Cement

Cement is a substance used in construction that hardens. Cements are rarely used on their own, but used to bind aggregates, such as sand and gravel, together to make concrete. Cements can also be mixed with fine aggregates to make mortar for masonry.

Aircrete is a type of concrete made from cement that uses air bubbles as it's aggregate.

Cement production and mining is the source of about 8% of the world's carbon dioxide emissions.

Portland cement

Portland cement is the most commonly used type of cement. It is made from burning and grinding limestone with clay or shale to make a powder. When mixed with water, the cement has a chemical reaction that causes it to harden.