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In the event that he will let you do something, it is a good plan to
have a written contract specifying clearly what are the contractor's
responsibilities and what you are to furnish. In this way neither of you
will be expecting more than should be required, and unpleasantness
can be avoided. Sample contracts of this sort may be available from
branch offices of cement manufacturers, or you may write to the
Portland Cement Company, 33 West Grand Avenue, Chicago 10,
Illinois, for information on contracts and specifications for concrete
work. This latter company also offers some helpful little booklets which
give pictures of projects, tables of quantities needed for formulae for
various projects, and other useful information on concrete and how
backyard craftsmen can emplov it to improve their homes and gardens.
. . "how much of what?"
There is no single formula which can be given for universal use in
every project for which concrete may be used. The formula will vary
vith the purpose for which it is to be employed. In some uses concrete
nust be watertight; in others it must be strong for bearing a load; while
n other locations it will be its ability to stand up under heavy wear
CONCRETE MIXTURES RECOMMENDED FOR
VARIOUS KINDS OF WORK
|
Kind Of Work
|
Proportions
|
Water Required Per Sack of Cement When Aggregates Are . . .
|
|
|
Cement
(sacks)
|
Sand
(cu.ft.)
|
Gravel
(cu.ft.)
|
... Wet
(gals.)
|
... Moist
(gals.)
|
... Dry
(gals.)
|
Very thin sections-2"-4"
thick (fence posts, garden
furniture, step stones . . .).
|
|
12
|
2
|
31/2
|
33/4
|
41/2
|
Exceptional watertightness
and resistance to abrasion-
sections 4"-8" thick (pools,
planters, etc.).
|
1
|
2
|
3
|
33/4
|
41/2
|
|
General reinforced and
watertight work-sections
8"-12" thick (basement
walls, retaining walls,
pavements, step).
|
1
|
21/2
|
31/2
|
41/2
|
5
|
61/2
|
Mass concrete of moderate
strength, not watertight
(footings, foundation walls).
|
1
|
3
|
5
|
5
|
6
|
7
|
NOTE: Under the column "Water Required Per Sack of Cement When Aggre-
gates Are . . ." you will note three quantities given under headings of "Wet,"
"Moist," and "Dry." So that there will be no confusion regarding what is meant,
we shall explain this. Wet aggregates (sand, gravel, etc.) will require less water
than will be needed for mixing concrete with Dry aggregates, hence Wet (ist
column) aggregates need 31/2 gals, of water; Moist aggregates need (2nd column)
3% gals, water; while Dry aggregates need (3rd column) 41/2 gals, of water. Since
sand and gravel are seldom really dry (whether they come from the gravel pit
or are stored outdoors in your own yard), due to rain and other natural moisture,
the second column is probably the safest to use.
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