The
cement should be stored carefully. Otherwise it may absorbed moisture
from the atmosphere and may become useless for the structural work.
Following precaution are to be taken for the storage of cement
(1). Moisture:
If
moisture is kept away from cement, it is found that cement will
maintain its quality for indefinite period. An absorption of one to two
percent of moisture has no appreciable effect on quality of cement. But
if moisture absorption exceeds five percent the cement becomes totally
useless. Hence when cement is to be stored for a long period it should
be stored in air tight containers.
(2). Period of Storage:
The
loose cement may be stored indefinitely in air tight containers. But it
is advisable to avoid storing off cement in jute bags for a period
longer than three months. If it is unavoidable the cement should be
tested to ascertain its properties.
(3). Piles:
The
cement bags are stacked in piles. It is economical to form a pile of 10
bags of cement. A distance of about 300 mm should be kept between the
piles of cement bags and exterior walls of building. The passages of
width about 900 mm should be provided between the piles. For long
storage the top and bottom of piles should be covered with tarpaulins or
water proof paper.
(4). Quality of Cement:
The
cement which is finely ground is more active and consequently it
absorbs moisture rapidly from the atmosphere. Hence extraordinary
precaution should be taken to store finely ground cement.
(5). Removal of Cement:
When
cement bags are to be removed from piles of sufficient height the steps
should be formed by taking out two or three bags from front piles. It
is also advisable to remove cement in order of its storage period i.e.
cement which is stored previously should be taken out first. In other
words the rule of first in, first out should be followed.
(6). Storage Sheds:
For
storing cement for a sufficient long period the storage sheds of
special design should be constructed. The walls, roof and floor of such
sheds should be of water proof construction.
Few
small windows should be provided and they should be kept tightly shut.
The floor should be above ground. If necessary the drainage should be
provided to drain water collected in vicinity of such shed. For
determining the size of storage shed it is found that 20 bags or 10 bags
of cement will require about 1 m3 of space.
It
should be noted that cement even if stored in the most
favorable conditions loses its activity when stored for a long time. For
instance the storage duration of 3 months and 12 months will cause a
reduction in the activity of cement to the extent of about 20 percent
and 40 percent respectively.
Hence
it is advisable to reactivate the cement stored for prolonged period.
The most effective method of reacting such cement consists in
vibro-grinding which ensure greater fineness and makes cement fit for
use.
