If it's well maintained, a polished concrete floor can add value to your home. Concrete is a low-maintenance and durable material that can appeal to homebuyers, especially if they prefer industrial and modern designs. Naturally, higher quality floors will add more value. 

No, you cannot permanently seal concrete. The porous nature of concrete means that it’s always vulnerable to water intrusion and staining, even under the best sealants. Although some concrete sealing products can last for a long time, a genuinely permanent concrete seal remains elusive.

You can whiten concrete for unsealed and unfinished concrete with a solution or either muriatic acid or bleach and water—but never both. However, if your concrete does have a stain, finish, or polish, keep in mind that these hard chemicals could damage the topcoat. Your best bet otherwise is to power wash outdoor concrete slabs or clean indoor ones with a gentle cleaner such as laundry or dish detergent.

To keep your stamped concrete surfaces shiny, experts recommend resealing them every two or three years. Regularly cleaning your stamped concrete (at least twice per year, as part of routine maintenance) is another way to increase its sheen. Also, if you notice any spills or leaks, you should clean your stamped concrete as soon as possible to preserve its shine and prevent long-term damage.