Cement basically refers to pulverized brick and volcanic ash additives that are added to burnt lime to obtain a hydraulic binder. Natural cement consists of clay and limestone mainly.
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The ingredients used to make cement are Calcite from limestone, Silica, Aluminan plus small amounts of Iron. These ingredients can be collected by mixing limestone and shale ground together and then fired up in a kiln to about 1400°C.
Cement is made up of limestone, clay and cement rock. One pound of cement contains in it 150 billion grains and cement was first made in the early 19th century by burning powdered limestone and clay.