Arizona Concrete Essay

This essay has a total of 1285 words and 7 pages.

Arizona Concrete

Arizona Concrete


John McCollam
Geology 101, Section 12262
Randy Porch
20 November 1996



According to the Mine Faculty at the University of Arizona, cement is
manufactured primarily from suitable limestone and shale rocks. Arizona had two
dry-process cement plants in 1969, namely the Arizona Portland Cement Company
plant in Pima County, near Tucson, and the American Cement Corporation plant at
Clarkdale, in Yavapai County (52-53).
The use of cementing materials goes back to the ancient Egyptians and
Romans, but the invention of modern portland cement is usually attributed to
Joseph Aspdin, a builder in Leeds, England, who obtained a patent for it in 1824.
Currently, the annual world production of portland cement is around 700 million
metric tons (Danbury).
Many people use the words concrete and cement interchangeably, but
they're not. Concrete is to cement as a cake is to flour. Concrete is a mixture
of ingredients that includes cement but contains other ingredients also (Day 6-
7).
Portland cement is produced by pulverizing clinker consisting
essentially of hydraulic calcium silicates along with some calcium aluminates
and calcium aluminoferrites and usually containing one or more forms of calcium
sulfate (gypsum) as an interground addition. Materials used in the manufacture
of portland cement must contain appropriate proportions of calcium oxide, silica,
alumina, and iron oxide components. During manufacture, analyses of all
materials are made frequently to ensure a uniformly high quality cement.
Selected raw materials are crushed, milled, and proportioned in such a
way that the resulting mixture has the desired chemical composition. The raw
materials are generally a mixture of calcareous (calcium oxide) material, such
as limestone, chalk or shells, and an argillaceous (silica and alumina) material
such as clay, shale, or blast-furnace slag. Either a dry or a wet process is
used. In the dry process, grinding and blending operations are done with dry
materials. In the wet process, the grinding and blending are done with the
materials in slurry form. In other respects, the dry and wet processes are very
much alike.
After blending, the ground raw material is fed into the upper end of a
kiln. The raw mix passes through the kiln at a rate controlled by the slope and
rotational speed of the kiln. Burning fuel (powdered coal, oil, or gas) is
forced into the lower end of the kiln where temperatures of 2600°F to 3000°F
change the raw material chemically into cement clinker, grayish-black pellets
about the size of 1/2-in.-diameter marbles.
The clinker is cooled and then pulverized. During this operation a small
amount of gypsum is added to regulate the setting time of the cement. The
clinker is ground so fine that nearly all of it passes through a No. 200 mesh
(75 micron) sieve with 40,000 openings per square inch. This extremely fin gray
powder is portland cement (Kosmatka and Panarese 12-15).
Dany Seymore of Show Low Ready Mix said that the cement used by Show Low
Ready Mix is trucked in by Apex Freight Company and comes from the cement plant
in Clarkdale, Arizona, now know as Phoenix Cement. Their aggregate comes from
Brimhall Sand and Rock in Snowflake, Arizona. Show Low Ready Mix uses Fly Ash
from the A.P.S. power plant just out side of Joseph City, Arizona, in their
cement. The mixtures they use are as follows:

Silicia Dioxide Cement 21% Ash 62%
Aluminum Trioxide Cement 4% Ash 23%
Ferric Oxide Cement 3% Ash 6%
Calcium Oxide Cement 64% Ash 3.5%
Mag. Oxide Cement 2.5% Ash 1.2%
Sulfur Trioxide Cement 3% Ash .2%

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