MC-Bauchemie MC-Injekt FS
A moisture-triggered, fast-foaming polyurethane injection resin engineered to shut down active, high-pressure water ingress in cracks and construction joints within seconds.
What is it?
A single-component hydrophilic polyurethane injection resin from MC-Bauchemie that reacts with water and foams rapidly to seal live leaks in concrete.
Where is it used?
Basements, underground car parks, metro and railway tunnels, lift pits, water-retaining structures and sewage works where water is actively flowing through cracks or joints.
Why use it?
It gels in as little as 5 to 30 seconds and expands 10 to 25 times, so it can hold back moving water and buy time for a permanent repair when other resins wash out.
How is it applied?
Injected under 2 to 8 bar through mechanical packers set in 12 to 13 mm holes drilled at 30 to 45 degrees across the crack, using a standard single-component injection gun.
About MC-Bauchemie MC-Injekt FS
MC-Injekt FS is the resin engineers reach for when water is already pouring in and there is no time to lose. Unlike rigid structural injection systems that need a dry, controlled crack to work, this single-component polyurethane is designed for the opposite situation: an active, high-flow leak under pressure. The moment the liquid resin meets the water in the crack it begins to react, gelling in 5 to 30 seconds and foaming out to fill the void. That foam expands 10 to 25 times its liquid volume, pushing into fine channels and pressing back against the water head until the flow stops. For a site facing a flooded basement or a leaking tunnel segment during the monsoon, that speed is the difference between a controlled repair and an emergency.
At Space Arc Engineering we position MC-Injekt FS specifically as a first-response, water-stop product rather than a final structural fix. It is supplied in 330 ml cartridges that load into any standard injection gun, so a crew can carry it to site and start work without mixing or specialist rigs. The cured product is a flexible, closed-cell foam that is waterproof and chemically resistant, tolerating the movement and aggressive water often found in below-grade and effluent structures. Because the reaction is driven by moisture, the resin performs best exactly where dry-cure products fail, and it can be accelerated further for the most violent leaks. Once the water is under control, the permanent seal follows with a rigid PU or cementitious system.
The technical insight
The chemistry that makes MC-Injekt FS work is a hydrophilic polyurethane pre-polymer carrying reactive isocyanate groups. In a dry crack nothing happens; the resin simply sits at its low working viscosity of 200 to 400 mPa.s, thin enough to travel deep into a crack from 0.3 mm. The reaction only fires when the isocyanate meets water. That reaction generates carbon dioxide, which drives the foaming and the 10 to 25 times expansion, while the polymer cures into a flexible closed-cell matrix. The elegance for leak-stopping is that the more water present, the faster and more vigorously the resin reacts, so a fast, wet leak accelerates the seal rather than washing the resin away. A gel time of 5 to 30 seconds and full foam inside 60 to 180 seconds mean the foam sets before the water head can flush it out. The closed-cell structure gives a compressive strength of about 0.3 to 0.8 MPa, enough to hold position under moderate pressure while staying flexible enough to accommodate joint movement. For the most extreme flows, adding MC-Injekt Accelerator at 1 to 5 percent pulls the gel time down to 3 to 10 seconds.
Where it is used
- Emergency stopping of active water ingress through cracks in basement and retaining walls
- Sealing live leaks in metro, railway and utility tunnel segments and linings
- Curtain and crack injection in underground car parks and lift pits during high water table conditions
- Construction-joint leak closure in water supply reservoirs, sumps and sewage structures
- Pre-treatment water stop ahead of a permanent rigid PU or cementitious repair
- Monsoon-season flood control in below-grade utility chambers and service ducts
- Sealing of gushing leaks around pipe penetrations and cold joints in concrete
- Temporary control of high-flow seepage in tunnels and diaphragm walls before structural grouting
Key advantages
- Reacts and gels in 5 to 30 seconds, so it holds against moving water where slower resins wash out
- High 10 to 25 times foam expansion fills large voids and irregular crack paths from a modest resin volume
- Single-component and moisture-triggered, needing no on-site mixing of two parts
- Low 200 to 400 mPa.s viscosity penetrates cracks from 0.3 mm before it foams
- Supplied in 330 ml cartridges usable with standard injection guns for fast mobilisation
- Cured foam is flexible and closed-cell, accommodating joint movement without cracking
- Chemically resistant, suiting sewage, effluent and aggressive groundwater environments
- Reaction speed is fully tunable with MC-Injekt Accelerator for the most violent leaks
Limitations & considerations
- It is a temporary water-stop, not a permanent structural repair, and must be followed by a rigid PU or cementitious system
- The very short gel time leaves little room for error and demands trained, experienced injection crews
- Foam compressive strength of 0.3 to 0.8 MPa is low, so it seals leaks but does not restore structural integrity of the crack
- Reaction depends on water contact, so behaviour in a genuinely dry crack is unpredictable and inefficient
- The resin foams vigorously on skin contact with moisture, making strict PPE and careful handling essential
- Once curing starts the reaction cannot be paused, so equipment and packers must be prepared before injection begins
Selection & best practice
Plan the injection before opening a cartridge, because with a 5 to 30 second gel time there is no time to improvise mid-pour. Drill 12 to 13 mm packer holes at 30 to 45 degrees so they cross the crack plane at depth, spacing them along the leak so the foam fronts overlap. Fit and tighten mechanical packers, then inject at 2 to 8 bar, starting from the lowest point and working upward so rising foam displaces water ahead of it. For fast-flowing leaks, flush the crack with water first to confirm the reaction path, and dose MC-Injekt Accelerator at 1 to 5 percent when the flow is too strong for the standard gel time. Keep the resin thin and cool for good penetration, and stop each port once foam returns or pressure builds. Crews must wear safety glasses and nitrile gloves throughout, since the resin foams aggressively on any wet skin. Once the leak is stopped and the foam has fully developed, schedule the permanent repair promptly with MC-Injekt 2K rigid PU or a cementitious waterproofing system rather than treating the foam as the final seal.
Specifications
| Product type | Single-component hydrophilic polyurethane foaming injection resin |
| Reaction / gel time | 5 to 30 seconds from water contact |
| Full foam development | 60 to 180 seconds |
| Expansion ratio | 10 to 25 times liquid volume with excess water |
| Viscosity (liquid) | 200 to 400 mPa.s |
| Cured foam compressive strength | 0.3 to 0.8 MPa |
| Injection pressure | 2 to 8 bar |
| Minimum crack width | From 0.3 mm |
| Pack size | 330 ml cartridge (standard injection-gun compatible) |
Industry use cases
Metro & Tunnels
Stops live seepage through segment joints and linings during and after construction, holding back water pressure until structural grouting follows.
Commercial Basements & Car Parks
Shuts down active leaks in retaining walls, lift pits and slabs when the water table rises, protecting parking levels and services.
Water & Sewage Infrastructure
Seals leaking construction joints in reservoirs, sumps and effluent tanks, with a chemically resistant foam suited to aggressive water.
Monsoon Emergency Repair
First-response product for flooded below-grade chambers and ducts across Delhi NCR, where seconds-fast gelling controls ingress before permanent works.
Utility & Service Structures
Closes gushing leaks around pipe penetrations and cold joints in underground utility structures to prevent flooding of critical equipment.
Frequently asked questions
Is MC-Injekt FS a permanent waterproofing repair?
How fast does it actually stop water?
Can it seal a leak that is already gushing?
What crack widths and equipment does it need?
Does it need mixing on site?
What safety precautions apply?
How we position MC-Bauchemie MC-Injekt FS
MC-Injekt FS is the emergency water-stop in the MC-Bauchemie injection family and is meant to be paired, not confused, with the permanent solution: once the leak is halted, specify MC-Injekt 2K rigid structural PU or a cementitious waterproofing system to complete the repair, and add MC-Injekt Accelerator when flows are extreme. For teams standardised on Fosroc, the closest equivalent from our Fosroc range is Nitofill UR63, a water-reactive foaming PU for stopping active leaks. Space Arc supplies both families along with complementary waterproofing lines such as Dr. Fixit and Sika, so specifiers can match the resin to their approved-vendor list without compromising on leak-stopping performance.
Fosroc Nitofill UR63 — Choose the Fosroc option when the project or client specification is standardised on Fosroc-approved materials, as Nitofill UR63 is an equivalent water-reactive foaming PU for stopping active leaks through cracks.
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