About Fosroc Concure WB309

Fosroc Concure WB309 is a ready-to-use, water-based concrete curing compound used to retain the mix water inside freshly placed concrete during the critical first days of hydration. Chemically it is a low-viscosity wax emulsion that carries a special alkali-reactive breaking system. When the white liquid is sprayed onto a green concrete surface, the alkalinity of the cement triggers the emulsion to “break”, instantly forming a continuous, non-penetrating coating. As the water phase evaporates this film clears and bonds tightly to the surface, leaving a moisture barrier that holds back evaporation until the concrete has gained enough early strength.

In the Indian context this matters enormously. Across the plains of Delhi NCR, Rajasthan, Gujarat and much of the country, summer site conditions combine 38–45°C ambient temperatures, low relative humidity and hot drying winds — exactly the conditions that pull water out of a slab faster than bleed water can replace it. The result is plastic shrinkage cracking, soft dusting surfaces and concrete that never reaches its design strength because hydration stalled early. Traditional remedies such as ponding, wet hessian and continuous hosing are labour-heavy, consume scarce water and are almost impossible to maintain uniformly on a 5,000 m² industrial floor or a kilometre of pavement. Concure WB309 replaces that effort with one spray pass, giving consistent, measurable moisture retention across the whole pour.

Because it is water-based, Concure WB309 is non-flammable and low-odour, which makes it far safer to use in enclosed areas, basements and occupied industrial buildings than older solvent/resin-based curing compounds. The clear grade leaves no permanent stain, while the white-pigmented grade reflects sunlight to keep the slab cooler and gives an instant visual check that every square metre has been coated — a genuine quality-assurance benefit for site engineers and third-party inspectors. Space Arc Engineering supplies Concure WB309 as an authorised Fosroc distributor with batch documentation, technical support and pan-India logistics from our Delhi NCR base.

The technical insight

The performance of any membrane-forming curing compound is judged by how little water the concrete loses through it, and Concure WB309 is engineered to meet the recognised benchmarks. Tested to BS 7542 it delivers a curing efficiency index of 75% or greater, and it complies with ASTM C309 and AASHTO M148 as a Type 1 (clear/translucent) curing compound. Independent water-loss testing to ASTM C156 shows moisture loss held below 0.55 kg/m² over the test period — comfortably inside the limit that defines an effective curing membrane.

The chemistry behind this is the alkali-reactive emulsion-breaking system. Unlike a solvent-borne resin that relies on solvent flash-off to form a film, the WB309 wax emulsion is destabilised by the high-pH cement paste itself. This means the film forms reliably on a damp, freshly finished surface — the exact moment curing protection is needed — rather than requiring the surface to be touch-dry first. Timing is the key technical discipline: the compound must be applied as soon as the surface sheen of bleed water has disappeared but while the concrete is still green. Apply too early, over standing bleed water, and the emulsion is diluted and the film is compromised; apply too late, after evaporation has already started, and shrinkage cracking may already be underway. The white grade additionally carries a titanium-bearing pigment giving high surface reflectance (typically >60%), which lowers peak slab temperature under direct sun and reduces thermal-gradient cracking in mass pours.

Where it is used

• Curing of large-area industrial and warehouse floor slabs, including power-floated and vacuum-dewatered floors
• Highway, expressway and rural-road concrete pavements (PQC) and runway/taxiway/apron slabs at airports
• Bridge decks, flyover slabs and other exposed structural RCC where wet curing is impractical
• Raft foundations, ground-bearing slabs and large pour-volume civil structures
• Canal linings, reservoir slabs, water-retaining structures and irrigation works
• Precast concrete yards and segment-casting facilities needing fast cycle times
• RCC roof slabs and podium decks in commercial and residential construction
• Concrete in hot, dry or windy conditions where rapid surface evaporation risks plastic shrinkage cracking

Key advantages

• Delivers 75%+ curing efficiency to BS 7542 and complies with ASTM C309 / AASHTO M148 Type 1
• Single spray application replaces continuous ponding, hessian and hosing — major labour and time savings
• Conserves water, a critical advantage on large pours and in water-scarce regions of India
• Water-based, non-flammable and low-odour — safe for enclosed, basement and occupied-building use
• Reduces plastic-shrinkage and drying cracking, dusting and soft surfaces for more durable concrete
• White grade gives instant visual confirmation of full coverage, aiding site QA and inspection
• White grade reflects solar heat, lowering peak slab temperature and thermal cracking risk
• Economical coverage of 3.5–5.0 m²/litre keeps in-place curing cost low on big areas

Limitations & considerations

• Forms a wax-based film that can impair adhesion of subsequently applied toppings, coatings, screeds, tiles, render or membranes — the residual film must be mechanically removed (grinding/shot-blasting) or a removable-type curing aid used where bonding is required
• Timing-sensitive: must be applied after bleed-water sheen disappears but while concrete is green; misapplication reduces effectiveness
• Not a substitute for proper mix design, placing and finishing — it controls evaporative water loss only, not bleed or thermal issues in mass concrete
• Single-coat membrane is not intended as a permanent protective, decorative or chemical-resistant coating
• White pigment can leave temporary surface whitening; clear grade preferred where final appearance matters
• Performance depends on uniform, unbroken film — under-application, dilution by rain, or mechanical damage compromises the moisture barrier
• Shelf life and storage are temperature-sensitive; product must be protected from freezing and excessive heat

Selection & best practice

Specifications

Industry use cases

How we position Fosroc Concure WB309

Concure WB309 is Fosroc’s general-purpose, permanent-film water-based curing compound — the workhorse choice for large slabs and pavements where wet curing is impractical and where no bonded finish will follow. Within the Fosroc range, choose Concure WB White or Concure WB Clear where you need broadly the same wax-emulsion performance in a specific finish, and consider a removable/degradable curing aid or simply wet curing on areas that must later receive screeds, toppings, tiles or coatings, since the WB309 wax film otherwise has to be ground off. For pre-finished or critical zones, pair the curing strategy with Fosroc surface treatments and floor systems (e.g. Nitoflor hardeners and toppings). Against the wider Indian market, Concure WB309 competes with Sika Antisol / Sika curing compounds, MYK / MBS curing membranes, Dr. Fixit Pidicure-type curing compounds and STP curing aids — all ASTM C309-class products; the practical selection usually comes down to verified efficiency data, grade availability (clear vs white), film removability for follow-on finishes, and reliable supply with batch documentation. As an authorised Fosroc distributor in Delhi NCR serving pan-India, Space Arc Engineering supplies genuine Concure WB309 with technical guidance on grade choice, coverage and follow-on compatibility so the right curing compound is matched to each pour.

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