How is cement made?
Raw materials such as limestone, shale, clay, iron ore, and sand are heated in a rotary kiln to approximately 2700 °F to form a partially molten mass. This partially molten mass is called clinker’. The clinker is cooled and ground into a fine powder called portland cement. The raw materials that feed the kiln have to be carefully proportioned to contain the desired amount of calcium oxide, silica, alumina, and iron oxide. When water is added to cement, a chemical process called hydration occurs, the paste then hardens to a stonelike mass. This paste is used as an adhering binder, which glues’ together the stone and sand to form a solid mass called ‘concrete’. Concrete is the most versatile and commonly used building material in the world! Portland cement gets its name from the English mason Joseph Aspdin, who in 1824 patented this product. He said it resembled the natural limestone quarried on the Isle of Portland, a peninsula in the English Channel.
A. The four steps to cement manufacturing are: 1. Virgin raw materials such as limestone and small quantities of sand and clay come from a quarry usually located near the cement manufacturing plant. The materials are blended and ground together. 2. The materials are heated in a kiln, which reaches temperatures of 1,870 degrees Centigrade or 3,400 degrees Fahrenheit. During this process, an intermediate product called clinker is formed. 3. Once cooled, the clinker is ground with a small amount of gypsum, forming a fine gray-colored powder called portland cement.
