Granite, limestone and marble are used as construction materials. Cement, which is made from limestone, is used to make concrete. However reinforced concrete has better properties for construction work than concrete alone.
The materials used in the construction industry include:
Granite is much harder than marble, which is much harder than limestone.
Limestone and marble are both forms of calcium carbonate, CaCO3. They are important materials, but they need to be obtained through mining or quarrying. The UK’s limestone deposits are in areas of great natural beauty, and this creates environmental problems. The table summarises some benefits and drawbacks of quarrying limestone.
|Limestone is a valuable natural resource that is used to make things such as glass and concrete.||Limestone quarries take up land. They are visible from long distances and may permanently disfigure the local environment.|
|Limestone quarrying provides employment opportunities that support the local economy in towns near the quarry.||Quarrying is a heavy industry that creates dust, noise and heavy traffic. This has a negative impact on local people’s quality of life.|
Limestone and marble are mostly calcium carbonate. This breaks down when heated strongly. The reaction is called thermal decomposition. Here are the equations for the thermal decomposition of calcium carbonate:
calcium carbonate calcium oxide + carbon dioxide
CaCO3 CaO + CO2
Other metal carbonates decompose in the same way. For example, here are the equations for the thermal decomposition of copper(II) carbonate:
copper(II) carbonate copper(II) oxide + carbon dioxide
CuCO3 CuO + CO2
Copper(II) carbonate is often used at school to show thermal decomposition. It is easily decomposed and its colour change, from green copper(II) carbonate to black copper(II) oxide, is easy to see.
Cement and concrete are made from limestone,
Chemical reactions happen in the mixtures and eventually they set hard.
Concrete is often reinforced with steel. A steel support is made by joining steel bars or cables together and this is then usually surrounded by a mould. Concrete is poured into the mould, where it fills the gaps in the steel support and sets hard. Reinforced concrete is an example of a composite material.
Reinforced concrete is a composite material made from concrete and steel. It is a better construction material than concrete alone because:
The composite material combines the best properties of both materials, so that it is hard and strong when squashed or stretched. This makes it useful for building bridges.