Fosroc Conbextra P
A pumpable, chloride-free, non-shrink cementitious grout engineered to flow long distances into narrow 10-40 mm gaps beneath machine bases, stanchions and horizontal ducts.
What is it?
A ready-to-use, single-component dry powder grout based on an ‘all fines’ Portland cement mix with a gaseous expansion system. Adding only water on site produces a free-flowing, non-shrink cementitious grout designed specifically to be pumped over long distances into narrow gaps of 10-40 mm.
Where is it used?
Precision grouting beneath machine base plates, steel stanchion and column bases, crane and rail track bases, and the filling of horizontal ducts and cable trenches, particularly where the gap is narrow and access for trowel or poured placement is restricted.
Why use it?
It is one of the few cementitious grouts in the Conbextra family formulated to be pumped rather than poured, so it reaches confined gaps that conventional flowable grouts cannot fill reliably. It is iron-free and chloride-free, avoiding rust staining and reinforcement corrosion, and develops high early strength for fast plant commissioning.
How is it applied?
The substrate is saturated and free water removed, formwork is sealed, the powder is machine-mixed with the specified water, and the grout is pumped continuously from one side into the prepared gap so that air is displaced ahead of the advancing front, then cured.
About Fosroc Conbextra P
Fosroc Conbextra P is a factory pre-packaged, non-shrink cementitious grout supplied as a ready-to-use dry powder that needs only the addition of clean water on site. It belongs to Fosroc’s well-known Conbextra range of construction grouts, but it occupies a specialised niche within that family: where products such as Conbextra GP and GP2 are designed primarily for poured or free-flow placement, Conbextra P is purpose-built to be pumped long distances into narrow gaps. The product targets gap widths of 10 to 40 mm, the band where conventional poured grouting becomes unreliable because the grout cannot travel far enough under gravity alone to fill the void completely. The material is described by Fosroc as an “all fines” mix based on Portland cements and additives that impart controlled expansion in the plastic state while minimising water demand. The absence of coarse aggregate is deliberate: it keeps the mix mobile and pumpable through hoses and into tight sections without the segregation or blockage that a graded grout would risk. A gaseous expansion system compensates for the natural shrinkage and settlement that cement-based materials undergo as they set, which is the single most important requirement for any grout that must maintain full, load-bearing contact between a base plate and its foundation. For engineers, consultants and procurement teams in India who are specifying or buying grout for plant installation, Conbextra P answers a specific question: how to achieve continuous, void-free, non-shrink support in a gap too narrow to pour into. It is worth noting that Conbextra P is formulated and primarily distributed for Middle East conditions, with official Fosroc datasheets published for Egypt, Jordan, Saudi Arabia and the UAE. For Indian projects, Space Arc Engineering can advise on whether Conbextra P, an Indian-market equivalent such as Conbextra GP2, or a higher-strength variant is the correct specification, and can confirm current technical values against the live regional technical data sheet before order placement.
The technical insight
The defining feature of Conbextra P is the combination of an “all fines” particle structure with low water demand. By removing coarse aggregate and relying on fine Portland-cement-based solids plus flow-modifying additives, the grout stays homogeneous and mobile under pump pressure, which is what lets it be driven long distances into confined gaps without bleeding or aggregate settlement. Low water demand matters because the water-to-cement ratio is the primary control on hardened performance: keeping it low raises early and ultimate compressive strength, reduces permeability and improves long-term durability, while still leaving the mix fluid enough to pump. The expansion mechanism is gaseous and acts in the plastic (pre-set) state, gently expanding the grout to counter plastic settlement and drying shrinkage so that positive contact is preserved across the full bearing area, this is a different mechanism from the iron-oxidation expansion used in older grouts, and it is why Conbextra P is iron-free and produces no rust staining. The chloride-free composition is significant for any work near embedded steel or reinforcement, since chlorides accelerate corrosion. The practical consequence of these design choices is a grout that behaves predictably on site: uniform mixing, minimal segregation and bleeding, and reliable gap filling. Because exact compressive strength, fresh density and yield figures vary by region and are governed by the current Fosroc technical data sheet, project specifications and method statements should always cite verified values from the applicable regional TDS rather than generic figures.
Where it is used
- Precision grouting of narrow 10-40 mm gaps beneath machine and equipment base plates
- Pumped grouting under steel stanchion, column and crane rail bases where access is restricted
- Filling of horizontal ducts, cable trenches and confined voids in concrete structures
- Installation of reciprocating and rotating plant requiring full, non-shrink bearing contact
- Bedding of base plates over long travel distances where the grout must be pumped from one side
- Industrial flooring and structural support locations needing chloride-free, iron-free grout near embedded steel
Key advantages
- Engineered to be pumped long distances into narrow gaps, unlike most poured free-flow grouts
- Gaseous expansion system compensates for plastic shrinkage and settlement, maintaining full bearing contact
- Chloride-free composition develops high early strength without risk of corroding embedded steel
- Iron-free, so there is no metallic content to oxidise and cause rust staining or expansive deterioration
- Low water demand gives high early and ultimate strength plus low permeability for long-term durability
- Factory pre-packaged powder eliminates site batching variation and gives consistent, reproducible results
- All-fines mix design minimises segregation and bleeding, producing a uniform, homogeneous grout
- High early strength facilitates rapid installation and early commissioning of plant and equipment
Limitations & considerations
- Restricted to the 10-40 mm gap band; wider sections may need an aggregate-loaded grout (e.g. Conbextra TS) and very thin sections a different product
- Cementitious grout, so it does not match the chemical resistance or dynamic-load capacity of epoxy grouts such as Conbextra EP10
- Primarily formulated and distributed for Middle East conditions; Indian projects should confirm local availability and an equivalent specification
- Pumped placement requires suitable mixing and pumping equipment and trained operatives for continuous, void-free filling
- Performance depends on correct water dosage, substrate saturation and curing; over-watering reduces strength and can cause bleeding
- Exact strength, density and yield values must be verified against the current regional Fosroc technical data sheet before specification
Selection & best practice
Saturate the prepared concrete substrate with clean water for several hours ahead of grouting and remove all free-standing water before placement. Seal and brace formwork tightly with a grout-tight, leak-free box, leaving a head or hopper on the pour side. Machine-mix the powder with the manufacturer’s specified quantity of clean water to a uniform, lump-free consistency, mixing only what can be placed within the working time. Pump continuously and from one side only, so the advancing grout front displaces air ahead of it and avoids trapping voids in the narrow gap. Maintain an unbroken supply to prevent cold joints, then cure the exposed surfaces immediately with wet hessian, curing membrane or ponding to protect against rapid drying, especially in hot Indian site conditions. Always work to the current Fosroc technical data sheet and a project-specific method statement, and confirm water dosage, gap range and curing requirements with Space Arc Engineering before starting.
Specifications
| Product type | Non-shrink cementitious grout (single-component, pumpable) |
| Base composition | “All fines” mix of Portland cements plus expansion and flow additives |
| Form | Ready-to-use dry powder; site addition of clean water only |
| Gap width range | 10 – 40 mm |
| Placement method | Pumped (free-flow); designed to travel long distances into narrow gaps |
| Expansion system | Gaseous expansion, acting in the plastic state to compensate shrinkage and settlement |
| Chloride content | Chloride-free composition |
| Iron content | Iron-free (no metallic aggregate to corrode) |
| Early strength | High early strength (chloride-free); exact values per current regional TDS |
| Durability | High ultimate strength and low permeability |
| Compressive strength / fresh density / yield | Verify against current Fosroc regional TDS (values vary by market and water dosage) |
| Official datasheet regions | Egypt, Jordan, Saudi Arabia, UAE |
Industry use cases
Power and process plant
Pumped grouting of narrow gaps under turbine, pump and compressor base plates where continuous, non-shrink bearing contact is critical for vibration control and alignment.
Industrial and manufacturing
Bedding of machine base plates and equipment skids on factory floors, filling 10-40 mm voids that are too narrow to pour into reliably.
Structural steel erection
Grouting under stanchion, column and crane rail base plates, pumping from one side to fill the full bearing area without trapped voids.
Infrastructure and civil works
Filling horizontal ducts, cable trenches and confined concrete voids where a mobile, pumpable, non-shrink grout is required.
Procurement and contracting
Specifying a factory pre-packaged grout to eliminate site batching variation, giving consistent, auditable quality across repeat installations on large projects.
Frequently asked questions
Is Fosroc Conbextra P a cementitious or epoxy grout?
What gap widths is Conbextra P designed for?
Why is Conbextra P pumped instead of poured?
Is Conbextra P safe to use near steel reinforcement?
Is Conbextra P available for projects in India?
How should the exact strength and yield figures be confirmed?
How we position Fosroc Conbextra P
Within Fosroc’s Conbextra range, Conbextra P sits as the pumpable, narrow-gap (10-40 mm) cementitious grout, distinct from the poured general-purpose grades Conbextra GP and GP2 and the higher-strength Conbextra GP3 and HS. For wider gaps or large machine bases an aggregate-filled grout such as Conbextra TS is more economical, while applications with severe chemical exposure or high dynamic and impact loading call for an epoxy grout like Conbextra EP10, which Space Arc already supplies. Among competitor products, comparable pumpable or free-flow non-shrink cementitious grouts include Sika SikaGrout and MasterFlow from MBCC/Master Builders Solutions (MBS), with Dr. Fixit (Pidilite) and STP offering broadly equivalent general-purpose cementitious grouts in the Indian market. The honest positioning is that Conbextra P is a strong choice specifically when the requirement is to pump a non-shrink grout into a confined gap, since not every grout in this class is designed to be pumped; for routine poured grouting or for the Indian market specifically, an equivalent such as Conbextra GP2 or a comparable Sika or MBS product may be more readily available. Space Arc Engineering, as an authorised Fosroc distributor and applicator, can match the grout to the gap geometry, load and exposure and confirm current verified data before specification.
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