Fosroc Nitofill PU 1R
Single-component, water-reactive polyurethane injection grout that foams and expands to stop active water leakage through cracks in concrete and masonry.
What is it?
A one-part, MDI-based hydrophobic polyurethane injection resin that reacts with water to form a semi-flexible, expanding foam which seals leaking cracks and joints in concrete and masonry.
Where is it used?
Pressure-injected into cracks in basements, water tanks, retaining walls, tunnels, lift pits, sewage structures and below-grade slabs where water is actively seeping.
Why use it?
It stops live, flowing-water leaks that cementitious grouts cannot, expanding over 10 times its volume to fill voids and form a durable, chemical-resistant barrier.
How is it applied?
Injected as a single component (no on-site mixing of two parts) through packers/ports using a single-component injection pump; it cures on contact with moisture in the crack.
About Fosroc Nitofill PU 1R
Fosroc Nitofill PU 1R is a single-component, solvent-free polyurethane injection grout engineered specifically to seal active water leakage through cracks and joints in concrete and masonry. It belongs to the Fosroc Nitofill crack-injection family and is positioned as the semi-flexible, water-reactive member of that range. The product is supplied as a ready-to-use brown liquid based on methylene diphenyl diisocyanate (MDI) and polyether polyols, with a built-in accelerator that drives a fast reaction the moment the resin meets water inside a leaking crack.
Unlike epoxy or low-viscosity acrylic systems that need a dry substrate, Nitofill PU 1R is designed to perform in wet conditions. When it contacts water it foams and expands by more than ten times its liquid volume, driving the resin deep into hairline cracks, honeycombing and construction joints before it cures into a tough, closed-cell, semi-flexible foam. That expansion is the working principle: it physically displaces the water that is flowing through the defect and replaces it with a chemically stable solid that bonds to the crack faces and resists wash-out.
For a distributor-led market like Delhi NCR and the wider Indian infrastructure sector, this is a remedial-injection product rather than a coating. It is the chemical a waterproofing contractor reaches for when a basement raft, a water-retaining wall or a metro tunnel segment is leaking under hydrostatic pressure and the leak must be stopped from the negative side. Because it is a single component, it is simpler to pump and clean down than two-part PU systems, and the 20 kg pack format suits site-scale remedial campaigns. Space Arc Engineering supplies Nitofill PU 1R as part of its Fosroc waterproofing and injection portfolio for projects across Delhi NCR and Pan-India.
The technical insight
The chemistry that matters here is the MDI-polyether prepolymer plus a built-in accelerator. The free isocyanate (-NCO) groups in the prepolymer react with water, generating carbon dioxide gas; that gas is what foams and expands the resin by more than 10x, while the polymer network simultaneously crosslinks into a semi-flexible solid. This is why the product is classed as hydrophobic and water-activated rather than water-soluble: it consumes water as a reactant instead of being diluted by it, so it cures even in a flooded crack. The reaction profile is fast and tunable to site water content. At 25 degrees C with about 10 percent water, the typical cream time is 20 to 30 seconds, rise time is 150 to 180 seconds and tack-free time is up to about 750 seconds, giving the resin enough mobility to penetrate fine cracks before it sets. The 250 to 500 mPa.s viscosity at 25 degrees C is low enough for capillary penetration yet viscous enough to stay in the crack rather than bleed away. The semi-flexible (as opposed to rigid or highly elastic) character is the design trade-off: it accommodates minor movement and thermal cycling while retaining more strength than the fully elastic Nitofill PU 1F, making it a balanced choice for cracks that are essentially static but exposed to water.
Where it is used
- Stopping active water seepage through cracks in basement walls and raft slabs under hydrostatic pressure
- Sealing leaking construction joints and cold joints in water-retaining structures such as STPs, sumps and overhead/underground water tanks
- Curtain and crack injection in metro tunnels, cut-and-cover sections and underground utility ducts
- Arresting leaks in lift pits, machine foundations and below-grade plant rooms
- Void filling and water-cut-off in retaining walls, diaphragm walls and sheet-pile interfaces
- Remedial waterproofing of honeycombed or porous concrete in bridge abutments, culverts and dam galleries
- Sealing leaks around pipe penetrations and embedded services passing through wet concrete
Key advantages
- Single-component supply means no on-site batching of two parts, reducing mixing error and speeding injection
- Reacts with the water already in the crack, so it works on wet and actively leaking substrates where epoxies cannot
- Expands more than 10 times in volume to fill voids and follow the leak path to its source
- Low viscosity (250 to 500 mPa.s at 25 C) for penetration into fine cracks and capillaries
- Semi-flexible cured foam tolerates minor movement and thermal cycling without re-cracking
- Hydrophobic and resistant to chemical degradation, including saline and mineral-bearing groundwater
- Solvent-free and non-toxic when cured, suitable for confined below-grade work
- High flash point of over 160 C, improving site handling safety versus solvented grouts
Limitations & considerations
- Requires the presence of water to react and cure fully; a bone-dry crack may need pre-wetting
- Foaming, expanding chemistry makes it a leak-stopping grout, not a structural crack-bonding resin like a Fosroc Nitofill epoxy LV
- Needs a single-component PU injection pump and packers/ports, plus a trained injection crew
- Fast cream and rise times (20 to 30 sec / 150 to 180 sec) leave a limited working window in warm conditions
- Semi-flexible foam suits essentially static cracks; for joints with movement above ~10 percent the more elastic Nitofill PU 1F is more appropriate
- Isocyanate-based resin demands gloves, goggles and ventilation during handling; uncured material must not contact skin or eyes
- Performance depends heavily on correct port spacing, injection pressure and water-content judgement on site
- 12-month shelf life and sensitivity to moisture mean opened or poorly stored drums can react prematurely
Selection & best practice
Condition the drum to site temperature for at least 12 hours and roll or shake it, then briefly remix with a clean, dry paddle on a slow drill so the resin is homogeneous before loading the pump. Drill injection ports/packers across the crack at a staggered spacing (typically following Fosroc’s port layout for the crack width and wall thickness), flush the crack with clean water to establish the leak path and provide reaction water, then pump Nitofill PU 1R through a dedicated single-component PU injection pump starting from the lowest port and working upward. Inject at controlled pressure until resin appears at the adjacent port, then move on; the resin will foam and expand to chase the water back to its source. Keep the pump and lines primed and flush immediately with the recommended cleaner after use, because cured PU cannot be removed from equipment. Always wear nitrile gloves and eye protection, work with ventilation in confined pits, and keep unopened material sealed at 10 to 38 C and use within the 12-month shelf life. Match the grade to the job: choose PU 1R for static, water-bearing cracks and step up to the elastic PU 1F where the joint genuinely moves.
Specifications
| Product type | Single-component, solvent-free polyurethane injection grout (water-reactive) |
| Chemical basis | MDI (methylene diphenyl diisocyanate) and polyether polyols, with built-in accelerator |
| Appearance / colour | Brown liquid |
| Density | 1.18 +/- 0.05 g/cm3 at 25 C |
| Viscosity | 250 to 500 mPa.s at 25 C |
| Flash point | >160 C |
| Cream time | 20 to 30 sec (at 25 C, 10% water) |
| Rise time | 150 to 180 sec (at 25 C, 10% water) |
| Tack-free time | <=750 sec |
| Expansion ratio | >10x in volume on contact with water |
| Cured nature | Semi-flexible, hydrophobic, chemical-resistant closed foam |
| Pack size | 20 kg pack |
| Shelf life | 12 months (unopened, stored at 10 to 38 C) |
Industry use cases
Metro & Tunnelling
Curtain and crack injection to stop groundwater ingress through segment joints and shotcrete linings in metro and utility tunnels across Indian cities.
Water & Wastewater
Sealing leaking joints and cracks in sewage treatment plants, clear-water sumps and elevated/underground tanks where saline or chemically aggressive water is present.
Commercial & Residential Basements
Negative-side leak stopping in deep basements, lift pits and parking rafts of high-rise developments in Delhi NCR subject to high water tables during monsoon.
Infrastructure & Bridges
Remedial waterproofing of culverts, bridge abutments, retaining walls and diaphragm walls where honeycombing or cracks admit water under pressure.
Industrial Plants
Arresting leaks in machine foundations, basements and below-grade ducts of power, process and manufacturing facilities without lengthy shutdowns.
Frequently asked questions
What is Fosroc Nitofill PU 1R used for?
How does Nitofill PU 1R cure?
How is Nitofill PU 1R different from Nitofill PU 1F?
Can it be used on a leaking, wet crack?
What equipment is needed to apply it?
What is the pack size and shelf life, and how should it be stored?
How we position Fosroc Nitofill PU 1R
Within the Fosroc range, Nitofill PU 1R sits in the crack-injection / leak-sealing family alongside the more elastic Nitofill PU 1F (for moving joints) and rigid water-stopping resins such as Nitofill WS60; for structural crack bonding rather than leak stopping, a low-viscosity epoxy like Fosroc Nitofill LV is the correct counterpart. It is best paired downstream with Fosroc cementitious waterproofing or Renderoc repair mortars to reinstate the treated surface. Against competitors, it is directly comparable to Sika’s water-reactive PU injection resins (the SikaFix / Sika Injection-200 PU family), to MBCC/Master Builders Solutions MasterInject and MasterSeal injection grouts, and to Indian-market systems from Dr. Fixit (Pidilite) and STP Limited. The honest positioning is that Nitofill PU 1R is a single-component, semi-flexible, water-activated grout: it is simpler to pump than two-part PU systems and excels at stopping live leaks in static cracks, but it is not a structural epoxy and is not the right choice for genuinely moving joints, where an elastic grade such as PU 1F or a comparable Sika/Dr. Fixit elastic PU should be specified instead.
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