What is quicklime? Lime is the main raw material often used in building houses in our life. Lime is divided into quicklime and hydrated lime, but many friends can't understand what quicklime is and what uses quicklime has? What is the difference between quicklime and hydrated lime? Let's have a look
What is quicklime
Calcium oxide is what we usually call quicklime, so how does lime come from? All natural rocks with calcium carbonate as the main component, such as limestone or dolomitic limestone, can be used to produce lime. Quicklime is the carbon dioxide discharged after burning the main natural rock that becomes calcium carbonate at an appropriate temperature, and the obtained carbon oxide is the main quicklime. Although quicklime is extracted from any rock, it plays a very important role in our daily life and has a very high position.
Main components of quicklime
Since quicklime is decomposed by calcination at high temperature in natural rock, the main component of quicklime after removing decomposition of carbon dioxide is calcium oxide. Of course, it also contains other components in addition to calcium oxide. Lime contains underfire lime and overfire lime. Underfire lime means that calcium carbonate is not completely decomposed, and overfire lime is a rice plant with very high structure. After calcination, the surface is covered with a layer of molten material, which ripens very slowly. In addition to calcium oxide, the main component of quicklime also includes magnesium oxide. According to the content of magnesium oxide, quicklime can also be divided into calcareous lime and magnesian lime.
Function of quicklime
We all know that lime can be used as building materials, but the role of quicklime is not far limited to this. After absorbing moisture or adding water, quicklime can become hydrated lime. In this way, it can be mixed into stone mortar, lime paste and lime mortar as coating materials. In addition to being used as building materials, quicklime can also be used as filling materials in rubber, plastics, paper, toothpaste and cosmetics. At the same time, quicklime can also be used as desiccant and disinfectant, This use is widely used in daily life. In addition, in agriculture, quicklime can also be transformed into fertilizer. After mixing quicklime, it can improve the structure of soil and supplement calcium for plants.
Difference between quicklime and hydrated lime
(1) Hydrated lime
Lime can be divided into quicklime and hydrated lime. The main component of quicklime is calcium oxide (CAO), white solid, refractory and insoluble. Limestone with high CaO content can be obtained by calcining it above 900 ℃ in a ventilated lime kiln. It has water absorption and can be used as desiccant. It is commonly used by Chinese people to prevent the moisture return of sundries. React with water (release a lot of heat at the same time), or absorb moisture in humid air, that is, mature lime [calcium hydroxide Ca (OH) 2, also known as' slaked lime '. Slaked lime dissolves 1.56 g (20 ℃) in a liter of water, and its saturated solution is called' lime water ', which is alkaline and absorbs carbon dioxide in the air to form calcium carbonate precipitation.
(2) Transformation and hardening with hydrated lime
The process in which quicklime (CAO) reacts with water to produce calcium hydroxide is called the slaking or digestion of lime. The calcium hydroxide produced by the reaction is called hydrated lime or hydrated lime.
The lime will release a lot of heat during slaking, and the volume will increase by 1-2.0 times. The lime with good calcination and high calcium oxide content will mature faster, and the heat release and volume will increase more. There are two methods commonly used for slaking lime on the construction site: slaked lime mortar method and slaked lime powder method.
In the lime slurry formed after slaking of quicklime, the lime particles form calcium hydroxide colloidal structure, the particles are very fine (the particle size is about 1 & mu; m) and the specific surface area is large (up to 10 ~ 30m2 / g) , a thick water film is adsorbed on its surface, which can adsorb a large amount of water, so it has a strong ability to maintain water, that is, it has good water retention. Adding it into cement mortar and mixing it into mixed mortar can significantly improve the workability of mortar.
Lime is hardened by dry crystallization and carbonization. Due to the low content of carbon dioxide in the air and the hard shell of calcium carbonate formed after carbonization prevents the penetration of carbon dioxide into the interior and hinders the outward evaporation of water, the hardening is slow and the strength after hardening is not high. The 28d compressive strength of 1:3 lime mortar is only 0.2 ~ 0.5MPa. When in a humid environment, the If water does not evaporate and carbon dioxide cannot penetrate, the hardening will stop; in addition, calcium hydroxide is slightly soluble in water, and the hardened lime will dissolve and collapse in water. Therefore, lime should not be used in a long-term humid and water soaked environment.
During the hardening process of lime, a large amount of water will evaporate, causing significant volume shrinkage and prone to dry shrinkage cracks. Therefore, lime should not be used alone. Generally, it should be mixed with human sand, paper reinforcement, hemp knife and other materials to reduce shrinkage, increase tensile strength and save lime.
Lime has strong alkalinity and can react with glassy activated silica or activated alumina at room temperature to produce hydraulic products and cement. Therefore, lime is also an important raw material in building materials industry.
What are the functions of quicklime after making mature lime
Lime is an important material in our daily life or industrial use, while quicklime generally has a small role. Most of them need us to make quicklime into hydrated lime. In fact, this process is very simple, that is, add an appropriate amount of water, but after adding water, quicklime will begin to react with water, and a large amount of heat will be released in this process, so whether or not it is in When operating around us, we must pay attention to controlling the danger, because hydrated lime is very corrosive and easy to hurt our skin, so we use it carefully.
When we use quicklime to make hydrated lime, all this will become very simple, and we can use these substances in all aspects, whether for interior decoration coating or other process improvement, the final result will actually become very simple. This is also why many people like to use hydrated lime, because it has good stability and The possible problems are also relatively clear and will not produce some adverse consequences, so this matter will be very important.
In some places, quicklime will be used to make hydrated lime for agriculture. Because of its strong existence, it can effectively kill some pests. Therefore, we prefer the existence of such substances, which has obvious effects, and can also be applied in all aspects, especially in some places where there is demand. In fact, we are familiar with their characteristics, but It may be necessary to pay attention to some places during use, such as the characteristics of easy hardening, and more mixing is required to prevent adhesion from affecting the use.