Sandpaper is not typically used for grinding or smoothing concrete surfaces. Concrete is a hard and abrasive material, and sandpaper is not designed to withstand the rigors of grinding concrete effectively. Instead, specialized tools and abrasives, such as diamond-embedded grinding discs or pads, are used for concrete grinding and surface preparation.

Diamond grinding discs or pads are specifically designed to handle the hardness of concrete and are capable of efficiently removing the top layer of the concrete to achieve a smoother surface. These tools have a much higher abrasive strength compared to sandpaper, which is more suitable for lighter tasks like sanding wood or finishing delicate surfaces.

If you are looking to smooth or refine a concrete surface, it is recommended to use proper concrete grinding equipment and abrasives designed specifically for that purpose. This will ensure effective results and prevent damage to the concrete or premature wear of the sandpaper. Consulting with Concrete Grinding professionals or renting specialized concrete grinding equipment would be the best approach for achieving the desired outcome.