MC-Bauchemie Centrament Guniting
A chloride-free dry-mix accelerator engineered to set sprayed concrete rock-hard within minutes of jetting — built for crews who cannot afford slow strike times on tunnel, shaft and repair sites.
What is it?
A powder (also supplied as a liquid) admixture from MC-Bauchemie, dry-blended into the guniting or shotcrete mix on site to accelerate setting, boost early strength, plasticise the mix for easier jetting, and cut rebound losses.
Where is it used?
Tunnel linings, mine drifts and shafts, hill-road retaining walls and slope stabilisation, basement and podium guniting repair, canal and reservoir lining repair, and any overhead or vertical spray-applied concrete or mortar work.
Why use it?
It sets sprayed mortar rock-hard within minutes of jetting, carries no chlorides so there is no corrosion risk to embedded steel, waterproofs the sprayed layer, and lets crews build thicker layers in a single pass with less material lost to rebound.
How is it applied?
Dosed at 1.0% to 5.0% by weight of cement into the properly graded dry mix before spraying. MC-Bauchemie’s own instructions call for a site trial, typically starting at 3%, with the dosage nudged up or down depending on the setting time observed for that specific cement, aggregate grading and site temperature — water is withheld from the dry mix until jetting actually begins because the set, once gauged, is fast.
About MC-Bauchemie Centrament Guniting
Centrament Guniting — sold in some older literature under its legacy name MC-Torkrethilfe BE — is MC-Bauchemie’s dry-mix guniting aid for sprayed concrete and mortar. It was developed for exactly the situation Indian tunnelling and mining contractors run into constantly: a working face with active water seepage, a need to close it fast, and a specification that will not tolerate calcium chloride anywhere near reinforcement. The reactive components in the powder combine rapidly with cement particles the moment water is added, accelerating hydration so the sprayed layer goes from workable to rock-hard within minutes rather than the hours a plain OPC mortar would take. That speed is the entire point of a guniting aid — it lets a nozzleman build up a seal or a structural lining layer by layer, in overhead or vertical positions, on ground that is actively wet, without the layer sagging or sloughing off before it sets.
For Space Arc’s Delhi NCR and pan-India project base, Centrament Guniting sits in the practical, well-proven end of the guniting-admixture spectrum — it is a straightforward powder or liquid dosed by hand or batcher into a conventional dry-mix gunite rig, not a metered nozzle-side liquid system. That makes it a natural fit for metro and road-tunnel water-seepage sealing, hydro-project drift and shaft support, hill-road retaining-wall stabilisation, and repair guniting on basements, podiums and water-retaining structures, where crews are working with standard dry-mix equipment and need a chloride-free accelerator they can dose and trial on site without importing a specialised liquid-dosing pump.
The technical insight
Centrament Guniting works as a mineral-based set accelerator: its reactive components combine with the aluminate and silicate phases of the cement as soon as gauging water hits the dry mix, pulling forward the hydration reactions that would otherwise take hours to develop enough rigidity to resist gravity and rebound. Because it is chloride-free, that acceleration comes without the long-term corrosion risk that dogged the calcium-chloride accelerators of an earlier generation of guniting work — a genuinely important distinction on reinforced tunnel linings and repair jackets where the whole point of guniting is to protect steel, not compromise it.
It is worth being clear-eyed about where this sits in the current shotcrete-accelerator landscape. Centrament Guniting is a classic dry-mix powder/liquid guniting aid, hand- or batcher-dosed into the dry mix ahead of spraying — the technology that most manual and semi-mechanised Indian guniting rigs still run on. Larger, mechanised wet-mix shotcrete operations (tunnel boring support, robotic arm application) have increasingly moved to alkali-free liquid accelerators dosed at the nozzle, such as MC-Bauchemie’s own MC-Montan Shotcrete HA 01 in its tunnelling-systems range, which offer more consistent long-term strength retention and lower alkalinity exposure for the nozzle crew. Centrament Guniting remains the right call for straightforward dry-mix guniting and repair spraying; for large mechanised wet-mix drives, ask MC-Bauchemie or Space Arc about the alkali-free liquid alternatives in the same product family.
Where it is used
- Tunnel lining and portal guniting to seal active groundwater seepage
- Mine shaft, drift and gallery support shotcrete in underground and hydro projects
- Hill-road and highway slope or retaining-wall stabilisation shotcrete
- Basement, podium and retaining-wall repair guniting
- Overhead soffit, beam and column jacket repair by spray application
- Canal, reservoir and water-retaining structure lining repair
- Emergency structural repair where a fast, reliable set is critical
- General dry-mix sprayed concrete and mortar for civil and industrial structures
Key advantages
- Sets sprayed mortar rock-hard within minutes of jetting
- Completely chloride-free — no corrosion risk to reinforcement
- Plasticises the mix, making jetting and pumping easier
- Increases the water impermeability of the sprayed layer
- Enables overhead guniting and spraying onto moist surfaces
- Remains effective at lower ambient temperatures
- Allows thicker layers to be built in a single pass, saving time
- Reduces material lost to rebound, cutting real material cost on site
Limitations & considerations
- Dosage is not fixed on the data sheet — it must be optimised through a site trial for every cement, aggregate grading and temperature combination, a step crews sometimes skip under schedule pressure
- Working time after gauging is short by design, so batching and crew coordination discipline is essential to avoid wasted mix
- The manufacturer’s technical literature on file does not carry independent compressive-strength, specific-gravity or IS/EN compliance test data — specifiers needing certified figures should request current test certificates from MC-Bauchemie directly
- Formulated for dry-mix guniting rigs; large mechanised wet-mix or robotic-arm shotcrete operations are generally better served by nozzle-dosed alkali-free liquid accelerators
- Powder form is moisture-sensitive and must be stored in unopened packaging, away from rain, direct sun, heat and frost
- Cold weather slows the intended acceleration further at the working-time stage, sometimes requiring warm gauging water or heated aggregate to hit target setting times
Selection & best practice
Always run a preliminary job-site trial before full-scale spraying — start at roughly 3% dosage by weight of cement, observe the setting time, then reduce toward 1% if it sets too fast or increase toward 5% if it is too slow, keeping the cement type, cement age and aggregate grading constant across trials so the comparison is fair. Mix the powder thoroughly into the dry mix and do not add gauging water until jetting is actually about to begin, since the set accelerates quickly once water is introduced. In cold weather, compensate for the naturally shorter working window by using warm gauging water or pre-warmed aggregates. Keep unopened bags, pails or drums under cover, away from rain, direct sunlight, heat and frost, and use stock within its 12-month shelf life from date of manufacture.
Specifications
| Product type | Chloride-free guniting aid (set accelerator / plasticiser) |
| Form | Powder or liquid |
| Colour | Off white |
| Dosage / mixing ratio | 1.0% to 5.0% by weight of cement (site-trial optimised) |
| Chloride content | Nil — chloride-free |
| Compatible cements | OPC, rapid-hardening Portland cement, Portland blast-furnace cement |
| Shelf life | 12 months from date of manufacture |
| Pack sizes | 250 kg drums, 30 kg pails, 30 kg sacks |
| Storage | Unopened packaging; protect from rain, direct sunlight, heat and frost |
Industry use cases
Tunnelling & metro infrastructure
Sealing active groundwater seepage in tunnel drives and portals ahead of final lining, and building up guniting layers on wet rock faces.
Mining & hydro projects
Support shotcrete in drifts, shafts and adits where a fast, reliable set on overhead and wall surfaces is essential to crew safety.
Hill-road & highway works
Slope stabilisation and retaining-wall guniting on hill sections where access and curing conditions rule out conventional formed concrete.
Building repair & retrofit
Overhead soffit, beam and column jacket repairs where a quick set avoids the need for temporary formwork or propping.
Water infrastructure
Canal lining and reservoir or tank wall guniting repairs where the sprayed layer also needs to improve water-tightness.
Frequently asked questions
How is Centrament Guniting different from newer alkali-free liquid shotcrete accelerators?
Can it be used in a wet-mix or robotic shotcrete system?
What dosage should we start with on a new site?
Is it safe to use on reinforced concrete?
Can it be sprayed overhead or onto wet surfaces?
What pack sizes and shelf life should we plan a site around?
How we position MC-Bauchemie Centrament Guniting
Centrament Guniting sits within MC-Bauchemie’s broader Centrament admixture family — alongside products like Centrament Rapid 621, a chloride-free powdery hardening accelerator aimed more at precast and ready-mix concrete than spray application — and complements the Centrilit range used for high-performance and high-density concrete work. For contractors moving from manual dry-mix guniting toward mechanised wet-mix or robotic shotcreting, MC-Bauchemie’s dedicated tunnelling-systems accelerators, such as MC-Montan Shotcrete HA 01, are the natural next step and worth discussing with Space Arc alongside this product. Cross-brand, Fosroc’s Conplast SC occupies similar territory as a shotcrete accelerator and is a name specifiers sometimes ask for by default on Fosroc-specified projects; it is a reasonable alternative to evaluate where the specification is brand-locked to Fosroc’s admixture range or where a project’s mechanised spraying method favours a different accelerator chemistry, though Space Arc has not independently verified a like-for-like technical comparison between the two and recommends checking current data sheets from both manufacturers before substitution.
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