The vast majority of cement is used to make concrete and concrete products. The manufacturing of and use of cement products make cement one of the most valuable and useful mineral products in the world.
Cement manufacture involves a mix or raw materials, typically about 85% limestone (or similar rocks like marble or marl) with the rest mainly clay or shale. This mixture is heated until it nearly melts, and is then ground into a powder. It takes about 1.7 tons of raw materials to make 1 ton of cement.
When cement is mixed water, it creates a paste. When that "paste" is then mixed with other materials, such as aggregates (sand, gravel and rocks), the paste binds them all together and makes an extremely tough and hard product, usually called concrete. The mixture hardens because a chemical reaction occurs between all of the mixed parts, not because the water "evaporates". During this reaction, called hydration, crystals radiate outwards from the cement grains and mesh with other adjacent crystals or adhere to the adjacent aggregates. A typical mixture (by volume) to make concrete is about 10 to 15 percent cement, 60 to 75 percent aggregates and 15 to 20 percent water.
For all practical purposes, the only type of cement used in modern construction is called Hydraulic cement, and there are two major types of cement: portland cements and masonry cements. More than 95% of the cement produced in the United States is portland cement; masonry cement used for stucco and mortar accounts for most of the balance.
It is not known who invented portland cement but it was patented by Joseph Aspdin in England in 1824. He called it Portland cement because its color resembled the stone quarried on the Isle of Portland off the southern British coast.
The name cement is derived from the Latin word caementum meaning rough stone. The name concrete is derived from the Latin word concretus; concretus is the past participle of the word concrescere meaning to grow together, to harden.
Cement manufacture requires an abundant, close by, supply of limestone or similar rocks. About two-thirds of the states in the United States make cement. These states produce about 90 million tons of cements each year; that's more than 850 pounds of cement for every person living in the United States. The largest cement-producing states are California, Texas, Pennsylvania, Michigan, Missouri, and Alabama. Together these states account for 50% of the annual U.S. cement production.
About 20% of the cement consumed in the Untied States is imported from other countries, with Canada, Thailand and China being the major suppliers.
About 75% of all the cement produced is used to make ready-mix concrete, which is used to make buildings, bridges, sidewalks, walls, and all sorts of constructed structures. The rest is used to make building materials such as concrete blocks, pipes, and pre-cast slabs; in road building and repairs, and other assorted uses.
Substitutes for cement and cement products include a variety of materials such as wood, glass, steel, aluminum, fiberglass, stone, clay brick, and asphalt. The substitute chosen depends on the item being constructed and the physical properties it needs to have.
In the United States there is increased use of a material called pozzolans in place of concrete. Pozzolans are materials that, when mixed with lime, harden like hydraulic cement. These materials include some volcanic rock and some industrial by-products such as fly ash and blast furnace slag.