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Cobblestones or concrete pavers can be found on many sidewalks or garage entrances. You often see them in plain grey, but they are also available in many other colours. Regardless of the colour, the joy of the new stones is clouded by white spots that often form shortly after laying. And many owners think there is something wrong with their concrete pavement. You can agree with that in principle, but the white spots are usually a natural phenomenon that can be removed with simple means.
White spots
Where are the white spots coming from?
White spots on the concrete paving usually do not come from "above" but form out of the paving stones. They come from inside the stones, i.e. from "below". That is why they are also called efflorescence in technical jargon. In contrast to a white spot on plaster or masonry, efflorescence on concrete is not salt, but limescale.
Whether and to what extent these limescale deposits occur depends on the cement that was used for the concrete. The amount of limestone in the cement is important here. While most of the limestone is bound, there may be excess that is not bound. This excess is triggered by penetrating water and slowly comes to the surface. As the water evaporates over time, the white limescale deposits remain on the floor.
deposits
Do the white spots damage the concrete pavement?
The white deposits do not damage the concrete. However, many garden owners find them annoying because they don't look particularly pretty on the paving stones. They usually appear on young paving stones that are no more than five years old. In addition, the paving stones must also be wet regularly so that the excess lime can be dissolved. This is why they usually no longer occur with older concrete paving stones, as after a few years all the excess limestone has been removed from the paving stones.
Deposits on paving stones
Tip: As natural deposits, the white spots also disappear by themselves after a while because they are washed away by the rain.
elimination
Removing white spots
Efflorescence can be removed with water or with chemical agents.
Stain removal with water
This form of stain removal is the best for nature and the environment, since only water is used in this case. In addition to the water, you still need a brush for scrubbing.
clean cobblestones
To remove, do the following:
- apply water
- Scrubbing until all efflorescence is removed
- Rinse cobblestones thoroughly with water
Tip: A warm, overcast day is ideal for removing the white deposits.
A high-pressure cleaner is only suitable for removing stains to a limited extent, as it widens the pores of the stones, which promotes dirt and corrosion. It is therefore better to use a brush and mop, even if this means more effort.
Chemical stain removal
The removal of efflorescence using chemicals is controversial in the professional world, especially when it comes to acidic cleaning agents, as these agents attack the stones. Colored stones can also change the color of the surface. If you still resort to such a remedy, then the concrete must be well wetted before treatment. In addition, cleaning should be done quickly so that the acid cannot penetrate deeper into the concrete. After cleaning, the concrete pavement must be rinsed thoroughly with water. It is best to carry out the chemical stain removal on an overcast and windless day with a temperature between 10 and 20 degrees Celsius.
Tip: When buying the cleaning agent, make sure that it is suitable for your paving stones and follow the instructions exactly. You should also test the product on a small area.
road salt stains
White spots from road salt
White spots often appear on the concrete pavement after long and cold winters. These could be caused by road salt, even if you have not used road salt in the garden, as it is also spread on the stones by the soles of shoes. Although these unsightly stains will disappear over time, they can also be removed with water, just like limescale deposits.
road salt stains
Seal paving stones
Seal and impregnate paving stones
Sealing or impregnation of paving stones is not absolutely necessary. However, it protects the stones from fading and also makes them shinier. In addition to these optical improvements, the stones are also protected from other influences.
These include, among others:
- weather influences
- frost
- foreign matter
- road salt
- Moss, algae and lichen
moss
Sealing and impregnation for concrete blocks are special agents based on epoxy resin or dispersion. In order for the protection to be effective, care must be taken to ensure that the joints are also sealed. You can get the right sealant for concrete pavers from specialist retailers. It is important that the agent does not completely seal off the soil, as this can promote frost damage. The paving stones must therefore remain open to diffusion, i.e. water must be able to rise despite the protection.
Before starting the sealing, the paving stones must be thoroughly cleaned. At best, they should look like new. Then they have to dry well. Only then can the sealing be started.
Tip: Always test the sealant on a small area before treatment.
Although the sealing protects the paving stones from the weather and dirt, the stones still need to be cleaned regularly. In order for the stones to last a long time, they should be cleaned thoroughly once a year.