Composite Materials - Concrete

Concrete is a well-known composite material that has been used for a long time in the construction of buildings and bridges.

Concrete is made from small stones and gravel called aggregate, sharp sand and cement. The small stone and gravel (aggregate) is the reinforcement and the cement is the matrix that binds it together. Concrete has good strength under compression but it is weak in tension. It can be made stronger under tension by adding metal rods, wires, mesh or cables to the composite. The concrete is cast around the rods. This is called reinforced concrete.

Lintels are the beams used above doors, windows and fireplaces. They support the weight of all the bricks bearing down on the window frames, doorframes or fireplace openings. When houses were first built the lintels were made from solid, heavy beams of timber. Most lintels these days are made from reinforced concrete.

Concrete can also be cast; unlike other casting materials it never really becomes a liquid. All of the composites mentioned in the above task should first be mixed dry and then mixed with water. Once poured into a mould the mix should be left to set. Concrete is best cast into wooden moulds that are screwed together and so can easily taken apart to allow the casting to be removed. Internal features may be formed by using expanded polystyrene. When you wish to remove the polystyrene it may be dissolved using acetone, which is a chemical agent. The acetone will not affect the concrete.

The image below shows modular concrete seating

Mud Bricks
Car Tyres
Composite Materials