About Fosroc Nitofill PU12F

Fosroc Nitofill PU12F is a single-component, water-reactive flexible polyurethane crack-injection resin developed for one of the toughest jobs in waterproofing – sealing cracks that are not only leaking but are still actively moving. According to Fosroc’s official product information, it is injected into moving cracks in concrete to eliminate water pathways, including high-volume leaks such as those found in diaphragm walls, and it forms a high-strength bond within the crack. The defining feature is its water-reactive chemistry: the resin reacts very quickly on contact with water – even water that is in motion – so it can be used in situations where the leak cannot be stopped or dewatered first. This makes it fundamentally different from conventional epoxy grouts, which need a dry or near-dry crack to bond properly. Once cured, Nitofill PU12F remains highly elastic, absorbing structural movement without breaking, and it does not shrink after hardening, so the seal does not pull away from the crack faces over time. Fosroc describes the reaction time as adjustable, allowing the applicator to tune how fast the resin gels to suit the flow rate and crack geometry on site. Cured material is reported to be non-flammable, solvent-free and non-toxic, which matters for confined-space work such as tunnels, tanks and basements. For Indian projects, Space Arc Engineering positions Nitofill PU12F as a specialist remedial-injection grout for negative-side and active-leak situations across Delhi NCR and pan-India infrastructure, building and water-retaining works. Because regional Fosroc formulations and pack sizes vary, the exact numeric properties – viscosity, density, reaction/gel time, tensile strength and elongation – must always be read from the current local Technical Data Sheet supplied with the batch, and Space Arc can provide the India-specific TDS and MSDS on request before specification or purchase.

The technical insight

The performance of Nitofill PU12F comes from its hydrophilic/hydrophobic water-reactive polyurethane chemistry. As a one-part prepolymer it carries reactive isocyanate groups that consume the very water causing the leak: when resin meets moisture inside the crack, the reaction generates CO2 and drives the prepolymer to expand and cure into a closed, elastic barrier rather than being washed out. Because the curing agent is the leaking water itself, no separate hardener or precise mixing ratio is needed – a key reliability advantage on a wet, awkward site. The flexible (rather than rigid) polymer backbone is what lets the cured seal elongate and recover as the crack breathes with thermal and structural cycles, which is why Fosroc markets it for moving cracks specifically. The adjustable reaction time is typically controlled with an accelerator dosage and by the amount of water present, letting the applicator balance deep penetration (slower gel) against rapid plugging of a heavy gusher (faster gel). For Space Arc’s technical guidance, the practical takeaway is that PU12F is a water-stop grout first and a structural bonder second – where the goal is to monolithically re-bond a dry, dormant crack and restore load transfer, a rigid low-viscosity epoxy such as Nitofill LV is the correct tool, and PU12F is reserved for the leaking, live, or moving cracks epoxies cannot handle.

Where it is used

• Stopping active water leakage through moving cracks in concrete where dewatering is not possible
• Sealing high-volume water pathways and gushing leaks in diaphragm/slurry walls and retaining walls
• Crack injection in basement raft slabs, retaining walls and lift pits with negative-side water pressure
• Water-stop injection in tunnels, metro tunnels, cut-and-cover and underground structures
• Leak sealing in water-retaining structures – tanks, reservoirs, STP/WTP/ETP and treatment plants
• Remedial injection at construction joints, cold joints and honeycombed zones subject to seepage
• Curtain/contact grouting behind concrete to cut off water ingress from the soil side

Key advantages

• Water-reactive – reacts and cures even against flowing water, so leaks need not be stopped or dried first
• Forms a high-strength bond within the crack, eliminating the water pathway
• Highly elastic when cured – absorbs ongoing crack movement without cracking or debonding
• Does not shrink after hardening, so the seal stays intact against the crack faces
• Adjustable reaction time to suit flow rate, crack width and depth of penetration
• Single-component – no mixing ratios or catalyst metering errors on site
• Non-flammable, solvent-free and non-toxic when cured – suited to confined, occupied and water-contact spaces

Limitations & considerations

• A water-stopping and flexible-sealing grout – not a structural re-bonding resin; use a rigid epoxy (e.g. Nitofill LV) to restore load transfer in dry, dormant cracks
• Performance depends on correct packer spacing, injection pressure and pump selection – requires trained applicators and single-component PU injection equipment
• Requires the presence of water (seepage or pre-introduced) to cure fully; behaviour and expansion depend on available moisture
• Reaction time and expansion must be controlled on site – over-fast gel can block penetration, over-slow gel can wash out in heavy flow
• Exact numeric properties and pack sizes vary by region; always verify against the current India Technical Data Sheet before specifying
• Surface preparation, crack mapping and removal of loose/contaminated concrete remain essential for a durable result

Selection & best practice

Specifications

Industry use cases

How we position Fosroc Nitofill PU12F

Nitofill PU12F sits in Fosroc’s crack-injection range as the flexible, water-reactive specialist for stopping active leaks in moving cracks – the situation where epoxies fail. Within the Fosroc family it complements rather than competes with Nitofill LV and Nitofill TH (rigid low-viscosity/thixotropic epoxies for structurally re-bonding dry, dormant cracks) and sits alongside other Fosroc PU injection grouts such as Nitofill PU 1F and the Nitofill UR/WS foaming and water-stop resins; the right choice depends on whether the crack is dry and structural (epoxy) or wet and moving (PU). Against the wider Indian market it is a direct alternative to Sika’s polyurethane injection resins (e.g. the Sika Injection / SikaFix PU range), MBCC/Master Builders Solutions MasterInject PU grouts, Dr. Fixit’s PU injection/crack-seal systems and STP Ltd’s polyurethane injection grouts. For specifiers and contractors in Delhi NCR and pan-India, Space Arc Engineering’s role is to match the leak condition (flow rate, crack width, movement, exposure) to the correct product – PU12F or a complementary Fosroc system – and to supply the verified India TDS, application guidance and authorised-distributor pricing rather than a generic substitution.

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