Frequently Asked Questions

Does Dekguard W perform as well as the solvent-based Dekguard S for anti-carbonation protection of concrete facades?

Yes — for the primary function of anti-carbonation protection, both Dekguard S and Dekguard W provide equivalent performance in terms of CO2 diffusion resistance, crack-bridging capability, UV resistance, and vapour permeability. The equivalent air layer thickness for CO2 diffusion resistance exceeds 100 metres for both products applied at the specified minimum dry film thickness of 200 to 250 microns, which represents highly effective anti-carbonation protection well above the threshold needed for concrete protection in typical Indian urban pollution conditions. The main practical difference is that Dekguard W (waterborne) has a minimum application temperature of approximately 8 to 10 degrees Celsius, below which the waterborne acrylic dispersion does not film-form correctly — in winter on concrete bridge projects in North India (Delhi, Agra, Lucknow) where night temperatures fall below 10 degrees Celsius from December to February, application must be timed to the warmest part of the day or Dekguard S (solvent-based, with lower minimum application temperature) should be used instead. In Mumbai, Chennai, and other South Indian locations where temperatures rarely fall below 15 degrees Celsius, this distinction is immaterial and Dekguard W is equally practical to Dekguard S throughout the year.

Can Dekguard W be applied to a new concrete building facade immediately after curing and formwork removal?

Dekguard W should not be applied to freshly struck concrete that has been exposed within the previous 28 days and is still at early curing age. New concrete releases significant moisture vapour as it continues to hydrate and dry out over the first weeks and months after casting, and the moisture content of very new concrete is high. Applying Dekguard W to very new concrete before sufficient carbonation age traps the high moisture content behind the coating, which can cause blistering and loss of adhesion of the elastomeric film as the trapped moisture vapour pressure builds during warm weather. The recommended minimum age for application of Dekguard W to new concrete is 28 days (6 weeks or more is better), at which point the initial rapid moisture release has slowed significantly and the concrete surface moisture content is within the acceptable range for waterborne coating application. A damp meter or relative humidity probe test should be used to confirm the concrete surface is at or below 75 per cent relative humidity before Dekguard W is applied — if above this level, further drying time is required before coating.

What primer should be used under Dekguard W and is a primer always needed before application to concrete?

For application on sound, well-prepared concrete with good surface porosity (typically concrete that has been lightly ground or etched to open the surface pores), a primer coat using Nitoprime 25 (water-based, low-viscosity primer) is recommended before Dekguard W. The Nitoprime primer penetrates the concrete surface pores, consolidates any fine surface powder or laitance, improves adhesion of the elastomeric topcoat to the concrete, and reduces the suction of highly porous or variable-porosity concrete substrates that would otherwise cause uneven absorption of the first Dekguard W coat. On very dense, smooth, or form-finished concrete with low porosity (such as high-quality precast panels), a light mechanical abrasion (grinding or medium-grit sanding) to open the surface combined with the Nitoprime primer gives the best adhesion of the Dekguard W system. The primer is not optional where the concrete has been contaminated with curing compound, release agent, or any other surface treatment that could impair adhesion — all such contamination must be removed before priming. The complete system (primer + 2 coats Dekguard W) is the basis of the Fosroc guarantee for the anti-carbonation performance of the system.