Fosroc Dekguard A Plus
Water-based acrylic anti-carbonation and weather-protective coating for reinforced concrete, conforming to BS EN 1504-2.
What is it?
A single-component, water-based acrylic pigmented protective coating, usually applied over a penetrating silane-siloxane primer, that shields atmospherically exposed reinforced concrete and masonry from carbonation and chloride attack.
Where is it used?
Atmospherically exposed RCC structures, columns, beams, soffits, facades, bridges, flyovers, chimneys, water-retaining structures (external faces) and coastal buildings, on both new and repaired concrete.
Why use it?
It forms a breathable barrier that blocks CO2, chloride ions, oxygen and rainwater that drive reinforcement corrosion, while letting water vapour escape, thereby extending the service life of concrete and giving a durable decorative finish.
How is it applied?
Surface is prepared and primed; two coats are then applied by brush, roller or airless spray at about 5.5 m2/litre/coat to achieve a minimum 150-micron dry film, with 6-8 hours between coats at 20 degrees C.
About Fosroc Dekguard A Plus
Fosroc Dekguard A Plus is an advanced single-component, water-based acrylic pigmented protective coating engineered to defend atmospherically exposed reinforced concrete and cementitious substrates against the two main drivers of premature deterioration in Indian conditions: atmospheric carbonation and chloride-ion ingress. As airborne carbon dioxide penetrates concrete, it lowers the pH of the cover zone and destroys the passive layer that normally protects embedded steel; once that passivity is lost, corrosion, cracking and spalling follow. Dekguard A Plus addresses this by laying down a continuous, pigmented film that acts as an excellent barrier to carbon dioxide, chloride ions, oxygen and liquid water, while remaining breathable enough to let water vapour migrate out of the structure rather than become trapped behind the coating. The product is normally specified as a two-part system: a penetrating silane-siloxane primer that consolidates and water-repels the surface, followed by the pigmented Dekguard A Plus topcoat. It is supplied ready for site use in white and a range of neutral and decorative shades, with BS 4800 and RAL colours available on request, so a single material delivers both long-term durability and architectural finish. The coating conforms to BS EN 1504-2, the European standard for surface protection systems for concrete, and is suitable under principles 1.3 (protection against ingress), 2.2 (moisture control) and 8.2 (increasing resistivity). For Space Arc Engineering’s clients in Delhi NCR and across India, that makes it a dependable choice for protecting new concrete from day one and for sealing repaired concrete after a Renderoc reinstatement, on everything from high-rise facades to coastal and industrial structures.
The technical insight
The performance of an anti-carbonation coating is governed by its carbon-dioxide diffusion resistance relative to its water-vapour permeability, not by film thickness alone. Dekguard A Plus is formulated to present a high resistance to CO2 (equivalent to a thick diffusion-equivalent air layer) while keeping a low resistance to water vapour, so the cover concrete can dry out while remaining protected. This balance is why it is classified under BS EN 1504-2: a true anti-carbonation coating must demonstrate a CO2 diffusion-equivalent air layer thickness above the EN 1062-6 threshold yet keep its water-vapour diffusion-equivalent air thickness low enough to be Class I (breathable). Achieving the rated performance on site depends almost entirely on building the specified dry film thickness of at least 150 microns over the full system; thin or pinholed films collapse the CO2 barrier disproportionately because carbonation resistance scales with film integrity. The silane-siloxane primer is the second technical lever: it penetrates and reacts within the pore structure to create a hydrophobic lining that reduces capillary water (and dissolved chloride) uptake before the acrylic topcoat even goes on, so the system attacks both the carbonation and the chloride pathway. Because the acrylic binder is water-based with very low VOC (around 4 g/L), it cures by coalescence and is sensitive to low temperature and high humidity during film formation, which is why application above 5 degrees C and above the dew point is critical to developing the dense, crack-free film the carbonation rating assumes.
Where it is used
- Anti-carbonation protection of new reinforced concrete facades, columns, beams and soffits
- Sealing and protecting concrete repaired with the Fosroc Renderoc reinstatement system
- Protection of bridges, flyovers, elevated road structures and parking structures from chloride and CO2
- Coating of chimneys, cooling-tower exteriors and other tall industrial RCC structures
- Weather-protective decorative finishing of building facades and external concrete and masonry
- Protection of structures in coastal and marine-influenced environments against chloride-laden air
- Refurbishment coating of ageing concrete structures showing early carbonation
Key advantages
- Excellent barrier to carbon dioxide, chloride ions, oxygen and liquid water
- Breathable film allows trapped water vapour to escape, preventing blistering and entrapment
- Conforms to BS EN 1504-2 (principles 1.3, 2.2 and 8.2) for concrete surface protection
- Water-based and very low VOC (around 4 g/L), with low odour and easy water clean-up
- Single-component topcoat, ready for immediate site use with no on-site mixing of base and hardener
- High resistance to long-term weathering, UV and rain across varied climatic conditions
- Available in white plus a range of decorative shades, with BS 4800 and RAL colours on request
- Applicable by brush, roller or spray, giving flexibility across complex structures
- Combined protective and decorative function reduces the number of products on a project
Limitations & considerations
- Being water-based, it must be applied above about 5 degrees C and above the dew point, and protected from rain until cured, which constrains monsoon and winter-night working
- Full anti-carbonation performance depends on achieving the specified minimum 150-micron dry film thickness; thin or pinholed application compromises the CO2 barrier
- Not a crack-bridging coating; on substrates with active or moving cracks, an elastomeric grade such as Dekguard Elastic is more appropriate
- Surface must be sound, clean and properly prepared; blowholes and pitting need a fairing coat (e.g. Renderoc FC) before coating
- It is a protective and decorative coating, not a structural repair material, so deteriorated concrete must first be reinstated
- Performance over the design life assumes correct primer use and adequate film build, so it is best applied by trained applicators
- Limited resistance to standing water, chemical immersion or heavy abrasion, as it is designed for atmospheric exposure
Selection & best practice
Specify and apply Dekguard A Plus as a complete system, not just a topcoat. Begin by ensuring the concrete is sound, clean, dry and free of laitance, curing compounds, oil and loose material; reinstate any deteriorated concrete with the appropriate Renderoc mortar and allow it to cure. Fill blowholes and surface pitting with a fairing coat such as Renderoc FC so the substrate is closed before coating. Apply the penetrating silane-siloxane primer (or the recommended site-diluted primer coat) to consolidate and water-repel the surface, then apply at least two coats of Dekguard A Plus by brush, roller or airless spray at roughly 5.5 m2 per litre per coat, allowing 6 to 8 hours between coats at 20 degrees C. Confirm a total dry film thickness of not less than 150 microns using a wet-film comb during application, since the carbonation rating depends on film build. Work only when the substrate and air temperature are above 5 degrees C and the surface is above the dew point, and protect freshly coated areas from rain until the film has formed. For best long-term results, use trained applicators, keep batch and colour records, and let Space Arc Engineering’s technical team validate the substrate condition and coverage before mobilising.
Specifications
| Product type | Single-component, water-based acrylic pigmented protective coating |
| System | Penetrating silane-siloxane primer + pigmented acrylic topcoat |
| Standard | BS EN 1504-2 (principles 1.3, 2.2 and 8.2) |
| Key protection | Barrier to CO2 (carbonation), chloride ions, oxygen and water; breathable to water vapour |
| Coverage | Approx. 5.5 m2 per litre per coat |
| Number of coats | 2 coats (minimum 3 on rough substrates) |
| Dry film thickness | Minimum 150 microns (total system) |
| Wet film thickness | Approx. 180 microns |
| Overcoat / drying time | Touch dry approx. 6 hours; recoat after 6-8 hours at 20 degrees C |
| Minimum application temperature | 5 degrees C (and above dew point) |
| VOC content | Approx. 4 g/L |
| Application method | Brush, roller or spray |
| Colours | White plus decorative shades; BS 4800 / RAL on request |
| Pack size | 10 litre |
Industry use cases
Infrastructure / Bridges
Anti-carbonation and anti-chloride protection of bridge piers, decks soffits and flyover columns exposed to traffic pollution and de-icing or coastal salts.
High-rise & Commercial Buildings
Combined protective and decorative coating on RCC facades, columns and beams to slow carbonation and give a durable, colour-stable finish.
Coastal & Marine Structures
Protection of buildings and structures in chloride-laden coastal air, where the silane-siloxane primer plus acrylic film reduces salt-driven reinforcement corrosion.
Industrial Plants
Coating of chimneys, cooling-tower exteriors and process-plant concrete to resist aggressive atmospheres and weathering.
Concrete Repair & Refurbishment
Final protective coat over Renderoc-reinstated concrete, sealing repairs and unifying appearance while preventing re-carbonation of the cover zone.
Parking & Multi-storey Structures
Atmospheric protection of exposed external faces, columns and facades of car parks against CO2 and airborne chlorides.
Frequently asked questions
What exactly is Fosroc Dekguard A Plus used for?
How much area does one litre of Dekguard A Plus cover?
Does Dekguard A Plus meet any recognised standard?
Do I need a primer, and which one?
How is it applied and in what conditions?
How does it compare to Dekguard S, Dekguard Elastic or competitor coatings?
How we position Fosroc Dekguard A Plus
Within Space Arc Engineering’s Fosroc protective-coatings range, Dekguard A Plus is the workhorse water-based anti-carbonation coating for atmospherically exposed concrete that does not have active cracking. It sits alongside the wider Dekguard family: Dekguard S, another acrylic protective and decorative coating in the same class; Dekguard Elastic, the crack-accommodating elastomeric grade for substrates that move or carry fine cracks; and impregnation or specialist grades such as Dekguard CP and Dekguard PU100 for specific exposure or trafficking needs. It is most powerful when paired with the Fosroc concrete-repair ecosystem: deteriorated concrete is reinstated with Renderoc mortars, blowholes are closed with a Renderoc FC fairing coat, embedded steel is treated with Nitozinc or Nitoprime primers, and Dekguard A Plus is then applied as the final protective and decorative layer to prevent re-carbonation of the repaired cover zone. Against the broader Indian market, credible alternatives that specifiers may evaluate include Sika’s Sikagard anti-carbonation coatings, MBS, Dr. Fixit and STP protective-coating systems. The honest position is that Dekguard A Plus is a well-proven, EN 1504-2-conformant choice with a strong CO2 and chloride barrier and good colour range, but it is not crack-bridging; where movement or visible cracking is expected, Dekguard Elastic or an equivalent elastomeric competitor product is the more appropriate specification. Space Arc Engineering, as an authorised Fosroc distributor and applicator serving Delhi NCR and Pan-India, can advise on the right grade, validate the substrate and supply the full repair-and-protect system rather than a coating in isolation.
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