There are many ways of “hand mixing,” all having the same good results.
The way described here we believe to be the one best calculated to
obtain good results with a minimum of labor. In this description, and
the accompanying illustrations, we have taken as a basis a “Two-Bag
Batch” of 1: 2: 4 concrete.
First load your sand in wheelbarrows from the sand pile, wheel on to
the “Board,” and fill the sand measuring box, which is placed about
two feet from one of the 10-foot sides of the board, as shown by the
diagram in Fig. 3. When the sand box is filled, lift it off and spread
the sand over the board in a layer 3 or 4 inches thick, as shown in
Fig. 4. Take the two bags of cement and place the contents as evenly
as possible over the sand (see Fig. 4). With the two men at points
marked “x” and “xx” on the sketch below Fig. 4, start mixing the sand
and cement, each man turning over the half on his side of the line AA.
Starting at his feet and shoveling away from him, each man takes a
full shovel load, turning the shovel over at the points marked 1 and
2 respectively in Fig. 4. In turning the shovel, do not simply dump
the sand and cement at the points marked 1 and 2 in the diagram under
the cut, but shake the materials off the end and sides of the shovel,
so that the sand and cement are mixed as they fall. This is a great
assistance in mixing these materials. In this way the material is
shoveled from one side of the board to the other, as shown in Figs. 5
and 6. Fig. 5 shows the first turning, and Fig. 6 the second turning.
The sand and cement should now be well mixed and ready for the stone
and water. After the last turning, spread the sand and cement out
carefully, place the gravel or stone measuring box beside it as shown
in Fig. 7, and fill from the gravel pile. Lift off the box and shovel
the gravel on top of the sand and cement, spreading it as evenly as
possible. With some experience, equally good results can be obtained
by placing the gravel measuring box on top of the carefully leveled
sand and cement mixture, and filling it, thus placing the gravel on
top without an extra shoveling. This method is shown in Fig. 8. Add
about three-fourths the required amount of water, using a bucket and
dashing the water over the gravel on top of the pile as evenly as
possible. (See Fig. 9). Be careful not to let too much water get near
the edges of the pile, as it will run off, taking some cement with it.
This caution, however, does not apply to a properly constructed mixing
board, as the cement and water cannot get away. Starting the same as
with the sand and cement, turn the materials over in much the same way,
except that instead of shaking the materials off the end of the shovel,
the whole shovel load is dumped as at points 1 or 2 in the diagram
under Fig. 4 and dragged back toward the mixer with the square point
of the shovel. This mixes the gravel with the sand and cement, the wet
gravel picking up the sand and cement as it rolls over when dragged
back by the shovel. (See Fig. 10). Add water to the dry spots as the
mixing goes on until all the required water has been used. Turn the
mass bade again, as was done with the sand and cement. With experienced
laborers, the concrete should be well mixed after three such turnings;
but if it shows streaky or dry spots, it must be turned again. After
the final turning, shovel into a compact pile. The concrete is now
ready for placing.
[Illustration]
[Illustration: Fig. 5.—First Turning, Sand and Cement.]
[Illustration]
[Illustration: Fig. 6.—Second Turning, Sand and Cement.]
[Illustration]
[Illustration: Fig. 7.—Filling the Stone (or Gravel) Measuring
Box—First Method.]
[Illustration]
[Illustration: Fig. 8.—Filling the Stone (or Gravel) Measuring Box
When on Top of Mixed Sand and Cement—Second Method.]
[Illustration: Fig. 9—Placing the Water on the Stone (or Gravel) which
is on Top of the Mixed Sand and Cement.]