Fosroc Conplast RP2000
Chloride-free, lignosulphonate-based water-reducing and retarding admixture engineered to control set, extend workability in Indian heat and improve strength and durability in mass and ready-mix concrete.
What is it?
A chloride-free, lignosulphonate-based liquid admixture from Fosroc’s Conplast range that simultaneously reduces mixing water and retards the initial set of concrete, giving longer working time without sacrificing ultimate strength.
Where is it used?
Ready-mix and site-batched concrete for large mass pours, rafts, transfer slabs and water-retaining structures, plus any job placed in hot weather or requiring long haul/discharge times across Delhi NCR and Pan-India.
Why use it?
It buys controlled extra working time to avoid cold joints in continuous pours, holds slump during transport in summer, and lets you cut water (or cement) for higher strength and better durability in one product.
How is it applied?
Dosed into the concrete at the batching plant or mixer at roughly 0.3 to 0.8 litres per 100 kg of cementitious material, added to the gauging water or with the final portion of mix water; never to dry aggregate or cement.
About Fosroc Conplast RP2000
Fosroc Conplast RP2000 is a ready-to-use liquid admixture from the Conplast RP family, formulated to do two jobs at once: reduce the water needed for a given workability and retard the initial setting of the concrete in a controlled, predictable way. It is built on selected lignosulphonate raw materials, the same well-proven chemistry that runs through Fosroc’s RP-series (RP200, RP264), and it is supplied as a chloride-free solution that disperses instantly in water.
The retarding action is the headline feature. By delaying the early hydration of the cement, RP2000 keeps the concrete plastic and placeable for longer. For an Indian site that matters in two very common situations: long ready-mix haul and discharge cycles in summer, and large continuous pours where the previous layer must still be live when the next one lands. In both cases the extra working window is what prevents cold joints and the loss of monolithic behaviour that consultants worry about in rafts, water tanks and transfer structures.
The water-reducing action runs in parallel. Because the lignosulphonate disperses the fine cement particles, the same slump can be reached with less water, which lifts compressive strength at all ages and tightens the pore structure for better durability. The contractor can spend that benefit three ways: keep the mix as-is and gain strength, hold strength and improve workability, or hold strength and trim cement content for a more economical mix. A slight, incidental air entrainment also improves cohesion in mixes built on poorly graded or fine-deficient sands, reducing bleed and segregation.
RP2000 is chloride-free, so it is safe in reinforced and prestressed concrete where chloride-induced corrosion of steel is a design concern. It is intended to be batched with the mixing water, never added neat to dry cement or aggregate, and it is compatible with ordinary Portland cement and common blended cements used across the country. For Space Arc Engineering customers, it slots neatly between a plain plasticiser and a high-range superplasticiser when the real requirement is set control plus modest water reduction rather than very high slump.
The technical insight
The performance of RP2000 comes from lignosulphonate adsorbing onto cement grains, giving them a like charge so they repel and deflocculate; that releases trapped water and is what reduces the water demand. The same adsorbed layer temporarily slows the dissolution of C3A and C3S, which is the mechanism behind the controlled retardation, hence its place in the water-reducing/retarding family (broadly ASTM C494 Type B/D territory and IS 9103:1999). The practical engineering lesson is that dosage and temperature, not just the product, set the result: at the low end of 0.3 L/100 kg you get mainly water reduction with light retardation; toward 0.8 L/100 kg retardation lengthens noticeably. Overdosing is rarely catastrophic with this chemistry, because adequate moist curing recovers ultimate strength, but it does increase entrained air and set delay, so summer trial mixes at the actual ambient temperature, with the actual cement, are non-negotiable before a big pour.
Where it is used
- Hot-weather concreting where slump must survive long haul, queuing and discharge times
- Large mass and continuous pours such as rafts, mat foundations and pile caps where cold joints must be avoided
- Ready-mix concrete supplied over distance, to hold workability between plant and site
- Water-retaining structures, tanks and basements where reduced water content improves impermeability and durability
- High-strength mix designs where water reduction lifts compressive strength at all ages
- Economical mixes where cement content is trimmed at constant strength by exploiting the water reduction
- Slip-form and slow-rising pours that need extended, controlled stiffening time
- Prestressed and reinforced elements requiring a strictly chloride-free admixture
Key advantages
- Chloride-free, safe for reinforced and prestressed concrete
- Controlled, predictable retardation extends working life and prevents cold joints
- Water reduction raises compressive strength at all ages and improves durability
- Lets you cut cement at constant strength, or boost workability at constant cement
- Maintains placeability through long transport and discharge in Indian summers
- Slight air entrainment improves cohesion and reduces bleed and segregation in lean or fine-deficient mixes
- Disperses instantly in water and integrates easily into normal batching
- Compatible with OPC and common blended cements; no special site equipment needed
Limitations & considerations
- Not a high-range product; for very high slump or self-compacting concrete a superplasticiser such as Conplast SP430 / Auramix is the correct choice
- Retardation is temperature-sensitive, so set times in cold weather can extend more than expected and need trial-mix confirmation
- Must be added to the mixing water, never neat to dry cement or aggregate, to avoid flash effects
- Overdosing increases entrained air and prolongs set; strength relies on adequate, continued moist curing
- Effect varies with cement chemistry and source, so behaviour should be verified with the project’s actual cement
- Provides only slight, incidental air entrainment, so it is not a substitute for a dedicated air-entraining agent where a specified air content is required
Selection & best practice
Always establish dosage by trial mix at the site’s real summer temperature using the project’s actual cement and aggregates, starting near the lower end of the range and increasing only as needed for the target set time. Add RP2000 to the gauging water or with the final portion of mixing water, never onto dry materials, and keep the dosing consistent batch to batch. Confirm compatibility before combining it with any superplasticiser in the same mix, and plan curing in advance, since this chemistry relies on sustained moist curing to deliver its full strength after the retarded set.
Specifications
| Product type | Water-reducing and retarding admixture (liquid) |
| Chemical base | Selected lignosulphonate materials |
| Appearance | Brown liquid that disperses instantly in water |
| Chloride content | Chloride-free (water-soluble chloride content nil to negligible, in line with the Conplast RP series) |
| Air entrainment | Slight, incidental air entrainment improving cohesion |
| Typical dosage | 0.3 to 0.8 litres per 100 kg of cementitious material (confirm by trial mix) |
| Primary functions | Water reduction, controlled retardation, set/stiffening control, prevention of cold joints |
| Standards (family) | Conforms to the water-reducing/retarding admixture requirements of IS 9103:1999 and ASTM C494 (Type B / Type D family); older RP lineage referenced BS 5075 |
| Suitable concrete | Reinforced, prestressed and mass concrete; OPC and common blended cements |
| Addition point | Into the gauging/mixing water at the plant or mixer; not added neat to dry cement or aggregate |
Industry use cases
Ready-mix concrete (RMC)
Plants supplying Delhi NCR sites in summer use a retarding water-reducer like RP2000 to hold slump across long delivery and pump queues, protecting placeability and avoiding rejected loads.
Infrastructure and foundations
Large rafts, pile caps and mat foundations are poured continuously with extended working time so successive layers knit without cold joints, preserving monolithic strength.
Water-retaining and underground structures
Tanks, basements and retaining walls benefit from the reduced water content, which lowers permeability and improves long-term durability of the cover concrete.
High-rise and commercial buildings
Transfer slabs and heavily reinforced sections gain strength from water reduction while the retardation gives crews time to place and consolidate dense rebar zones.
Precast and prestressed yards
The chloride-free formulation suits prestressed elements where corrosion protection of strands is critical, while controlled set helps manage casting cycles in hot conditions.
Frequently asked questions
Is Fosroc Conplast RP2000 a water reducer or a retarder?
What dosage of Conplast RP2000 should I use?
Is Conplast RP2000 chloride-free and safe for reinforced concrete?
How do I add RP2000 to the concrete?
Will overdosing ruin the concrete?
How is RP2000 different from a superplasticiser like Conplast SP430?
How we position Fosroc Conplast RP2000
Within Fosroc’s Conplast range, RP2000 sits in the water-reducing and retarding (RP) family alongside Conplast RP200 and Conplast RP264, all built on lignosulphonate chemistry; the differences are largely in dosage window and degree of retardation, and Space Arc can advise which RP grade fits a given pour. Where the requirement shifts from set control to high water reduction or very high slump, the right step up is a superplasticiser such as Conplast SP430 or the Auramix / Auracast PCE ranges; where the issue is integral waterproofing rather than set, Conplast WL or Conplast Crystalline are the relevant siblings, and a plain water-reducer like Conplast R covers jobs needing no retardation. Against competitor portfolios, the directly comparable retarding water-reducers are Sika Plastiment / SikaRetarder, BASF/MBS (Master Builders) Pozzolith and MasterSet retarders, and the relevant grades from Dr. Fixit (Pidilite) and STP. RP2000 is the sensible specification when a project wants Fosroc’s proven, chloride-free RP chemistry with a slightly wider dosage range for hot-weather and large-pour set control, backed locally by Space Arc Engineering as an authorised Fosroc distributor and applicator across Delhi NCR and Pan-India. Buyers should note that RP2000 is an older/regional designation in the RP series and should confirm current pack sizes, shelf life and the exact project-specific datasheet with Space Arc at the time of order.
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