About MC-Bauchemie MC-Montan Injekt FS

MC-Montan Injekt FS belongs to MC-Bauchemie’s Montan Injekt family — a set of two-component polyurethane injection resins built for one job: getting into places cementitious grout can’t reach and sealing them permanently. The “FS” marks it out as the slow-reacting member of the FR/FN/FS trio; where FR sets in 20-30 seconds and FN in about a minute, FS gives the applicator roughly an hour of working time. That extended window matters on a real site — it lets the resin travel further into fine fissures, micro-cracks and porous ground before it starts to gel, which is exactly what’s needed when the injection point is deep or the fracture network is unpredictable, as it usually is on Indian tunnelling, metro-shaft and basement-shoring work.

For Space Arc’s Delhi NCR and pan-India project base, this is the resin we reach for on the harder waterproofing jobs — an active leak through a diaphragm wall, a water-bearing seam in a tunnel face, or ground that needs consolidating before a raft slab goes down — rather than routine terrace or slab waterproofing, where a membrane or coating system does the job at a fraction of the cost. It sits alongside the faster FR and FN grades and MC-Bauchemie’s epoxy-based MC-Injekt range in our injection portfolio, so the choice on any given site usually comes down to reaction speed, water pressure and how far the resin needs to travel, not the underlying chemistry.

The technical insight

The number that matters most on the datasheet is the ~60-minute application time (ASTM D7/487) — long by injection-resin standards, and the reason FS can even be run through a single-component pump like the MC-I 510 instead of always needing a two-component rig. At approx. 300 ± 50 mPa·s dynamic viscosity, a mixed density of ~1.13 kg/dm³, and a 1:1 mix with the MC-Montan Injekt F hardener, the resin stays thin enough to migrate through hairline fissures under injection pressure well before it starts to gel. On contact with groundwater it foams into a closed-cell rigid structure, expanding 2-10 times depending on the counter-pressure it’s working against — that expansion is what physically displaces water out of the void, rather than just bonding around it. Cured strength (50 N/mm² compressive, 25 N/mm² flexural tensile) is high enough to contribute real load-bearing capacity under a slab or footing too, not just watertightness, which is why it shows up in ground-stabilisation specs as often as pure sealing ones. On a site with running water or high flow, the FR or FN grade from the same range is the correct swap — not a different product family.

Where it is used

• Sealing rock and subsoil against water ingress in tunnelling, shaft and metro construction
• Stopping active water flow through cracks, construction joints and cold joints in concrete
• Consolidating loose or water-bearing ground ahead of raft foundations and base slabs
• Sealing building pits and shoring systems during deep excavation
• Raising the load-bearing capacity of soil beneath settling floor slabs and footings
• Sealing voids, joints and fissures in masonry and natural stone in structural repair work
• Curtain and contact grouting behind retaining walls and diaphragm walls
• Emergency water-stopping in basements and underground water-retaining structures

Key advantages

• Long ~60-minute working time gives deep, controlled penetration that faster resins can’t match
• Low viscosity (approx. 300 mPa·s) travels into hairline fissures and fine soil pores under pressure
• Reacts even in active water flow — the substrate doesn’t need to be dried out first
• Cures to a closed-cell rigid foam that is permanently watertight, not just water-resistant
• High compressive (50 N/mm²) and flexural tensile (25 N/mm²) strength adds real structural value, not just sealing
• Reactivity can be sped up on site with MC-KAT 27 accelerator if conditions demand a faster set
• Slow reaction lets it run on a single-component pump (e.g. MC-I 510), simplifying smaller injection jobs
• Meets DIBt criteria for impact on soil/groundwater and is REACH-assessed for relevant exposure scenarios

Limitations & considerations

• Requires trained applicators and proper 1- or 2-component injection pumps — not a brush, trowel or DIY product
• Application is temperature-bound (5-40°C substrate/material) — plan around Delhi’s cold winter mornings and peak summer surface temperatures
• Equipment must be flushed with MC-Verdünnung PU thinner, never water — a cleanup mistake can seize the pump
• A rigid injection resin, not a flexible sealant — movement joints still need a dedicated joint-sealant system
• Premium PU chemistry costs meaningfully more per litre than cementitious grout, so it’s overkill for routine, dry-substrate waterproofing
• The injection concept — packer spacing, depth, pressure — has to be engineered per site; there’s no generic dosage rate to quote off a chart

Selection & best practice

Specifications

Industry use cases

How we position MC-Bauchemie MC-Montan Injekt FS

MC-Montan Injekt FS sits in the slow-reacting slot of MC-Bauchemie’s Montan Injekt range, alongside the fast-setting FR and medium-speed FN grades — all three share the same MC-Montan Injekt F hardener, so a contractor can stock one hardener and switch resin speed to match site conditions. For lighter-duty building crack injection and water-stopping — a leaking construction joint in a residential basement rather than a tunnel face — Fosroc’s Nitofill PU 23R is a genuine, more accessible alternative that many specifiers reach for first; Space Arc stocks both and recommends based on whether the job is heavy ground/rock consolidation (Montan Injekt FS) or standard building crack sealing (Nitofill PU 23R). Within MC-Bauchemie’s own catalogue, the epoxy-based MC-Injekt resins are the alternative when a rigid, high-strength structural bond is the priority rather than PU’s water-reactive sealing behaviour.

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