Fosroc Nitofill PU23
Two-component, solvent-free polyurethane injection resin that foams and expands on contact with water to seal active leaking cracks and stabilise wet or dry ground.
What is it?
A two-component, solvent-free polyurethane resin injection grout from Fosroc that reacts and expands rapidly on contact with water to form a rigid foam, sealing water-carrying cracks and consolidating soil.
Where is it used?
Diaphragm walls, basement and retaining walls, tunnels, sumps, lift pits, water tanks and any wet structural concrete where active leaks need stopping or ground needs consolidation.
Why use it?
It chases and stops flowing water that conventional epoxy and cementitious grouts cannot, foams even without abundant water, bonds strongly inside the fissure and is non-flammable and solvent-free.
How is it applied?
Mixed in the correct ratio and injected through packers into the crack using suitable two-component PU injection equipment; the resin penetrates, reacts with moisture, expands and cures in place.
About Fosroc Nitofill PU23
Fosroc Nitofill PU23 is a two-component polyurethane resin injection grout engineered for one of the most stubborn problems on Indian construction and rehabilitation sites: water that is actively moving through a crack while you are trying to seal it. Most repair systems demand a dry, static substrate. Nitofill PU23 is the opposite. The resin is designed to react with the very water it is meant to stop, expanding rapidly into a rigid foam that physically blocks the water path and bonds high-strength into the fissure. According to Fosroc’s product literature, it is a low-viscosity, solvent-free, non-flammable system that produces rigid foam even where free water is not present, which makes it forgiving across the variable site conditions encountered in basements, tunnels and underground structures. Because it grips concrete, mortar, brick and metal, it suits the mixed substrates of older, repeatedly modified structures common across Delhi NCR and other Indian metros. Space Arc Engineering supplies Nitofill PU23 as an authorised Fosroc distributor, pairing the material with guidance on packer selection, injection sequencing and the right companion products so the repair holds rather than simply diverting the leak to the next weak point.
The technical insight
The defining chemistry of Nitofill PU23 is moisture-triggered, gas-generating polyurethane. The two components are blended and injected; on contact with water the isocyanate chemistry reacts, releasing gas that drives a rapid volumetric expansion into a closed rigid foam. This expansion is the working mechanism, not a side effect. It lets the resin travel along the wetted crack, fill voids it could not otherwise reach, and exert a sealing pressure against the crack walls. Two engineering consequences matter on site. First, low initial viscosity is essential so the resin penetrates fine, branching cracks before it starts to foam, then the expansion takes over to close them. Second, because the reaction is water-driven and exothermic, the speed of foaming depends on how much water is present and on temperature, so the injection rate and packer spacing must be matched to the actual flow, not a textbook value. Unlike a flexible water-stopping foam that stays rubbery to absorb movement, PU23 cures to a rigid, high-strength mass, which is why Fosroc positions it for both sealing and ground/soil consolidation where load-bearing stiffness is wanted rather than elasticity. For movement-prone joints a flexible PU grade is the better tool; for stopping a leak and stiffening the surrounding zone, the rigid foam is the point.
Where it is used
- Sealing water-carrying cracks and low-pressure infiltration in diaphragm and retaining walls
- Stopping active leaks in basement walls, lift pits and underground car parks
- Water ingress control in tunnels, shafts, sumps and underground services
- Consolidation of loose or water-bearing soil and ground ahead of or behind structures
- Sealing leaking construction joints and honeycombed zones in below-grade concrete
- Curtain and crack injection in water-retaining structures and treatment-plant basins
Key advantages
- Reacts and expands rapidly on contact with water, chasing and stopping flowing leaks that epoxy and cementitious grouts cannot
- Forms rigid foam even when free water is not present, giving reliable cure across variable site moisture
- Low viscosity so the resin penetrates fine and branching cracks before it foams
- Strong adhesion to concrete, mortar, brick and metal, suiting mixed and aged substrates
- Develops a high-strength bond inside the fissure for sealing plus ground/soil consolidation
- Solvent-free and non-flammable, easing handling and storage on confined Indian sites
- Backed by Fosroc’s documented Nitofill injection system and Space Arc’s local technical support
Limitations & considerations
- Two-component system that requires correct ratio mixing and dedicated PU injection equipment, not a hand-applied product
- Cures to a rigid, not elastic, foam, so it is not the first choice for joints with significant ongoing movement where a flexible PU grade is preferred
- Reaction speed and expansion depend on available water and temperature, demanding skilled operators to match injection rate to actual flow
- Performs as a localised injection treatment, not a substitute for full positive-side waterproofing on new build
- Numeric performance values are issued in Fosroc’s region-specific datasheet rather than published openly, so the project TDS must be obtained and followed
- Health and safety precautions for isocyanate-based products (ventilation, gloves, eye protection) must be observed
Selection & best practice
Always begin with diagnosis, not injection. Identify the source and pressure of the water, map the crack network, and where flow is heavy, flush and pre-treat. Drill and fit packers at an angle that intersects the crack at depth, spacing them to the crack width and observed flow. Mix the two components in Fosroc’s specified ratio only as fast as you can inject, because the pot is short once moisture is involved. Inject from the lowest packer upward (or follow the wet front), watching for resin and foam emergence at the next packer before moving on. Match injection pressure to the structure and let the foam build sealing pressure rather than forcing the resin. For leaks with high flow, a flexible PU water-stopping resin can be used first to choke the flow, with Nitofill PU23 following to consolidate and strengthen. Confirm with the current region-specific Fosroc TDS and SDS supplied by Space Arc before starting, use trained injection operators, and protect skin, eyes and airways throughout. Treat the injection as crack and leak remediation, complemented where appropriate by surface waterproofing, not as a stand-alone waterproofing layer.
Specifications
| Product type | Two-component polyurethane resin injection grout |
| Primary function | Sealing water-carrying cracks; soil/ground consolidation |
| Reaction with water | Expands rapidly on contact with water, even when water is flowing |
| Foam behaviour | Produces rigid foam even when free water is not present |
| Viscosity | Low viscosity (penetrates fine cracks) |
| Adhesion | Good adhesion to concrete, mortar, brick and metal |
| Bond | Creates a high-strength bond within the fissure |
| Solvent / flammability | Solvent-free; non-flammable |
| Application method | Injection via packers using two-component PU injection equipment |
| Manufacturer | Fosroc (Constructive Solutions) |
| Detailed numeric data | Per Fosroc region-specific TDS (obtain current sheet before use) |
Industry use cases
Metro & Tunnelling
Stopping water ingress through segment joints, construction joints and cracks in metro tunnels, shafts and underground stations across Delhi NCR and other Indian metro networks.
Commercial & Residential Basements
Sealing active leaks in deep basements, lift pits and underground parking of high-rise and IT-park developments where dewatering alone cannot keep the structure dry.
Water & Wastewater Infrastructure
Crack and joint injection in water-retaining tanks, treatment-plant basins and pumping stations to arrest leakage in below-grade reinforced concrete.
Civil & Geotechnical
Consolidation of loose or water-bearing ground behind diaphragm and retaining walls, and stabilising soil around excavations and foundations.
Repair & Rehabilitation
Remediating leaking, honeycombed or cracked concrete in ageing bridges, dams, culverts and industrial structures during waterproofing and strengthening contracts.
Frequently asked questions
What exactly is Fosroc Nitofill PU23 used for?
How is Nitofill PU23 different from a flexible PU like Nitofill PU 1F?
Can it stop a crack that is actively leaking water?
How is Nitofill PU23 applied on site?
Is Nitofill PU23 available in Delhi NCR and across India?
Where can I get the exact technical figures such as density and gel time?
Does Nitofill PU23 replace waterproofing the whole structure?
How we position Fosroc Nitofill PU23
Nitofill PU23 sits in Fosroc’s Nitofill polyurethane injection-grout family as the rigid, two-component, water-reactive option for stopping active leaks and consolidating ground. Within the Fosroc range it pairs naturally with flexible water-stopping grades such as Nitofill PU 1F (single-component elastic foam for moving cracks) and the Nitofill UR63 flexible PU resin system, while Nitofill LV/EPLV epoxy resins remain the choice for structural crack bonding in dry conditions. Against competitors, the closest alternatives are Sika’s injection PU range (for example the Sika InjectoCem/Sikadur-Combiflex and PU injection resins), MBCC/Master Builders Solutions MasterInject and MasterSeal injection systems, STP’s polyurethane injection grouts, and Dr. Fixit’s PU injection grout offerings within Pidilite’s waterproofing line. Honestly assessed, no single PU resin is universally best: rigid grades like PU23 win on strength and consolidation but trade away the flexibility that movement joints need, and the real differentiator on Indian sites is correct product selection, packer technique and a reliable, technically supported supply chain. That is where Space Arc Engineering adds value, matching the right Fosroc grade to the leak, the substrate and the movement regime rather than defaulting to one product.
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