Slag cement is a type of blended cement made by grinding granulated blast-furnace slag, a byproduct of iron and steel production. It is used in concrete to enhance durability and reduce permeability, making structures more resistant to environmental factors like moisture and chemicals. This cement is often mixed with Portland cement to improve the overall performance of concrete. The use of slag cement can also contribute to sustainability by recycling industrial waste, reducing the carbon footprint associated with traditional cement production.