C1aL6 Uses of Limestone

Key Words

Cement - a material that bonds other materials together;

Clay - often found below the soil, a soft claggy material made of very fine particles.

Concrete - a mixture of cement, sand, and chippings and water  that sets to make a strong and hard material.

Glass - a transparent solid and brittle material used in windows.

Kiln - a large oven used to heat materials to high temperatures.

Limestone - a rock containing calcium carbonate as its main mineral.

Mortar  - a mixture of sand, cement, and water that is used to bind bricks or stones together.

Sand - fine particles of eroded rock;

Sodium carbonate - Na₂CO₃

Grade E

Limestone has a wide range of uses.  The most common is to make cement, a mixture of limestone and clay which is heated in a kiln.  Cement is then used to make:

• Concrete, which is a mixture of sand, cement, water., and rock chippings.  It is hard, strong, and difficult to squash.

• Mortar, which is sand, water, and cement without the chippings.  It is not as strong as concrete, but binds bricks together strongly.

Concrete is very strong in compression (when it's squashed), but quite weak in tension (when it's pulled apart).

Limestone is also used in glass making.  Glass is a mixture of sand, limestone, and sodium carbonate.

Grade C

When water is added to mortar or concrete, the cement absorbs the water and hardens.  The mortar or concrete sets (or "goes off").  The hydrated cement crystals bind the particles of sand (in mortar) or sand and rock chippings (in concrete).

You can see the tight interlocking crystal structure that gives the strength.  For the concrete, you can see the rock chippings.

Glass is made by heating a mixture of limestone, sand (silicon dioxide), and sodium carbonate to 1300 ^oC.  The calcium carbonate and sodium carbonate break down, and strong covalent bonds are formed between the silicon atom and oxygen atoms.  The material cools to form a giant irregular structure that traps sodium and calcium ions.  Other minerals can be added to give glass a distinctive colour.

Grade A

Glass is actually a super-cooled liquid.  It does not have a crystal structure.  Old glass is often thicker at the bottom than the top, because it flows very, very, slowly.

You can tell old glass because the view through the window is distorted.