Construction

A construction site     People have constructed buildings from ancient times as homes to provide shelter, monuments or places of worship. Earth, wood and stone have always been used as building materials. Bricks made from hardened clay were first used in the Middle East in about 3000 BC. Concrete is made by mixing sand, cement, water and gravel or other aggregates. Reinforced concrete dates from the late 1800s. It is often used in modern buildings, containing steel wires or rods to provide extra strength.

Types of buildings

A pile-driver, a huge mechanical hammer

      Buildings belong to one of two types. The first type has solid walls, called load-bearing walls, that support the floors and roof of the building. The second type has a framework of wood, steel or concrete that bears the weight of the building. Most buildings need foundations (a solid base) to prevent them from sinking into the ground or falling over. Foundations can be footings (underground walls), flat rafts, or underground supporting pillars, called piles, that are driven into the ground. An architect plans the design of the building, while engineers work out how to make it strong and safe.

Tower crane

Tower crane

      Many machines are used in the construction of a tall building. A tower crane is a vital machine. It lifts heavy building materials, such as steel girders and concrete slabs (which form the building's floors and walls) to the upper floors.

Concrete mixer

Concrete mixing, pumping and spreading         The drum of the concrete mixer spins round, mixing the ingredients—cement, sand and crushed rock (known as aggregate) and water—together. The concrete mixer keeps the concrete in liquid state by constantly turning the drum. The interior of the drum is fitted with a spiral blade. Rotating the drum in one direction, the concrete is pushed deeper into the drum while the concrete is being transported to the building site. This is called charging the mixer. Rotating the drum in the other direction forces, or discharges, the concrete out of the drum into chutes or into a concrete pump.

Bulldozer, digger and dumper truck

Bulldozer, digger and dumper truck

    A bulldozer uses its blade to push earth and rubble. A digger (also called a JCB or backhoe loader) can tear into the ground using the “teeth” on its loader bucket or backhoe. It scoops up the rubble and pours it into the back of a dumper truck. To dump its load, the truck body tips up, the tailgate at the back swings open and the rubble slides out.



Many construction vehicles have caterpillar tracks instead of wheels. They provide extra grip and spread the vehicle's weight, allowing it to move over muddy ground without slipping or sinking in.

Haul truck

Timeline

• c.3000 BC 
  Concrete is first used by the ancient Egyptians,
•  Chinese and Greeks.
• 600 BC 
  The first cranes are used in ancient Greece.
• 1770 
  British inventor Richard Edgeworth invents
•  the caterpillar track.
• 1867 
  Reinforced concrete is invented by
•  French gardener Joseph Monier.
• 1884 
  The first skyscraper, the Home Insurance Building, 
• is built in Chicago, USA.
• 1920 
  The first dumper truck is built in Canada by 
• Robert T. Mawhinney.
• 1923 
  The first bulldozer is constructed in the USA.