Oil and grease are just some of the most damaging things that could spill on a concrete floor. You must keep in mind that concrete is a very porous material. This is the reason why dirt and spills penetrate the surface, causing unpleasant damage like ugly stains and horrible discoloration. A sealer helps cover up the little, tiny pores of a concrete slab, preventing anything from getting in. This means spills and dirt stay on the surface, ready to be wiped or swept off.