Did you know that our world basically depends on lime? Limestone products are in greater demand today than ever before in history, and products and tools made from these building materials date back far into antiquity.
At present practically all civil engineering and architecture structures are made in some way with lime, therefore this material that comes from limestone rock is one of the most important in the world.
In addition, it has a million applications and is of vital importance in a lot of industries and for everyday life.
What is lime? (Calcium Oxide)
Definition: The word “lime” refers to products derived from burnt (calcined) limestone, such as quicklime and hydrated lime. Limestone is an abundant and naturally occurring sedimentary rock consisting of high levels of calcium carbonate and/or magnesium, and/or dolomite (calcium and magnesium carbonate), along with small amounts of other minerals.
Therefore, lime is extracted from quarries and underground mines around the world.
What is quicklime?
Basically, quicklime is a powder that is made up of calcium oxide and that has formed from the calcination of limestone. It includes all types of lime and will only vary in composition and purity.
This material is characterized by being highly reactive and has a high affinity for water. Its chemical formula is CaO.
Types of lime and its properties
Lime is classified into fat lime, hydraulic lime and poor lime:
Fat or air lime
It is made up of 95 percent calcium oxide and when water is added it quenches vigorously and its volume increases 2 to 2(1/2) times.
It is white in color and its properties are:
- slowly hardens
- has a high degree of plasticity
- sets slowly in the presence of air
- White color
- goes off vigorously.
Hydraulic lime
Contains clay and ferrous oxide, depending on the percentage of clay present, it is divided into the following three types:
- Weakly hydraulic (5 to 10% clay content)
- Moderately hydraulic (11 to 20% clay content)
- Eminently hydraulic (21 to 30% clay content)
The properties of hydraulics are:
- The color is not perfectly white.
- It forms a thin paste with water and does not dissolve in water.
- Its binding property is improved if its fine powder is mixed with sand and kept in a heap for a week before using it.
Poor or slaked lime
It contains more than 30% clay, its color is cloudy and it has a low reaction rate. The mortar made with such lime is used for inferior works. IS 712-1973 classifies lime as class A, B, C, D and E.
Class A: is predominantly hydraulic lime. It is normally supplied as hydrated lime and is commonly used for structural work.
Class B: contains hydraulic lime and fat lime. Supplied as hydrated lime or quick lime. It is used to make mortar for masonry work.
Class C: is predominantly fat file, supplied as both a fast file and a coarse file. It is used for finishing the plaster layer and for whitewashing.
Class D: This lime contains a large amount of magnesium oxide and is similar to fat lime.
This is also commonly used for whitewashing and finishing coat in plaster.
Class E: It is an impure lime stone, known as kankar. It is available in modular and block form. Supplied as hydrated lime. It is commonly used for masonry mortar.
The lime cycle How is it formed?
After processing, limestone-derived products have the unique ability to return to their original chemical form. The lime cycle consists of the first burning of limestone to form quicklime, in a kiln at 900°C.
Later, hydrated lime is generated by adding water to the quicklime. Finally, carbon dioxide in the atmosphere or from industrial processes reacts with the hydrated lime to turn it back into limestone, in a process called carbonation.
This cycle is called the lime cycle. The time it takes for quicklime or hydrated lime to turn back into limestone can last from less than an hour with the help of certain industrial processes to several years if left in atmospheric conditions..
Importance of lime
What do you think of when you hear the word “lime”?
Lime is a versatile mineral, the building block of construction and human progress that is a fundamental part of your everyday life, whether you realize it or not.
Lime is used to neutralize and clean our drinking water.
It is also used in the sugar refining process, to help clarify and reduce impurities from beets or cane.
Lime products are used to clean soft drink water, provide a binding agent for dough in tortillas, and even serve as a calcium supplement in orange juice or baby food.
But it is also used as an additive in asphalt for the roads we drive on, helping to improve its cohesion, reduce stripping and slow down the aging process.
And the main use is still the purification of steel and the creation of other construction products such as mortar and plaster.
Most likely, the office you are sitting in was built using at least one type of lime product.
Also, the paper you use every day for reports or homework has probably been bleached by calcium hypochlorite, another lime product.
Lime uses
Although it is believed that this material only has applications in the construction industry, the truth is that it is used for many more activities and industries as detailed below:
- It is used to neutralize and make water drinkable
- In our homes for copper, dry bleaches, dyes, glass, gold, lawn and garden neutralizers, leather, masonry, mortar, paint, paper, pharmaceuticals, plaster and stucco, sugar, table salt, toothpaste, and flour tortilla.
- In our communities for agricultural liming, apple storage, asphalt, sewage treatment and water treatment.
- For the preservation of our environment in the treatment of mine tailings drainage, reduction of air pollutants, control of epidemic diseases, remediation, wastewater treatment.
- In the industries of alumina, barium, glass, lead, lithium, magnesium, nickel, oil refining, silver, sodium alkali, solar grade silica, steel, uranium, wood pulp, zinc.
- For the manufacture of mortar for masonry and plaster work.
- To produce lime sand bricks.
- For soil stabilization.
- As a refractory material for the lining of open hearth furnaces.
- To make cement.