FIGURING
CUBIC FOOTAGE:
The biggest problem for the nonprofessional is figuring the amount
of concrete needed and then figuring the amount of materials or
ingredients needed to make up the concrete. Here are several tips
to make the job go easier: Measure
the inside of the form and then convert all dimensions to inches.
Multiply the width times the length times the height or depth of
the concrete depending on whether the placement is a slab or wall.
This will provide the cubic volume in inches. To get cubic feet,
divide this figure by 1,728. Multiply the length times the width
of the slab. Then refer to the amount given for the depth of slab.
The table gives the amounts for 1 cubic foot. Multiply the proportions
for each material by the amounts given in the table. The result
will give you a good idea of the amounts needed of each component
material.
If you
are building a large patio or driveway, you should work in terms
of cubic yards. To convert from cubic feet, divide the footage by
27. It's a good idea to plan for more concrete than you need. The
amount of extra material depends on the project. Plan for between
10 and 15 percent for walls and footings and 20 percent for slabs.
It's
a good idea to plan for more concrete than you need. The amount
of extra material depends on the project. Plan for between 10 and
15 percent for walls and footings and 20 percent for slabs.
MEASUREMENT
TECHNIQUES:
Once you have determined the amount of concrete needed, the next
step is to determine how much of the different materials you will
need--if you are mixing the concrete yourself.
Volume
method-
This is perhaps the easiest method. Use a shovel to move the cement,
sand, and gravel into the mixing location and then just count the
shovelfuls. If you're using a power mixer, turn on the mixer and
throw in the shovelfuls. The dry materials will mix together as
you go.
Weight
method-
Use a specially marked bucket. Weigh the bucket and then determine
a set weight such as 10 pounds. Weigh each ingredient separately
and make an identifying mark for the level of 10 pounds for each
ingredient. Then just count the bucketfuls as you put the correct
proportions into the mixing container. Cement: red; sand: yellow;
gravel: green.
Adding
water-
Measure the amount of water you add. If you get too much water and
do not have enough cement to add to it to correct the situation,
you can ruin an entire batch of concrete. Use a bucket that has
a known capacity so you can make an accurate measurement.
The strength
of the concrete will depend on the amount of water used. If too
little water is used, there won't be enough to provide a good fluid
state that can be worked easily and will ensure that each and every
solid particle is coated and bonded. You should use as much water
as possible without creating a problem with the workability and
smoothness of the concrete. Too much water results in concrete that
is unworkable and hard to set up. The cement particles will float
up to the surface and, worst of all, weaken the concrete.
As a
rule of thumb, professional masons consider 6 to 7 gallons of water
the correct amount of water per bag of cement, depending on the
dampness of the sand the size of the aggregate.
thank you