Fosroc Conplast SP337
High-range water-reducing superplasticising admixture for high-workability, high-strength, impermeable concrete – chloride-free and compliant with IS 9103, ASTM C494 Type F and BS 5075 Part 3.
What is it?
Fosroc Conplast SP337 is a high-range water-reducing superplasticising admixture based on a blend of specially selected organic polymers, supplied as a dark brown liquid that is instantly dispersible in water. It is an SNF-family superplasticiser – not a lignosulphonate plasticiser and not a polycarboxylate ether (PCE).
Where is it used?
Used across Indian ready-mix concrete (RMC), precast yards and infrastructure works where high workability and high early strength are required – from high-rise raft and column pours to bridges, water-retaining structures and hot-weather placements.
Why use it?
It delivers substantial water reduction (10-20%), producing high early compressive strength, dense impermeable concrete and improved durability without sacrificing workability. It is chloride-free to IS:456, making it safe for reinforced and prestressed concrete.
How is it applied?
Dosed at 500 ml to 1.5 litres per 100 kg of cement for high workability (higher dosages on Fosroc advice), it is added to the gauging water or run-on mixed concrete and dispersed instantly – never onto dry aggregate or cement.
About Fosroc Conplast SP337
Fosroc Conplast SP337 is a high-range water-reducing superplasticising admixture engineered to produce high-workability, high-strength, durable and impermeable concrete. Contrary to a common misclassification, it is NOT a lignosulphonate-based mid-range plasticiser – its chemistry is based on a blend of specially selected organic polymers, placing it in the SNF (sulphonated naphthalene formaldehyde) family of superplasticisers. It is supplied as a dark brown liquid that is instantly dispersible in water, allowing rapid, uniform dispersion through the concrete matrix.
The product is formulated to dramatically lower the water-cement ratio while maintaining or improving workability. At normal dosage it gives substantial water reduction of 10-20%, which translates directly into higher early and ultimate compressive strengths, reduced permeability and improved long-term durability. Alternatively, the same admixture can be used to boost workability for easier placement and compaction of congested or deep sections without adding water.
Conplast SP337 is chloride-free to IS:456, so it carries no risk of chloride-induced corrosion of reinforcement or prestressing steel. It entrains only approximately 1% additional air, so it does not significantly alter the air content or yield of the mix. At higher dosages used without water reduction, it can retard setting by approximately 1-2 hours – a useful characteristic for hot-weather concreting and long-haul RMC deliveries common across Delhi NCR and Pan-India projects.
As an authorised Fosroc distributor and applicator, Space Arc Engineering supplies genuine Conplast SP337 with full technical support. For projects evaluating alternatives, the SNF superplasticiser category also includes products such as BASF Master Builders (MasterRheobuild), Sika (Sikament) and Chryso – but Conplast SP337 remains the proven Fosroc benchmark for Indian RMC, precast and infrastructure concrete.
The technical insight
Conplast SP337’s performance comes from its SNF-based organic-polymer chemistry, which adsorbs onto cement particles and disperses them electrostatically, releasing trapped water and breaking down cement flocs. This is why it achieves a high-range water reduction of 10-20% – markedly more than a conventional lignosulphonate plasticiser (which is why classifying SP337 as a mid-range/Type A or Type D admixture both understates and misrepresents the product). The result is concrete with a substantially reduced water-cement ratio that develops high early compressive strength and a dense, low-permeability microstructure. Because it is chloride-free to IS:456 and entrains only about 1% additional air, it does not compromise reinforcement durability or air-content design. The mild set retardation (approximately 1-2 hours) seen at higher dosages without water reduction extends workability retention – valuable for hot Indian summers and extended RMC transit times. SP337 is compatible with all Portland and slag cements but must not be used with High Alumina Cements.
Where it is used
- High-strength, high-workability RMC for high-rise rafts, columns and transfer slabs
- Precast and prestressed concrete elements requiring high early strength and demoulding speed
- Bridges, flyovers and infrastructure works demanding durable, low-permeability concrete
- Water-retaining and water-excluding structures where impermeability is critical
- Hot-weather concreting and long-haul RMC deliveries needing workability retention
- Densely reinforced or deep sections needing flowable, easily compacted concrete
Key advantages
- High-range water reduction of 10-20% for high early and ultimate compressive strength
- Produces dense, impermeable and durable concrete with reduced water-cement ratio
- Chloride-free to IS:456 – safe for reinforced and prestressed concrete
- Instantly dispersible dark brown liquid for rapid, uniform mixing
- Entrains only about 1% additional air, with minimal effect on yield
- Mild set retardation (approx. 1-2 hours) at higher dosage aids hot-weather and long-haul placements
- Compliant with IS 9103:1999, IS 2645:1975, BS 5075 Part 3 and ASTM C494 Type F
- Compatible with all Portland and slag cements
Limitations & considerations
- Not suitable for use with High Alumina Cements
- Should be added to gauging water or wet concrete – not onto dry cement or aggregate
- Optimum dosage must be established by site trials within the recommended range; dosages above 1.5 L/100 kg only on Fosroc advice
- At higher dosage without water reduction it will retard set by approximately 1-2 hours, which must be accounted for in scheduling
- Overdosing can cause excessive retardation or segregation if the mix is not adjusted
- Store between 2-40 C; shelf life is 12 months
Selection & best practice
Always establish the optimum dosage by trial mixes within the recommended range of 500 ml to 1.5 litres per 100 kg of cement, using site materials and target slump. Add Conplast SP337 to the gauging water or to the run-on wet concrete – never directly onto dry cement or aggregate – to ensure instant, uniform dispersion. Where it is used purely for water reduction, hold the mix water back and exploit the full 10-20% reduction to maximise strength and impermeability. For hot-weather pours and long RMC transit, leverage the mild set retardation at higher dosages, but adjust the mix design and placing schedule accordingly. Do not use with High Alumina Cements, and store sealed containers between 2-40 C, using within the 12-month shelf life. Consult Fosroc or Space Arc Engineering’s technical team before exceeding 1.5 L/100 kg cement.
Specifications
| Chemical base | Blend of specially selected organic polymers (superplasticiser) |
| Appearance | Dark brown liquid, instantly dispersible in water |
| Dosage | 500 ml to 1.5 litres / 100 kg cement (high workability); higher on Fosroc advice |
| Water reduction | Substantial water reduction (10-20%) gives high early compressive strength |
| Chloride content | Nil to IS:456 (chloride free) |
| Air entrainment | Approx. 1% additional air entrained |
| Setting time | At higher dosage without water reduction, retards setting 1-2 hours approx. |
| Standards compliance | IS 9103:1999, IS 2645:1975, BS 5075 Part 3, ASTM C494 Type F |
| Compatibility | All Portland and slag cements except High Alumina Cements |
| Packaging / shelf life | 5, 20, 200 litre and 250 kg containers; 12 months shelf life at 2-40 C |
| Primary use | Superplasticising admixture for high-workability, high-strength, durable, impermeable concrete |
Industry use cases
Ready-Mix Concrete (RMC)
Used by Indian RMC plants to produce high-strength, high-workability concrete with a 10-20% lower water-cement ratio, while the mild set retardation at higher dosage preserves workability over long transit times to site.
Precast & Prestressed
Delivers high early compressive strength for faster demoulding and bed turnover in precast yards, with chloride-free chemistry that protects prestressing strands.
Infrastructure & Bridges
Specified for bridges, flyovers and heavy infrastructure where dense, impermeable, durable concrete compliant with IS 9103 and ASTM C494 Type F is required.
Water-Retaining Structures
Produces low-permeability, impermeable concrete for tanks, reservoirs and basements where water-tightness and durability are critical.
Hot-Weather Concreting
Across Delhi NCR and Pan-India summer pours, the approx. 1-2 hour set retardation at higher dosage helps maintain workability and reduce the risk of cold joints.
Frequently asked questions
Is Fosroc Conplast SP337 a plasticiser or a superplasticiser?
What standards does Conplast SP337 comply with?
What is the recommended dosage of Conplast SP337?
How much water reduction does Conplast SP337 give?
Is Conplast SP337 safe for reinforced and prestressed concrete?
Which cements is Conplast SP337 compatible with?
Does Conplast SP337 affect setting time?
How is Conplast SP337 packaged and stored?
How we position Fosroc Conplast SP337
Fosroc Conplast SP337 is positioned as a proven, standards-compliant SNF high-range water-reducing superplasticiser for Indian RMC, precast and infrastructure concrete. Space Arc Engineering, an authorised Fosroc distributor and applicator serving Delhi NCR and Pan-India, supplies genuine SP337 with full technical backing. It is the Fosroc benchmark within a category that also includes alternatives such as BASF Master Builders (MasterRheobuild), Sika (Sikament) and Chryso superplasticisers.
Related Concrete Admixtures products
Source Fosroc Conplast SP337 for your project
Authorised distribution, technical advice & professional application across Delhi NCR and Pan-India.