Fosroc Conplast SP555
A chloride-free, polymer-modified naphthalene-sulphonate superplasticiser engineered for high-quality rheoplastic, pumpable and high-strength concrete with extended workability retention.
What is it?
A chloride-free, high-range water-reducing concrete admixture (superplasticiser) based on a selected polymer-modified naphthalene sulphonate dispersant, supplied as a brown liquid.
Where is it used?
Ready-mix and site-batched structural concrete across India — piling, large mass pours, pumped concrete, precast/prestressed elements and micro-silica high-performance mixes.
Why use it?
It lets you cut mix water sharply while holding workability, producing dense, durable, high-strength concrete without raising cement content — and it is safe for reinforced and prestressed work because it is chloride free.
How is it applied?
Dosed by calibrated dispenser at 0.5–2.5 litres per 100 kg of cement, added to the wet mix with the gauging water and blended at high speed for at least two minutes; never added to dry cement or aggregate.
About Fosroc Conplast SP555
Fosroc Conplast SP555 is a high-range water-reducing admixture — a superplasticiser — developed for producing high-quality rheoplastic concrete that holds its workability at a low water-cement ratio. Chemically it is a chloride-free dispersion based on a selected polymer-modified naphthalene sulphonate. In simple terms, when the admixture is added to the mix it acts by electro-kinetic action, dispersing the cement particles so the water already in the mix can work far more efficiently. The practical result is that a concrete producer can either remove a substantial volume of water while keeping the same slump, or keep the water and gain a large jump in flow and pumpability.
For Indian projects, where ambient temperatures, long haul distances from the batching plant and congested reinforcement all conspire to make concrete stiffen before it can be placed, SP555 fills a clear gap. It is positioned a step above the everyday Conplast SP430-class superplasticisers: Fosroc specifically markets it for workability retention, improved cohesion and pumpability in demanding pours. That makes it a natural choice for bored cast-in-situ piles, large raft and mass foundations, basement rafts and any structure being concreted by pump over a distance or to height.
Because it is chloride free and conforms to BS EN 934-2, SP555 is safe in reinforced, precast and prestressed concrete — settings where chloride-bearing admixtures are prohibited because of the corrosion risk to embedded steel and strands. It is also fully compatible with the cement-replacement materials that now dominate Indian durability specifications: PFA (fly ash), GGBFS (slag) and micro silica. The product carries a distinct high-dosage window for micro-silica high-performance concrete, which is exactly the territory of M50-and-above grades used in metro, bridge and high-rise work. Space Arc Engineering supplies Conplast SP555 as an authorised Fosroc distributor across Delhi NCR and Pan-India, with technical support on dosage trials and dispensing.
The technical insight
SP555 is a naphthalene-sulphonate formaldehyde condensate (SNF) dispersant that has been polymer-modified to extend slump life — Fosroc’s own literature states that higher workability levels are maintained for longer than with plain sulphonated melamine and naphthalene admixtures. Mechanistically, SNF superplasticisers work primarily through electrostatic repulsion: the long anionic polymer chains adsorb onto cement grains and impart a negative surface charge so the particles repel each other and de-flocculate, releasing trapped water and reducing inter-particle friction. This is the electro-kinetic action the datasheet refers to, and it is what separates a high-range water reducer (15–25 percent water reduction territory) from an ordinary plasticiser. The trade-off versus a modern polycarboxylate ether (PCE) is slump-retention duration — PCEs add a steric (physical spacer) component that holds flow longer — but a well-formulated, polymer-modified SNF such as SP555 narrows that gap and remains highly cost-effective and robust across variable Indian cements and aggregates. The standards behaviour is dosage-dependent and worth understanding: under ASTM C494 the same product is classed as a Type B (retarding), Type D (water-reducing and retarding) or Type G (high-range water-reducing and retarding) admixture as dosage rises, which is why overdosing pushes the mix toward retardation rather than failure. Provided curing is adequate, that extra retardation does not impair — and often increases — ultimate strength, but it is amplified when sulphate-resisting cement or heavy cement-replacement levels are present, and overdosing can also entrain air and cost strength. The takeaway: dosage must always be fixed by trial mixes on the actual job materials, not by ratio alone.
Where it is used
- Bored cast-in-situ piling concrete, where high cohesion and self-flowing behaviour around dense rebar cages are essential
- Large mass and raft pours, where a low water-cement ratio limits heat of hydration and thermal cracking
- Pumped concrete delivered over long horizontal distances or to height, needing sustained pumpability
- High-performance micro-silica concrete for M50+ grades in bridges, metros and high-rise cores
- Precast and prestressed elements, where the chloride-free formulation protects strands and reinforcement
- Ready-mix concrete requiring extended workability retention during long site hauls in hot Indian conditions
- Durable, low-permeability concrete for water-retaining and marine/coastal structures without excess cement
Key advantages
- Chloride free — safe for reinforced, precast and prestressed concrete, conforming to BS EN 934-2
- High water reduction enables high-strength, dense, durable concrete without raising cement content
- Longer workability retention than conventional sulphonated melamine and naphthalene admixtures
- Improved cohesion and particle dispersion that minimises segregation and bleeding and aids pumping
- Fully compatible with OPC, PPC, PSC and cement replacements — PFA, GGBFS and micro silica
- Distinct higher-dosage window optimised for micro-silica high-performance concrete
- Tolerant of overdosing — extra retardation generally does not impair ultimate strength with proper curing
- 12-month shelf life and a wide 2–50°C storage range suited to Indian site and depot conditions
Limitations & considerations
- Naphthalene-based chemistry gives shorter slump retention than premium polycarboxylate (PCE) superplasticisers in very long-haul or hot-weather mixes
- Optimum dosage must be established by job-specific trial mixes; ratio alone is unreliable
- Overdosing (around double dosage) increases retardation and can entrain air and reduce strength — effects are amplified with sulphate-resisting cement or high cement-replacement levels
- Must be added only to the wet mix with gauging water — never to dry cement or aggregate
- Requires high-speed blending of at least two minutes for full, uniform dispersion
- Should not be pre-mixed with other admixtures before addition; each must be dosed separately
- Needs daily re-circulation (10 minutes) in storage and freezes at about -2°C, requiring care in cold storage
Selection & best practice
Always fix the working dosage by trial mixes using the actual cement, aggregates, supplementary materials and site temperature, starting at 0.5–2.0 L/100 kg cement for normal concrete and 1.5–2.5 L/100 kg for micro-silica high-performance mixes. Dispense by a calibrated unit, introduce SP555 with the gauging water into the wet mix only, and blend at high speed for at least two minutes so the dispersant fully de-flocculates the cement. Keep each admixture separate — never pre-blend SP555 with other products. Where sulphate-resisting cement or high PFA/GGBFS contents are used, re-trial the mix because setting time and overdose sensitivity shift. Store between 2°C and 50°C, re-circulate the drum/tank for ten minutes once a day, and verify shelf life (12 months) before use.
Specifications
| Product type | High-range water reducer / superplasticiser (concrete admixture) |
| Chemical base | Chloride-free, selected polymer-modified naphthalene sulphonate dispersant |
| Appearance | Brown liquid |
| Specific gravity | 1.155 ± 0.02 at 25°C |
| Chloride content | Nil (to BS EN 934) |
| Standards compliance | BS 5075, BS EN 934-2; ASTM C494 Type B, D and G (dosage-dependent) |
| Dosage (normal concrete) | 0.5 – 2.0 litres per 100 kg of cement |
| Dosage (micro-silica HPC) | 1.5 – 2.5 litres per 100 kg of cement |
| Freezing point | Approximately -2°C |
| Storage temperature | 2°C to 50°C (re-circulate 10 min once daily) |
| Shelf life | Minimum 12 months in correct storage |
| Flammability | Water-based, non-flammable |
| Packaging / supply | 210 litre drum, 1000 litre totes or bulk |
Industry use cases
Deep Foundations & Piling
Bored cast-in-situ piles for high-rise and infrastructure benefit from SP555’s high cohesion and self-flowing character, which fills congested reinforcement cages without segregation while keeping the water-cement ratio low.
Infrastructure & Bridges
Pier caps, decks and large mass pours use SP555 to achieve pumpable, durable, low-permeability concrete and to limit thermal cracking in big sections through a reduced water content.
Precast & Prestressed Plants
Being chloride free, SP555 is safe around prestressing strand and rebar, producing dense high-early-strength units suited to faster demoulding and stripping cycles.
High-Rise & Commercial RMC
Ready-mix suppliers serving Delhi NCR towers use SP555 for sustained workability over long hauls and for pumping concrete to upper floors and core walls.
High-Performance Concrete (M50+)
In micro-silica-blended mixes for metros, water-retaining structures and aggressive-exposure work, the dedicated 1.5–2.5 L/100 kg dosage window delivers very high strength and low permeability.
Frequently asked questions
Is Fosroc Conplast SP555 a superplasticiser or a normal plasticiser?
Is Conplast SP555 chloride free and safe for reinforced and prestressed concrete?
What is the recommended dosage of Conplast SP555?
How does SP555 compare with polycarboxylate (PCE) admixtures like the Auramix range?
Can Conplast SP555 be used with fly ash, slag and micro silica?
What happens if SP555 is overdosed?
How we position Fosroc Conplast SP555
Within the Fosroc Conplast superplasticiser family, SP555 sits above the everyday SP430-class naphthalene products as a workability-retention and pumpability specialist for rheoplastic, piling and micro-silica concrete, while remaining a naphthalene-sulphonate chemistry rather than a polycarboxylate. For projects needing the longest slump life or self-compacting performance, Fosroc’s polycarboxylate-based Auramix and Auracast (PCE) ranges are the step up, and Conplast P505 or SP430 serve more routine water-reduction needs at lower cost. Against competitor lines, SP555 competes with Sika’s ViscoCrete and Sikament superplasticiser families, MBS (Master Builders Solutions) MasterGlenium and MasterRheobuild, BASF-legacy admixtures, and the admixture offerings from STP Limited; Dr. Fixit (Pidilite) is positioned more in integral waterproofing and repair than in high-range superplasticisers, so it overlaps less directly here. Honest guidance: choose SP555 when you need dependable, cost-effective high-range water reduction with good cohesion for piling, mass and pumped concrete; step to a PCE (Auramix/ViscoCrete/MasterGlenium) when extreme slump retention, very high slump flow or self-compacting concrete is the priority. Space Arc Engineering, as an authorised Fosroc distributor in Delhi NCR and Pan-India, supplies SP555 with trial-mix and dispensing support to match the right admixture to the pour.
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