Fosroc Conplast SP418
Chloride-free sulphonated-naphthalene superplasticiser for high-strength, water-reduced and flowing concrete — supplied and supported by Space Arc Engineering.
What is it?
A chloride-free, high-range water-reducing concrete admixture from Fosroc, based on selected sulphonated naphthalene polymers blended with supporting polymers, supplied as a brown liquid that disperses instantly in the mixing water.
Where is it used?
Ready-mix and site-batched concrete for high-rise frames, bridges, water-retaining structures, precast and prestressed elements, pumped concrete and any mix where high strength or flowing placement is required.
Why use it?
It cuts the water/cement ratio sharply to lift early and ultimate strength, or boosts workability to a flowing consistency without adding water — improving cohesion, reducing bleed and easing pumping and compaction.
How is it applied?
Dispensed into the mixing water or added to the freshly mixed concrete at the batching plant; never onto dry cement. Typical SNP-superplasticiser dosing is in the order of 0.5–2.0 L per 100 kg cementitious — confirm the project rate against the current SP418 TDS and trial mixes.
About Fosroc Conplast SP418
Fosroc Conplast SP418 is a high-range water-reducing admixture (superplasticiser) engineered for concrete that has to perform at the upper end of strength, durability or placeability. Chemically it is built on selected sulphonated naphthalene polymers (the SNP / SNF family) reinforced with other polymers, and it is supplied as a brown solution that disperses instantly the moment it meets the mixing water. Critically for Indian construction, where chloride-induced corrosion of reinforcement is a recurring durability problem, SP418 is chloride-free, which makes it suitable for reinforced, prestressed and post-tensioned concrete without contributing to the chloride load of the mix.
The admixture works by adsorbing onto cement particles and imposing a negative charge that disperses the flocculated grains. That dispersion frees up trapped water, so the same workability can be reached with far less water, or the same water content can be turned into a much higher slump. From this single mechanism flow the two ways contractors actually use SP418: as a water-reducer to drive down the w/c ratio for high-strength, dense, durable concrete; or as a flow agent to produce free-flowing, self-levelling-style concrete that places and compacts with minimal effort and labour. Compared with older sulphonated-melamine plasticisers, the naphthalene chemistry holds workability for longer, which matters on jobs with longer haul or placing times.
For specifiers and procurement teams in Delhi NCR and across India, SP418 sits in Fosroc’s well-known Conplast admixture range alongside products such as Conplast SP430 (a high-early-strength superplasticiser), Conplast SP432 and the everyday water-reducer Conplast WL. Space Arc Engineering, as an authorised Fosroc distributor and applicator, supplies SP418 with batching guidance, trial-mix support and TDS documentation so the grade can be specified and used correctly on site. Because exact dosage and physical values can vary by region and revision, the figures below are presented as the verified product type plus typical SNP-superplasticiser ranges — always cross-check against the live Fosroc TDS issued for your project.
The technical insight
The performance of an SNP superplasticiser like SP418 is governed by how it is added, not just how much. Adding it to the mixing water or, better, into already-wetted concrete after the cement has begun to hydrate gives markedly better dispersion than introducing it onto dry cement, where it can be absorbed before it can act. The water reduction achievable (commonly 12–20% for SNP-type high-range reducers) lets you target high characteristic strengths or a low w/c ratio for durability classes without a harsh, unplaceable mix. The trade-off is slump retention: naphthalene-based admixtures give a strong initial slump that falls back over roughly 30–60 minutes, so for long pumping distances or hot Indian site conditions, either redose at the pump, run trial mixes to fix the dosage, or consider a PCE-based or retarding-blend product where extended retention is essential.
Where it is used
- High-strength structural concrete for columns, cores and transfer beams in high-rise buildings
- Flowing concrete for heavily congested reinforcement, raft foundations and deep sections
- Pumped concrete where improved cohesion and reduced bleed aid pumpability over height and distance
- Water-retaining and durability-critical structures (tanks, basements, STPs) needing low w/c ratio
- Precast and prestressed elements requiring high early strength for faster demoulding and stressing
- Bridge decks, piers and infrastructure concrete where dense, low-permeability concrete is specified
- Ready-mix concrete (RMC) plant production of designed high-performance and self-compacting-leaning mixes
Key advantages
- Chloride-free — safe for reinforced, prestressed and post-tensioned concrete with no added chloride load
- Major water/cement ratio reduction enabling high-performance, high-strength concrete
- Produces free-flowing concrete that places and compacts faster with less labour and vibration
- Longer workability retention than ordinary sulphonated-melamine plasticisers
- Higher early-age strength without increasing cement content, supporting faster construction cycles
- Improved cohesion and particle dispersion that minimise segregation and bleeding
- Better pumpability for tall and long-distance placements
- Backed in India by Fosroc technical support and, via Space Arc, local stock and applicator guidance
Limitations & considerations
- Slump retention is time-limited (typically ~30–60 min); not ideal alone for very long haul/pumping without redosing or a retarder
- Overdosing can cause excessive retardation, segregation or bleeding — trial mixes are essential
- Performance depends on cement chemistry and fines; compatibility should be checked for each cement source
- Not an air-entrainer or waterproofing admixture — pair with the right product where freeze-thaw or integral waterproofing is needed
- Must be dispensed into mixing water/wet concrete, not onto dry cement, to disperse effectively
- Liquid admixture requires frost protection in storage and accurate dosing equipment at the plant
- Exact dosage, SG and standards must be confirmed against the current region-specific Fosroc TDS, not assumed
Selection & best practice
Always establish the optimum dosage by laboratory and site trial mixes using the actual cement, aggregates and fines for the job, rather than defaulting to a mid-range figure. Dispense SP418 into the mixing water or into the freshly mixed wet concrete — never onto dry cement — and keep dosing equipment calibrated. For high-strength work, fix the w/c ratio first and use SP418 to recover workability; for flowing concrete, hold the water constant and dose up to the slump target while watching for the onset of bleed or segregation. On hot days or long pumping runs, plan for slump loss (redose at the pump or combine with a compatible retarder). Store drums sealed, off the ground, out of direct sun and protected from frost, and use within shelf life. Confirm grade suitability and the exact dosage window against the current Fosroc TDS for your region before specifying.
Specifications
| Product type | High-range water-reducing admixture / superplasticiser (concrete) |
| Chemical base | Selected sulphonated naphthalene polymers (SNP/SNF) with supporting polymers |
| Chloride content | Chloride-free (suitable for reinforced & prestressed concrete) |
| Appearance | Brown liquid; disperses instantly in water |
| Primary functions | Water reduction / high-strength concrete and flowing (high-workability) concrete |
| Typical dosage (indicative, SNP family) | ~0.5–2.0 litres per 100 kg of cementitious material — confirm via TDS & trial mix |
| Typical specific gravity (indicative) | ~1.15–1.22 (verify against current SP418 TDS) |
| Typical water reduction (SNP type) | Approx. 12–20% depending on dosage and mix |
| Air entrainment | Does not entrain significant air at normal dosage |
| Relevant standards (admixture family) | Designed to meet high-range water-reducer requirements of IS 9103, ASTM C494 (Type F/G) and BS 5075 / EN 934-2 — confirm certification on the project TDS |
| Storage | Keep sealed, cool, dry and frost-protected; use within stated shelf life |
Industry use cases
High-Rise & Commercial Buildings
Used to achieve high characteristic strengths in columns, shear walls and transfer structures while keeping mixes placeable through congested rebar, reducing vibration and labour on each pour.
Ready-Mix Concrete (RMC)
Batched at the plant to produce designed high-performance and flowing concrete for supply across Delhi NCR projects, improving pumpability and cohesion during long deliveries.
Infrastructure & Bridges
Helps deliver dense, low-permeability, high-strength concrete for piers, decks and foundations where durability and reduced water ingress are specified.
Water-Retaining & Sewage Structures
Enables low w/c ratio concrete for tanks, basements and STP structures, improving impermeability and resistance to aggressive exposure — chloride-free chemistry protects the reinforcement.
Precast & Prestressed Yards
Boosts early-age strength without extra cement so elements can be demoulded and stressed sooner, raising mould turnover and production throughput.
Frequently asked questions
Is Fosroc Conplast SP418 a real product?
What is Conplast SP418 used for?
What is the recommended dosage of Conplast SP418?
Is Conplast SP418 safe for reinforced and prestressed concrete?
How does SP418 compare with Conplast SP430?
How do I buy Conplast SP418 in Delhi NCR or Pan-India?
How we position Fosroc Conplast SP418
Conplast SP418 belongs to Fosroc’s Conplast admixture range and is best understood alongside its siblings: Conplast SP430 (favoured where very high early strength is the goal), Conplast SP432 and the general-purpose water-reducer Conplast WL, plus integral waterproofing options such as Conplast X421IC for mixes that also need permeability control. Against the wider market, SP418’s SNP chemistry competes with naphthalene-based superplasticisers from Sika (e.g. Sikament-type products), MBS/Master Builders Solutions (MasterRheobuild and the MasterGlenium PCE line), Dr. Fixit (Pidiproof/Pidicrete admixtures) and STP Limited. Where extended slump retention or very high water reduction is critical, a modern polycarboxylate-ether (PCE) superplasticiser — such as Fosroc’s Auramix/Structuro range or MasterGlenium — may outperform a naphthalene product, so the selection should follow the strength, durability class and placing time the job demands rather than brand alone. As an authorised Fosroc distributor and applicator for Delhi NCR and Pan-India, Space Arc Engineering supplies SP418 with genuine product, current TDS data, trial-mix support and on-site applicator guidance, and can recommend the correct Conplast grade or a PCE alternative for your specific mix.
Related Concrete Admixtures products
Source Fosroc Conplast SP418 for your project
Authorised distribution, technical advice & professional application across Delhi NCR and Pan-India.