Fosroc Conplast SP365
Chloride-free high-range water-reducing superplasticiser engineered for extended workability retention in low water-cement ratio, durable, high-performance concrete.
What is it?
A chloride-free, high-range water-reducing (HRWR) superplasticising admixture based on a blend of specially selected organic polymers, formulated to deliver strong water reduction together with an extended workability-maintenance period.
Where is it used?
Ready-mix and site-batched structural concrete, transit-mixed pours, pumped concrete, raft and pile foundations, columns, slabs and other reinforced or prestressed elements where slump must be held over longer placing times.
Why use it?
It lets you cut mix water for higher strength and lower permeability without sacrificing workability, and crucially it holds that workability longer than a conventional superplasticiser, reducing slump loss during transit and placement.
How is it applied?
Added to the gauging water or dispensed into the mixer with the final water at 0.5-1.6 litres per 100 kg of cementitious material; never added to dry cement. Trial mixes establish the optimum dosage for the target slump, retention time and strength.
About Fosroc Conplast SP365
Fosroc Conplast SP365 is a high-range water-reducing superplasticiser that sits within Fosroc’s well-established Conplast admixture range. It is supplied as a ready-to-use liquid that disperses instantly in water and works by deflocculating and dispersing the fine cement particles in the mix. Once dispersed, the entrapped water that would otherwise be locked between cement grains is released to lubricate the mix, so the same concrete can be made far more workable, or alternatively the water content can be cut sharply while keeping workability constant.
What distinguishes SP365 from a basic superplasticiser is its emphasis on workability maintenance. Ordinary high-range water reducers can give a dramatic initial slump but lose it quickly, which is a real problem on Indian sites where ready-mix concrete may travel through heavy Delhi NCR or metro traffic before it reaches the pour. SP365 is formulated to extend the period over which the concrete stays placeable, giving site teams a longer, more predictable window to discharge, pump and compact without re-tempering with water (which would dilute strength and durability).
The product is chloride-free, which makes it suitable for reinforced and prestressed concrete where chloride-induced corrosion of steel must be avoided. It is water-based and non-flammable, and being a liquid it is straightforward to dispense accurately through automatic batching systems at an RMC plant or by hand-measured dosing on smaller sites. For Space Arc Engineering’s customers, SP365 is best thought of as a workability-retention superplasticiser, positioned for jobs where the distance or time between batching and placing is the controlling factor rather than purely the headline water reduction.
The technical insight
The performance of SP365 rests on adsorption-dispersion chemistry. The organic polymers adsorb onto the surface of cement particles immediately after mixing and break up the flocculated clusters that normally trap mixing water. Releasing that trapped water is what produces the plasticising effect, so a given paste flows freely at a much lower free-water content. Because the dispersion is driven mainly by the physical effect of the adsorbed polymer rather than by aggressive chemistry, SP365 does not entrain significant air, does not introduce chlorides, and is compatible with ordinary Portland cement (OPC), PPC and PSC blends as well as blended mixes containing fly ash (PFA), GGBS or silica fume. The deliberately slower, sustained adsorption profile is what gives the extended workability window: the polymer continues to keep particles dispersed as hydration begins, slowing the rate of slump loss compared with a conventional SNF superplasticiser. Practically, this means a designer can push the water-cement ratio down to improve compressive strength and reduce capillary porosity (and therefore chloride and water permeability) while still meeting the slump required at the point of discharge. Optimum results depend on the cement source, ambient temperature and supplementary cementitious materials, so dosage should always be confirmed by site trial mixes rather than assumed.
Where it is used
- Ready-mixed concrete that must retain slump during long transit times in congested Delhi NCR and other metro corridors
- High-strength structural concrete (columns, beams, shear walls, transfer slabs) requiring low water-cement ratios
- Pumped concrete for high-rise and infrastructure pours where sustained pumpability is critical
- Raft foundations, pile caps and large-pour mass concrete where placing and compaction take time
- Reinforced and prestressed concrete elements where chloride-free admixtures are mandated
- Durable concrete for marine, water-retaining and aggressive-exposure structures needing low permeability
- Hot-weather concreting in northern and western India, where rapid slump loss is a recurring site problem
Key advantages
- Significant water reduction enabling higher early and ultimate compressive strengths without extra cement
- Extended workability-maintenance period that reduces slump loss during transport and placing
- Chloride-free formulation, safe for reinforced and prestressed concrete
- Lower water-cement ratio gives reduced permeability and improved long-term durability
- Improved cohesion and easier placing, compaction and finishing, reducing honeycombing
- Compatible with OPC, PPC, PSC and blended mixes containing fly ash, GGBS or silica fume
- Liquid form disperses instantly and dispenses accurately through automatic RMC batching plant
- Helps avoid on-site re-tempering with water, protecting the designed strength and durability
Limitations & considerations
- Overdosing can cause excessive retardation, segregation or bleeding; dosage must be set by trial mix
- Performance varies with cement source, SCMs and ambient temperature, so field trials are essential
- As an SNF-type superplasticiser, slump retention is good but generally not as long as modern polycarboxylate-ether (PCE) admixtures in very hot or very long-haul conditions
- Liquid admixture is sensitive to storage; should be protected from frost and from prolonged high temperatures
- Not a substitute for sound mix design, adequate cement content or proper curing
- Should not be added directly to dry cement; must be batched with the gauging water
- Compatibility with other admixtures (e.g. retarders, air-entrainers) must be verified before combined use
Selection & best practice
Always establish the working dosage by laboratory and site trial mixes using the actual cement, aggregates and supplementary cementitious materials for the job, targeting the required slump at the point of discharge rather than at the plant. Add SP365 to the gauging water or with the final portion of mixing water, never to dry cement, and avoid prolonged dry-mixing. Keep within the 0.5-1.6 litre per 100 kg cementitious range unless a higher dosage is justified by trial and approved by the consultant. Take slump readings both at the plant and on arrival to confirm the retention is adequate for the haul time, and resist any temptation to add water on site. Store containers in shade, protected from frost and direct sun, and use stock in date order. For very long hauls or extreme heat, discuss a PCE-based alternative with Space Arc’s technical team before specifying.
Specifications
| Product type | High-range water-reducing superplasticiser (workability-retaining) |
| Chemical base | Blend of specially selected organic polymers (SNF-type), chloride-free |
| Form / appearance | Liquid; disperses instantly in water |
| Chloride content | Chloride-free (nil), to relevant admixture standards |
| Typical dosage | 0.5-1.6 litres per 100 kg of cementitious material (approx. 0.5-1.6% by weight of cement) |
| Air entrainment | Does not significantly entrain air at normal dosage |
| Standards compliance | Complies with EN 934-2:2010 Tables 3.1 & 3.2 (high-range water reducer / superplasticiser); Conplast superplasticiser family also conforms to IS 9103, BS 5075 Part 3 and ASTM C494 |
| Cement compatibility | OPC, PPC, PSC and blends with fly ash, GGBS and silica fume |
| Flammability | Water-based, non-flammable |
| Primary functions | Water reduction, increased strength, extended workability retention, reduced permeability |
Industry use cases
Ready-Mix Concrete (RMC)
RMC plants supplying long-haul deliveries across Delhi NCR use SP365 to hold slump through traffic so concrete arrives placeable without water addition, protecting the designed grade.
High-Rise & Commercial Construction
For pumped, high-strength columns and core walls, SP365 enables low water-cement ratio mixes while keeping the concrete fluid enough to pump and compact through congested reinforcement.
Infrastructure & Foundations
On raft foundations, pile caps and large mass pours where placing takes hours, the extended workability window allows continuous, well-compacted concrete with fewer cold joints.
Marine & Water-Retaining Structures
The chloride-free, low-permeability concrete produced with SP365 supports durability requirements for water tanks, basements and structures in aggressive or coastal exposure.
Precast & Prestressed Elements
Because it is chloride-free, SP365 suits prestressed girders, beams and precast units where steel corrosion risk must be eliminated and consistent finish is needed.
Frequently asked questions
What is Fosroc Conplast SP365 used for?
What is the recommended dosage of Conplast SP365?
Is Conplast SP365 chloride-free and safe for reinforced concrete?
How is SP365 different from Fosroc Conplast SP430?
How should Conplast SP365 be added to the concrete?
Does Space Arc Engineering supply Conplast SP365 across India?
How we position Fosroc Conplast SP365
Within the Fosroc Conplast admixture family, SP365 occupies the workability-retention niche among the high-range water reducers. It is closely related to Conplast SP430 and SP430ES2 (general-purpose SNF superplasticisers focused on water reduction and strength) and to SP366, while products such as Conplast WP and Conplast X421 address integral waterproofing and other specialist needs. Where a project demands the longest possible slump life or the highest strengths in hot conditions, a polycarboxylate-ether (PCE) admixture such as Fosroc’s Auracast/Structuro range may be a stronger fit than an SNF product like SP365. Among competing brands commonly specified in India, credible alternatives include Sika ViscoCrete and Sikament, MBS (Master Builders Solutions) MasterGlenium and MasterRheobuild, Dr. Fixit’s admixture range, and STP (Pidilite) admixtures. SP365 is the right pick when you want a proven, chloride-free, liquid SNF superplasticiser with good workability retention at a sensible cost; for extreme retention or ultra-high strength, talk to Space Arc Engineering about a PCE option before finalising the specification.
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