Fosroc Nitofill PU 11R
Water-reactive polyurethane injection resin that foams on contact with moisture to seal actively leaking cracks, construction joints and voids in concrete under hydrostatic pressure.
What is it?
A single-component, solvent-free polyurethane injection resin supplied with a separate accelerator. It reacts with water (or moisture in the crack) to expand into a tough closed-cell foam that bonds to and seals the concrete, stopping active water ingress.
Where is it used?
Pressure-injected into cracks, construction joints, honeycombed concrete and water-seepage paths in basements, water-retaining tanks, tunnels, retaining walls, lift pits, diaphragm walls, dams and below-grade structures where water is actively flowing.
Why use it?
Conventional gun- or pour-grade sealants cannot be placed against running water. Nitofill PU 11R is engineered for exactly that — it cures even in wet, submerged conditions, expands ~30 times to fill voids, and resists high hydrostatic pressure, making it a go-to remedial water-stopping resin.
How is it applied?
Drilled injection ports (packers) are set at 45 degrees across the crack at 150-500 mm spacing, then the accelerated resin is pumped in with a single-component PU injection pump. The resin foams in the crack, and reaction time is tuned by varying accelerator dose (up to 10% by weight).
About Fosroc Nitofill PU 11R
Fosroc Nitofill PU 11R sits in the crack-injection and water-stopping family of the Fosroc range, alongside resins such as Nitofill PU 1F, Nitofill PU 1R and the Nitofill WS series. It is important to set expectations correctly at the outset: despite the “PU” name that it shares with elastomeric sealants, this is not a movement-joint sealant applied from a cartridge or a pouring grade poured into a sawn floor joint. It is a low-viscosity polyurethane resin that is pumped under pressure into the body of the concrete to chase and seal water that is already leaking through a crack or a defective construction joint. That distinction governs everything about how it is specified, ordered and applied on site. The resin is single-component and solvent-free, supplied as a 20 kg pack of brown resin together with a separate 2 kg accelerator, and it is moisture-triggered: the water in the crack is what kicks off the reaction. On contact with that water the resin generates a closed-cell polyurethane foam that expands rapidly, drives back into the seepage path, and cures into a tough, semi-flexible mass that is bonded to the concrete and impermeable to further water. Because the cure is driven by water rather than by ambient air, the product performs in conditions that defeat ordinary sealants — damp substrates, standing water, and joints under active hydrostatic head. For contractors and waterproofing specialists in India dealing with leaking basements, water tanks, tunnels and retaining structures, it is one of the standard remedial tools for stopping live water before a more permanent internal lining or coating is applied.
The technical insight
The performance of Nitofill PU 11R comes from its water-reactivity and its controllable cure kinetics. The resin has a low viscosity (in the region of 350-450 mPa.s at 25 C, with the accelerator far thinner at around 30-40 mPa.s), which lets it penetrate fine cracks and migrate along the seepage path before it gels. When it meets water it foams and expands by roughly 30 times its liquid volume, generating internal pressure that pushes the resin into branching cracks and voids the injection ports could never reach directly. The reaction speed is not fixed — by dosing up to 10% accelerator by weight the applicator can shift the working window, with a cream time of roughly 12 seconds and a rise time of about 48-55 seconds at full accelerator dose, giving an effective adjustable reaction band of roughly 3-14 minutes depending on dose and temperature. That tunability is the crux of good site practice: fast reaction to choke off heavy, fast-flowing leaks; slower reaction to allow deeper penetration where the flow is a slow weep. The cured foam is semi-flexible rather than glass-rigid, so it tolerates the minor dimensional changes of a crack better than a brittle epoxy would, while still developing a strong adhesive bond to concrete, mortar, brick and even metal substrates. Density of the liquid resin is around 1.08 g/cm3. Note that because it cures into an in-situ foam rather than spanning a designed movement joint, the product does not carry a sealant-style movement accommodation factor (MAF) or an ISO 11600 / ASTM C920 sealant classification — those metrics belong to elastomeric joint sealants such as Nitoseal or Thioflex, not to an injection resin.
Where it is used
- Sealing actively leaking structural and shrinkage cracks in basement walls and rafts
- Stopping water ingress at defective construction joints and cold joints in water-retaining structures
- Curtain / void-filling injection behind diaphragm walls and secant pile walls
- Plugging leaks in tunnels, metro cut-and-cover sections and underground car parks
- Remedial water-stopping in water and wastewater treatment tanks
- Sealing seepage at lift pits, sump pits and below-ground service ducts
- Crack injection in retaining walls, culverts, manhole joints and stormwater structures
- Consolidating and water-proofing honeycombed or fractured concrete and rock around the structure
Key advantages
- Cures in the presence of water — works against active leaks and on submerged or damp concrete where ordinary sealants fail
- Low viscosity allows deep penetration into fine cracks and seepage paths
- Expands around 30 times to fill voids and branching cracks the injection ports cannot reach directly
- Adjustable reaction time via accelerator dose (up to 10% by weight) to suit fast or slow leaks
- Solvent-free and non-flammable, with a high flash point — safer for confined below-grade work
- Develops a strong bond to concrete, mortar, brick and metal
- Semi-flexible cured foam tolerates minor crack movement better than brittle resins
- Resists high hydrostatic pressure once cured
- 12-month shelf life in sealed packs stored at 10-38 C
Limitations & considerations
- Not a movement-joint sealant — cannot be gunned from a cartridge or poured into expansion/floor joints; it must be pressure-injected
- Requires a single-component PU injection pump and packers, plus a trained applicator — not a DIY product
- No ISO 11600 / ASTM C920 sealant rating and no movement accommodation factor, since it is an injection resin not a joint sealant
- Performance depends on correct port spacing, drilling angle and injection technique; poor workmanship leaves untreated seepage paths
- Reaction is moisture-driven, so in genuinely dry cracks the crack must be pre-flushed with water to initiate foaming
- Best treated as a water-stopping first step — a durable internal waterproofing coating or lining is usually still required for a complete system
- Mixed/accelerated resin has a short pot life; it must be pumped promptly once accelerator is added
- Resin and accelerator must be kept sealed and dry until use to avoid premature reaction
Selection & best practice
Treat Nitofill PU 11R as an injection process, not a sealant bead. Begin by tracing the full extent of the crack or leaking joint, then mark injection ports along it — typically at 150-500 mm centres, with closer spacing for fine or fast-flowing cracks. Drill the holes at about 45 degrees so the bore intersects the crack within the body of the concrete rather than at the face, install and tighten the mechanical packers, and surface-seal the crack face between ports (with a product such as a fast-setting plug mortar) so the resin builds pressure inside the crack instead of bleeding out. Select the accelerator dose to match the leak: a high dose (up to 10%) for fast, heavy water where you need an almost instant choke; a lower dose where you want the resin to travel further before foaming. Inject from the lowest port upward on vertical cracks (and from one end on horizontal/overhead work), moving to the next port once resin or foam shows. In dry conditions, pre-flush the crack with clean water to trigger the reaction. Always pump with a single-component PU injection pump and keep the accelerated resin moving — once mixed, pot life is short. After the foam has cured and the leak is stopped, remove packers, make good the surface, and follow up with the appropriate internal waterproofing coating or render system for a durable, complete result. Confirm the current Fosroc TDS and SDS for the India market before specifying quantities, and size resin against the estimated crack volume plus the ~30x foam expansion.
Specifications
| Product type | Single-component, solvent-free water-reactive polyurethane injection resin (supplied with separate accelerator) |
| Function | Crack-injection / water-stopping resin for active leaks under hydrostatic pressure |
| Application method | Pressure injection via packers using a single-component PU injection pump |
| Appearance | Brown liquid resin; clear liquid accelerator |
| Viscosity at 25 C | approx. 350-450 mPa.s (resin); approx. 30-40 mPa.s (accelerator) |
| Density at 25 C | approx. 1.08 g/cm3 (resin) |
| Accelerator dose | Up to 10% by weight of resin, to tune reaction time |
| Cream time (10% accelerator) | approx. 12 seconds |
| Rise time (10% accelerator) | approx. 48-55 seconds |
| Adjustable reaction window | approx. 3-14 minutes depending on accelerator dose and temperature |
| Foam expansion | approx. 30 times liquid volume |
| Cured character | Tough, semi-flexible closed-cell polyurethane foam, bonded and impermeable |
| Substrate adhesion | Concrete, mortar, brick, metal |
| Pack size | 20 kg resin + 2 kg accelerator (separate pack) |
| Shelf life | 12 months in sealed packs stored at 10-38 C |
| Movement accommodation factor (MAF) | Not applicable – injection resin, not an elastomeric movement-joint sealant |
| Primer | Not required (injection resin) |
Industry use cases
Basement & below-grade waterproofing
Stopping live leaks through cracks and construction joints in basement rafts and retaining walls before an internal coating or lining is applied — common in Delhi NCR high-rise and commercial basements.
Water & wastewater infrastructure
Remedial water-stopping of cracks and cold joints in RCC water tanks, sumps, STP/ETP tanks and reservoirs where water is actively seeping.
Tunnels & metro
Plugging seepage in cut-and-cover sections, metro stations and underground car parks where hydrostatic pressure is driving water through the lining or joints.
Diaphragm & secant pile walls
Curtain / void-filling injection behind deep retaining walls to cut off water paths in deep excavations.
Dams, retaining walls & marine
Sealing leaking cracks in dams, spillways, retaining walls and marine structures exposed to permanent water head.
Lift pits & service ducts
Sealing chronic water ingress at lift pits, cable/service ducts and manhole joints in basements and plant rooms.
Frequently asked questions
Is Fosroc Nitofill PU 11R a joint sealant?
How does it stop water that is actively leaking?
Do I need special equipment to apply it?
How is the reaction time controlled?
What pack size and price should I expect in India?
Does it fully waterproof the structure on its own?
How we position Fosroc Nitofill PU 11R
Within the Fosroc range, Nitofill PU 11R belongs to the crack-injection and water-stopping family rather than the elastomeric joint-sealant family. The closest siblings are other Nitofill PU injection resins — such as Nitofill PU 1F and Nitofill PU 1R and the Nitofill WS series — which cover the spectrum from highly flexible foaming resins for moving cracks to rigid resins for permanent structural sealing; PU 11R sits in the semi-flexible, high-expansion, water-stopping bracket. It should not be confused with Fosroc’s true movement-joint sealants: Nitoseal (polyurethane and MS-polymer gun-grade sealants), Thioflex 600 (polysulphide) and Colpor 200PF (pouring-grade for trafficked/floor joints) are the products specified where a designed expansion, construction or floor joint must accommodate movement and be sealed with a flexible bead. Against the wider market, the comparable water-reactive PU injection resins come from suppliers such as Sika (the Sika InjectoCem / SikaFix PU injection range), MBCC/Master Builders Solutions (the MasterInject / MasterSeal injection systems) and STP / specialist injection-grout brands; the corresponding elastomeric sealant alternatives are Sika Sikaflex, MasterSeal joint sealants and STP sealant lines. As an authorised Fosroc distributor and applicator serving Delhi NCR and Pan-India, Space Arc Engineering can advise whether PU 11R injection is the right remedial water-stopping route for a live leak, or whether a movement-joint sealant or a coating/lining system is the correct specification for your structure, and supply genuine Fosroc material with current TDS/SDS documentation.
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