A cement is a binder. It is a substance that sets and hardens and can bind other materials together. Cement is usually in a form of powder which is being mixed with other materials and water. The most important uses of cement are as a component in the production of mortar in masonry, and of concrete, a combination of cement and an aggregate to form a strong building material. Cements used in construction can be characterized as being either hydraulic or non-hydraulic, depending upon the ability of the cement to set in the presence of water.