Calcium carbonate is a white powder commonly found in
rocks and in shells of marine and land organism, pearls, and egg shell. The
main applications of calcium carbonate are in paper, construction industry,
paints, plastics, ceramics and food. It is also found in agricultural
lime which adjusts soil properties and acts as a fertilizer. It is
commonly used as a calcium supplement or antacid. Calcium carbonate is
processed into different types; grounded or GCC, precipitated or PCC and coated
precipitated or CPCC.
The Romans named calcium carbonate calx. It was used to make
cement, by heating calx to obtain calcium oxide and carbon dioxide gas is
driven off. The calcium oxide is mixed with water to form cement, which was
then used to bond the stones together upon drying up in building amphitheatres
and aqueducts. The Egyptians also use calcium carbonate to build pyramids.
Most industrial calcium carbonate is extracted by mining or
quarrying. The pure form can be produced from pure quarried sources such as
marble. Pure calcium carbonate minerals include calcite, aragonite and
vaterite. Industrial sources of calcium carbonate include rocks such as
limestone, chalk, marble and travertine, and shells such as eggshells and seashells.
Ground calcium carbonate (GCC) is made from crushing limestone to create a
powder like form which is graded by size and other properties for different
It can be prepared from calcium oxide. Water is added to calcium
oxide to give calcium hydroxide, and carbon dioxide is passed through
calcium hydroxide to precipitate calcium carbonate. Precipitated calcium
carbonate (PCC) is derived from this method, which has very fine and controlled
particle size on the order of 2 microns in diameter. Coated calcium carbonate
is made from precipitating calcium carbonate by coating it with stearic acid.
Typically, GCC is used in the construction industry, as building
material by itself, such as marble, or as an aggregate of limestone for road
building. It is also a raw component of cement or as a starting material for
lime which is important for materials such as glass by burning in a kiln. It is
also used to make mortar for bonding, building materials such as bricks,
concrete blocks, stones and tiles.
Typically, CPCC is used as filler in plastics to improve
mechanical properties such as tensile strength and elongation and electrical
properties such as volume resistivity. Polypropylene compounds are filled with
calcium carbonate to increase rigidity, especially to withstand high
temperatures. It is used as filler in thermosetting resins, and is mixed with
other ingredients to form compression molded poker chips.
Calcium carbonate is known as whiting, and it is commonly used
for many glazes in its white powdered form. The whiting acts as a flux material
in the glaze when the glaze is fired in a kiln. Ground calcium carbonate will
not scratch most materials such as glass and ceramics, and have a moderate
effect on softer metals such as copper.
Typically, PCC is used as an extender in paints, particularly in
the matte emulsion paint which has chalked or marble typically 30% by weight in
the paint. PCC is used by itself as it can be used as a white pigment or with
additives as white paint or in whitewashing. In the paper industry, PCC
and GCC is used as a filler in paper during the alkaline paper making process
to make the paper bright and smooth. It can also be used to coat the paper