Cement is a fine, dry powder that, when mixed with water, forms a paste that hardens and sets over time. It is primarily used as a binding material in construction, most notably in the production of concrete and mortar. The most common type of cement is Portland cement, which is made by grinding a mixture of limestone, clay, and other materials, then heating them in a kiln to create a substance called clinker. The clinker is then ground into the fine powder known as cement.