Fosroc Conplast RP264M2
Chloride-free lignosulphonate water-reducing and set-retarding admixture for ready-mixed concrete, hot-weather pours and long-haul deliveries.
What is it?
A chloride-free, lignosulphonate-based liquid admixture from the Fosroc Conplast RP264 family that combines water reduction with controlled set retardation. The ‘M2’ suffix denotes a specific supply/concentration variant of the standard RP264 formulation, dispatched and dosed identically as a Type B/Type D admixture under ASTM C494.
Where is it used?
Ready-mixed concrete plants, long-haul truck-mix deliveries, hot-weather concreting, large-volume raft and pile pours, slip-form work and any situation where extended workability or controlled retardation is needed.
Why use it?
It lets you cut mixing water while holding workability, which raises compressive strength and durability, and it delays initial set so concrete stays placeable through transport delays and high ambient temperatures without cold joints.
How is it applied?
Added to the concrete mixing water (never to dry cement) at the batching plant, typically 0.28-0.60 litres per 100 kg of cementitious material, with the optimum dosage fixed by site trials on the actual mix.
About Fosroc Conplast RP264M2
Fosroc Conplast RP264M2 belongs to the long-established Conplast RP264 family of concrete admixtures and is engineered for projects where workability has to survive heat, distance and time. It is a chloride-free water-reducing and retarding admixture based on selected lignosulphonate materials, supplied as a brown liquid that disperses instantly in the mixing water. Functionally it does two jobs at once: it disperses the fine cement particles so that less water is needed for a given slump, and it delays the initial hydration of the cement so the concrete sets more slowly in a controlled way. The ‘M2’ designation in the product code is a Fosroc supply variant within the RP264 line; the chemistry, classification and performance role remain those of the parent RP264 retarding water-reducer. For contractors, RMC producers, consultants and procurement teams across India, that translates into a single admixture that improves strength economics on one hand and buys placing time on the other. Space Arc Engineering, as an authorised Fosroc distributor and applicator serving Delhi NCR and Pan-India, supplies RP264-series admixtures with batch documentation and on-site dosing guidance so the product performs to specification on real jobs rather than just on paper.
The technical insight
RP264M2 works through adsorption: the anionic lignosulphonate molecules coat the cement grains, neutralising the inter-particle attraction that causes flocculation. Deflocculated cement releases the water trapped between particles, so the same paste flows at a lower water-cement ratio, and a lower w/c ratio is the single biggest lever on compressive strength and on the low-permeability that drives long-term durability. The same molecules temporarily slow the C3A and C3S hydration reactions, which is what produces the controlled retardation rather than a true set accelerator effect. Classified as ASTM C494 Type B (retarding) and Type D (water-reducing and retarding) and compliant with IS 9103, it is deliberately a moderate-range water reducer, not a high-range superplasticiser, so retardation and workability retention are the headline benefits rather than very high slump. Practically, the degree of retardation scales with dosage and is amplified by higher ambient temperatures, so the dosage that gives a comfortable two-to-three hour working window in a Delhi winter pour may over-retard in peak summer unless re-trialled. It carries only slight air entrainment (typically under 2% additional air), which improves cohesion in mixes short of fines without compromising strength.
Where it is used
- Ready-mixed concrete requiring extended workability retention during transit and placement
- Hot-weather and summer concreting across North and West India where rapid slump loss is a risk
- Large-volume pours such as rafts, mat foundations and pile caps where cold joints must be avoided
- In-situ bored piling and diaphragm-wall concrete needing a longer placement window
- Slip-form construction where controlled, uniform stiffening improves surface finish
- Long-haul truck-mixed deliveries to distant or congested urban sites
- Pumped concrete where reduced bleed and improved cohesion lower the risk of line blockages
- Reinforced and prestressed concrete, being chloride-free and safe for embedded steel
Key advantages
- Reduces mixing water for a given workability, raising compressive strength at all ages and improving durability through lower permeability
- Controlled, predictable set retardation that extends working life and prevents cold joints in large or staged pours
- Chloride-free, so it is safe for reinforced and prestressed concrete and does not promote rebar corrosion
- Helps maintain workability of ready-mixed concrete delivered in hot weather and over long distances
- Slight air entrainment improves cohesion in harsh or poorly graded mixes, reducing bleed and segregation
- Allows a specified strength grade to be achieved at reduced cement content or, alternatively, increased workability
- Liquid form disperses instantly in water for easy, accurate plant dosing
- Backed in India by authorised supply, batch traceability and trials support from Space Arc Engineering
Limitations & considerations
- It is a normal/medium-range water reducer, not a high-range superplasticiser, so it cannot deliver the very high slump or flowing concrete of an SP-series PCE admixture
- Retardation increases with dosage and ambient temperature; overdosing or a hot-weather mix can over-retard the set and delay strength gain
- Optimum dosage must always be established by site trials on the actual mix design, materials and conditions before production use
- Set-retardation behaviour can vary with cement chemistry and supplementary cementitious materials (PFA, GGBS, microsilica), so changes in the binder need re-trialling
- Not designed as a primary slump-retention superplasticiser for very long-haul or high-performance self-compacting concrete on its own
- Performance can be affected if dosed onto dry cement or added inconsistently; it must enter via the mixing water
- Like all lignosulphonate retarders, it should not be relied on as a corrosion inhibitor, waterproofing additive or accelerator
Selection & best practice
Always add RP264M2 to the concrete mixing water, never to the dry cement, and dose it accurately at the batching plant. Establish the working dosage by trial mixes using the project’s own cement, aggregates, SCMs and expected site temperature before committing to production, and re-trial whenever the binder or ambient conditions change significantly. Start within the typical range of 0.28-0.60 litres per 100 kg of cementitious material and adjust for the retardation window you need, remembering that hot weather increases the retarding effect. Keep the standard slump-test and cube-test regime running so that water reduction and strength gains are verified, not assumed. Store sealed drums in a cool, shaded, dry place within the stated temperature range and use within the 12-month shelf life. For prestressed or high-exposure work, confirm compatibility with any other admixtures in the mix and dispense each admixture separately.
Specifications
| Product type | Chloride-free water-reducing and retarding concrete admixture (Conplast RP264 family) |
| Chemical base | Selected lignosulphonate materials |
| Appearance | Brown liquid |
| Specific gravity | Typically 1.20 at 25°C (India market data 1.170-1.190 at 30°C) |
| Chloride content | Nil to BS 5075 (typically <0.05% by weight) |
| Alkali content | Typically less than 5.0 g Na2O equivalent per litre |
| Air entrainment | Typically less than 2% additional air at normal dosage |
| Standards compliance | ASTM C494 Type B & Type D; BS 5075 Part 1; IS 9103-1999 (retarding admixture) |
| Typical dosage | 0.28-0.60 litres per 100 kg cementitious material (incl. PFA/GGBS/microsilica) |
| Function | Water reduction + controlled set retardation; safe for reinforced & prestressed concrete |
| Pack sizes | 5, 20 and 200 litre containers |
| Shelf life / storage | Minimum 12 months in original sealed containers stored cool and dry |
Industry use cases
Ready-Mixed Concrete (RMC)
RMC plants supplying urban and peri-urban sites use RP264M2 to hold slump through traffic and transit delays, so concrete arrives placeable instead of stiffened, reducing rejected loads.
Infrastructure & Foundations
On large rafts, pile caps and bored piles, controlled retardation keeps successive layers live long enough to knit together, eliminating cold joints in continuous mass pours.
High-Rise & Commercial Construction
For pumped concrete on tall structures, the improved cohesion and reduced bleed lower pump-line blockage risk while water reduction supports the higher strength grades these projects specify.
Hot-Weather Concreting
Across North and West India in summer, the admixture offsets rapid slump loss and accelerated set, giving crews a workable placing window in 40°C-plus ambient conditions.
Precast & Prestressed Elements
Being chloride-free, it is used in reinforced and prestressed members where the strength gain from water reduction is captured without any risk to embedded or tensioned steel.
Frequently asked questions
Is Fosroc Conplast RP264M2 a real product, and how does it differ from RP264?
What is the recommended dosage of Conplast RP264M2?
Does it contain chloride, and is it safe for reinforced and prestressed concrete?
Is it a superplasticiser?
Which standards does it comply with?
What are the pack sizes and shelf life?
How we position Fosroc Conplast RP264M2
Within the Fosroc admixture range, Conplast RP264M2 sits in the water-reducing/retarding (ASTM Type B & D) tier – a step up in placing-time control from the simpler Conplast R retarder and Conplast WL/W water-reducers, but distinct from the high-range Conplast SP430, SP440 and Auramix PCE superplasticisers that target very high slump and self-compacting mixes. A common, well-proven strategy on hot-weather or long-haul jobs is to pair a Conplast SP-series superplasticiser for slump with an RP264-type retarder for workability retention. Against competitors, the most direct alternatives in the Indian market are Sika’s Plastiment/Retarder range and BASF/Master Builders Solutions’ MasterSet and Pozzolith retarding water-reducers; Dr. Fixit (Pidilite) and STP focus more on waterproofing and repair systems than on this exact retarding-WR niche, so they are partial rather than like-for-like substitutes here. RP264M2’s edge is the combination of a long, dependable Fosroc track record on Indian infrastructure, clear IS 9103 / ASTM C494 compliance, and – through Space Arc Engineering as an authorised distributor and applicator in Delhi NCR and Pan-India – genuine batch traceability and on-site trial support rather than grey-market supply. For projects needing only water reduction without retardation, consider Conplast WL; for high-flow concrete, move up to the Conplast SP or Auramix lines.
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