About Sika Sikagard-550 W Elastic

Sikagard-550 W Elastic is Sika’s workhorse anti-carbonation coating for concrete that has to move without letting the surface tear open. It is a single-component, water-based system, so there is no mixing on site and no aromatic solvent to manage; you stir it, prime the substrate and apply. What sets it apart from an ordinary exterior emulsion is the acrylate chemistry, which stays flexible rather than turning brittle, so the film keeps stretching over hairline and thermal cracks instead of splitting along them. That elasticity holds even in cold conditions, which is why the coating is rated for crack-bridging performance right down to -20 C under EN 1062-7.

For engineers in India, the value is less about winter temperatures and more about durability in an aggressive, humid, coastal and industrial climate. Reinforced concrete fails from the inside out: carbon dioxide and chloride ions creep through the cover, the pore water turns acidic, the steel de-passivates and rust expands until the cover spalls. Sikagard-550 W Elastic attacks that chain at the surface. Its film is a strong diffusion barrier to CO2 yet remains permeable to water vapour, so the structure can still breathe and dry out. Applied over a suitable Sikagard primer, it forms part of a certified EN 1504-2 surface-protection system, making it a specification-grade choice for structures where a repair has to last decades, not seasons.

The technical insight

The coating works on two competing physics problems at once, and the acrylate binder is what lets it satisfy both. To protect steel, the film must be a dense barrier to carbon dioxide: at only ~160 microns dry, Sikagard-550 W Elastic delivers a CO2-equivalent air-layer thickness (SD,CO2) of around 51 m, comfortably clearing the 50 m benchmark that classifies a coating as genuinely anti-carbonation. That barrier is equivalent to putting roughly 50 metres of still air between the atmosphere and the concrete. Yet the same film must not trap moisture, or blistering and delamination follow. Here its water-vapour resistance is deliberately low, with an SD,H2O near 0.35 m at ~230 microns, so liquid is kept out while vapour passes freely and the slab stays dry. The third demand is movement. Because the polymer is plasto-elastic rather than rigid, it records roughly 120 percent elongation at break at room temperature and still around 70 percent at -20 C, which is what allows it to span live cracks and cyclic thermal movement without rupturing. Build the film thicker, to about 340 microns across two or three coats, and you unlock the full durability set, the top EN 1062-7 crack-bridging classes, adhesion after thermal cycling and long-term weathering resistance, rather than just the minimum anti-carbonation function.

Where it is used

• Anti-carbonation protection of exposed RCC facades, columns and soffits on high-rise and commercial buildings
• Elastic top coat over Sika repair and levelling mortars as the final layer of a concrete-repair system
• Protection of bridge piers, girders, flyovers and elevated corridors subject to thermal and traffic-induced movement
• Coating of multi-storey and basement car-park concrete exposed to de-icing salts and vehicular chlorides
• Coastal and marine-zone structures (outside the splash zone) needing a chloride and carbonation barrier
• Overcoating existing firmly bonded, adhesion-tested coatings during refurbishment without full removal
• Precast concrete panels and fibre-cement elements where a decorative, crack-tolerant finish is required
• Water-retaining and effluent structures where a breathable, tough external skin extends service life

Key advantages

• One-part and ready to use, no site mixing, no measuring of components and no pot-life pressure
• Bridges live and thermally cycling cracks, retaining elasticity even at temperatures as low as -20 C
• High CO2 diffusion resistance meaningfully slows carbonation and the onset of reinforcement corrosion
• Water-vapour permeable, so the concrete continues to breathe and dry rather than trapping moisture
• Water-based and free of toluene and aromatic solvents, with VOC below 40 g/l for safer site handling
• Certified to EN 1504-2 as a surface-protection product, supporting specification and audit requirements
• Applies by brush, roller or airless spray and is easily maintained later by simple overcoating
• Low tendency to pick up dirt, with very good resistance to weathering, ageing and UV over the long term

Limitations & considerations

• Not a standalone product; it needs a compatible Sikagard primer (552 W Aquaprimer or 551 S Elastic Primer) for reliable adhesion
• Achieving the full crack-bridging and durability performance requires building ~340 microns dry film across two to three coats, not a single thin pass
• Application demands dry conditions: no rain expected, relative humidity below 80 percent and substrate at least 3 C above dew point
• Not suitable for ozone or electrolysis water-treatment environments, or exposure to high chlorine concentrations that can cause chalking and discolouration
• Dark and intense colour shades may fade faster and can need an earlier refresher coat than lighter tones
• New concrete must be at least 28 days old and properly prepared; it will not mask a poorly cured or contaminated substrate

Selection & best practice

Specifications

Industry use cases

How we position Sika Sikagard-550 W Elastic

Sikagard-550 W Elastic is the elastic, crack-bridging tier of Sika’s surface-protection range. Where a substrate is sound and cracking is not a concern, the rigid anti-carbonation coating Sikagard-550 W IN (Sika India’s 10 kg/25 kg grade) is the more economical choice; step up to 550 W Elastic when the concrete moves. It is always specified with a Sika primer, either Sikagard-552 W Aquaprimer or Sikagard-551 S Elastic Primer, and pairs naturally with Sika MonoTop repair mortars and Sikagard-720 EpoCem levelling mortar to form a complete EN 1504 repair-and-protect system. Space Arc also supplies genuine equivalents from other brands we distribute, so specifiers can match brand approvals on a given project. If a Fosroc-approved specification is required, the closest counterpart is Dekguard Elastic.

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