With very few exceptions, every porous mineral building material, including stone, tile, masonry, concrete and grout, will benefit from being well sealed.
To maximize these benfits the selection of the most suitable sealer is critical. There are two main types of sealers, namely, surface topical sealers and impregnating sealers. A surface topical sealer will provide a physical film or barrier over the surface. The result is a darkening of the surface. These coatings are less hard than the origianl surface and will wear and weather relatively quickly, often make the surface more slippery when wet and must be completely stripped off when re-coating. Salts and water may also build-up under the surface, causing the coating to appear cloudy and peel. Impregnating sealers can be classified as those that repel water and those that repel both water and oil based stains (the ones germs cling to).
Impregnating sealers usually have little effect on the frictional properties and appearance of the surface but will not completely stop dirt and rubber getting into the open pores of the surface. When comparing similar sounding impregnating sealers the two most important questions are: (a) is it permanent? and (b) how deep does it penetrate below the surface? A good depth of penetration is critical to provide protection against traffic wear and weathering.