Cork insulation; a complete illustrated textbook on cork insulation ...

HANDLING CONCRETE 491
the material remains on the platform. Cement need not be measured
because, as already explained, one sack can be considered as 1
cubic foot in volume. A pail might also be used in proportioning
concrete. For example, a 1:2:3 batch of concrete would be measured
by taking 1 pail of portland cement, 2 pails of sand and 3 pails
of pebbles or stone.
FIG. 219.—SIMPLE TOOLS FOR MAKING AND PLACING CONCRETE—WATER
BARREL AND BUCKET; STEEL-PAN WHEELBARROW FOR HANDLING
DRY AGGREGATE, AND CONCRETE TO FORMS; SAND SCREEN FOR
PROPER GRADING OF AGGREGATES; SQLTARE POINTED SHOVEL FOR
TURNING AND MIXING CONCRETE; WOODEN FLOAT FOR FINISHING.
Mixing the Materials.—Concrete may be mixed either by hand or
by machine. Machine mixing is to be preferred as in this way thorough
mixing is easier to obtain and all batches will be uniform.
However, first-class concrete can be mixed by hand. Whichever
way mixing is done, it should continue until every pebble or stone
is <strong>complete</strong>ly coated with a thoroughly mixed mortar of sand and
cement.
Mixing Platform.—For hand mixing a watertight platform at
least 7 feet wide and 12 feet long should be provided. A platform of
this size is large enough to permit two men using shovels to work
upon it at one time. Such a platform should preferably be made of
boards at least IH inches thick, tongued and grooved so that the
joints will be tight and the platform rigid. These planks may be