Fosroc Conplast SP911
Superior high range water reducer (Type G superplasticiser) for high-strength, low-permeability rheoplastic and flowing concrete.
What is it?
A chloride-free, naphthalene-sulphonate based high range water reducing admixture (superplasticiser) that produces rheoplastic, flowing concrete while sharply cutting the water-cement ratio.
Where is it used?
High-grade RMC and precast plants, pump mixes, prestressed and reinforced members, microsilica/PFA/GGBFS blended concrete and dense waterproof structures across India.
Why use it?
It lets you strip water from the mix at constant workability, raising early and ultimate strength, durability and pumpability without adding cement, lowering cost per cubic metre.
How is it applied?
Dosed by calibrated dispenser at 0.5-3.0 L per 100 kg cement, added to the gauging water in a wet mix and high-speed mixed for at least two minutes; never added to dry cement or aggregate.
About Fosroc Conplast SP911
Fosroc Conplast SP911 is a high range water reducing admixture (superplasticiser) engineered for high-quality rheoplastic and high-performance concrete. It is a chloride-free liquid based on selected polymer-modified naphthalene sulphonate dispersives. Once introduced into the mix, the admixture disperses by electro-kinetic action, neutralising the surface charges that cause cement grains to flocculate. The cement particles deflocculate and repel one another, freeing the water trapped between them so the water phase of the concrete works far more efficiently. For Space Arc Engineering’s clients across Delhi NCR and Pan-India, this means a single admixture can be deployed two ways: to keep workability constant while removing a large volume of mixing water (boosting strength and durability), or to dramatically increase flow at the same water-cement ratio for self-levelling, easily pumped placements. The product is supplied as a brown liquid with a specific gravity of 1.170 plus or minus 0.02 at 25 degrees C, and conforms to BS:EN 934-2 and ASTM C494 as a Type G admixture depending on dosage. Because it contains no chloride, SP911 is fully suited to prestressed and reinforced concrete where chloride-induced reinforcement corrosion must be avoided. It is compatible with all Portland cements and with cement replacement materials such as PFA, GGBFS and microsilica, making it a natural fit for the blended, durability-focused mixes increasingly specified on Indian infrastructure and high-rise projects. SP911 sits in the upper tier of the Conplast superplasticiser family, positioned for ready-mix and precast operations that need strong workability retention and high strength gain without raising cement content.
The technical insight
The defining technical trait of Conplast SP911 is its naphthalene-sulphonate (SNF) backbone, which works through electrostatic (electro-kinetic) dispersion rather than the steric repulsion of newer polycarboxylate ether (PCE) admixtures. In practice this gives a powerful, immediate water-reduction and slump boost with workability loss that is slower than ordinary superplasticisers but still shorter-lived than a PCE. The published dosage window is unusually wide: 0.5 to 2.0 litres per 100 kg of cement for normal concrete, rising to 1.5 to 3.0 litres per 100 kg for high-performance concrete, so the same product spans plasticising and full rheoplastic duties. A critical control point flagged in the TDS is overdosing: doubling the dose increases retardation (ultimate strength is generally not harmed if curing is adequate, and may even rise) but can also raise air entrainment, which reduces strength. The retardation effect is amplified when sulphate-resisting cement or cement replacements are used, so trial mixes with the actual site materials are essential. The admixture must be added with the mixing water in a wet mix and blended at high speed for at least two minutes; it must never be batched onto dry cement or aggregate, where it cannot disperse effectively.
Where it is used
- High-strength RMC for columns, cores and transfer slabs in high-rise construction
- Precast and prestressed elements (beams, hollow-core slabs, segments) needing high early strength for fast demoulding
- Pumped concrete for tall pours and long horizontal runs requiring flow and workability retention
- Durable, low-permeability concrete for water-retaining structures, basements and marine/coastal works
- High-performance and microsilica/GGBFS/PFA blended concrete for infrastructure and industrial projects
- Rheoplastic / flowing concrete for congested reinforcement where compaction access is limited
Key advantages
- Chloride-free, safe for prestressed and reinforced concrete with no risk of chloride-induced reinforcement corrosion
- Allows large water reduction at constant workability, increasing both early and ultimate strength without extra cement
- Produces flowing rheoplastic concrete for easier placing, faster compaction and lower labour cost
- Slower workability loss in high-workability concrete than typical superplasticisers
- Lowers water-cement ratio to give low-permeability, more durable concrete with reduced shrinkage-cracking potential
- Fully compatible with microsilica, PFA, GGBFS and all Portland cements
- Wide dosage band (0.5-3.0 L/100 kg) covers both plasticising and high-performance rheoplastic mixes
- Conforms to BS:EN 934-2 and ASTM C494 Type G; long 12-month shelf life; water-based and non-flammable
Limitations & considerations
- Naphthalene-based (SNF) chemistry gives shorter slump retention than modern PCE superplasticisers in long-haul or hot-weather transit
- Overdosing increases retardation and can raise air entrainment, reducing strength if not controlled by trial mixes
- Retardation and overdose effects are amplified with sulphate-resisting cement or high cement-replacement levels
- Must be added to a wet mix with the gauging water and high-speed mixed for at least 2 minutes; cannot be batched onto dry cement or aggregate
- Requires daily re-circulation (10 minutes) in storage and must be kept between 2 degrees C and 50 degrees C; freezing point is around -2 degrees C
- Optimum dosage must be established by site trial mixes, not assumed from the guideline range
- Liquid admixture, not a finished concrete or repair material; performance depends on overall mix design and curing
Selection & best practice
Always establish the optimum dose by trial mixes using the actual site cement, aggregates and ambient temperature rather than fixing it from the guideline band. Start near 0.5-1.0 L/100 kg for normal mixes and step up toward 3.0 L/100 kg only for genuine high-performance concrete. Add SP911 to the gauging water in a wet mix, never onto dry cement or aggregate, and mix at high speed for at least two minutes to fully develop dispersion. Where high flow must survive a long transit (common in Delhi NCR summer hauls), pair it with a Conplast retarder or plan a redose at site after a trial, and verify air content if dosing toward the upper end. Keep stock between 2 and 50 degrees C and re-circulate the drum or tank for 10 minutes daily.
Specifications
| Product type | High range water reducer / superplasticiser (rheoplastic concrete) |
| Chemical basis | Selected polymer-modified naphthalene sulphonate dispersives |
| Appearance | Brown liquid |
| Specific gravity | 1.170 plus/minus 0.02 at 25 degrees C |
| Chloride content | Nil (to BS:EN 934) |
| Standards compliance | BS:EN 934-2; ASTM C494 Type G (dosage dependent) |
| Dosage – normal concrete | 0.5 – 2.0 litres per 100 kg of cement |
| Dosage – high-performance concrete | 1.5 – 3.0 litres per 100 kg of cement |
| Freezing point | Approximately -2 degrees C |
| Storage temperature | 2 degrees C to 50 degrees C; re-circulate 10 min daily |
| Shelf life | Minimum 12 months (within stated storage conditions) |
| Packaging | 210 litre drum, 1000 litre totes or bulk |
| Flammability | Water-based, non-flammable |
Industry use cases
Ready-Mix Concrete (RMC)
High-grade M40-M60 commercial mixes where water reduction at constant slump lifts strength and durability without raising cement, controlling cost per cubic metre.
Precast & Prestressed
Beams, hollow-core slabs and segments that need high early strength for rapid demoulding and bed turnover, achieved through deep water reduction rather than extra cement.
High-Rise & Infrastructure
Pumped concrete to columns, cores and transfer slabs requiring flow, workability retention and low permeability for long-term durability.
Water-Retaining & Marine Structures
Reservoirs, basements and coastal works where a low water-cement ratio and chloride-free dosing give dense, low-permeability, corrosion-resistant concrete.
Blended / High-Performance Concrete
Microsilica, GGBFS and PFA mixes for industrial and durability-critical projects where SP911 maintains workability in low water-cement designs.
Frequently asked questions
Is Fosroc Conplast SP911 a real Fosroc product?
What is the recommended dosage of Conplast SP911?
Is Conplast SP911 chloride-free and safe for reinforced concrete?
What standards does Conplast SP911 comply with?
How is Conplast SP911 different from a PCE superplasticiser like Auramix or Structuro?
What is the shelf life and how should Conplast SP911 be stored?
How we position Fosroc Conplast SP911
Conplast SP911 is Fosroc’s naphthalene-based (SNF) high range water reducer aimed at high-strength precast and ready-mix concrete that needs powerful water reduction and good strength gain without added cement. Within the Fosroc range it sits alongside other Conplast superplasticisers such as Conplast SP430 and SP337; where longer slump retention and self-compacting performance are required, Fosroc’s polycarboxylate (PCE) ranges (Auramix and Structuro) are the step-up choice. Comparable competitor products in the Indian market include Sika ViscoCrete and Sikament PCE/SNF superplasticisers, Master Builders Solutions (MBS) MasterGlenium and MasterRheobuild, and BASF-legacy admixtures; Dr. Fixit and STP (Pidilite/STP) compete more in waterproofing admixtures than in high-range superplasticisers. As an authorised Fosroc distributor, Space Arc Engineering positions SP911 as a dependable, IS/ASTM/BS-compliant SNF superplasticiser for high-strength and durability-focused mixes, and will recommend a PCE alternative from the Fosroc range when long-haul retention or self-compacting concrete is the genuine requirement.
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