Gypsum can be used to speed the hardening of cement.
Gypsum is a naturally occurring mineral that is mined from deposits formed by ancient seabeds. Gypsum can be dried in one of two ways; the method selected depends on whether it is being used as a drying agent in cement or as a base for drywall.
Identification
Gypsum is a crystallized mineral called hydrated calcium sulfate and is used to make certain types of cements, as well as plaster of Paris and drywall. It can also be used to turn soft water hard, if this is necessary. Those who work with concrete sometimes need to slow down the rate at which it dries and, according to the Lehigh Heidelberg Cement Group, gypsum has the ability to slow hydration reactions, thus causing the concrete to harden at a slower rate.
History
In 1894, Augustine Sackett, who is widely recognized as the man who invented drywall, began to experiment with placing composite materials of thin plaster between sheets of wood felt paper to create wallboard. However, it was soon discovered that the felt edges were quick to wear away, making it an unsatisfactory material for this function. Based on this original invention, however, gypsum board was developed over the first few decades of the 1900s and proved to be ideal for use as a base wall covering.
Function
Gypsum is mainly used in wallboard panel, or drywall, where layers of gypsum are pressed between two pieces of fiberglass or heavy paper and placed in a drying chamber. Once the middle layer of gypsum "sets," it becomes rigid and can then be used as a drywall. Another common use for gypsum is in ceiling board, which is made in a similar fashion. According to the Gypsum Association, over 30 billion square feet of gypsum board are used on an annual basis in the United States and Canada.
Drying of Natural Gypsum
Gypsum in its crystal form is found in sedimentary rock formations and, after it is mined, is crushed into a fine powder. Each hundred pounds of gypsum rock contains about ten quarts of chemically combined water. In order to dry gypsum, it is heated to a minimum temperature of 350 degrees Fahrenheit, which causes the evaporation of 3/4 of this water. This process is called calcining and, once it is completed, the gypsum is ready to be used as a plaster base.
Drying Gypsum Board
To produce a sheet of gypsum board, water and other additives are combined with the calcined gypsum and the mixture is then placed between layers of paper or fiberglass. This is then moved down a conveyor line where the gypsum crystallizes and returns to its original hard state. After it has bonded to the core, it is placed in a dryer to remove any leftover moisture that may still be present, thereby producing a "drywall."
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