Fosroc Conbextra PM
A single-component, water-mixed cementitious mortar built for pumping into precast joints and for high-strength pointing where a fluid grout would simply run out.
What is it?
A single-pack, cement-based pumpable and pointable mortar from Fosroc, pre-blended from cements, fine aggregates and admixtures with a maximum grain size under 1 mm. You add only clean water on site.
Where is it used?
Grouting gaps between precast concrete units, joints and keyways, plus high-strength pointing on masonry and concrete where a runny grout cannot be retained.
Why use it?
It stays where you place it. The thixotropic, shrinkage-compensated mix pumps cleanly into tight joints, resists slumping in vertical and overhead pointing, and gains strength fast so precast erection keeps moving.
How is it applied?
Mix with clean water to a pumpable consistency, then pump or trowel into the joint. Tool the surface to the required profile while the mortar is still workable and protect from moving water and heavy rain until set.
About Fosroc Conbextra PM
Fosroc Conbextra PM sits in a specific niche within the Conbextra grout family. Where the free-flow members of the range are made to self-level under base plates, Conbextra PM is deliberately the opposite: a thixotropic mortar engineered to be pumped or worked into a joint and then hold its shape. That makes it the right choice for grouting the gaps between precast concrete elements and for high-strength pointing, two jobs where a fluid grout would bleed out before it ever set. Supplied as a single pre-blended pack, it removes the site-batching guesswork that plagues hand-mixed sand-cement mortars, so every batch across a large precast job behaves the same way.
For contractors erecting precast frames, panels and modular units across Delhi NCR and the wider Indian market, the appeal is practical. The mortar needs only clean water, no separate primer and no shop mixing of aggregates, which suits the tempo of a precast site where joints are sealed in sequence as units land. Its fine sub-1 mm aggregate lets it flow into narrow keyways and pockets under pump pressure, while the same body that makes it pumpable also lets it be trowelled and tooled into a clean pointing profile. Space Arc supplies Conbextra PM as an authorised Fosroc distributor and applicator, with technical support on consistency, joint preparation and curing for the conditions on your site.
The technical insight
The behaviour that defines Conbextra PM is thixotropy. At rest the mortar is stiff and holds its position, but under the shear of pumping or trowelling it flows freely; the moment that shear stops, it stiffens again. This is why a single material can be pumped deep into a precast keyway and yet be pointed onto a vertical or overhead face without slumping. The tightly graded aggregate, capped below 1 mm, keeps the mix cohesive and lets it penetrate narrow gaps that a coarser mortar would bridge and leave voided. Because the pack is factory-blended, the cement, graded fine aggregate and admixtures are already in fixed proportion, so the only variable left on site is water, and controlling water is what controls both consistency and ultimate strength. The formulation is shrinkage-compensated, which matters in a joint: an ordinary cement mortar shrinks back from the faces it is meant to bond, opening a hairline path for water, whereas a compensated mix maintains contact and keeps the joint tight as it cures.
Where it is used
- Grouting the gaps and joints between precast concrete units in framed and panel construction
- High-strength pointing on masonry and concrete where a fluid grout cannot be retained
- Filling keyways, pockets and connection joints in precast erection
- Making good and re-pointing joints on precast facades and cladding
- Grouting narrow gaps under pump pressure where sub-1 mm penetration is needed
- Structural pointing on retaining and civil concrete exposed to weather
- Sealing joints in modular and prefabricated building assemblies
- General cementitious grouting where a non-slump, pumpable mortar is preferred over a free-flow grout
Key advantages
- Single pre-blended pack needs only clean water, eliminating site-batching variation
- Thixotropic body holds its shape in vertical and overhead joints without slumping
- Pumps cleanly for fast, continuous filling of precast joints
- Fine sub-1 mm aggregate penetrates narrow gaps and keyways
- Shrinkage-compensated to keep the joint tight and in contact with both faces
- Rapid strength gain supports a quick precast erection sequence
- No priming step required, simplifying the on-site workflow
- Weather- and abrasion-resistant once cured, suiting exposed pointing
Limitations & considerations
- Not a free-flow base-plate grout; for self-levelling flow under plates use a fluid Conbextra grade instead
- Thixotropic mix will not self-level, so joints must be actively pumped or packed
- Final strength depends on water content, so over-watering to ease pumping weakens the mortar
- Requires a minimum ambient and substrate temperature (around 3 C) and protection from freezing during cure
- Fresh mortar must be protected from moving water and heavy rain until it has set
- Shelf life shortens markedly in hot, humid storage, so stock should be rotated and kept dry
Selection & best practice
Prepare the joint first: it should be sound, clean and free of dust, oil and loose material, and pre-dampened to a saturated surface-dry condition so the substrate does not rob the mortar of water. Add Conbextra PM to a measured quantity of clean water, not the reverse, and mix mechanically to a smooth, consistent, pumpable body; resist the urge to add extra water to speed pumping, as this is the single most common cause of weak, shrinking joints. Pump or pack the mortar fully into the gap so no voids remain, then tool the exposed face to the required pointing profile while it is still workable. Do not apply below the minimum temperature or into a joint with moving water. Cure the finished work by protecting it from rapid drying, heavy rain and moving water until it has set and gained early strength. Store unopened bags in dry, shaded conditions and use older stock first, since heat and humidity cut the shelf life.
Specifications
| Product type | Single-component cementitious pumping and pointing mortar (thixotropic) |
| Composition | Pre-blended cements, fine aggregates and admixtures |
| Maximum aggregate size | Less than 1 mm |
| Mixing | Add clean water only; no priming required |
| Consistency | Non-slump, pumpable and trowellable |
| Volume change | Shrinkage-compensated |
| Pack size | 20 kg bag |
| Approx. yield | ~10.5 litres of mortar per 20 kg bag |
| Shelf life | 12 months in cool, dry storage (reduced to ~4 months in hot/humid conditions) |
Industry use cases
Precast & Prefab Construction
Sealing and grouting the joints, keyways and pockets between precast units as a frame or panel building is erected, batch after consistent batch.
Facades & Cladding
High-strength pointing and joint make-good on precast facades and cladding panels exposed to weather and wind-driven rain.
Civil & Infrastructure
Structural pointing on retaining walls, culverts and exposed civil concrete where a non-slump, abrasion-resistant joint is needed.
Modular Building
Grouting connection joints in modular and volumetric construction, where fast strength gain keeps the assembly sequence on schedule.
Repair & Refurbishment
Re-pointing and repairing deteriorated joints on existing concrete and masonry with a pumpable, single-pack mortar.
Frequently asked questions
Is Conbextra PM the same as a base-plate grout like Conbextra GP2?
How much water do I add?
How much mortar does one bag make?
Can it be pumped, or only trowelled?
What is the minimum temperature for application?
How should it be stored and how long does it last?
How we position Fosroc Conbextra PM
Conbextra PM occupies the pumping-and-pointing corner of Fosroc’s Conbextra grout family, so the right cross-sell depends on the job. When the requirement is flow under a base plate or machine base rather than a held joint, move to the free-flow grades: Conbextra GP2 for general precision base-plate grouting, or a high-strength variant where higher 28-day strength is specified. For anchoring bolts, dowels and starter bars, a Fosroc epoxy anchor grout is the better fit. Where the underlying issue is concrete repair rather than jointing, pair it with the Renderoc repair-mortar range. Alongside our Fosroc line, Space Arc also supplies grouts and pointing mortars from MC-Bauchemie and Sika, so on projects where a client has standardised on another brand we can match Conbextra PM to an equivalent from that stable and keep the specification consistent.
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