Once concrete has completely cured, it’s hard, strong, and durable. It’s also porous. From water to spilled motor oil, liquids can penetrate any concrete surface. The result can lead to ugly stains that are virtually impossible to remove. In addition, road salt and other contaminants can harm the surface of your concrete, etching away the cement that holds the aggregate together. Over time, the surface can roughen or even flake away. The key to maintaining your concrete’s clean appearance is to seal it regularly with a high-quality penetrating sealant.