About Fosroc Auramix 700SR

Fosroc Auramix 700SR is a member of Fosroc’s Auramix SR family of slump-retaining superplasticisers, engineered for the ready-mixed concrete industry. It is built on a blend of polycarboxylate (PCE) polymers that are specially formulated to delay their absorption onto the cement particles. This controlled, time-released dispersion is what gives the admixture its defining characteristic: the concrete stays fluid and placeable for a prolonged window after batching, rather than stiffening rapidly during transit. Critically, this retention is achieved without classic sugar/lignosulphonate-style set retardation, so early strength development is not sacrificed. Within the Fosroc Auramix SR superplasticiser range, the 700SR sits below the higher-retention Auramix 740SR (which targets up to roughly 4 hours of retention) and alongside other SR-coded grades such as Auramix 420SR, giving the specifier a ladder of retention levels to match haul time, ambient temperature and slump class. For contractors and ready-mix producers in Delhi NCR and across India, this matters most where concrete is batched at a central plant and trucked through traffic to high-rise, infrastructure or tunnel sites, or pumped to significant heights. A conventional plasticiser would lose slump on that journey, forcing site re-tempering with water (which quietly destroys the design strength and durability). Auramix 700SR is positioned to protect the as-designed mix from plant to placement. Being chloride-free, it is suitable for reinforced and prestressed concrete where embedded steel must be protected against corrosion, and it is compatible with all common Portland cements and with high-replacement cement-replacement materials such as GGBS, PFA (fly ash) and micro-silica that dominate modern low-carbon Indian concrete. As an authorised Fosroc distributor and applicator, Space Arc Engineering supplies Auramix 700SR with technical back-up on dosage trials and mix optimisation.

The technical insight

The functional chemistry here is steric (physical) dispersion, not just the electrostatic repulsion that older sulphonated naphthalene/melamine (SNF/SMF) superplasticisers rely on. A polycarboxylate-ether molecule has a charged backbone that anchors to the cement grain and long side chains (the ‘comb’ or ‘graft’ structure) that project outward; those side chains physically keep adjacent cement particles apart, freeing trapped water and slashing the water demand for a given workability. The ‘slump-retaining’ behaviour is engineered into the molecular design and polymer blend: a portion of the polycarboxylate is formulated to adsorb gradually onto cement and onto the fresh hydration surfaces that keep forming as the mix ages, so dispersing action is continuously topped up over time rather than spent in the first few minutes. That is why an SR-grade can hold slump for hours yet still set and gain strength on schedule. Practically, dose Auramix 700SR with the bulk of the mixing water (delayed addition gives better efficiency than adding it to dry materials or to the first water), and lock the dosage with trial mixes on the actual site cement and aggregates, because PCE response is sensitive to the cement’s C3A content, fineness, sulphate balance and the supplementary cementitious materials in the blend. Overdosing does not improve performance; in PCE superplasticisers it typically shows up as segregation, excessive bleeding and a sticky or unstable mix, so the dispenser calibration and the upper dose limit matter.

Where it is used

• Ready-mixed concrete batched centrally and delivered over long distances or through heavy traffic where slump must be retained in transit
• Self-compacting concrete (SCC) and high-workability flowing concrete that must fill congested reinforcement without vibration
• High-rise and pumped concrete where the mix must stay fluid up the pump line and at the point of discharge
• High-strength / low water-to-cement ratio concrete for columns, transfer girders and structural elements
• Concrete using high replacement levels of GGBS, PFA (fly ash) or micro-silica for durability and lower embodied carbon
• Reinforced and prestressed concrete requiring a chloride-free admixture to protect embedded steel
• Infrastructure pours (bridges, metro, tunnels, water-retaining structures) where consistent placement over a long pour window is needed

Key advantages

• Extended slump / workability retention so concrete arrives essentially as batched, reducing site re-tempering with water
• High-range water reduction enabling lower w/c ratio, higher strength and improved durability
• No set retardation and excellent early (24-hour) strength development despite the retention
• Chloride-free, making it safe for concrete with embedded and prestressed steel
• Compatible with all Portland cements and with GGBS, PFA and micro-silica blends
• Produces low-viscosity, easily pumpable and self-compacting mixes with good rheology
• Robust, consistent performance across different cement sources and slump classes
• Water-based and non-flammable, simplifying plant storage and handling

Limitations & considerations

• ‘SR’ here means Slump Retention, NOT sulphate resistance – it does not make concrete chemically sulphate-resistant; that requires the correct cement type and mix design
• Optimum dosage must be confirmed by trial mixes on actual site materials; PCE response varies with cement chemistry and SCMs
• Overdosing causes segregation and excessive bleeding rather than better performance
• Should be dispensed accurately at the plant via a calibrated dispenser; it is not a hand-added or on-site top-up product
• Must not be pre-mixed with other admixtures before addition to the concrete
• Performance and retention are temperature-sensitive; very hot weather can shorten the effective retention window
• Like all PCE superplasticisers, it can show cross-sensitivity with certain cements/clays in aggregates, occasionally needing a different SR grade or sacrificial dose

Selection & best practice

Specifications

Industry use cases

How we position Fosroc Auramix 700SR

Within Fosroc’s own catalogue, Auramix 700SR belongs to the slump-retaining PCE family alongside Auramix 740SR (the higher-retention grade for the longest hauls and SCC) and Auramix 420SR, sitting above the standard Auramix superplasticisers such as Auramix 200, 300/300 Plus, 400 and 500 that prioritise water reduction over extended retention. For workability retention combined with a built-in set control on hot-weather or very long pours, it pairs conceptually with retarding water-reducers like Conplast RP264, and on the same project it commonly works alongside Fosroc curing and surface products (e.g. Concure curing compounds) and repair systems (Renderoc/Nitomortar) – never pre-mixed, but part of the same concrete package. Against the wider Indian market, credible alternatives in the slump-retaining/high-range PCE category include Sika ViscoCrete and Sika Plastiment grades, BASF/Master Builders Solutions MasterGlenium and MasterEase, and Chryso/CICO/Dr. Fixit (Pidilite) PCE superplasticisers; for retarders and conventional plasticisers, products from STP and Dr. Fixit also compete. Fosroc’s positioning for 700SR is consistency ‘as batched at the plant, so on site’ across varied cements and high SCM replacement – the practical decision for a specifier is matching the SR retention level to haul time, temperature and slump class, which is where Space Arc Engineering, as an authorised Fosroc distributor and applicator in Delhi NCR and pan-India, adds trial-mix and dosage support. (Note: the 700SR-specific datasheet figures should be confirmed against the current Fosroc India TDS; family values here are drawn from the Auramix SR range, with the directly comparable Auramix 740SR TDS as the verified reference.)

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