C1.2 Rocks and building materials

This covers:

2.1 Limestone and its uses

2.2 Reactions in carbonates

2.3 The limestone reaction cycle

2.4 Cement and concrete

2.5 Limestone issues

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C1.2 Rocks and building materials
2.1 Limestone and its uses
Limestone is a metal carbonate and can be expressed by its chemical name of calcium
carbonate (CaCO 3)
It has been used for centuries in building materials such as bricks and even as cement to
hold these bricks together ­ many old cathedrals and churches use this method
When limestone is heated, it breaks down in calcium oxide and carbon dioxide ­ this
process is called thermal decomposition
Thermal decomposition is where a substance is broken down using heat
CaCo3 CaO + CO2
We usually use a rotary lime kiln for the thermal decomposition of calcium carbonate
The limestone is crushed and placed in the bottom of the kiln and a strong supply of hot
air is pushed into the kiln
This then rotates to ensure the full thermal decompositionof calcium carbonate with the
As the waste gases are produced, they are released from the top of the kiln and the
calcium oxide is taken from the bottom of the kiln

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Reactions in carbonates
To test for carbon dioxide, the most common test is with limewater
When carbonates are reacted with acids, they produce a salt, carbon dioxide and water
Limewater is alkaline (CaOH) so when reacted with slightly acidic carbon dioxide, an
insoluble precipitate is formed in the neutralisation reaction (calcium carbonate is the
Also, when metal carbonates are heated they decompose
2.…read more

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Limestone issues
Limestone has to be quarried
This has disadvantages and advantages
The quarry scars the landscape and causes noise pollution for the residents nearby as the
limestone has to be blasted (this involves the use of explosives to retrieve limestone)
However, this process allows us to retrieve a widely used resource ­ limestone and we can
reuse quarries for reservoirs or as leisure activities for example, the popular shopping
centre Bluewater was built in an area where there was previously a quarry…read more


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