working upward on vertical cracks, until resin appears at the next port — then move up and repeat to refusal. Because PU25 LV tolerates damp substrates, light dampening of the crack is acceptable, but free-running water under head should be controlled first. Allow full cure before removing packers and grinding back the surface seal. Always wear gloves and eye protection, ensure ventilation in confined spaces such as tanks and sewers, and store the components in their original sealed containers away from heat and moisture. For high-pressure active leaks, pre-inject a water-reactive PU foam (Fosroc Nitofill PU 1F / PU130 / PU150) to stop flow, then follow with PU25 LV for the durable elastic seal.
Specifications
| Product type | Two-component polyurethane injection resin |
| Cure mechanism | Two components react with each other (not water-activated) |
| Viscosity class | Low viscosity — formulated to penetrate fine cracks (LV designation) |
| Cured character | Elastic / flexible solid (non-foaming) |
| Volume change on cure | No shrinkage; does not swell in contact with water |
| Adhesion | Bonds to concrete and metal without primer |
| Water reactivity | Does not dry out; non-corrosive to metals when cured |
| Composition | Solvent-free and phthalate-free |
| Application method | Pressure injection via packers/ports and injection pump |
| Typical use cracks | Cracks, fissures and joints in walls, floors, sewers and concrete |
| Substrate condition | Suitable for both wet and dry cracks |
| Exact numeric data (mix ratio, density, pot life, pack size) | Refer to current regional Fosroc technical data sheet |
Industry use cases
Basements & below-grade
Sealing damp cracks in basement and retaining walls of commercial towers and metro/parking structures where moisture on the crack face rules out many epoxies.
Water-retaining structures
Repairing cracks in RCC water tanks, reservoirs and swimming pools, restoring a flexible watertight seal that tolerates thermal cycling.
Sewerage & STP infrastructure
Sealing cracks and joints in sewers, manholes and sewage treatment plant concrete, where a non-corrosive, water-resistant elastic seal is required.
Bridges, tunnels & culverts
Injecting fine cracks in infrastructure concrete subject to slight live-load and thermal movement, where a rigid repair would re-fracture.
Industrial & commercial floors
Filling cracks and movement-prone joints in floor slabs to seal against water and contaminants while accommodating minor deflection.
Frequently asked questions
Is Fosroc Nitofill PU25 LV a structural crack repair product?
Can it be used on wet or damp cracks?
How is PU25 LV different from Fosroc’s PU 1F, PU130 and PU150 grouts?
Does it need a primer before injection?
What equipment is needed to apply it?
Where can I buy Fosroc Nitofill PU25 LV in India?
How we position Fosroc Nitofill PU25 LV
Fosroc Nitofill PU25 LV sits in the elastic-sealing tier of the crack-injection market, between rigid structural epoxies and aggressive water-reactive foams. Within the Fosroc range, specify PU25 LV when you want a flexible, non-foaming water seal in fine or damp cracks; step up to Fosroc Nitofill LV / EPLV (epoxy) when the goal is structural re-bonding of a static crack, or to Fosroc Nitofill PU 1F / PU130 / PU150 when an active, high-pressure leak must be foamed off first. Against competitor systems, it competes with Sika’s polyurethane injection resins (e.g. the Sikadur/Sikadur-injection and SikaFix PU lines), MBS (MYK Schomburg) injection PUs, Dr. Fixit’s crack-injection and PU grout solutions, and STP Ltd’s polyurethane injection grouts. The honest differentiators for PU25 LV are its low viscosity for fine-crack penetration, its tolerance of damp substrates without a primer, and its permanently elastic, shrink-free cure. As with all injection systems, the right product depends on whether the crack is moving, wet and whether structural strength must be restored — Space Arc Engineering helps applicators across Delhi NCR and Pan-India match the system to the defect, and recommends confirming exact numeric properties against the current regional Fosroc technical data sheet before final specification.
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