Master Builders Solutions MasterRoc MP 355 1K DW
A single-component polyurethane resin that foams the moment it meets water — built to stop active leaks in tunnels, mines and below-grade structures, with drinking-water contact certification built in.
What is it?
A solvent-free, single-component PU injection resin that reacts with moisture or flowing water to expand into a closed, flexible foam, plugging the fissure or void it was injected into.
Where is it used?
Underground works carrying active water — metro and road tunnels, mine drifts, basements, diaphragm walls, lift pits, manholes, and drinking-water tanks or transmission tunnels where the “DW” certification matters.
Why use it?
Cementitious grouts shrink and epoxies dislike wet substrates; this resin bonds to a running leak, foaming on contact with the very water causing the problem instead of needing a dry surface first.
How is it applied?
Injected neat, or blended with up to 10% MasterRoc MP 355 1K accelerator, through packers or drilled ports using a single-component injection pump; moisture triggers foaming within 15-130 seconds depending on temperature.
About Master Builders Solutions MasterRoc MP 355 1K DW
MasterRoc MP 355 1K DW is a single-component, solvent-free polyurethane injection resin from Master Builders Solutions’ MasterRoc range. It stays a stable, yellowish liquid in storage but reacts the moment it meets moisture, expanding into a closed, flexible foam that plugs the fissure or void it was injected into — reacting with the water causing the leak, rather than needing a dry substrate first, is what separates a PU injection resin from a conventional cementitious or epoxy grout. The “DW” suffix marks this resin as certified for contact with drinking water, so it can be injected near potable-water infrastructure — service reservoirs, transmission tunnels, treated-water structures — where standard MasterRoc MP 355 1K would not be appropriate.
Engineers reach for it when water is actively moving through a structure and needs to be stopped fast: a TBM or NATM bore hitting a water-bearing seam, a diaphragm-wall joint weeping into a basement, a mine drift needing ground consolidation, or a manhole letting groundwater into a sewer line. It is injected neat or blended on site with up to 10% MasterRoc MP 355 1K accelerator to speed the reaction in fast or cold water. As an authorised Master Builders Solutions distributor and applicator for Delhi NCR and pan-India, Space Arc supplies the resin and accelerator with the injection pumps, packers and trained crews this work needs — it is not a shelf product for casual DIY use.
The technical insight
The chemistry is isocyanate-moisture polymerisation: reactive groups meet water and release carbon dioxide, which inflates the resin into foam inside the crack. MBS lab data shows reaction starting around 15 seconds at 20°C and stretching past two minutes at 5°C, with foam expansion of 20-30 times the injected volume at a 10% accelerator dose. Don’t confuse this with its relatives: MasterRoc MP 355 (no “1K”) is a two-component resin with a different dosing regime, while MasterRoc MP 355 1K is identical chemistry without drinking-water certification — on any scope with a potable-water interface, specify the DW grade by name.
Where it is used
- Sealing active water inflows in TBM and NATM tunnel bores during metro and road-tunnel excavation
- Ground consolidation and water control in mine drifts and adits, alongside rock-bolting work
- Stopping through-wall seepage in basements, lift pits and diaphragm walls below the water table
- Sealing manhole chambers and utility ducts where groundwater infiltrates joints
- Pre-grouting ahead of a tunnel face advancing through water-bearing fissured rock
- Repairing leaking joints in tanks, reservoirs and galleries needing drinking-water certification
- Sealing the annular space around pipe-jacking and micro-tunnelling casings
- Emergency stop-leak injection in hydropower tunnels and inspection adits
Key advantages
- Reacts with the water causing the leak instead of needing a dry substrate first
- Single-component resin removes the mixing-ratio risk of two-part systems
- Reaction time is field-adjustable from about 15 seconds to a few minutes via accelerator dose
- Cures into a flexible, rubber-like foam that tolerates minor ground movement
- Certified for contact with drinking water, so usable near potable-water infrastructure
- Bonds well to wet and even actively running surfaces
- Solvent-free formulation, relevant for crews working inside confined shafts
- Backed by a MasterRoc range specified on major metro and tunnelling programmes
Limitations & considerations
- Stops water and consolidates minor voids; not a structural, load-bearing anchoring resin
- Needs a single-component injection pump, packers and a trained crew, not a retail product
- Reaction time and expansion shift with temperature, so a field trial batch is needed first
- Large, fast-flowing paths sometimes need a higher-expansion first pass before this fine seal
- 24-month shelf life with strict cool, dry, frost-free storage rules out casual stockpiling
- Sold and applied through trained applicators rather than over the counter
Selection & best practice
Run a field trial at the actual ground and water temperature before full-scale injection — reaction start time moves from about 15 seconds at 20°C to over two minutes at 5°C, and a wrong accelerator dose either washes resin out before it gels, or sets it too early. Flush a dry borehole with water first so there is moisture to react against; keep the pump charged with unaccelerated resin during short breaks; and flush the line with MasterRoc MP 230 CLN once injection is complete.
Specifications
| Chemistry / system | Single-component, solvent-free polyurethane (moisture-cure) injection resin |
| Resin density (20°C) | 1.16 g/cm³ |
| Resin viscosity (23°C) | 700 mPa·s |
| Accelerator (MasterRoc MP 355 1K) density (20°C) | 0.98 g/cm³ |
| Application temperature range | 5°C to 40°C |
| Maximum foam expansion ratio | 20-30x injected volume (at 10% accelerator dose) |
| Reaction time at 20°C, 10% accelerator | Starts ~15 sec, complete ~60 sec |
| Pack sizes | Resin: 22 L pail; Accelerator: 2.5 L bottle |
| Shelf life | 24 months, sealed, 5-35°C, protected from frost |
Industry use cases
Metro & underground rail
TBM/NATM tunnel bore active seepage control during excavation
Basements & below-grade structures
Diaphragm wall and lift-pit through-wall leak sealing below the water table
Mining & tunnelling
Drift and adit water control combined with ground consolidation around rock-bolting
Water & public utilities
Leak sealing in potable-water transmission tunnels and service reservoirs
Hydropower & dam infrastructure
Emergency stop-leak injection in tunnels, galleries and inspection adits
Frequently asked questions
What does the “DW” in MasterRoc MP 355 1K DW mean?
Is this the same product as MasterRoc MP 355 without the “1K”?
Do I need the MasterRoc MP 355 1K accelerator every time?
What equipment does a contractor need to inject this resin?
Can this fix a leaking basement in Delhi NCR with a high water table?
How is it packed, and what is the shelf life?
How we position Master Builders Solutions MasterRoc MP 355 1K DW
Within the MasterRoc family sold through Space Arc, this DW grade sits alongside standard MasterRoc MP 355 1K (no drinking-water certification), the two-component MasterRoc MP 355, and the MasterRoc MP 230 CLN flushing agent — specifiers on a mixed tunnelling and water-infrastructure scope usually standardise on the DW grade throughout. Outside MBS, the natural comparison is the PU injection-resin ranges from Fosroc and Sika; Space Arc does not currently list a verified Fosroc equivalent to this specific DW-certified grade, so where drinking-water certification is a hard requirement, MasterRoc MP 355 1K DW remains the more directly documented choice.
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Authorised distribution, technical advice & professional application across Delhi NCR and Pan-India.