Although the terms cement and
concrete often are used interchangeably, cement is actually an
ingredient of concrete. Concrete is basically a mixture of
aggregates and paste. The aggregates are sand and gravel or
crushed stone; the paste is water and Portland cement.
Cement is a fine binding powder, which is never used alone. It
is made most commonly of limestone, clay, shells, and silica
sand. These materials are crushed and then combined with other
ingredients (including iron ore), and then heated to about 2,700
F. This material, called Clinker, is ground into a fine powder.
It is used to make both concrete and mortar.
Both mortar and concrete are widely used building materials. They
cannot be substituted for each other without compromising the
integrity of a build.
Concrete is much stronger and more durable than mortar.
Because it needs a low water to cement ratio, it is much thinner
when mixed, making it difficult to use as a bonding element.
Concrete is used in structural projects and is often reinforced
with steel rebar to maintain its structural integrity. It is
best used for support, such as beams, walls, or other building
foundations. Its unique characteristic is that it starts out as
a simple, dry mixture, becomes a liquid flexible material
capable of forming into any mold or shape, and ends up as a
hard-as-rock material.
Gunite is a very
durable mixture of cement, sand, and water that is sprayed on a
surface under pneumatic pressure. It is used for tunnels,
underground structures, slope stabilization, structural repairs,
and swimming pools. Gunite or shotcrete material is mortar or
small-aggregate concrete applied using a wet or dry process.
Mortar is used
to hold building materials such as brick or stone together. It
is composed of a thick mixture of water, sand, and cement. The
water is used to hydrate the cement and hold the mix together.
The water to cement ratio is higher in mortar than in concrete
in order to form its bonding element. When mixed, it is a much
thicker substance than concrete, making it ideal as a glue for
building materials like brick.
Bottom line, a hydrated cement mixture forms the base of all
three materials, the rock chipping in cement makes it much
stronger for use in structural projects, and mortar is thicker,
which makes it a better bonding element.
Incidentally, the name Portland cement comes from Joseph
Aspdin, who first produced cement during the 1800s in England.
He thought its color was like the color of stone from quarries
on the island of Portland off the coast of England.