Fosroc Cebex 300
Aluminium-free, iron-free plasticising and gaseous-expansion powder admixture that turns ordinary cement into a low-permeability, non-shrink grout.
What is it?
A dry powder admixture that combines a plasticiser with a gas-producing expansion medium, dosed into site-batched cement grout. It is aluminium-free and contains no metallic iron, so it expands without the corrosion-staining risk of iron-based systems.
Where is it used?
Bed grouting under base plates and machinery, post-tensioning duct and cable grouting, non-shrink infilling, jointing and cable-anchorage filling — wherever a fluid, settlement-free cementitious grout is mixed on site.
Why use it?
It lets you cut water content for higher strength and lower permeability while a controlled gaseous expansion cancels plastic settlement and shrinkage, giving full interfacial contact under the plate or in the duct.
How is it applied?
Blended dry with OPC (and sand where required) and a measured low water content, machine-mixed to a smooth fluid consistency, then poured, pumped or injected continuously and cured immediately.
About Fosroc Cebex 300
Fosroc Cebex 300 is a powder admixture engineered to upgrade an ordinary, site-batched cement grout into a fluid, non-shrink, durable grout without resorting to a costly pre-bagged system. Supplied as a free-flowing powder, it is a dual-action product: one component is a plasticiser that disperses cement particles so the same workability can be achieved at a markedly lower water/cement ratio, and the other is a gas-generating expansion medium that produces a controlled positive expansion in the plastic grout. Together these counteract the two classic failures of neat cement grout — bleeding/plastic settlement and drying shrinkage — that otherwise leave voids beneath a base plate or along a tendon duct. Crucially, Fosroc specifies Cebex 300 as an aluminium-free expansion system with no metallic iron content, which sets it apart from older iron-filings “non-shrink” grouts that can rust and stain. The product was formulated for hot Middle East climates and is supplied through Fosroc’s regional operations (technical datasheets are published for markets such as Saudi Arabia and Jordan), but the same chemistry is directly relevant to Indian site conditions, where high ambient temperatures and aggressive curing environments make low-permeability, settlement-free grout a genuine durability requirement rather than a luxury. For contractors who already stock cement and clean sand, Cebex 300 is the economical route to a structural-quality grout; for those who prefer a ready-to-use bagged product, Fosroc positions Conbextra HF as the pre-packed alternative. Space Arc Engineering supplies Cebex 300 alongside the wider Fosroc Cebex and Conbextra ranges across Delhi NCR and Pan-India, with technical support on dosage and placement.
The technical insight
The engineering value of Cebex 300 lies in decoupling fluidity from water content. Neat cement grout is normally made fluid by adding water, but every extra litre raises permeability, lowers strength and increases bleed. The plasticiser in Cebex 300 disperses the cement electrostatically so the mix flows at a reduced water/cement ratio — the strength and low-permeability gains follow directly from that lower water demand and are most pronounced when the grout is cured under restraint. The second mechanism is a gaseous (hydrogen-evolving) expansion that occurs while the grout is still plastic, typically completing within the first couple of hours of mixing. This is fundamentally different from a hardened-state expansive grout: the gas slightly inflates the fresh grout to offset the volume lost to plastic settlement and bleed, so when expansion is restrained by the base plate or duct wall the grout stays in intimate contact across the full interface. Because the expansion system is aluminium-free and the powder carries no metallic iron, there is no later rust expansion or brown staining — a meaningful advantage for exposed bedding and architectural plinths. The trade-off is procedural: the gas window is short, so the grout must be placed quickly and continuously, and overdosing simply produces excess gas and frothing rather than more useful expansion. Performance therefore depends as much on disciplined batching, mixing and immediate placement as on the admixture itself.
Where it is used
- Bed grouting beneath structural steel base plates, columns and stanchions
- Grouting of machinery bases, pump skids, compressors and crane rails where settlement-free contact is critical
- Post-tensioning cable and tendon duct grouting in bridges and prestressed structures
- Non-shrink infilling of pockets, recesses and holding-down bolt boxes
- Jointing and filling of precast connections and segmental joints
- Anchor and starter-bar grouting where a fluid, low-permeability cement grout is specified
- Cavity and void filling in repair work using site-batched cement grout
Key advantages
- Aluminium-free expansion system — controlled gaseous expansion without aluminium-based reactions
- No metallic iron content, so no rust expansion, staining or rust-related deterioration
- Plasticising action allows a reduced water/cement ratio, giving higher strength and lower permeability
- Gaseous expansion compensates for plastic settlement and shrinkage, ensuring full interfacial contact
- High grout fluidity at low water content makes pouring, pumping and injection easy
- Chloride-free chemistry suitable for use around reinforcement and prestressing steel
- Economical — upgrades ordinary site cement rather than requiring a fully pre-bagged grout
- Formulated for hot climates, making it well suited to Indian summer site conditions
Limitations & considerations
- It is an admixture, not a grout — final performance depends on the quality of the cement, sand, water and mixing discipline on site
- The plastic-state gaseous expansion has a short working window; grout must be placed and finished quickly and continuously
- Overdosing increases gas generation and can cause frothing rather than improving performance
- Not a replacement for a precision-engineered high-strength bagged grout where guaranteed strengths/flow are specified (use Conbextra HF or a Conbextra grade instead)
- Like other Fosroc Cebex products it is not compatible with High Alumina Cement
- Exposed grout surfaces must be cured immediately; in hot, windy conditions inadequate curing will undermine the durability benefit
- Powder must be kept dry — high temperature and humidity in storage shorten shelf life
- Country-specific datasheet values (dosage, pack size) should be confirmed against the current Fosroc India/regional TDS before specification
Selection & best practice
Always design the grout mix and dosage from the current Fosroc datasheet for your region rather than from memory, and trial-batch before the pour. Measure the (deliberately low) water content accurately into the mixer first, then add cement, sand if used, and Cebex 300, and mix mechanically for about five minutes to a smooth, even, lump-free consistency — a high-shear paddle or vane mixer gives far better results than hand mixing. Pre-wet clean, sound substrates and keep the unrestrained surface area of the grout to a minimum so the expansion works against restraint. Because the gaseous expansion is short-lived, place the grout promptly and as one continuous operation, using a holding tank with gentle agitation for large pours. Cure all exposed faces immediately with water, wet hessian or a Fosroc Concure curing membrane. Do not overdose to “get more expansion” — it only causes frothing. Clean tools with water before the grout sets.
Specifications
| Product type | Powder admixture for cementitious grouts and concrete |
| Chemical system | Plasticising agent + gas-producing expansion medium |
| Expansion system | Aluminium-free; gaseous (in plastic state) |
| Metallic iron content | None |
| Function on water demand | Plasticiser allows reduced water/cement ratio |
| Effect on durability | Low permeability; high strength when cured under restraint |
| Recommended ready-to-use alternative | Conbextra HF (pre-packed cement-based grout) |
| Cement compatibility | Portland cement; NOT compatible with High Alumina Cement |
| Climate suitability | Formulated for hot (Middle East) conditions |
| Form / handling | Dry powder; keep in original packaging in a dry store |
Industry use cases
Industrial & power plants
Grouting heavy machinery bases, turbine and compressor plinths and pump skids where a settlement-free, low-permeability bed under the base plate is essential for vibration performance.
Bridges & infrastructure
Post-tensioning duct and cable grouting and bearing-pedestal grouting, where a fluid, chloride-free, non-shrink cement grout protects tendons and ensures full duct filling.
Structural steel & PEB
Bed grouting under column base plates and stanchions in factories, warehouses and pre-engineered buildings, giving uniform load transfer to the foundation.
Precast & prestressed concrete
Jointing precast connections and filling holding-down bolt pockets with a fluid grout that expands to fill the pocket completely.
General building & repair
Site-batched non-shrink infilling and void filling where an economical upgrade of ordinary cement grout is preferred over a fully bagged product.
Frequently asked questions
What exactly is Fosroc Cebex 300?
How is Cebex 300 different from Cebex 100?
Is Cebex 300 a grout by itself?
Does it contain chlorides or iron that could corrode steel?
How much Cebex 300 do I add per bag of cement?
Can I get Cebex 300 in Delhi NCR or elsewhere in India?
How we position Fosroc Cebex 300
Within Fosroc’s own range, Cebex 300 sits between two extremes: it is a step up from neat cement grout but is an admixture rather than a finished grout. Where a project simply needs a fluid, non-shrink cement grout batched on site, Cebex 300 (or its sibling Cebex 100) is the economical choice; where guaranteed strengths and flow are specified, Fosroc directs users to ready-to-use bagged grouts such as Conbextra HF, Conbextra GP or higher-grade Conbextra products, and to the dedicated Cebex Cable Grout / Cebex NK products for post-tensioning. Curing should be paired with a Fosroc Concure membrane for best durability. Against competitors, the closest equivalents are Sika’s grout-admixture and pre-bagged grout lines (e.g. SikaGrout and Intraplast expanding admixtures), MBS/MC-Bauchemie and BASF-lineage Master Builders Solutions grouts (MasterFlow), and, in the Indian market, Dr. Fixit (Pidilite) and STP (Shalimar) cementitious grout/admixture systems. Most of these vendors offer both an admixture route and a fully pre-packed non-shrink grout, so the practical decision is the same one Fosroc frames: choose an admixture like Cebex 300 when you want to upgrade site cement economically, and a pre-bagged grout when you need certified, repeatable performance straight from the bag. Space Arc Engineering can advise on the right fit and supply the appropriate Fosroc product for the specification.
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