Calcium Carbonate

   Limestone is mainly Calcium Carbonate (CaCO₃)                                                   Thermal Decomposition is the breaking down of a substance through heat. Thermal decomposition of CaCO₃ produces Calcium Oxide (CaO) a useful substance used in building and construction.

Limestone is heated in a 'rotary lime kiln': a rotating drum; the movement makes sure that the Calcium Carbonate is thouroughly mixed with the hot air so that is decomposes completley. 

As limestone travels through the kiln, the temperature increases and it breaks down to produce CaO and CO_{2 .} Here's the formula for the process:

CaCO₃ > CaO +CO_2, Calcium Carbonate (limestone) > Calcium Oxide + Carbon Dioxide

Limestone, like all other metal carbonates, reacts with acid to form a salt and water. The aftermath of these reactions can be seen on corroded limestone statues.

                     Metal Carbonate + Acid > Salt + Water + Carbon Dioxide                           Calcium Carbonate + Sulfiric Acid (in acid rain)>Calcium Sulfide+Water+Carbon Dioxide

Like all other metal carbonates, Calcium Carbonate goes through thermal decomposition to produce a metal oxide and carbon dioxide:

  metal carbonate > metal oxide + carbon dioxide                                                     Calcium Carbonate > Calcium Oxide + Carbon Dioxide                                               Copper Carbonate > Copper Oxide + Carbon Dioxide

The Calcium Oxide produced here reacts with water to produce Calcium Hydroxide (Ca (OH) _{2 .}                                                                                                                                                                                  Calcium Oxide + Water > Calcium Hydroxide ( CaO + H2O > Ca (OH)2))

Calcium Hydroxide, once also added to water, becomes Calcium Hydroxide solution. AKA, limewater.

Limewater is known to be a test for carbon dioxide. This is because once carbon dioxide is added to calcium hydroxide (limewater) it reacts to form Calcium Carbonate (precipitate) and water                                                                                                                                             Calcium Hydroxide + Carbon Dioxide > Calcium Carbonate + Water                                                       Ca (OH) ₂ + CO2 > CaCO₃ + H₂O

Egyptian Motar =       [ HEAT(Limestone) ] + Water

Roman Motar =          [ HEAT(Limestone) ] + Water + Sand + Calcium Hydroxide                                                                 Egyptian Motar + Sand + Ca (OH) ₂

Calcium Hydroxide allows the motar to harden even in wet conditions as it reacts with the CO2 in the air to produce CaCO₃ and water

                Calcium Hydroxide + Carbon Dioxide > Calcium Carbonate + Water                                                       Ca (OH) ₂ + CO2 > CaCO₃ + H₂O

Cement =    Powdered Limestone + Powdered Clay  

                   ^              HEAT IN KILN                   ^

Concrete =  Cement + Sand + Water + Aggregate ( small stones / crushed rocks )

                                            (Motar + Aggregate)

Reinforced Concrete = Concrete > Steel Rods