Cochise College Student Papers in Geology
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Roger Weller, geology instructor
wellerr@cochise.edu
Concrete
Andrew Haldorson
Physical Geology
Fall 2005
What is Concrete and Why Is It
So Ugly?
Hi, in this paper I plan on explaining briefly what concrete really is. Have you ever driven around on a highway, in a city, or even a small town? Sometimes concrete is so close that you could be even standing on, yea wow there’s a lot of concrete out there. I am sure you have seen that endless drab color of gray on barriers, walls, and sidewalks. But what do we use it for, why is there so much of it, why is it so great, and what is it made of? Why is it so unattractive? There is a growing world out there of new ideas in the preparation of the old favorite concrete. I would like to explain to you what where and why we use this great stuff.
So what do we use this great stuff for? The Romans
adopted it for use on roads, large buildings, and engineering works, like the
aqueduct or the coliseum. The Romans found they could form enormous spaces which
could be roofed without large supports. Before concrete most buildings where
built with wood and stone, which made the walls extremely thick, good for
keeping in the heat, but took up lots of floor space. In the 20th
century
concrete is used to make pavements, buildings, foundations, roads, overpasses,
parking structures, bases for gates/fences/poles, and cement in brick or block
walls. According to the Portland Cement Assoctiation “the
U.S. uses about 340 million cubic yards (260 million cubic meters) of
ready-mixed concrete each year.”
The use of concrete
in roadways is two fold. For one the cost of laying concrete and the materials,
is very expensive which makes it very easy to run down bugets in local or state
funds. One of the reasons it is so expensive is the fact it is poured very
think, most highways could be 6 to 8 inches thick, and being thick means it’s a
lot of material. But on the positive side it takes very little upkeep, to be
useable. Most driveways and highways will last almost forever, or in a driveway
much long then the house itself.
Concrete's outstanding long life and low maintenance requirements improve its economic benefits. Concrete is not likely to rot, or decay as other building materials i.e. wood or steal. Concrete has the ability to be molded into almost any shape. Concrete is a non flammable material which makes it fire-safe and able withstands high temperatures. It is resistant to wind, water, rodents, and insects. Therefore concrete is often used for safety shelters. The ingredients of concrete are easy to find for a supply and take less of a toll in their mining than other construction materials, i.e. cross cutting of forests for lumber. As a inert material, concrete is a great medium for recycling waste products. Many materials which would end up in a landfill can be used instead to make concrete. Waste products such as scrap tires are used to fuel the manufacture of cement. Old concrete itself can be reused as the aggregate for new concrete.
So
what is this stuff made of you ask, the concrete the Romans used, was formed by
combining a volcanic earth with lime, broken stones, bricks, and tuff. I like to
think of it like making a cake. There are several different types of cake and
there are several different types of concrete. But it all has basic ingredients,
water, sand, stone and cement. In a cake you would use the egg to hold
everything together; well that’s what the cement does in concrete. In a cake you
have flower which acts mostly like a filler, if you didn’t have flower you would
have a pretty flat and small cake. The stone and sand act as the flower in
concrete, the filler you could say. Cement, together
with water, creates the paste that binds aggregate together to form concrete.
Concrete quality depends upon the quantity and quality of the aggregate and the
paste, as well as the bond between the two. As much as it sounds like a
cake I would not recommend taking a bite of this “cake” unless you like the
taste of sand dirt and cement. So now that we know what basically goes into
concrete let me explain those ingredients, and how much of each you need.
The number
1 ingredient would be the cement, number one in the fact that it is the most
expensive of the whole concrete process. Typically the price reflects the amount
of work it takes to create it, like most things. There is a detailed process of
drying and burning of lime and clay and the crushing the mixture into the common
powered form of Portland cement.
The second most important
ingredient would be the most common, water. When water mix’s with the cement it
forms a binding agent which bonds the aggregates (stones or rock) together. When
you add water to cement it rehydrate’s the cement changing it to the paste form.
The amount of water which is added to the mixture is important, too much water
and the concrete strength is reduced, too little and it’s too hard to work with.
The last
ingredient would be the one which makes up most of the mix, the aggregate. This
material can range anywhere from rocks, sand, glass, recycled cars or junk that
would otherwise end up in the land fill. 70 to 80% of concrete is aggregate
keeping the cost of concrete low.
So
what does the future hold for the drab gray friend of ours? In the late 90s
groups of people started to experiment with ideas of etching old concrete and
then staining it to change the color. The ideas have become more advanced and
now concrete even looks like expensive tile floors. The idea of using a big
stamp and placing it on the concrete before it hardens will change how it looks
after. You can even add a pigment to the concrete to change the color of it.
The use of
concrete will never fade; there will almost always be a need for it. Don’t
forget concrete is made of cement; cement is the powder and concrete is the
final product.
Works cited
Kerkhoff, Beatrix, Effects of Substances on Concrete and Guide to Protective Treatments, IS001, Portland Cement Association, 2001, 36 pages.
Federal Highway Administration, Portland Cement Concrete Pavement (PCCP) Research: www.tfhrc.gov/pavement/pccp/pccp.htm
Websites
http://nrmca.org/aboutconcrete/environmental.asp
http://www.cement.org/basics/index.asp
http://www.concrete.com/index.htm
http://www.greenerbuildings.com/