Chemistry-Rocks and building materials

Rocks and building materials

Rocks and building materials

Limestone and its uses

  • Limestone is made mainly of calcium carbonate CaCO3
  • Limestone is used as a building material and ot make calcium oxide and cement 
  • Cement mixed with sand, aggregate and water makes concrete
  • Calcium carbonate decomposes when heated to make calcium oxide and carbon dioxide. This is done on a large scale in lime kilns. The equation for this reaction is:
  • Calcium carbonate       Calcium oxide + carbon dioxide 
  • CaCO3                        CaO                  CO2
  • This type of reaction is called thermal decomposition
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Rocks and building materials

Reactions of carbonates

  • Metal carbonates decompose when heated to produce the metal oxide and carbon dioxide
  • Carbonates react with acids to produce a salt, water and carbon dioxide
  • Carbon dioxide turns limewater cloudy
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Rocks and building materials

The "Limestone reaction cycle"

  • Thermal decomposition of calcium carbonate produces calcium oxide and carbon dioxide
  • Calcuim oxide reacts with water to produce calcium hydroxide
  • Calcium hydroxide is an alkali that can be used to neutralise acids
  • Calcium hydroxide reacts with carbon dioxidr to produce calcium carbonate
  • Steps:
  • Step 1: Calcium carbonate- heat- carbon dioxide is given off and calcium oxide
  • Step 2: Add a little water to the calcium oxide- calcium hydroxide
  • Step 3: *** more water and filter- make calcium hydroxide solution
  • Step 4: Add carbon dioxide ( this is the test for CO2)- makes calcium carbonate
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Rocks and building materials

Cement and concrete

  • Cement is made by heating limestone which clay in a kiln
  • Mortar is made by mixing cement and sand with water
  • Concrete is made by mixing aggregate with cement, sand and water
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Rocks and building materials

Limestone issues

  • There are good and bad points about quarrying for limestone 
  • Limestone, cement and concrete are needed as building materials
  • Quarrying and processing limestone and its products have negative impacts on the environment
  • Advantages:
  • More employment opportunities for local people
  • More customers and trade for local businesses
  • Improved roads
  • Disadvatages:
  • Dust and noise
  • More traffic
  • Loss of habitats for wildlife
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