Floor Sealants for concrete floors protect the concrete slab from any moisture building up, preventing any damage caused by water. Concrete is a porous substrate. Therefore, applying a sealant will fill the pores with an impermeable coating. Depending on the product and the texture of the concrete will determine the sheen. For example, broom-finished concrete will have a less glossy shine unless you apply multiple coats, whereas a flat concrete slab will have a more polished look with fewer coats.