Wauwatosa news. [volume] (Wauwatosa, Wis.) 1900-1948, 1913-06-13
WATERPROOFlNG
CONCRETE WORK
BY F. M. WHITE,
Wisconsin college Of Agriculture.

wisconsin college OF agriculture.
The old question whether concrete
can be made watertight or waterproof
without the addition of some special
waterproofing treatment. arises in the
mind of prospective builders of
concrete tanks. cisterns or retaining
walls, and reinforced concrete struc-
lures.
In some structures, such as base
ment walls or cellar floors, it is essen
tial that no water be allowed to pene-
trate the structure, and even damp
ness should be prevented. In rein
forced concrete work, if water comes
in contact with the steel, there may
be a weakening of the structure and
even total failure of the concrete it.
self.
If we are to prevent the penetra-
ton or absorption of any water in the
concrete mass, special precautions
must be taken. We should not ex-
peel to make a watertight structure
with materials which are themselves
rapid absorbents of moisture. This
stone or porous rock and sand of any
nature. Sand and gravel must be
clean, free from organic matter, and of
various sizes and shapes, ranging, in
case of the stone, from material that
will pass through one and one-fourth
inch sieve and that will be retained on
a one-fourth-inch mesh sieve; and
sand that will pass through a one
fourth inch sieve and not more than
IL per cent. pass No. 80 sieve. The
cement must exactly fill the inter
stices In the sand, and the cement and
sand exactly fill the interstices in the
stone. This requires proportions rang
ing from one-one-two mixture to a
1-2h-4M mixture, that is, one part of
cement and two and onehalf parts of
sand, and four and one-half parts of
stone, as indicated.
The consistency of the mixture, or
the amount of water used, also has an
important influence on the waterproof
ing of the structure. The amount of
water necessary in the mixing will
vary according to the dryness of the
materials. The correct consistency
might be described as "quaking," or
about that of jelly, so that when lamp |
ed the moisture will easily flush to
the surface.
A good method of determining the |
best proportions to be used Of the |
materials at hand is to fill a narrow |
cylinder partially full of trial mix
ture, say one-two-four, mixed to the |
consistency recommended, and care |
fully mark the height reached in the |
cylinder. Next try the same weight |
of a different mixture in the same |
cylinder, say one-two and one-half- |
three. and notice the volume of this
new mixture. These trials may be |
carried on until a mixture is found |
which gives the least volume. The
least volume secured, always keeping
tho total weight the same, will give
the densest concrete For ordinary
work, the above method will give a
concrete that will be good enough for
small tanks and walls. IL larger
tanks are to be built, it is advisable
to take further precautions.
There are various waterproofing
compounds on the market which may
be mixed with the carefully proper
toned concrete materials. They con
tain varying proportions Of alum and
bydrated lime. which are water repeL
liant A combination Of liquid and
powder is sometimes used, and Is
known ~ the Sylvester Process" In