Why protect the concrete surface?
Most damage to reinforced concrete starts at the surface: this is where water, carbon dioxide, chlorides and sulphates enter the concrete. Surface protection slows these processes down and extends the service life of both new and repaired structures — without it, carbonation and chlorides go on doing their work in the areas next to the repair. This is especially important for bridges, flyovers, car parks, cooling towers, facades, hydraulic and underground structures.
EN 1504-2 identifies three methods of surface protection: hydrophobic impregnation, impregnation and coating. Under EN 1504-9, impregnations and coatings primarily serve protection against ingress, moisture control and increasing the resistivity of the concrete (principles 1, 2 and 8), while special coatings also provide physical and chemical resistance (principles 5 and 6).
Hydrophobic impregnations
Products based on silanes and siloxanes soak into the pores of the concrete and make the pore walls water-repellent. No film forms on the surface: the concrete looks almost the same as before and continues to “breathe”, but capillary absorption — and with it the ingress of dissolved salts — drops sharply, the concrete becomes drier and its electrical resistivity increases. This is one of the most effective measures against chlorides and freeze–thaw in the presence of salts.
- Penetration depth. The main indicator of impregnation quality. EN 1504-2 divides impregnations into classes by penetration depth; the highest, class II, corresponds to 10 mm or more. The actual depth depends on the concrete and the application rate, so it is confirmed on trial areas; the Sikagard-705 L data sheet, for example, recommends achieving at least 5 mm for marine structures and corrosion protection.
- Liquid or cream. Liquid silanes are applied in several passes; cream-like thixotropic products do not run off vertical and overhead surfaces and allow the required dose to be applied in one or two passes.
- Limitations. Impregnations are intended for concrete that is not in permanent contact with water and are not a substitute for waterproofing; wide cracks are repaired before treatment — the data sheets state what crack width the impregnation can still bridge and at what application rate.
Examples in this guide: Sikagard-705 L, Sikagard-706 Thixo.
Protective coatings
Anti-carbonation coatings
Thin acrylic or methacrylate films with a high resistance to carbon dioxide diffusion. Their protective capacity is expressed as the equivalent air layer thickness for CO₂ — Sd CO₂; technical data sheets quote a requirement of at least 50 m for a protective coating. At the same time, the coating must let water vapour through so that moisture can escape from the concrete: for vapour-permeable coatings, Sd H₂O must be no more than 5 m. Both values depend on the film thickness, so the manufacturer specifies a minimum and a maximum thickness. Examples: Sikagard-680 S Betoncolor, Fosroc Dekguard S.
Elastic crack-bridging coatings
Plasto-elastic coatings bridge hairline and shrinkage cracks that continue to “breathe” with temperature and load, including at sub-zero temperatures. The crack-bridging class is stated in the data sheet together with the number of coats and the test temperature. They are used on facades, bridges and structures at risk of cracking. Examples: Sikagard-550 W Elastic, Fosroc Dekguard E2000, Elastocolor Paint made by Mapei.
Chemical-resistant coatings and linings
For bunds, channels, floors and tanks exposed to chemicals, epoxy, novolac and vinyl ester systems are used — they are covered in the “Chemical protection” section. We confirm resistance to a specific medium by our questionnaire: substance, concentration, temperature and regime. Protective coatings for floors are in the “Resin flooring” section.
How to choose protection
- The main aggressive agent. Chlorides and freeze–thaw with salts — hydrophobic impregnation, sometimes combined with a coating. Carbonation — an anti-carbonation coating. Cracks — an elastic coating. Chemical media — a chemical-resistant system.
- Local conditions. In Central Asia, concrete often has to cope with saline soils and groundwater, salt-laden dust, sharp temperature swings, intense sunshine and winter freezing. Below-ground and plinth sections, bridge piers, channels and canals need protection against salts; exposed structures against ultraviolet light and carbonation.
- Appearance. An impregnation preserves the look of the concrete, a clear sealer brings out its texture, and a pigmented coating evens out the colour of repaired areas.
- Moisture and age of the substrate. Impregnations need dry, absorbent concrete; most coatings need concrete at least 28 days old, unless the manufacturer specifies otherwise.
- Maintenance. Coatings are renewed over time; with many systems, a maintenance coat is applied without primer to a well-cleaned surface.
In Uzbekistan, requirements for the corrosion protection of building structures are set by ShNK 2.03.11-24; the European EN 1504-2 performance values are convenient for comparing materials, but the final requirements are set by the design.
Procedure
- Preparation: mechanical cleaning — by abrasive blasting, high-pressure water or steam — back to sound concrete free of laitance, dirt, oils, efflorescence, moss and old loose coatings.
- Repair and pore filling: spalls are reinstated with repair mortars, and blowholes and pores are filled with levelling compounds — see the “Levelling and finishing compounds” section.
- Old coatings: adhesion is checked with a pull-off test and compatibility on a trial area; weak coatings are removed completely.
- Primer as per the manufacturer’s system — depending on the absorbency of the substrate and the type of old coating.
- Main coats: with wet film thickness checked by comb gauge and consumption monitored for each work area; the overcoating intervals, temperature, air humidity and dew point are observed.
- Protection of the fresh coat from rain — for the periods given in the data sheet.
Common mistakes
- Impregnating damp concrete — the silane does not penetrate to the required depth.
- Applying a coating “by eye” without checking the thickness: a thin film does not achieve the required Sd CO₂, while one that is too thick stops letting vapour through.
- Coating over blowholes — blisters and thin spots; over dust and laitance — delamination.
- A rigid coating on a structure with moving cracks.
- An elastic facade coating on horizontal surfaces where water ponds, or in permanent contact with water — manufacturers exclude such conditions.
- Painting when rain is expected, at high air humidity or over condensation.
Materials in the catalogue
- Sikagard-705 L — Sika — class II silane hydrophobic impregnation protecting concrete against chlorides and moisture.
- Sikagard-706 Thixo — Sika — thixotropic class II silane impregnation cream for vertical and overhead concrete.
- Sikagard-550 W Elastic — Sika — elastic crack-bridging acrylic coating protecting concrete against carbonation.
- Sikagard-680 S Betoncolor — Sika — solvent-borne methacrylic coating protecting concrete against carbonation and weathering.
- Fosroc Dekguard S — Fosroc — solvent-based acrylic anti-carbonation coating protecting concrete and masonry.
- Fosroc Dekguard E2000 — Fosroc — water-based crack-accommodating elastomeric coating for protecting reinforced concrete.
- Elastocolor Paint — Mapei — crack-bridging elastomeric acrylic paint protecting concrete against carbonation.
- PenePoxy 2K — Penetron — two-component epoxy chemical-resistant concrete coating and tape adhesive.
- Colorite Beton — Mapei — semi-transparent acrylic paint protecting concrete from carbonation, keeping its texture.
- Mapecoat I 24 — Mapei — epoxy paint protecting concrete against acids, alkalis and petroleum products.
- Antipluviol S — Mapei — colourless siloxane water-repellent impregnation for concrete, render, brick and stone.
- Planiseal WR 40 — Mapei — water-based silane (40 %) hydrophobic impregnation for reinforced concrete.
- Planiseal WR 100 — Mapei — pure-silane water repellent for bridges, piles and marine structures, cuts chloride ingress.
- Duresil EB — Mapei — hydrocarbon-resin modified epoxy paint protecting concrete and steel from acids and sewage.
This list is not exhaustive. The final choice is made on the basis of the manufacturer’s documents and the project requirements.
Frequently asked questions
Which is better — an impregnation or a coating?
They are different tools. An impregnation reduces water absorption and chloride ingress while preserving the look of the concrete. For protection against carbonation, coatings with a specified resistance to CO₂ diffusion are used, and they also even out the colour. The two are often combined: a hydrophobic impregnation serves as a water-repellent primer under the coating.
Can concrete be painted with facade paint?
Ordinary facade paint does not necessarily protect concrete: its resistance to CO₂ diffusion may be insufficient and its adhesion untested. To protect reinforced concrete, coatings with performance values to EN 1504-2 are chosen.
How often should protection be renewed?
It depends on the material, the environment and the exposure to the sun. The condition of the coating is checked during scheduled inspections; dark colours fade faster and may need a maintenance coat sooner.
Does new concrete need protection?
If the structure will be exposed to an aggressive environment — salts, freeze–thaw cycles, chemicals — it pays to provide surface protection from the outset rather than repair the concrete a few years later.
We will select an impregnation or protective coating for your concrete — call us or message us on WhatsApp/Telegram: +998 94 094 52 27.