Concrete is a well-known composite material that
has been used for a long time in the construction of buildings
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 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 image below shows modular concrete seating