Portland cement is the basic ingredient of concrete. Together, with water, it creates the paste that binds the aggregate together to make concrete. Few construction projects can take place without utilizing Portland cement somewhere in the design, making it a key ingredient used in the nation’s construction industry.
U.S. cement production is distributed among 36 states utilizing 113 production facilities. U.S. cement consumption traditionally outpaces domestic production capacities with the shortfall being supplied with imports.
The majority of all cement shipments are sent to ready-mix concrete operators. The rest are shipped to manufacturers of concrete related products such as block and precast, oil well service companies, contractors and government entities.
The domestic cement industry is regional in nature with customers purchasing material from local sources. Nearly 98% of U.S. cement is shipped to its customers by truck. Barge and rail modes account for the remaining distribution modes. Portland cement consumption or demand is seasonal in nature with nearly two-thirds of the U.S. consumption occurring within a six month period between May and October.
Portland cement is made from common materials such as limestone, shale, clay, silica, and iron ore. The principle raw materials are a blend of 88% limestone, 6% shale, with the remaining raw materials being clay and iron ore. Generally, the limestone and shale are mined from quarries located on site with the production plant. These core ingredients are blended and crushed into a fine grind and then preheated and ultimately introduced into a kiln heated to about 2700 degrees F. Under this extreme heat, a chemical transformation occurs uniting the elements to form a new substance with new physical and chemical characteristics. This new substance is called clinker and it is formed into pieces about the size of marbles. The clinker is then cooled and later ground into a fine power that then is classified as Portland cement.