MC-Bauchemie MC-Montan Injekt FN
MC-Bauchemie’s fast-reacting two-component polyurethane resin that seals and consolidates rock, soil and structures against active water ingress on tunnelling and foundation works.
What is it?
A two-component, low-viscosity polyurethane injection resin from MC-Bauchemie’s MC-Montan geotechnical range. Mixed 1:1 with hardener MC-Montan Injekt F, it foams on contact with water into a rigid, closed-cell, waterproof body inside fissures and voids.
Where is it used?
Tunnel faces and shafts, deep excavation and shoring pits, foundation subsoil, settled floor slabs, and cracks or voids in concrete, masonry and natural stone — anywhere water-bearing rock, ground or structure needs consolidating under pressure.
Why use it?
It reacts in about a minute and expands 2–10 times against water pressure, choking an active leak fast, then cures to 50 N/mm² compressive strength — strong enough to bear load, not just plug a hole.
How is it applied?
Pumped through injection packers or lances (≥4 mm bore) with a two-component pump such as MC-I 700, components metered 1:1 by volume. Reactivity can be sped up with MC-KAT 27 accelerator; equipment is flushed only with MC-Verdünnung PU thinner, never water.
About MC-Bauchemie MC-Montan Injekt FN
MC-Montan Injekt FN sits in MC-Bauchemie’s MC-Montan family of geotechnical and tunnelling products — “Montan” is German for mining, and the range targets underground and heavy civil work rather than everyday building repair. It’s the middle grade of a three-speed set: MC-Montan Injekt FR reacts in roughly 20–30 seconds for fast-moving water, FS takes about an hour for controlled deep-penetration grouting, and FN lands around one minute — quick enough to stop a running leak before the crew moves to the next packer, slow enough to place without fighting the clock. All three share the same hardener, MC-Montan Injekt F, and the same 1:1 mixing ratio.
Chemically it is a solvent-free, low-viscosity PU resin (about 300 mPa·s mixed) that travels into fine fissures under pressure, then reacts with moisture to foam into a closed-cell, rigid body expanding 2–10 times depending on counter-pressure. That foam is rated to 50 N/mm² compressive and 25 N/mm² flexural strength, so it does structural consolidation work, not just gap-filling. MC-Bauchemie backs it with DIBt assessment for impact on soil and groundwater and REACH-assessed exposure scenarios — documentation that Indian metro, highway and dam contractors increasingly need for statutory clearances.
The technical insight
It’s worth being clear about what this isn’t: a hydrophilic crack-injection resin like MC-Injekt FS or the flexible single-component gels used for hairline structural cracks, which swell gently and stay elastic in a moving joint. Injekt FN is rigid and hydrophobic-reacting, built for rock, soil and mass-concrete consolidation — bigger voids, higher pressures, strength and volume rather than elasticity. Route moving hairline cracks in a basement wall to MC-Bauchemie’s flexible hydrophilic range; reserve Injekt FN for tunnel faces, shaft linings, foundation soil, pit cut-offs and slab-lifting, where the ground itself is the problem.
Where it is used
- Pre-grouting water-bearing rock ahead of tunnel or shaft excavation
- Sealing diaphragm walls and secant-pile shoring against groundwater ingress
- Curtain grouting around underground stations, adits and mine shafts
- Stabilising loose or water-saturated subsoil beneath foundations and raft slabs
- Controlled lifting and re-levelling of settled floor slabs and pavement panels
- Sealing construction joints, cold joints and voids in mass concrete
- Emergency cut-off of active water inflow under hydrostatic pressure
- Rock-mass consolidation in underground mining and infrastructure development
Key advantages
- About one minute reaction time keeps packer-to-packer cycle short on tunnelling and shoring programmes
- Reactivity is adjustable via MC-KAT 27 accelerator or the FR/FS sibling grades to suit ground conditions
- Expands 2–10 times against water pressure, choking an active leak before it fully cures
- 50 N/mm² compressive and 25 N/mm² flexural strength well above typical hydrophilic crack resins
- Cures to a permanent rigid closed-cell foam rather than a hydrophilic gel that can shrink back
- DIBt-assessed for soil and groundwater safety, with REACH-documented exposure scenarios
- Can be alternated with cement suspension for larger voids, controlling resin consumption on big jobs
- Backed by a complete MC-Bauchemie injection system — pumps, packers, accelerator and thinner
Limitations & considerations
- Needs a proper two-component injection pump and trained crew — not a hand-mixed cartridge product
- Roughly one-minute pot life demands flushing with MC-Verdünnung PU the moment work pauses
- Application limited to 5–40°C rock/material temperature; cold faces may need the FS grade instead
- Rigid on cure — not suited to hairline cracks or joints that need to keep flexing
- Supplied only in 20-litre canisters, sized for contractor-scale work rather than small patch repairs
- Exposed resin still needs a separate cosmetic or protective finish; it cures brown and foam-textured
Selection & best practice
Treat every shot as engineered work, not a product application: check injectivity and set a written injection concept — packer spacing, depth, pressure — before mobilising the pump. Hold component A:B strictly at 1:1 by volume, mixed at the pump head, and confirm rock or material temperature stays within 5–40°C, switching to MC-Montan Injekt FS or easing off MC-KAT 27 on cold faces. On large voids, alternate with a cement suspension to fill volume economically and save the PU resin for the final pressure-tight seal. Never clean with water — keep MC-Verdünnung PU thinner on site and flush the pump the instant a pour is interrupted, since cured resin can only be chipped out mechanically. Store canisters at 5–35°C, dry and frost-free, within the 18-month shelf life.
Specifications
| Chemistry / system | Two-component polyurethane (PU) injection resin |
| Mixing ratio (A : B) | 1 : 1 by volume with MC-Montan Injekt F hardener |
| Density, mixed | approx. 1.13 kg/dm³ (DIN EN ISO 2811-1) |
| Dynamic viscosity | approx. 300 ± 50 mPa·s (DIN EN ISO 3219) |
| Volume expansion in water | 2–10 times, depending on counter-pressure |
| Reaction / application time | approx. 1 minute (ASTM D7/487) |
| Compressive strength | 50 N/mm² (ISO 604) |
| Flexural tensile strength | 25 N/mm² (ISO 178, 2% deformation) |
| Pack size | 20 L canister each for component A (FN) and component B (F) |
Industry use cases
Metro & tunnelling contractor
Pre-grouting a water-bearing fissure zone ahead of an NATM tunnel face to cut inflow before shotcrete lining goes on.
Basement & shoring contractor
Sealing diaphragm-wall panel joints and the pit floor before the raft pour, to bring dewatering pumping down ahead of concreting.
Industrial floors & pavements
Slab-jacking a settled warehouse floor or approach slab back to level using the resin’s controlled expansion, without breaking out the panel.
Water & utility infrastructure
Stopping an active leak at a construction joint in an underground pump house or reservoir wall under standing hydrostatic head.
Mining & underground works
Consolidating fractured rock and sealing shaft linings during underground mine development or shaft sinking.
Frequently asked questions
Is MC-Montan Injekt FN the same as a normal crack-injection PU resin?
Can it actually be injected into a running leak?
What equipment does a contractor need to apply it?
How does FN differ from the FR and FS grades in the same range?
Can this resin be used to lift a settled concrete slab?
What is the shelf life, and can equipment be cleaned with water?
How we position MC-Bauchemie MC-Montan Injekt FN
Within MC-Bauchemie’s own range, Injekt FN is the fast-reacting middle grade alongside MC-Montan Injekt FR (very fast, for aggressive inflows) and MC-Montan Injekt FS (slow, for deep-penetration grouting), all sharing the same MC-Montan Injekt F hardener — letting a contractor standardise pumps and stock across a tunnelling or shoring programme. For structural crack and joint work rather than ground consolidation, MC-Bauchemie’s own MC-Injekt 2K PU, MC-Injekt FS and MC-Inject 1K hydrophilic resins are the lighter-duty siblings. The closest genuine cross-brand equivalent most Indian specifiers already carry in a Fosroc-based BOQ is Nitofill PU23, a two-component solvent-free PU injection resin — though it’s scoped for structural crack repair rather than DIBt-assessed geotechnical consolidation, so the two aren’t fully interchangeable on a tunnelling or deep-foundation scope.
Fosroc Nitofill PU23 — Specifiers standardised on Fosroc for two-component, solvent-free PU injection sometimes reach for Nitofill PU23 instead, though it is scoped for structural crack and joint repair rather than DIBt-assessed rock and ground consolidation.
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