The Manchester journal. [volume] (Manchester, Vt.) 1861-current, 1911-08-24
WATERPROOF CONCRETE.
How to Prepare Mixture So II 10 I'm.
pervious to Moisture.

| Concrete Is very largely employed
In many building constructions. aud
| In some situations II Is very important
that II should be at least practically
waterproof. There are several methods
OF rendering concrete more or less I'm
| permeable 10 water some simple and
| free TO anyone, and some involving
the use of secret OF patented com
| POUNDS. or the former the simplest
method IS TO mix hydrated lime or
finely divided clay With the concrete,
thus al least partially filling the yolds
| or interstices In the concrete and de.
creasing the percolation OF water
Another simple method Is TO mix
powdered alum with the cement aud
dissolve ordinary soap In the water to
| be used III mixing the concrete. Al
| though the latter materials have been
used for more than sixty years as a
wash for rendering masonry Impervi-
GUS TO water aud although In recent
years they have frequently been EN-
ployed rs ingredients OF concrete 10
make the entire mass impermeable, the
proportions TO be employed and the
reason for the effect seem 10 have had
little or no scientific consideration; OF
least the proportions used In practice
vnry very widely
To use the alum and soap method
OF decreasing the permeabillty OF NOR
tar or concrete the alum In powdered
forn may be mixed with the dry ce.
ment or the sand. and the soap may be
dissolved In the winter employed In
mixing the concrete. or both the alum
and the soap may be dissolved In the
water. The former is probably the
safer method In practice. since with
The latter method the winter must be
thoroughly stirred while the two are
being mixed. or the precipltate may
form In large masses. which II Is prac.
ticnlly impossible 10 break up; and
further, the water must be kept stirred
10 prevent the compound from ac-
cumulating on the surface These are
conditions that II IL not always easy
to be certain Of securing. However.
the alum Is more easily dissolved than
the soap. and hence the alum may be
dissolved 10. say. one.Hfth OF the water
aud the soap 10 the remaining four
tfths. and then the two portions may
be mixed together. being careful 70 stir
them as the milking progresses. The
alum 0nd the soap combine and form
a timely divided. iocculent. lnsoluble.
water repelling compound. which Hlls 1
The pores OF the concrete and decreases
Its permeabllity
The best proportions are. alum one
part and hard soap two parts, both by 4
weight Soap varies 10 its chemical
composition, and hence a single pro
portion cannot be stated which win be I
chemically exact for all cases. The 1
above proportion Is In round numbers.
ibe relative combining weights OF
alum and average hard soap. and 4
hence II Is The best proportion 10 use.
although widely different proportions
have been used 10 practice with sue
cess. Any reasonably pure soap VIII
do, but II soft soap Ia employed o
greater amount should be used In pro.
portion 10 the amount OF water In IT,
u is difficult TO dissolve more than
about 3 per cent Of hard soap In cold
water. aud hence this practically Him.
us The amount OF alum 10 10 per cent 4
and OF ibe soap TO per cent. These
amounts will give q precipItaie equal
TO about . per cent OF the weight Of
The total wafer The amount Of precip
lta'e formed In The pores OF the NOR.
tar or concrete Will depend upon the
amount Of wsier used 10 the mixing
OF course. II I, be Dissolved In o small
er quantity o. soap and alum the soap
could he nrsi dissolved IN smaller
quantity Of bot waier. which Is after.
ward mixed with the water used In
making the mortar. bot this Is hardly
prariicnbie OF uecrsssry.