Answer: by spreading a specific product on the tiles and then rubbing with a brush.
There are often non-slip tiles in damp rooms like the bathroom, or outside on the terrace. To eliminate traces of cement, there are specific products on sale in DIY stores to combat cement residues. It is enough to spread the product on the tiling, to let it act, then to rub with a brush until the traces disappear. Do not use a sponge, it will fall apart on non-slip. Alternatively, you can use products that may already be in your home, which will save you from having to make an additional purchase, such as hydrochloric acid (mixed with water in the following proportions: a quarter of acid for three quarters of water), or white vinegar. You too, send us your brico question