About Fosroc Auramix 402

Fosroc Auramix 402 is a high-range water-reducing concrete admixture built on polycarboxylic-ether (PCE) chemistry, sitting within Fosroc’s premium Auramix 400 series of superplasticisers. Unlike older naphthalene- or melamine-based superplasticisers, PCE molecules work by steric (physical) dispersion of cement grains rather than purely electrostatic repulsion, which is why Auramix 402 can unlock very high water reduction while holding workability for extended periods. For Indian contractors and ready-mix producers, that translates into concrete that flows and self-compacts at a low water-cement ratio, yet stays placeable long enough to survive transit and pumping in hot site conditions. Fosroc positions Auramix 402 specifically for self-compacting concrete, pumped concrete and mixes that demand long workability retention, and confirms it is compatible with all common supplementary cementitious materials (SCMs) such as GGBFS, fly ash and microsilica/silica fume. Its deliberately low viscosity is a defining feature: low-viscosity PCE admixtures reduce pumping pressure and make it practical to place concrete on the upper floors of high-rise structures without segregation. The end result is a denser, more durable matrix with lower permeability, reduced shrinkage and creep, improved bond to reinforcing and prestressing steel, and better resistance to carbonation and aggressive environments — the durability gains that follow naturally from a well-dispersed, low-water mix. As an authorised Fosroc distributor and applicator serving Delhi NCR and pan-India, Space Arc Engineering supplies Auramix 402 for batching plants, infrastructure contractors and structural projects, and supports site teams with trial-mix guidance and compatibility checks against project cement and SCMs.

The technical insight

The performance of Auramix 402 comes from its comb-shaped PCE polymer: a charged backbone anchors onto cement particles while long polyethylene-oxide side chains project outward, holding grains apart by steric hindrance. Because dispersion does not rely solely on surface charge, water demand drops sharply (high-range PCE admixtures routinely achieve water reductions well above 20-25%), and the side chains release their dispersing effect gradually, which is what gives the long slump/slump-flow retention without a heavy retarding dose. At a low water-cement ratio this produces a tight, low-capillary-porosity microstructure — the root cause of the lower permeability, higher early and ultimate strength, and improved durability Fosroc cites. The low-viscosity formulation matters hydraulically: pumping pressure rises steeply with paste viscosity, so a low-viscosity SCC-grade admixture is what makes tall-building placement feasible. One practical caution that follows from PCE chemistry: PCE admixtures are markedly more dosage-sensitive than older sulphonated types — a small overdose can cause bleeding, segregation or set retardation, so dosage must be dialled in by trial mix against the actual cement, SCM blend and aggregate moisture rather than assumed.

Where it is used

• Self-compacting concrete (SCC) for heavily reinforced sections, columns and architectural finishes where vibration is impractical
• High-rise pumped concrete requiring low pumping pressure and stable flow to upper floors
• High-performance and high-strength structural concrete at low water-cement ratios
• Ready-mix concrete needing extended workability retention during long transit or hot-weather placement
• Blended-cement concretes using GGBFS, fly ash or microsilica/silica fume
• Durable concrete for marine, coastal and aggressive-exposure structures where low permeability and carbonation resistance are required

Key advantages

• High water reduction enabling low water-cement ratios and higher compressive strength
• Long workability / slump-flow retention without excessive retardation
• Low viscosity for easier, lower-pressure pumping to higher floors
• Fully compatible with GGBFS, fly ash and microsilica as cement replacements
• Produces dense, low-permeability concrete with improved durability and carbonation resistance
• Reduced drying shrinkage and creep, and improved bond to reinforcing and prestressing steel
• Chloride-free formulation, safe for reinforced and prestressed concrete
• Complies with IS 9103 and ASTM C494 (Type G high-range water-reducing/retarding family), aiding specification compliance

Limitations & considerations

• Highly dosage-sensitive PCE chemistry — overdosing can cause bleeding, segregation or extended set; trial mixes are essential
• Performance varies with cement chemistry and SCM source, so site compatibility testing is needed before bulk use
• Not a substitute for correct mix design — poorly graded aggregate or excess water will still segregate an SCC mix
• Slump-flow retention and set behaviour shift with ambient temperature; hot-weather and cold-weather dosing differ
• Cross-compatibility with admixtures from other suppliers (or even other PCE generations) is not guaranteed and should be verified
• As a liquid admixture it must be protected from freezing and prolonged high temperatures during storage

Selection & best practice

Specifications

Industry use cases

How we position Fosroc Auramix 402

Auramix 402 belongs to Fosroc’s premium Auramix 400 series of PCE superplasticisers and is closely related to Auramix 400, 401, 403 and 450 — choose between them based on the rheology, retention and strength profile your mix design needs, and Space Arc can help match the right variant. For mixes needing built-in retardation, Fosroc’s Auramix 300 / 300 Plus retarding superplasticisers are the natural companions, while the older Conplast superplasticiser range (e.g. Conplast SP430/SP500) remains a cost option for conventional concrete where PCE-level performance is not required. Against the wider Indian market, credible alternatives include Sika’s ViscoCrete PCE superplasticiser range, BASF/Master Builders Solutions MasterGlenium, and the admixture lines from Dr. Fixit (Pidilite) and STP (Sika/STP) — though admixtures from different suppliers should not be mixed, and any switch should be re-validated by trial mix against the project cement and SCMs. Within this field Auramix 402 is positioned as a low-viscosity, pumpable, high-retention PCE option well suited to SCC and high-rise concrete; as an authorised Fosroc distributor and applicator across Delhi NCR and pan-India, Space Arc Engineering supplies it with trial-mix and compatibility support so specifiers get the documented Fosroc performance with local technical backup.

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