Master Builders Solutions MasterRoc MP 367 Foam
A two-component polyurea silicate injection foam that starts foaming in seconds flat, built for the moment a tunnel face or mine drive meets a cavity nobody planned for.
What is it?
A highly reactive, two-component, solvent-free polyurea silicate injection foam that expands up to roughly 30 times its liquid volume within about 40 seconds of mixing, filling voids and binding loose or fractured ground into a stable mass.
Where is it used?
Underground works: tunnel faces and TBM drives, cavities behind tunnel linings, fractured rock zones in coal and metal mines, mine ventilation seals, and old workings that need sealing against water or gas migration.
Why use it?
It reacts fast enough to keep an excavation moving (foaming starts in roughly 20 seconds and is done in under a minute), stays dimensionally stable once cured instead of continuing to swell if it later meets groundwater, and carries a DIN 4102-B2 fire-resistance rating that underground safety protocols look for.
How is it applied?
Part A and Part B are pumped in a fixed 1:1 ratio by volume through a two-component injection pump fitted with a static in-line mixer nozzle around 32 cm long, with both components conditioned to at least 15°C beforehand so the reaction runs predictably.
About Master Builders Solutions MasterRoc MP 367 Foam
MasterRoc MP 367 Foam sits in a different corner of the Master Builders Solutions catalogue than most of what a construction-chemicals distributor moves day to day. It isn’t a floor topping or a waterproofing coating for a basement — it’s a specialist ground-engineering product built for tunnelling and mining crews who need to fill a void, consolidate a pocket of loose rock or coal, or shut off a gas pathway before work can safely continue. The chemistry is a two-component polyurea silicate: a colourless, low-viscosity Part A and a pale-brown, thicker Part B, mixed 1:1 by volume through dedicated injection plant. Once triggered, foaming starts in around 20 seconds and finishes in under a minute at typical site temperatures, expanding up to 30-fold before settling into a stable, closed-cell mass that does not re-swell if it subsequently meets water — a meaningful difference from the hydrophilic polyurethane resins used for active water-stopping.
For Space Arc, this is a project-specification item rather than a shelf product. India’s underground construction pipeline — metro rail tunnelling in Delhi NCR and other cities, headrace and adit tunnels for Himalayan hydropower schemes, and coal mine development across Jharkhand, Odisha and Chhattisgarh — regularly runs into exactly the ground conditions MP 367 Foam is designed for: fractured strata, unexpected cavities, and the need to consolidate ground ahead of a TBM cutterhead or NATM face without stopping the job for days. As an authorised Master Builders Solutions distributor and applicator, Space Arc’s role on this product is less about stocking pallets and more about specifying the right MasterRoc injection system for the geology, sourcing genuine Part A/Part B material with verifiable batch traceability, and putting trained crews on site who know how to run the two-component pump and static mixer correctly.
The technical insight
The detail worth understanding before you specify this product is why it behaves so differently from the more familiar MasterRoc MP 355 polyurethane injection resins. MP 355 1K and 355 Thix are hydrophilic — they’re designed to keep reacting and expanding when they contact groundwater, which is exactly what you want when you’re chasing an active leak. MP 367 Foam is the opposite: its polyurea silicate chemistry is engineered to stay dimensionally stable once cured, so it will not continue swelling and potentially stressing a tunnel lining or mine support months after installation. That distinction is the whole reason a specifier would choose one MasterRoc foam over the other, and it’s why MP 367 Foam’s manufacturer data sheet reports foam expansion factor and free-rise density (45 kg/m³) rather than the water-reactive swell data you’d see on a leak-sealing resin’s sheet. The mixing ratio is also worth flagging: it’s 1:1 by volume, not by weight, and because Part A (1.40 kg/l) and Part B (1.25 kg/l) have different densities and viscosities (60 mPa.s versus 230 mPa.s), volumetric dosing pumps calibrated for this specific product are non-negotiable — eyeballing ratios with generic pumping plant risks an incomplete or off-ratio reaction underground, where there’s no easy way to inspect or redo the fill.
Where it is used
- Void and cavity filling behind tunnel linings and shotcrete to prevent trapped water or gas pockets
- Consolidation of fractured, loose rock strata encountered during underground excavation
- Ground pre-treatment ahead of TBM cutterheads on metro and rail tunnel drives
- Stabilisation of loose coal seams and surrounding strata in underground coal mining
- Sealing abandoned mine workings and old drives against gas migration
- Filling voids around shaft linings and mine ventilation seal structures
- Backfilling karstic or solution cavities encountered during metro, rail or hydel tunnelling
- Rapid emergency plugging of unforeseen voids where excavation cannot pause for slow-curing fills
Key advantages
- Extremely fast reaction — foaming starts in about 20 seconds and finishes in under a minute at 23°C, so excavation downtime is minimised
- High expansion factor of up to 30 times liquid volume fills irregular voids economically without excess material
- Dimensionally stable once cured — unlike hydrophilic PU foams, it does not re-swell on later contact with groundwater
- Good adhesion to wet and low-friction substrates, matching the damp rock and coal faces typical of underground conditions
- Fire resistance to DIN 4102-B2, relevant for confined tunnel and mine environments
- Simple, solvent-free 1:1 volume ratio with no complex on-site batching or catalyst weighing
- Uses the same two-component pump and static-mixer setup already common for MasterRoc MP 355 injection resins, so tunnelling contractors need no new plant category
- 24-month shelf life in unopened containers stored between 5°C and 35°C, workable for remote project stockholding
Limitations & considerations
- Reaction speed is temperature-sensitive — both components must be conditioned to at least 15°C before use, which needs planning at cold Himalayan portals or in winter stockyards
- Very fast pot life means it can only be placed through a purpose-built two-component injection pump with a static mixer — it is not a hand-mix, hand-pour product
- A specialist mining/tunnelling foam rather than a general-purpose construction grout, so pricing, minimum order quantities and lead times run well above routine cementitious grouts
- Requires trained injection crews, and the pump and hoses must be flushed immediately after use with MasterRoc MP 230 CLN or a water-free oil, or the equipment can be lost to cured foam
- The manufacturer’s data sheet publishes reaction, density and expansion figures but no compressive strength, bond strength, or IS/ASTM/BS equivalence values, so structural design allowables need to be confirmed case-by-case with Master Builders Solutions technical support
- Being an imported specialist item, India lead times and landed cost typically run higher than for locally stocked injection grouts
Selection & best practice
Condition both Part A and Part B to at least 15°C before pumping — this single step controls whether the reaction timing on site matches the data sheet figures, especially in cold tunnel portals or early-morning mine shifts. Fit a static in-line mixer of roughly 32 cm to the injection head rather than relying on the pump alone; under-mixed material sets unevenly and can leave weak pockets in the filled cavity. Run a small trial shot before committing to full-scale injection whenever ground or ambient temperature departs noticeably from 23°C, since reaction speed shifts with it. If the injection process pauses even briefly, pump Part A alone through the mixer to keep the line clear, and the moment work stops for the day, flush the entire pump and hose set with MasterRoc MP 230 CLN or a dry, water-free oil — cured foam left in the lines is not something you clean out later. Full PPE (gloves, overalls, eye protection) is required throughout, and spillage should be absorbed with sawdust or sand and disposed of per local regulations rather than washed to drain.
Specifications
| Chemistry | Two-component, solvent-free polyurea silicate injection foam |
| Part A (23°C) | Colourless; viscosity 60 mPa.s; density 1.40 kg/l |
| Part B (23°C) | Pale brown; viscosity 230 mPa.s; density 1.25 kg/l |
| Mixing ratio | 1:1, Part A to Part B, by volume |
| Reaction time (23°C) | Start of foaming 20s ± 10s; end of foaming 40s ± 15s |
| Foam expansion factor | Up to 30 times liquid volume |
| Free-rise foam density | 45 kg/m³ |
| Fire resistance | DIN 4102-B2 |
| Packaging | Part A: 34 kg cans / 284 kg drums; Part B: 30.6 kg cans / 250 kg drums |
| Shelf life | 24 months unopened, stored dry between +5°C and +35°C |
Industry use cases
Urban metro rail tunnelling
Filling cavities and consolidating loose overburden pockets encountered behind TBM-driven tunnel segments on Delhi NCR and other metro corridors.
Himalayan hydropower tunnels
Ground consolidation in fractured rock during headrace and adit tunnel excavation for hydel projects in hill states.
Underground coal mining
Consolidating loose coal seams and surrounding strata, and sealing old workings against gas migration, across coalfields in Jharkhand, Odisha and Chhattisgarh.
Highway and rail tunnels
Pre-injection ground treatment ahead of NATM excavation faces where geology varies unpredictably along the alignment.
Mine shaft and ventilation infrastructure
Sealing shaft linings and ventilation seal structures against air and gas leakage in active underground mines.
Frequently asked questions
Is MasterRoc MP 367 Foam the same as the polyurethane resins used for stopping water leaks?
What injection equipment does this product need?
How much working time do we have once the components are mixed?
Does Space Arc supply just the foam, or the injection pump too?
What’s the shelf life, and how should we store it on a remote tunnel or mine site?
Is this foam approved for use inside an active underground mine in India?
How we position Master Builders Solutions MasterRoc MP 367 Foam
Within the MasterRoc injection range, MP 367 Foam is the cavity-filling and ground-consolidation option, distinct from MasterRoc MP 355 1K, MP 355 1K DW and MP 355 Thix, which are hydrophilic polyurethane resins for stopping active water ingress, and from MasterRoc MP 350, used for permanent crack sealing and minor seepage. A specifier moving between these should think in terms of the problem, not just the brand: is water actively coming in (MP 355 family), is a crack simply seeping (MP 350), or is there a void or loose ground mass to fill and lock up before work continues (MP 367 Foam)? On the alternative-supplier side, this is a narrow enough niche that Space Arc’s current Fosroc range — built around Conbextra cementitious and epoxy grouts and the Lokfix anchor system — doesn’t carry a genuine one-for-one match for a fast-reacting polyurea silicate mining foam; those Fosroc products solve bedding, anchoring and precision-grouting problems rather than rapid underground cavity fill. Specifiers looking for a second source for this specific application would be better served checking with specialist ground-engineering suppliers than substituting a general Fosroc grout, and Space Arc’s honest recommendation here is to stay within the MasterRoc injection family and pick the right member of it for the ground condition in front of you.
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