Reinforced concrete and stone properties and structures

• 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

• 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

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