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This will prevent waste by using every bit of
excess concrete after any project, and you can utilize a partly-used or
full bag of extra cement by putting it to use this way, too. If you have
a partly-used bag which must be kept for a while, get a piece of
polyethylene plastic and make an enclosure from it large enough to
encase the cement sack. Using a hot electric iron over a folded piece of
aluminum foil will seal a seam in the plastic. The top can be left open
if you wish, merely by folding or rolling it several times to make a tight
joint, and then putting two laths on and clamping them together with
carpenter's C-clamps to hold it tightly closed. This will preserve the
cement and keep moisture from it for several weeks.
. . . what is "the ideal concrete mixture"?
It may take a little experience and observation to recognize the
proper consistency of concrete. The ideal mixture is one in which all
the spaces between the grains of sand are filled with liquid cement, with
the spaces between the larger gravel or stone aggregates filled with the
liquid sand-and-cement mixture, neither too wet nor too dry, but liquid enough to be of a workable consistency. The proper consistency for
a walk, driveway, or terrace pavement, when lightly troweled after being poured in place, should have all spaces between the gravel and
pebbles filled but no quantity of water being drawn to the surface by the
tooling. Even in a wetter mix (such as that used for footings or foundation walls) which is poured into casting forms to hold the moisture, a
little moderation in the use of water will make a stronger mixture.
Perhaps the clearest way to put it would be to say that the more water
is used the less strong the concrete will be, for as the cement is diluted,
its properties of strength are accordingly diminished. Also, a greater
proportion of aggregate to cement will weaken the concrete. It is true
that not all mixtures of concrete need to be stiff nor do they have to be
rich with cement, the proportions varying according to the purpose
for which the mixture will be used. (Note the chart p. 266.) The point
we wish to make is that you should stick fairly close to the formulae
given and not add more aggregates or more water than the amounts
specified; you may weaken the concrete and find to your sorrow later on
that it is not doing its job properly.
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