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Terrazzo floors have been in
existence for a very long time and several in the
Mediterranean area are more than 3,000 years old. One terrazzo
floor was found in excellent condition at Pompeii, where it
had lain covered in lava and volcanic ash for many centuries.
Good terrazzo has a smooth
surface which is 70 percent or more marble and almost 30
percent neat Portland cement matrix. The marble aggregate is
normally angular, rather than elongated and flaky, and is
carefully graded by size, depending on the different colors,
which contribute to the attractive, decorative effect. The
cement may be white or colored.
Terrazzo is generally laid on a
concrete base over which a screed is applied. The screed is a
grid arrangement of strips, usually metal, that divides the
terrazzo into sections and supports the necessary grinding or
honing to bring about a level, smooth surface. After the
terrazzo has been laid for about four days, it is ground with
a coarse abrasive stone and a plentiful supply of water to
produce a smooth, even surface. Final polishing is generally
carried out by machine, using carborundum as the abrasive.
Although attractive, terrazzo
floors tend to be hard, noisy and cold, but have extremely
good wearing properties and will withstand heavy floor
traffic. They are resistant to water and can stand up to
normal amounts used for cleaning.
Terrazzo floors are not
resistant to acids. These attack both the marble aggregate and
cement grouting, causing them to become pitted. Even mild
acids have a detrimental effect and must be avoided.
Some harsh alkaline cleaning
solutions will also do considerable damage to terrazzo. When a
floor is mopped with such a solution, it penetrates the small
open cells of the terrazzo. As the water evaporates, the
residual powder recrystallizes and expands, exerting much
pressure on the surrounding material. The result is that the
surface texture disintegrates into a fine dust. Continual
treatment of this sort will cause the floor to become pitted
and retain dirt. Proper selection of janitorial equipment and
cleaning solutions will reduce this problem.
If the surface has been damaged
by either acid or harsh alkaline powder materials, the surface
can be restored to its original smoothness by grinding.
Terrazzo floors usually have
good resistance to slip, particularly when polished to a fine
finish. If, however, the floor is too highly polished by the
use of very fine carborundum stones or other special polishing
aids, a slippery surface may result. Be sure to select the
correct janitorial supplies for maintaining terrazzo floors.
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