Fosroc Conplast SP337L
Chloride-free high-performance superplasticiser and water reducer for high-strength, high-workability, low-permeability concrete — supplied and supported Pan-India by Space Arc Engineering.
What is it?
A chloride-free, high-range water-reducing admixture (superplasticiser) based on specially selected and blended organic polymers, supplied as a brown liquid that disperses instantly in water. SP337L is the liquid grade of Fosroc’s Conplast SP337 family.
Where is it used?
Ready-mixed and site-batched structural concrete, precast and prestressed elements, pumped and flowing concrete, and high-strength / high-durability mixes across RCC, infrastructure and high-rise work.
Why use it?
It reduces water demand by 10-20% at constant workability — lifting early and ultimate strength, cutting permeability and shrinkage-cracking risk, and aiding pumping — without adding cement or chlorides.
How is it applied?
Dosed by dispenser at 500 ml to 1.5 litres per 100 kg of cementitious content, added with the gauging water (or with the final ~20% of mix water after pre-wetting). Optimum dosage is fixed by site trials.
About Fosroc Conplast SP337L
Fosroc Conplast SP337L is a high-performance, chloride-free superplasticising admixture used to make concrete behave better in two opposite but equally valuable ways: either far more workable at the same water content, or far stronger and denser at a sharply reduced water content. It belongs to Fosroc’s well-established Conplast SP337 series, marketed in India and South Asia as a high-range water reducer based on a blend of specially selected organic polymers. Supplied as a dark-brown liquid that disperses instantly in the mix, it works by separating and deflocculating cement grains so that more particle surface is exposed to hydration water. That improved dispersion is the mechanism behind every benefit the product delivers. For contractors, RMC plants and consultants in Delhi NCR and across India, SP337L is a workhorse admixture for structural concrete where strength, durability and pumpability all matter. Because it is chloride-free and complies with IS:456 for nil chloride content, it is safe in reinforced and prestressed concrete — a non-negotiable for bridge girders, post-tensioned slabs and precast yards. Space Arc Engineering, as an authorised Fosroc distributor and applicator, supplies SP337L with technical back-up on mix design and trials so that the dosage chosen on paper actually performs on the pour. The admixture is positioned for projects that want a dependable, mid-tier polymer superplasticiser rather than the latest PCE chemistry — it offers a controlled rate of workability loss, good cohesion, and a comfortable dosage window that tolerates real site conditions.
The technical insight
SP337L is a sulphonated/organic-polymer-based superplasticiser rather than a modern polycarboxylate ether (PCE), and that distinction explains its working envelope. The polymers adsorb onto cement particles and impart a dispersing charge that breaks up flocs, freeing trapped water and dramatically improving flow. Practically, this lets the engineer take one of three routes from a single admixture: hold workability and cut water by 10-20% for higher strength and lower permeability; hold the water:cement ratio and convert a stiff mix into flowing concrete; or trim cement at constant strength for cost and shrinkage benefit. At higher dosages used without water reduction, the same chemistry retards initial set by roughly 1-2 hours — useful for large pours, hot-weather concreting and longer haul times, but something that must be planned for, not stumbled into. Air entrainment is minimal at around 1% additional air, so strength is not compromised at correct dosage. The admixture is compatible with all ordinary Portland and slag cements (and with fly ash, GGBS and microsilica blends) but should not be used with High Alumina Cement. When combined with other Fosroc admixtures, each product must be batched separately into the mix rather than pre-blended in the same line.
Where it is used
- High-strength structural RCC for columns, transfer girders, rafts and shear walls in high-rise buildings
- Ready-mixed concrete (RMC) requiring controlled workability retention during transit and pumping
- Precast concrete production where high early strength accelerates de-moulding and bed turnaround
- Prestressed and post-tensioned elements — bridge girders, beams and PT slabs — needing chloride-free admixtures
- Pumped concrete over long distances and to height, where line friction must be reduced
- Flowing concrete for congested reinforcement, slender sections and self-levelling slabs
- High-durability, low-permeability concrete for water-retaining structures, basements and marine-exposed work
- Hot-weather and large-volume mass pours where the mild set retardation at higher dosage is advantageous
Key advantages
- Chloride-free to IS:456 — safe in reinforced and prestressed concrete with no corrosion risk to steel
- Cuts water demand by 10-20% at constant workability, raising early and 28-day compressive strength
- Lowers water:cement ratio to produce dense, impermeable, more durable concrete with less shrinkage cracking
- Improves pumpability by lubricating cement particles and reducing line friction
- Slower rate of workability loss than many standard superplasticisers, easing placement and compaction
- Increases strength without extra cement — useful for cost control and reduced heat of hydration
- Reduces bleeding and segregation through improved cohesion, giving a closed, uniform surface finish
- Wide, forgiving dosage window (0.5-1.5 L/100 kg cement) and compatibility with OPC, PSC and SCM blends
Limitations & considerations
- Not compatible with High Alumina Cement
- At higher dosages without water reduction it retards initial set by 1-2 hours, which must be planned for in cold weather or fast-track work
- Overdosing (around double the recommended rate) can accelerate setting, entrain extra air and slightly reduce strength
- Polymer (sulphonated-type) chemistry offers lower slump retention and water reduction than premium PCE superplasticisers like Auramix / ADVA
- Optimum dosage must be established by site trials with the actual mix — published ranges are a starting point only
- When used with other admixtures, each must be dosed separately into the mix, not pre-mixed
- Performance and set behaviour are sensitive to ambient temperature; shelf life and storage limits must be respected
- Not an integral waterproofer or air-entrainer — pair with the correct Fosroc product where those functions are needed
Selection & best practice
Always establish the optimum dosage by trial batches using your project’s actual cement, SCMs and aggregates rather than relying on the catalogue range. Dispense SP337L by a calibrated dispenser, adding the measured quantity with the gauging water at the batching plant, or with the final ~20% of mix water after the mix has been pre-wetted — never onto dry aggregate. Keep the admixture line separate from any other admixture. To gain strength, lock the workability target and reduce water to bring the W/C ratio down; to gain flow, hold water and let the admixture do the work, making minor mix-design tweaks to prevent bleeding. Plan for the 1-2 hour set retardation at higher dosages in large or hot-weather pours. Follow with proper curing — water ponding, wet hessian or a Fosroc Concure curing membrane — to realise the durability gains. Store drums in shade between 2°C and 40°C and use within 12 months of manufacture.
Specifications
| Type | Chloride-free high-range water-reducing superplasticiser (organic polymer based) |
| Base / Chemistry | Blend of specially selected organic polymers (sulphonated-type), liquid grade |
| Appearance | Dark brown liquid, instantly dispersible in water |
| Specific Gravity | 1.20 at 27°C |
| Chloride Content | Nil to IS:456 |
| Air Entrainment | Approx. 1% additional air entrained |
| Typical Dosage | 500 ml to 1.5 litres per 100 kg of cement (incl. fly ash / slag / microsilica) |
| Water Reduction | 10-20% at constant workability |
| Set Retardation | 1-2 hours approx. at higher dosage without water reduction |
| Standards Compliance | IS:9103:1999 (water-reducing admixture), IS 2645:1975, ASTM C494 Type F, BS 5075 Part 3 |
| Compatibility | All OPC and slag cements (and SCM blends); NOT High Alumina Cement |
| Packaging | 5 L, 20 L and 200 L containers; 250 kg drums |
| Shelf Life | 12 months from manufacture, stored at 2°C to 40°C in shade |
Industry use cases
High-Rise & Commercial Buildings
High-strength pumped RCC for columns, cores and transfer structures where water reduction lifts grade (e.g. M40-M60) without raising cement content or heat of hydration.
Precast Concrete Yards
Faster de-moulding and bed turnaround through high early strength at low W/C ratio, with a closed, uniform surface finish on architectural and structural units.
Bridges & Prestressed Works
Chloride-free dosing for PSC girders, PT slabs and post-tensioned beams where any chloride is unacceptable around stressed strand and reinforcement.
Ready-Mixed Concrete (RMC)
Controlled workability retention during transit and improved pumpability to height, reducing rejected loads and placement labour on congested sites.
Water-Retaining & Below-Grade Structures
Low-permeability, dense concrete for basements, tanks, STPs and retaining walls, reducing shrinkage cracking and water penetration.
Infrastructure & Mass Pours
Large rafts and foundations benefit from the mild set retardation at higher dosage, extending working time in hot Indian site conditions.
Frequently asked questions
Is Fosroc Conplast SP337L chloride-free and safe for reinforced and prestressed concrete?
What is the correct dosage of Conplast SP337L?
Which standards does Conplast SP337L comply with?
How much water reduction and strength gain can I expect?
Does SP337L retard the setting time of concrete?
What pack sizes are available and what is the shelf life?
How we position Fosroc Conplast SP337L
Conplast SP337L sits in the dependable mid-tier of Fosroc’s admixture range — a polymer-based (sulphonated-type) superplasticiser for everyday structural, precast and RMC work, rather than a specialist product. Within the Fosroc family it overlaps with Conplast SP430 (a higher-performance superplasticiser) and the polycarboxylate-ether Auramix range, which deliver greater water reduction and slump retention for very-high-strength or self-compacting concrete; it complements retarders such as Conplast RP264, integral waterproofers like Conplast X421IC / Conplast WL, and curing membranes such as Concure WB that protect the durability gains SP337L creates. Against the wider Indian market, SP337L is most directly comparable to Sika’s older naphthalene/melamine plasticisers such as Sikament-170 and to BASF/Master Builders Solutions products like MasterRheobuild, with Fosroc’s strength being the integrated system and on-site technical support. For ultra-high-range, low-W/C or SCC requirements, premium PCE admixtures (Sika ViscoCrete, MBS MasterGlenium/ADVA, or Fosroc Auramix) are the stronger choice; for integral waterproofing where a plasticiser is not the goal, Dr. Fixit and STP (Pidilite) offer alternatives. Space Arc Engineering positions SP337L as the right call when a contractor wants proven, forgiving superplasticiser performance with reliable supply and applicator support across Delhi NCR and Pan-India — and will recommend stepping up to a PCE grade when the mix genuinely demands it.
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