About Fosroc Supercast Acrylate 200

Fosroc Supercast Acrylate 200 is a specialist waterproofing injection resin, not a conventional gun-grade or pour-grade joint sealant. It belongs to Fosroc’s Supercast range of joint and crack treatment products and is designed for situations where water has to be stopped inside a crack, behind a wall, through an injection hose, or within the ground itself rather than in an open, accessible movement joint.

The product is a three-component system. A methacrylate resin (component A1) is combined with an accelerator (component A2) to form the “A” side, while a catalyst (component B2) is diluted with water to form the “B” side. The two sides are pumped at a fixed ratio and meet at the point of injection, where an in-situ chemical reaction converts the thin, water-thin liquid into a soft, elastic gel. That gel is hydrophilic: it absorbs and desorbs water reversibly, swelling when moisture returns so that the seal effectively “self-tightens” against renewed water pressure instead of shrinking and failing.

Two characteristics make Acrylate 200 different from paste sealants and from polyurethane injection foams. First, its viscosity is close to that of water, so it travels into hairline cracks, capillaries and fine soil voids that thicker resins simply bridge over. Second, its reaction speed is adjustable on site through the catalyst dilution, letting the applicator set a gel time that suits the flow conditions — fast where there is running water, slower where deep penetration is needed.

Because the cured gel contains no isocyanates, Fosroc positions it as suitable for contact with potable water, and it offers chemical resistance against most organic and inorganic liquids found in soils and groundwater. When installed in conjunction with a re-injectable hose system such as Fosroc Predimax, treated joints can be re-injected later in the structure’s life — a meaningful advantage for tunnels, tanks and below-grade structures that must remain serviceable for decades.

The technical insight

The defining property of Supercast Acrylate 200 is that it is a hydrogel-forming injection resin, and its performance is governed by penetration rather than by movement accommodation. Conventional elastomeric joint sealants (polyurethane, polysulphide, silicone) are rated by a Movement Accommodation Factor — the percentage of joint width they can repeatedly stretch and compress without failure. Acrylate 200 has no meaningful MAF in that sense: it is not gunned into an open joint to flex with thermal movement. Instead it is injected as a low-viscosity liquid that gels inside the crack or surrounding ground, and its “elasticity” refers to the soft, rubbery gel’s ability to deform locally and to re-swell when re-wetted, not to accommodate structural joint cycling.

This is why the chemistry matters. A methacrylate gel with water-like viscosity behaves almost like the water it is displacing, so it migrates to the actual leak path and to the soil-structure interface, then sets. Compared with PU injection foams that expand aggressively and can over-pressurise a crack, the acrylate gel forms a coherent, low-modulus mass that fills voids and forms a flexible curtain behind the structure. The catalyst-controlled gel time — typically adjustable from a fast set for high-flow leaks to a slower set for deep saturation — is the principal site-control variable, and getting it right is what separates a durable seal from a flash-set blockage at the injection point.

Where it is used

• Sealing live and dormant cracks in concrete foundations, piles, diaphragm walls and tunnel segments (tubbings)
• Curtain or gel injection behind basement walls, retaining walls and below-grade slabs to form an external waterproof barrier
• Waterproofing construction joints via injection through re-injectable hose systems (e.g. Fosroc Predimax)
• Consolidation and waterproofing of sandy or silty, water-bearing soil ahead of or around tunnels, shafts and trenches
• Stopping active water ingress at cold joints and honeycomb defects in water-retaining structures
• Re-injection of previously treated joints to renew the seal during the service life of tanks and tunnels

Key advantages

• Water-like viscosity penetrates hairline cracks, capillaries and fine soil voids that paste sealants and thicker resins cannot reach
• Forms a flexible, hydrophilic gel that swells reversibly when re-wetted, helping the seal stay watertight under fluctuating water pressure
• Gel/reaction time is adjustable on site through the catalyst, giving control over fast leaks versus deep penetration
• Isocyanate-free chemistry — suitable for contact with potable water
• Good chemical resistance against most organic and inorganic liquids present in soils and groundwater
• Re-injectable when used with a hose system such as Fosroc Predimax, extending the serviceable life of the seal
• Treats both the structure (cracks and joints) and the surrounding ground (soil consolidation) with one material system

Limitations & considerations

• It is an injection resin, not a movement-joint sealant — it is unsuitable for open, accessible expansion or movement joints, which need products such as Nitoseal, Thioflex or Colpor
• Requires specialist two-component injection equipment, packers/hoses and trained applicators; it is not a hand-applied or gun-applied product
• Performance depends on correct gel-time selection and pump ratio control; incorrect catalyst dosing can cause premature set at the injection point or an incompletely cured gel
• The gel relies on a moist environment to retain its swollen, sealing state and is best suited to permanently or intermittently wet conditions rather than dry, exposed surfaces
• Component handling and mixing must follow the safety data sheet; the uncured methacrylate components require appropriate PPE and ventilation
• Not a substitute for sound concrete or proper joint design — large structural cracks and active movement still require structural assessment

Selection & best practice

Specifications

Industry use cases

How we position Fosroc Supercast Acrylate 200

Within Fosroc’s joint and crack-treatment portfolio, Supercast Acrylate 200 sits firmly on the injection/waterproofing side rather than the movement-joint side. It is the right choice when water must be stopped inside a crack, behind a structure or within the ground — closely related to Supercast Acrylate 100 (a similar hydrophilic methacrylate gel) and complementary to the Supercast Predimax re-injectable hose system. It should not be confused with Fosroc’s elastomeric movement-joint sealants: Nitoseal (polyurethane/polysulphide gun-grade sealants) for general expansion and construction joints, Thioflex 600 (two-part polysulphide) for civil and water-retaining joints, and Colpor 200 (cold-applied pouring grade) for trafficked horizontal joints in pavements and floors. For comparable acrylate/PU injection and movement-joint solutions from other manufacturers, credible alternatives in the Indian market include Sika’s injection resins and Sikaflex sealant range, MBCC/Master Builders Solutions MasterSeal and MasterInject systems, and STP (Shalimar Tar Products) sealants and waterstops. The correct specification depends on whether the problem is an active leak to be injected (where Acrylate 200 excels) or an open joint that must flex (where a rated elastomeric sealant is required) — a distinction Space Arc Engineering can help resolve on site.

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