Reinforced concrete. Image credit surfcivil.blogspot.com

Reinforced concrete. Image credit surfcivil.blogspot.com

ZIMSEC O Level Combined Science Notes: Metal and metal alloy properties and their construction uses

  • Often building materials are combined when building a structure
  • The most common such mixture is reinforced concrete
  • It is a mixture of steel and concrete
  • Steel is able to withstand both compression and tension forces
  • It is however expensive
  • Concrete which is in turn a mixture of stone (usually quarry stones), sand, cement and water
  • Is much cheaper than steel
  • It can be moulded and precast in various shapes
  • It is also resistant to weathering
  • And is very strong in compression
  • but weak in tension
  • It is also brittle and develops many cracks
  • When a load/force is applied to a concrete beam it will bend
  • Also because it is weak in tension cracks might appear especially on its underside
  • These cracks mark the beginning of failure and might lead in the structure collapsing resulting in human life and destruction of property
  • Concrete can be made stronger by reinforcing it
  • Mild steel bars are placed in the concrete before it is set (during the casting process)
  • This reinforced concrete is then used  where tension occurs
  • The steel will be strong in tension
  • Also if the steel bars are placed longitudinally they will resist bending
  • Such bars are known as compression reinforcement
  • Also the deeper the beam is the more it can bend without bending

Stone

A stone house. Image credit hotel-r.net

A stone house. Image credit hotel-r.net

  • Stone is also used as a building material
  • Stone houses are highly coveted and often more expensive than brick and mortar structures
  • Stones resist corrosion more than steel
  • They are however inflexible and heavy
  • Most stones (naturally occurring ones) are irregular shaped and have to be filled with mortar (cement and mud)
  • This spreads the load and gives the structure stability
  • Regular stones (such as those used to make Great Zimbabwe walls) can be made using cutting tools
  • They give the structure better stability but are expensive to make

To access more topics go to the Combined Science Notes page


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