Rough or bumpy concrete can be smoothed if you use the right tools and techniques. An orbital sander is usually sufficient to achieve the desired results.
Still, careful consideration must be taken when selecting your grit – 40 to 60 grit may deliver the desired results when smoothing out resilient concrete with few imperfections.
More worn-out and distorted surfaces may require more intensive measures, such as a concrete grinder with a higher grit, depending on the texture you're aiming for. Don't underestimate the importance of picking the right equipment to attain a smooth outcome.