towards an analysis of errors made by university students ... - DSpace

Newsprint is used in the production of newspapers
owing to its relative
Doubtless
cheapness.
as man becomes more and more sophisticated
in his requirements there will be need for continual research
to provide a wider range of new and better
mateirals.
T4P - Text number 4 - Physics
CONCRETE
Nowadays the skeleton or frame of a building
is
usually either made of structural steel or reinforced concrete.
Concrete is made by mixing together small stones, sand, cement
and water.
It can be made by hand but it is usually mixed in a
rotating cylinder. When it is ready it is poured
into molds
made of wood or metal. The stones that are mixed in the
concrete give the mixture strength; the sand fills the spaces
between the stones and the cement secures the mixture
The less water we use to mix cement, the
together.
stronger
it will be. The difficulty however is that it is much more
difficult to mix if little water is used. When very
strong
concrete is needed it is mixed with a minimum of water, placed
in forms or molds and then "vibrated" with metal bars that
operate from electricity or compressed air. This
vibration
removes air bubbles and produces a good
mixture.
Engineers reinforce concrete with steel
and wire
to make it resistant to bending. These metal reinforcements are
put in the molds before the concrete is poured in.