Arkansas provides many great opportunities to explore nature, as the "Natural State" you will not want to forget your camera, a walking stick, and a buddy or two to go out and enjoy nature.
In this Earth Cache lesson we are going to learn about the application of limestone in commercial activities.
If you have been working on the Earth Caches on these trails you may have learned that limestone is a very versatile stone.
After completing this Earth Cache you will have a better understanding of:
- Why limestone has an enormous diversity of uses
- uses of limestone in commercial applications
- how commercial application of limestone is used at ground zero
- portland cement-a key component made from limestone
Limestone is a rock with an enormous diversity of uses. It could be the one rock that is used in more ways than any other. Most limestone is made into crushed stone and used as a construction material. In this lesson we are going to focus on how it is used as an aggregate in concrete. It is fired in a kiln with crushed shale to make cement, helping make the structure before you.
Some varieties of limestone perform well in these uses because they are strong, dense rocks with few pore spaces. These properties enable them to stand up well to abrasion and freeze-thaw. Although limestone does not perform as well in these uses as some of the harder silicate rocks it is much easier to mine and does not exert the same level of wear on mining equipment, crushers, screens and the beds of the vehicles that transport it.
Some additional but also important uses of limestone include:
Dimension Stone: Limestone is often cut into blocks and slabs of specific dimensions for use in construction and in architecture. It is used for facing stone, floor tiles, stair treads, window sills and many other purposes.
Roofing Granules: Crushed to a fine particle size, crushed limestone is used as a weather and heat-resistant coating on asphalt impregnated shingles and roofing. It is also used as a top coat on built-up roofs.
Flux Stone: Crushed limestone is used in smelting and other metal refining processes. In the heat of smelting, limestone combines with impurities and can be removed from the process as a slag.
Portland Cement: Limestone is heated in a kiln with shale, sand and other materials and ground to a powder that will harden after being mixed with water.
AgLime: Calcium carbonate is one of the most cost-effective acid neutralizing agents. When crushed to sand-size or smaller particles limestone becomes an effective material for treating acidic soils. It is widely used on farms throughout the world.
Lime: If calcium carbonate (CaC03 is heated to high temperature in a kiln the products will be a release of carbon dioxide gas (CO2) and calcium oxide (CaO). The calcium oxide is a powerful acid neutralization agent. It is widely used as a soil treatment agent (faster acting than aglime) in agriculture and as an acid neutralization agent by the chemical industry.
Animal Feed Filler: Chickens need calcium carbonate to produce strong egg shells so calcium carbonate is often offered to them as a dietary supplement in the form of "chicken grits". It is also added to the feed of some dairy cattle who must replace large amounts of calcium lost when the animal is milked.
Mine Safety Dust: Also known as "rock dust". Pulverized limestone is a white powder that can be sprayed onto exposed coal surfaces in an underground mine. This coating improves illumination and reduces the amount of coal dust that activity stirs up and releases into the air. This improves the air for breathing and it also reduces the explosion hazard produced by suspended particles of flammable coal dust in the air.
How Concrete is Made
In its simplest form, concrete is a mixture of paste and aggregates, or rocks. (Aggregates are normally defined as being hard, granular1, materials which are suitable for use either on their own or with the addition of cement, lime or a bituminous binder in con- struction.) The paste, composed of portland cement and water, coats the surface of the fine (small) and coarse (larger) aggregates. Through a chemical reaction called hydration, the paste hardens and gains strength to form the rock-like mass known as concrete.
Within this process lies the key to a remarkable trait of concrete: it's plastic and malleable when newly mixed, strong and durable when hardened. These qualities explain why one material, concrete, can build skyscrapers, bridges, sidewalks and superhighways, houses and dams.
Portland cement is the basic ingredient of concrete. Concrete is formed when portland cement creates a paste with water that binds with sand and rock to harden.
Cement is manufactured through a closely controlled chemical combination of calcium, silicon, aluminum, iron and other ingredients.
See an overview of the cement manufacturing process in this 7-minute animation.
Common materials used to manufacture cement include limestone, shells, and chalk or marl combined with shale, clay, slate, blast furnace slag, silica sand, and iron ore. These ingredients, when heated at high temperatures form a rock-like substance that is ground into the fine powder that we commonly think of as cement.
The most common way to manufacture portland cement is through a dry method. The first step is to quarry the principal raw materials, mainly limestone, clay, and other materials. After quarrying the rock is crushed. This involves several stages. The first crushing reduces the rock to a maximum size of about 6 inches. The rock then goes to secondary crushers or hammer mills for reduction to about 3 inches or smaller.
Did you Know?
Bricklayer Joseph Aspdin of Leeds, England first made portland cement early in the 19th century by burning powdered limestone and clay in his kitchen stove. With this crude method, he laid the foundation for an industry that annually processes literally mountains of limestone, clay, cement rock, and other materials into a powder so fine it will pass through a sieve capable of holding water.
Requirements: (please do not put your answers in the log)
Now that we learned a little bit about commercial application of limestone, take a moment to study ground zero. With the information above, and information at GZ you should be able to answer the following questions. You have 24 hours to send me an email (found in my geocaching profile) with the correct answers. Failure to do so will result in the removal of your "Found it log". Please add the GC code and title in the subject line. If you are sending answers for multiple people in your group, please add all the names in your email to ensure they don't have their log deleted :) Photos with you/group of the area would be greatly appreciated.
1 In your own words define aggregate
2 What are the 3 main types Limestone application?
3 What application of limestone is used at ground zero?
4 According to the placard what was the foundation built upon?
Sources:
Aggregate
Portland Cement
Limestone