Fosroc Cebex 705
Chloride-free air-entraining (plasticising) admixture that gives retarded sand:cement mortar a stable entrained-air system, better workability and improved frost resistance.
What is it?
A chloride-free, liquid multifunctional air-entraining (plasticising) admixture for mortar, designed to work alongside Fosroc Cebex retarders to produce ready-to-use retarded mortar.
Where is it used?
Site-batched and ready-mixed retarded masonry mortars, renders and screeds in building and brick/blockwork construction, including pigmented and lime-gauged mixes.
Why use it?
It entrains a controlled, highly stable air-bubble system that improves trowelling and cohesion, increases mortar yield, and raises resistance to frost and de-icing salt attack in the hardened mortar.
How is it applied?
Dosed into the mixing water by a recommended dispenser at typically 0.20-0.60 litres per 100 kg of cement (higher with lime), added separately from other admixtures, with optimum dosage confirmed by site trial mixes.
About Fosroc Cebex 705
Fosroc Cebex 705 is a multifunctional air-entraining admixture engineered specifically for mortar rather than structural concrete. It is supplied as a clear, chloride-free liquid that disperses instantly in the mixing water, and its core job is to introduce a controlled volume of very small, stable air bubbles into a sand:cement (or lime-gauged) mortar. Those bubbles act almost like a ball-bearing lubricant within the mix: they improve cohesion, make the mortar more workable and pleasant to trowel, and increase the volume (yield) the bricklayer or plasterer gets from a given quantity of cement and sand. Once the mortar has set, the same entrained-air structure is what gives it markedly better durability against freeze-thaw cycling and de-icing salts. Cebex 705 is most commonly specified as part of the Fosroc retarded-mortar system. Used in conjunction with Cebex retarding admixtures, it helps produce a pre-mixed, retarded mortar that stays usable for typically up to two working days, which is the practical basis of the ready-to-use silo and tub mortars that many sites now prefer over daily on-site batching. For contractors, consultants and procurement teams across Delhi NCR and Pan-India working with brick, block and stone masonry, Cebex 705 is the workability and durability component that sits behind a consistent, low-waste mortar supply chain. As an authorised Fosroc distributor and applicator, Space Arc Engineering positions Cebex 705 for masonry packages where mortar quality, trowelling comfort and frost/salt durability matter, and where a managed retarded-mortar workflow reduces wastage on multi-storey and large-footprint jobs.
The technical insight
Cebex 705 works by surfactant-driven air entrainment. When metered into the mix water it generates a stable system of discrete micro air voids distributed through the cement paste. Unlike accidental, entrapped air (large, irregular voids that simply weaken mortar), engineered entrained air is fine and uniform, which is why it improves workability and frost resistance without the same penalty. The datasheet target is an air content of approximately 18% in a sand:cement mortar at the typical dosage of 0.20-0.60 litres per 100 kg of cement; this is a mortar-level air content and should not be confused with the much lower 4-6% targeted in air-entrained structural concrete. The trade-off engineers must respect is the air-versus-strength relationship: each percent of entrained air reduces compressive strength, and the datasheet is explicit that doubling the intended dose significantly increases air, raises workability and reduces strength. That is why Fosroc insists optimum dosage be fixed by trial mixes using the actual site sand, cement and conditions. Where lime is present, the bubble system behaves differently and the dose typically rises to 0.30-1.00 litres per 100 kg, calculated on the combined lime-plus-cement content, not cement alone. Initial workability is controlled to a BS 4551 dropping-ball consistence of 12-14 mm so the retarded mortar retains predictable working properties over its extended life. Because the product is chloride-free (nil to BS 5075), it does not introduce a corrosion risk to any embedded metalwork such as wall ties or bed-joint reinforcement.
Where it is used
- Pre-mixed retarded masonry mortar (used with Cebex retarders) that stays workable for up to about two working days
- Site sand:cement bricklaying and blocklaying mortars needing better trowelling and cohesion
- Rendering and plastering mortars where smoother application and improved board life are wanted
- Pigmented/coloured mortars for facing brickwork and architectural masonry
- Lime-gauged and lime-free mortar mixes
- Mortars exposed to freeze-thaw cycling and de-icing salts, where hardened durability is critical
- Screeds and renders within the retarded-mortar workflow, where controlled curing is maintained
Key advantages
- Produces a highly stable entrained-air system that resists collapse during handling and laying
- Improves trowelling, cohesion and overall workability of fresh mortar
- Increases mortar yield, improving material economy per bag of cement
- Raises hardened-mortar resistance to frost and de-icing salt attack
- Chloride-free (nil to BS 5075), so no chloride-induced corrosion risk to wall ties or reinforcement
- Compatible with ordinary Portland cement and with other Fosroc admixtures in the same mix
- Suitable for both lime-containing and lime-free mixes, and for pigmented mortars
- Complies with BS 4887 Part 1 as an air-entraining (plasticising) mortar admixture
- Water-based and non-flammable, simplifying site storage and handling
Limitations & considerations
- It is a mortar admixture, not a structural-concrete air-entrainer; the ~18% air target is far higher than the 4-6% used in concrete and it should not be substituted there
- Air entrainment reduces compressive strength, so over-dosing (e.g. double dose) markedly increases air and lowers strength
- Optimum dosage cannot be assumed from the datasheet alone; it must be fixed by trial mixes with the actual site materials
- Dosage logic changes with lime: the dose must be based on total lime plus cement, and typically increases
- Performs best when dispensed through a recommended dispenser into the mix water; hand-dosing risks inconsistent air content
- Mixed retarded mortar must be protected from moisture loss (covered, non-porous container with lid) or it crusts over
- Full benefit on retarded mortar depends on pairing it with a Cebex retarder; on its own it does not extend mortar life to two days
- Shelf life is 12 months and the product must be kept between 2 C and 50 C; it freezes at about 0 C
Selection & best practice
Always establish the working dosage by trial mixes using the project’s own sand, cement and (where used) lime and pigment, targeting roughly 18% air and a BS 4551 dropping-ball consistence of 12-14 mm before fixing the site mix. Dispense Cebex 705 accurately into the mixing water through a recommended dispenser rather than estimating by eye, and where more than one admixture is used add each one separately to the mortar, never pre-blended. Base the dose on cement content for plain sand:cement mortar, but on total lime-plus-cement where lime is present, and avoid over-dosing since doubling the dose sharply raises air and cuts strength. Pair it with a Fosroc Cebex retarder when a true retarded, ready-to-use mortar is required, keep the mixed mortar in a covered non-porous container to prevent crusting, and maintain good curing, which matters most on retarded screeds and renders. Store sealed drums between 2 C and 50 C and use within the 12-month shelf life.
Specifications
| Product type | Multifunctional air-entraining (plasticising) admixture for mortar |
| Base / chemistry | Chloride-free, water-based liquid surfactant air-entrainer |
| Appearance | Clear opaque liquid |
| Specific gravity | Typically 1.00 at 20 C |
| Chloride content | Nil (to BS 5075) |
| Typical dosage (sand:cement) | 0.20-0.60 litres per 100 kg of cement |
| Typical dosage (with lime) | 0.30-1.00 litres per 100 kg (on total lime + cement) |
| Target air content | Approximately 18% in sand:cement mortar |
| Initial mortar consistence | 12-14 mm (BS 4551 dropping-ball test) |
| Standards compliance | BS 4887 Part 1 (air-entraining/plasticising admixture for mortar) |
| Retarded mortar life | Typically up to ~2 working days (used with Cebex retarders) |
| Pack size | 20 litre drums; bulk supply and storage tanks available |
| Shelf life | Minimum 12 months at 2 C to 50 C |
| Freezing point | Approximately 0 C |
| Fire / flammability | Water-based, non-flammable |
| Cement compatibility | All types of ordinary Portland cement |
Industry use cases
Ready-mix / retarded mortar suppliers
Used with Cebex retarders to manufacture pre-mixed, tub or silo-delivered retarded mortar that stays workable for up to about two working days, cutting on-site batching and waste.
Brick and blockwork contractors
Improves trowelling and cohesion of sand:cement bedding mortars so masons lay faster with less drop-off, while boosting yield per bag of cement.
Plastering and rendering
Gives renders smoother application and better board life, with the chloride-free formulation protecting any embedded metal lath or beads.
Facing and architectural masonry
Suitable for pigmented mortars, helping deliver consistent colour and workability in exposed brickwork and feature walls.
Cold-region and exposed structures
Entrained air raises hardened-mortar resistance to frost and de-icing salts, valuable for hill-station, high-altitude and externally exposed masonry across North India.
Heritage and lime-gauged work
Works in lime-containing mixes (dosed on total lime plus cement), supporting more workable, durable lime-gauged mortars for conservation and traditional masonry.
Frequently asked questions
Is Fosroc Cebex 705 the same as an air-entrainer for concrete?
What is the correct dosage of Cebex 705?
Does Cebex 705 reduce mortar strength?
Is Cebex 705 chloride-free and safe near reinforcement or wall ties?
How does Cebex 705 make ‘two-day’ retarded mortar?
What pack sizes and shelf life does Cebex 705 have, and how should it be stored?
How we position Fosroc Cebex 705
Within the Fosroc range, Cebex 705 sits firmly in the mortar-admixture family rather than the concrete one. It is most naturally specified together with a Cebex retarding admixture to build a complete retarded, ready-to-use mortar system, and it complements other Cebex mortar products. It should not be confused with grouting products that share the Cebex name (such as Cebex 100, the expanding grout admixture) or with concrete air-entrainers like Conplast AEA, which target the much lower air contents used in structural concrete; those are different tools for different jobs, and Space Arc can advise on the right one. Against the wider Indian market, the closest competitor positions are masonry/mortar plasticisers and air-entrainers from Sika (for example the Sika mortar-admixture and air-entraining range), the MBS / Master Builders Solutions admixture line, and general-purpose mortar plasticisers offered by brands such as Dr. Fixit (Pidilite) and STP. Cebex 705’s distinguishing strengths are its specific design for retarded-mortar workflows, its highly stable entrained-air system, its chloride-free BS 4887 compliance, and Fosroc’s site technical-advisory support. Where a project simply needs a basic mortar plasticiser, lower-cost alternatives may suffice; where a managed, durable, low-waste retarded-mortar supply is the goal, Cebex 705 within the Fosroc system is the stronger specification. As an authorised Fosroc distributor and applicator, Space Arc Engineering can supply Cebex 705, recommend the matching Cebex retarder, and support trial-mix design across Delhi NCR and Pan-India.
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