Fosroc Conplast SP500 M
High-range water-reducing superplasticiser based on sulphonated naphthalene polymers, engineered for high-strength, low-permeability and pumpable concrete.
What is it?
A chloride-free, high-range water-reducing (HRWR) superplasticising admixture based on sulphonated naphthalene polymers, supplied as a brown liquid that disperses instantly in water.
Where is it used?
Ready-mix and site-batched structural concrete, high-grade RCC, pumped concrete, precast and prestressed elements, and water-retaining or marine structures requiring low permeability.
Why use it?
Delivers up to 25% water reduction without losing workability, raising compressive strength and durability while improving flow for placing and pumping.
How is it applied?
Dosed into the mixing water or added to freshly batched concrete at typically 0.5-1.3 litres per 100 kg of cementitious material; never onto dry aggregate or cement.
About Fosroc Conplast SP500 M
Fosroc Conplast SP500 M is a high-performance superplasticising concrete admixture from the Conplast SP500 family, supplied by Space Arc Engineering as an authorised Fosroc distributor across Delhi NCR and Pan-India. It belongs to the high-range water-reducing (HRWR) class of admixtures and is built on a sulphonated naphthalene polymer (SNF) chemistry, supplied as a brown, free-flowing liquid that disperses instantly in the mixing water. The “M” designation denotes a regionally manufactured grade of the established SP500 product, formulated for Indian site and ready-mix conditions while retaining the same core performance signature: high water reduction, high cohesion and chloride-free composition.\n\nThe admixture works by adsorbing onto cement particles and imparting a strong negative charge that disperses cement flocs through electrostatic repulsion. This frees the water trapped inside those flocs, so the concrete can either be made far more workable at the same water content, or the water can be cut by up to 25% to drop the water-to-cement ratio sharply. A lower w/c ratio is the single most powerful lever for concrete strength and durability, which is why SP500 M is specified wherever high early strength, dense low-permeability concrete or reliable pumpability is required. Because it is chloride-free, it is safe in prestressed concrete, with sulphate-resisting cements and around steel reinforcement where chloride-induced corrosion must be avoided.\n\nIn Indian practice, Conplast SP500 M is used heavily in RMC plants producing M25-M50 and higher grades, in pumped concrete for high-rise construction, and in precast yards where rapid mould turnover depends on high early strength. It complies with IS 9103:1999 and BS 5075 Part 3, and conforms to ASTM C494 Type F (water-reducing, high range) and Type G (water-reducing, high range and retarding) depending on dosage. Space Arc Engineering supplies it with full technical-data-sheet support, trial-mix guidance and logistics for both project sites and batching plants.
The technical insight
The performance of SP500 M comes from electrostatic dispersion rather than the steric (side-chain) mechanism of newer PCE admixtures. SNF molecules coat cement grains and repel one another, breaking up flocculated clusters and releasing bound water almost instantly on mixing. This gives a fast, strong initial slump boost but a comparatively shorter workability-retention window than polycarboxylate ethers, which is the key design trade-off to plan around. For high water reduction (toward the 25% figure) the dosage moves to the upper end of the range and the mix behaves closer to ASTM C494 Type G, where mild set retardation accompanies the plasticising effect. The chloride-free, low-alkali nature of the SNF base is what makes it acceptable in prestressed and sulphate-resisting systems. In practice, the controlling variables are cement chemistry, fineness and ambient temperature: in Indian summer placing, the rapid slump loss typical of SNF admixtures often dictates re-dosing at site or a switch to a retarding mix design rather than simply increasing initial dosage.
Where it is used
- High-grade structural RCC (M25-M50 and above) requiring high strength and low permeability
- Pumped concrete for high-rise and long-distance placement
- Precast concrete elements needing high early strength for fast demoulding
- Prestressed and post-tensioned concrete where chloride-free admixtures are mandatory
- Ready-mix concrete (RMC) plant production with controlled w/c ratio
- Water-retaining structures, basements and marine works needing dense, low-porosity concrete
- Concrete using sulphate-resisting cement or marine aggregates
Key advantages
- Up to 25% water reduction without loss of workability, sharply lowering the w/c ratio
- Higher early and ultimate compressive strength when water reduction is exploited
- Denser, close-textured concrete with reduced permeability and improved durability
- Improved cohesion that minimises segregation and bleeding, aiding pumpability
- Chloride-free, safe for prestressed concrete, SRC and reinforced sections
- Complies with IS 9103:1999, BS 5075 Part 3 and ASTM C494 Type F & G
- Instantly dispersible brown liquid, easy to dose at plant or site
Limitations & considerations
- SNF chemistry gives shorter slump retention than polycarboxylate (PCE) superplasticisers, so rapid slump loss can occur in hot weather
- Overdosing can cause excessive retardation, segregation or bleeding and delayed setting
- Performance is sensitive to cement type, fineness and ambient temperature; site trials are essential
- Not a self-compacting concrete (SCC) solution on its own; very high flow/SCC targets are better served by PCE-based Conplast/Auracast ranges
- Not intended for use with high-alumina cement
- Liquid admixture requires protection from freezing and correct storage to avoid stratification
Selection & best practice
Always establish dosage by site trial mixes with the actual cement and aggregates before bulk use, starting near 0.5-0.7 litres per 100 kg of cementitious material and adjusting toward the upper limit only as needed for the target slump or water reduction. Add SP500 M to the mixing water or to freshly batched, already-wetted concrete; never dispense it directly onto dry cement or aggregate, as this prevents proper dispersion. When chasing maximum water reduction, reduce the mix water in step with the admixture rather than adding both. In hot Indian conditions, plan for slump loss by scheduling re-dosing or adopting a retarding mix design instead of simply raising the initial dose. Keep dosing equipment calibrated, store the drums in shade away from frost, and confirm compatibility when combining with other admixtures by adding each separately. Consult the current Fosroc TDS and Space Arc Engineering for project-specific recommendations.
Specifications
| Type | High-range water-reducing superplasticiser (HRWR) |
| Chemical base | Sulphonated naphthalene polymers (SNF) |
| Appearance / colour | Brown liquid, instantly dispersible in water |
| Specific gravity | Approx. 1.25 – 1.27 at 27°C (refer to current TDS) |
| Chloride content | Nil / chloride-free to IS:456 |
| Water reduction | Up to 25% (typically 15-25%) |
| Typical dosage | 0.5 – 1.3 litres per 100 kg of cementitious material (up to ~2.0 by trial) |
| Standards | IS 9103:1999; BS 5075 Part 3; ASTM C494 Type F & G |
| Shelf life | 12 months in unopened drums, stored correctly |
| Packaging | Drums (e.g. 250 kg); bulk on request |
Industry use cases
High-rise residential & commercial
Pumpable M30-M45 concrete for columns, cores and slabs, where high cohesion and low bleed allow reliable long-vertical pumping without blockage.
Ready-mix concrete plants
Consistent w/c control and water reduction across large batch volumes, improving strength and durability while meeting IS 9103 compliance.
Precast & prestressed yards
High early strength for faster demoulding and mould reuse; chloride-free composition is mandatory around prestressing strands.
Infrastructure & water-retaining structures
Dense, low-permeability concrete for basements, tanks, tunnels and bridge elements requiring durability and reduced porosity.
Marine & sulphate environments
Compatible with sulphate-resisting cement and marine aggregates, supporting low-permeability concrete in aggressive exposure.
Frequently asked questions
What is Fosroc Conplast SP500 M used for?
Is Conplast SP500 M chloride-free?
What is the recommended dosage?
Which standards does it comply with?
How is SP500 M different from a PCE superplasticiser?
How should it be added to the mix?
How we position Fosroc Conplast SP500 M
Conplast SP500 M sits in Fosroc’s mid-tier SNF superplasticiser range, above basic water-reducers like Conplast SP430 and alongside SP550, but below Fosroc’s polycarboxylate (PCE) Auracast / Conplast SP600-series admixtures that are chosen for long slump retention and self-compacting concrete. Choose SP500 M when you need strong, economical water reduction and high early strength for conventional and pumped concrete; step up to a PCE admixture (Fosroc Auracast, or competitor PCEs such as Sika ViscoCrete, BASF/Master Builders Solutions MasterGlenium, or STP) when extended workability, very high flow or true SCC is required. For competing SNF-class products, common alternatives include Sika Plastiment/Sikament, MBS MasterRheobuild and Dr. Fixit superplasticisers. Space Arc Engineering supplies SP500 M alongside the broader Fosroc admixture range and can advise on the right grade per mix design, exposure class and placing method.
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