In this article, we are going to shed light on the definition, meaning and use of lime for civil engineering students. Let’s first begin to shed light on the definition and meaning of lime and in the last section, you will learn about the use of lime.
Definition and meaning
The product obtained from burning more than 900 ℃ of limestone is called lime. You will remember that lime is not a thing that is available in a naturally free state, but it is obtained by burning lime.
How is lime formed?
When limestone i.s. calcium carbonate (caco3) is cooled, moisture and carbon dioxide (CO2) are removed and the lime i.e. calcium oxide (CaO) is released.
We hope that you now know about the definition, meaning and process of making lime. Let’s begin by explaining its use in this section:
Uses of lime
Although there are countless uses of lime in our lives, here are the most common uses of lime that you should be aware of as a student:
- Lime is used as binding material in mortar
- It is used to prepare concrete for foundations and floors
- It is used a lot in plastering of walls and white washing for rooms.
- It is also highly used as flux in steelmaking, prior to wood painting.
- Apart from the above short list, lime is also used to stabilize the soil and also helps in creating good sanitary conditions at foul, moist and dirty places.
Types of Lime In Civil Engineering (construction)
As far as types of lime goes, here are main types that have a frequent use in construction works:-
Limes made up mainly of calcium oxide or hydroxide that slowly harden in the air under the effect of carbon dioxide present in the air. In general, they do not harden under water, as they do not have hydraulic properties. They can be live limes or hydrated limes.
Live limes (Q):
Aerial limes are mainly made up of calcium and magnesium oxide, produced by the calcination of limestone and / or dolomite. Live limes have an exothermic reaction in contact with water. Live limes come in different granulometria ranging from lumps to finely ground material. They include calcium limes and dolomitic limes.
Limes (S): Aerial, calcium or dolomitic limes resulting from the controlled slaking of live limes. They are produced in the form of a dry powder, paste or grout.
Calcium limes (CL):
Limes mainly made of calcium oxide or calcium hydroxide, without the addition of pozzolanic or hydraulic materials.
NOTE – Shell limes are hydrated calcium limes produced by calcination of shells followed by slaking. Carbide limes are hydrated calcium limes that are a by-product of the manufacture of acetylene from calcium carbide.
Dolomitic limes (DL):
Limes are mainly made up of oxides or hydroxides of lime and magnesium, without the addition of pozzolanic or hydraulic materials.
Semi-hydrated dolomitic limes:
Hydrated dolomitic limes, consisting mainly of calcium hydroxide and magnesium oxide.
Fully hydrated dolomitic limes: Hydrated
Dolomitic limes consist mainly of calcium hydroxide and magnesium hydroxide.
Hydraulic lime (NHL): Natural hydraulic lime is a lime with hydraulic properties, resulting from the firing of clay or siliceous stones (including chalk), more or less limestone, with reduction to powder by slaking, with or without grinding. It has shaping properties and hardens when mixed with water and by reaction with carbon dioxide in the air (carbonation). The hydraulic properties result exclusively from the special chemical composition of the natural raw material. Up to 0.1% agents are allowed. Natural hydraulic lime does not contain any other additives. There are three classes according to hydraulicity.
Lime (HL): Hydraulic lime is a mixture of lime and other materials such as cement, blast furnace slag, fly ash, limestone filler (filler) and other suitable materials. It has the characteristic of setting under water. But atmospheric carbon dioxide also contributes to the hardening process. It is not necessary to declare the ingredients. There are three classes according to hydraulics.
Formulated Lime (FL):
Formulated lime is lime with hydraulic properties, composed mainly of air lime (CL) or natural hydraulic lime (NHL) with the addition of pozzolanic or hydraulic material. It has the characteristic of setting when mixed with water and also hardening by reaction with carbon dioxide in the air (carbonation). Apart from the degree of hydraulicity (FL5, FL3.5, FL2) there are subgroups A, B and C in each one, according to percentages of free lime, which may be higher in this lime than in the previous ones, especially if it is based in air lime. Its composition must be declared in percentages on the packaging.
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Thanks for reading.