Concrete sealer vs silicate-based impregnates. What to choose? How to avoid stains on concrete floors?


Polished concrete floor with visible signs of wear. If polyurethane varnish was used for concrete, the floor would be less damaged.

Polished concrete floor with visible signs of wear. If polyurethane varnish was used for concrete, the floor would be less damaged.

Concrete gains ground as decorative material. It is used both outdoors and indoors. Polished concrete floors, concrete tiles, furniture, window sills and concrete countertops are extremely popular today. Freshly polished or demoulded concrete is beautiful, smooth and flawless. Unfortunately, without adequate protection,  stains quickly appear on it.


Concrete protection

Because of its porosity, concrete is an absorbent material. Due to the penetration of moisture, dirt, stains or discoloration may appear on its surface. There are two groups of products for concrete protection:

  • penetrating agents having water-repellent properties
  • coating sealers protecting against water and dirt absorption


Penetrating agents

Penetrating agents give the surfaces water repelling properties (hydrophobicity). They prevent water from penetrating into the concrete structure. It looks like pearly drops of water appear on the newly impregnated concrete surface, which does not soak into the concrete, but almost bounces off it. For someone dealing with this material for the first time  it is really impressive.

The effect of hydrophobicity in this type of impregnation works very well on vertical surfaces (slabs or concrete walls), but unfortunately on floors this effect disappears very quickly. Just walk a few times over this type of surface and the effect of repelling water through the floor immediately goes out. For this reason, investors are often strongly disappointed, observing that the impregnated floor after a dozen or so days or weeks absorbs virtually anything.


Why are impregnates based on lithium silicate or potassium silicate not the best solution for new floors?

In theory, impregnates containing lithium, sodium or potassium silicate compounds are designed to penetrate deeply into the structure of concrete and fill its pores, creating additional bonds in floor concrete. Usually these products are applied with a roller or brush and then polished.

Very often, contractors of concrete floors (industrial and decorative) use impregnates based on lithium or potassium silicate as the final layer of protection, thinking that this type of impregnation will strengthen the concrete structure. Due to the nature of the concrete and its binding processes, which last several weeks, this type of solution is not effective enough. For lithium or potassium silicates to strengthen the concrete structure, you need free calcium hydroxide, which is the result of a concrete binding reaction.

Free calcium hydroxide compounds are formed very slowly in concrete. It takes a lot of time for the right amount of silicon compounds from the impregnate to react with free calcium hydroxide in concrete, causing it to strengthen. It can be assumed that a minimum of 3-4 weeks and more are needed for this type of impregnation to make sense. That is why impregnates based on lithium, sodium and potassium silicates are very effective for renovating old floors. There is already a lot of free calcium hydroxide in this type of concrete, because it has had time to form and it can now react with the silicon contained in the impregnante.

The above shows that the impregnation of fresh floors (after a few to several days after the floor has been made)does not make sense. Such a procedure does not bring the desired results and is economically unjustified. Simply speaking: it’s just a waste of money.


Coating agents: concrete sealer – the best solutions against stains and dirt

The second group of products are coating products, e.g. sealers. They are applied by roller, brush or by means of a pressure spray gun, and leave a transparent coating on the concrete surface. The varnish should be applied in a thin layer, taking care that there are no stains. The temperature must not be too low or too high, optimally between + 10 ° C and + 25 ° C. The varnish is dry after approx. 2 hours, after 24 hours you can walk on it gently and reach full strength after 7 days.

In the event that the concrete surface will often be exposed to water or soiling, we recommend the use of coating-forming agents. So kitchen countertops, bathroom countertops, concrete slabs between kitchen cabinets, new bathroom or hall floors – in all these places using penetrating agents will do little good. The optimal solution will be the use of concrete sealer.

PU FEST 2K is a highly durable, two-component polyurethane water-based varnish. It is colorless, resistant to UV rays, thanks to which it does not yellow. The varnish is characterized by very high mechanical and chemical resistance, excellent hardness and elasticity. PU FEST 2K varnish is suitable for use as a colorless finish on concrete floors, natural stone and other mineral surfaces indoors.


What are the advantages of PU FEST 2K concrete sealer?

  • The varnish covers all irregularities and gets deeper into the hollows and pores.
  • it protects against moisture and dirt absorption
  • it increases abrasion resistance
  • it does not allow mold and fungi to grow
  • it prevents discoloration
  • it makes cleaning easier
  • it provides excellent floor appearance for many years
  • it has excellent adhesion to many substrates – concrete, bricks, natural stone, tiles
  • it is flexible and impact resistant
  • it is suitable for use on floors, walls and other surfaces
  • it is easy to apply and safe (low VOC content)

Alternatively, in offices and bathrooms, to increase the mechanical and chemical resistance of the sealer, we suggest using the 3K plus additive.

Read more: Which microcement varnish should you choose?