تحت اشراف رئيس قسم البناء والاشناءات م.درياض عبد العباس علي قامت التدريسه فاتن هاشم بعمل نشاط مع طلبة المرحله الثانيه حول (Gypsum Manufacturing)
Gypsum is a rock-like mineral commonly found in the earth’s crust, extracted, processed, and used by Man in construction or decoration in the form of plaster and alabaster. Chemically it is CaSO4.2H2O i.e. Calcium Sulfate dehydrate.
Impurities: MgO , Al2O3, Fe2O3, SiO2, CaCO3, MgCO3.
Raw Material:
Gypsum rock (calcium sulfate dehydrate – CaSO4.2H2O) was formed in geological time through the evaporation of seawater. It is often laid down in beds, ranging in thickness from a few centimeters to several tens of meters. Because gypsum rock is slightly soluble in water, it is not usually found above ground in wet or damp areas, but may be found underground, where it is not affected by the water table. In dry regions it may also be found on the surface, sometimes in the form of gypsum sand.
Gypsum rock is usually white or colorless, although it may sometimes have gray, yellow, pink, or brown hues. Gypsum is much softer than minerals of similar color, such as calcite or quartz, and is the only one that can be scratched with a fingernail. If a piece of gypsum rock is held over a flame it will turn cloudy and opaque and give off water. Some gypsum sand deposits contain only about 60 percent gypsum, and these are not very suitable for producing a plaster; those containing more than 80 percent would be most suitable. The gypsum CaSO4 is consist of 79.1% calcium sulfate and 20.9% water by weight. Two types of gypsum are available in nature: gypsum rock and gypsum earth. The gypsum earth requires much less machinery since it does not have to be crushed