Oxford Democrat. [volume] (Paris, Me.) 1833-1933, 1916-08-08
AMONG THE FARMERS.
"sPExD THE PLow."

Il
Correspondence on practical Agricultural topic
10 solicited. Address all communications In
tended for this department to HE1Y ID
HAn0Np. Agricultural Editor Oxford Dem
ocrat. Paris. Ne.
Concrete: Do Net Abuse Il.
Charles Barto Brown of Technology Expert
| ment Station, 0rono.l
Concrete generally means q mixture Of
Portland cement, sand and either broken
stone or gravel. In this case, the word
"gravel" means collection of pebbles
and stones practically all of which are
larger than about IA inch in size. Such
concrete is usually mixed In the proper
ton Of one part of cement to two, or two
| and one-half parts of sand and four to
five parts of gravel or broken stone. Re-
Gently concrete has been specified as
meaning a mixture of cement and gravel; !;
in this case ''gravel" means the material
just as it comes from a gravel pit. This
material of course, includes both the
sand and the pebbles and larger stones.
crete are usually one part of cement to
six or eight parts Of grsvel-the idea be-
ing that these six to eight parts repre-
sent the two or two and one-half parts of
sand plus the four or five parts Of stone
as formerly used. Right here lies one OF
the most common abuses of concrete.
The gravel from most pits runs fine, that
is, very much more than one-third of the
material in the pit is sand. For example,
sixty pits located in various parts of
Maine were selected because Of their
good appearance. An analysis showed
that "A pits contained from S5 percent to
95 percent sand. The result is that when
six parts Of this gravel are used with one
part of cement, we do not have 1:2:4
mixture, but possibly more nearly Az
mixture, that s,-four parts Of sand and
two parts of stones to each part of ce-
ment. Experiment has proven that
/ "A 2 mixture Is less than half as strong
as 2:4 mixture.
The relations between proportions of
sand and gravel as stated above are
strictly true only when the measure
ments are made by weight. II the pit
gravel is not screened, and 1:24 mix
ture is desired, use one bag of cement to
A l-2 cubic feet of gravel.
In order to get the best results, ma
terial from the pit should be passed
through IA inch screen in order to
separate the sand.
Another feature where greater care
should be exercised is in taking the
gravel out of the pit. Not enough care
is used in removing the soil from over
the gravel. 1t also frequently happens
that the wall of the pit caves In, bringing
down with it several inches of loan.
While it Is true that a small amount of
goc.i clay in the gravel will probably
cause no trouble, such surface soil Is
composed largely of organic material, "a
very small amount of which destroys q
considerable portion of the strength of
concrete in which it is placed. The easi-
est way TO measure the cleanness OF
gravel is to take glass jar lone or two
quartz fill it three-quarters full OF clean
water, and then slowly empty into 1t
enough of the sand which has been
taken from the gravel to make depth
of about four inches. Let the jar stand
until the material has all settled. II
will be noted that the largest PARTICLES
of sand have gone to the bottom and
that the particles decrease in size from
the bottom upwards. At the top will be
found the layer Of clay which Is nearly
always present, and which can be dis
tinguished by its somewhat different
color from the sand. Do not confuse
the clay with the fine particles of sand
which are found directly under 1t. For
the best results, There ought not to be
more than a 4 inch layer of clay. Any
loam or organic matter will appear 10
thin layer on top OF the clay. Any per-
ceptible amount of this material is suffi-
cient to condemn that sand or gravel.
Large stones found in gravel pit
should be removed. Generally no stones
over l inches toS inches should be
used. OF course there are many excep-
tions to this. But under no circum-
stances should more than one-tenth OF
the stone be larger than the above size.
And when such are used, care should be
used in placing them In the concrete
structure, never more than one at time,
and in such manner that they will not
come nearer than inches or inches OF
apy face of the finished concrete, nor
within that same distance of each other.
When put into the concrete, they should
be thoroughly rammed into place.
In estimating the quantities OF the ma
terial needed for any concrete job, the
following will give very close results.
From the dimensions of the finished con-
crete, figure the number of cubic feet of
| concrete therein. Reduce this quantity
| by about percent and the result Will
| be the amount of coarse gravel (other
than sand) that viii be needed. That Is,
for every 100 cubic feet of finished con-
crete, there will be needed "a cubic feet
of gravel of more than about IA inch
size. Use half as many cubic feet Of
sand as there are cubic feet of gravel.
/ And use half as many bags of cement as
there are cubic feet of sand. Thus, the
100 cubic feet of concrete will require
about Oh cubic feet of coarse gravel, Al
cubic feet of sand and % 1-2 bags OF &C.
meut.
Great care should be used in storing
the cement. The bags of cement should
never be left on the ground. And even
when stored in q building where the
floor is but little above the ground, or
where the soil 10 damp, the cement
should be placed on temporary hoor
slightly raised above the main floor. ln
case any portion of a bag Of cement
llumps so hard that IL cannos readily De
broken up in the hand, such Jumps
should be thrown away.
To mix the concrete, build practical.
lly water-tight platform about s IT. to IL
LIZ. square. Out of 2 in. in. plank,
build a bottomless box which will be 2
Ift. wide and #. long on the inside, the
depth being the inches of the plank.
Place this box on the mixing platform
and fill il level full with sand. Lift on
1.-The box and spread the sand to a3 inch
| or 4 inch layer. Dump two bags of ce.
ment on top Of the sand. Now comes
lanother of the serious abuses In making
, concrete. These dry materials,-cemen'
and sand,-should be mixed by taking
up shovelful and letting 1t slide off the
shovel, not by dumping the sbovelfu
upside down, as in turning over the sol
in a garden. The entire mixture OF CO
msnt and sand should be shoveled ovel
at least three or four times In thi'
manner, and more II necessary, until th'
resulting mixture 10 blend OF one col
lor. Spread this dry mixture into laye
about 6 inches deep. On top OF 1t, place
| the same bottomless box a. used above
/ nan ia. ho~ laval full nth tha 0OarRl