Page 244 - Florida Pest Control Examinations

CONCRETE MIXING

By Frank Lorey

Concrete consists of four basic elements: cement; a fine aggregate such as sand; a coarse ag-
gregate such as crushed rock or gravel; and water.
The aggregates (sand and gravel) usually make up about 3/4ths of the volume of any finished
concrete. All aggregates must be clean and free of organic matter and contaminants.
The water used for mixing concrete should also be clean and free of acids, alkalines, oils and
sulfates.
Although the ingredients in concrete are always the same, the finished results depend on the
proper mix of the four elements. The proper mix of ingredients is determined by the intended
use of the concrete.

Foundations and retaining walls require the use of about 6-1/4 gallons of water for each sack
of cement if the sand is damp. If the sand is wet, 5-1/2 gallons of water should be all that is
needed.
For pouring sidewalks, stepping stones, and slabs, concrete will require about 5-3/4 gallons of
water per sack of cement if the sand is damp, and about 5 gallons if the sand is wet.
Heavy footings for walls where waterproofing is not a factor will require a concrete mix with 1
part cement, 3 parts sand and 4 parts gravel.
Small jobs such as sidewalks, steps, driveways, and repairs will use 1 part cement, 2 parts
sand and 3 parts gravel.
For small jobs, you can measure the ingredients using a pail or small bucket.

Always follow the mixing instructions on the bag when mixing your particular type of concrete.

Special Products for Concrete Jobs

While the test will require you to know about concrete mixing, there are many types of prepack-
aged concrete mixes available for smaller jobs such as small concrete patches, small slabs,
even setting fence posts. Many of these products would work for the type of repair work done
in pest control. There are also a number of other concrete products available by the sack that
will make quick and easy work of a wide variety of concrete patching and repair jobs. Follow
the instructions found on the package for proper use.

Quick-Setting Cement
As the name implies, quick-setting cement products are specially designed to set up faster than
the standard concrete mixes. These products are an ideal choice for a number of repair situ-
ations such as patching curbs, steps, concrete walls and other similar areas without having to
erect forms.
Vinyl Concrete
Vinyl concrete is specially designed for patching and resurfacing existing concrete, smoothing
out rough areas and repairing mortar joints. It will trowel on very smoothly on concrete areas,
stone, brick and other masonry surfaces, and can be used for a wide variety of repairs.
Latex Cement
Latex cement is great for more difficult repairs, such as patching or resurfacing existing con-
crete, repairing concrete steps, leveling uneven surfacing, and can be used for setting stone or
brick in some situations. This product consists of Portland cement mixed with fine sand along
with a liquid latex binder, typically packaged together in a bucket, which can double as a mixing
pail. No water is necessary with this type of cement.

With all types of cement or concrete repair, you will need to keep the repaired area moist to
avoid it setting up too quickly, especially during warmer weather. This can be done by spraying
the repaired area with a fine mist of water from a garden hose or spray bottle. Then cover the
patch with plastic or burlap-- even wet paper towels or rags can work.

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