Ceramsite, as its name implies, is a ceramic particle.Most of the appearance characteristics of ceramsite are round or oval spheres, but some imitation crushed stone ceramsite is not round or oval spheres, but irregular crushed stone.
The shape of ceramsite varies with different processes.Its surface is a hard shell, which is made of pottery or enamel, has the function of water and gas insulation, and endows ceramsite with high strength.
Because there are many raw materials and varieties for producing ceramsite, there are many colors.The color of baked ceramsite is mostly dark redOchre redThere are also some special varieties of grayish yellow, grayish black, grayish white, greenish gray, etc.The non fired ceramsite has different colors due to different solid wastes. It is generally gray black, and its surface has no gloss, so it is not as smooth as the baked ceramsite.
The particle size of ceramsite is generally 5~20mm, and the maximum particle size is 25mm.Ceramsite is generally used to replaceconcreteCrushed stone andPebble。
The lightness is the most important of many excellent properties of ceramsite, and also the main reason why it can replace heavy sand.The internal structure of ceramsite is fineHoneycombMicropores.These micropores areclosedNot connected.It is formed because the gas is wrapped into the shell, which is the main reason why ceramsite is light.
The fine particles of ceramsite are called ceramsite.There are many fine particles smaller than 5mm in ceramsite, which are used in productionScreening machineThis part of fine particles are screened out, which is customarily called pottery sand.The density of pottery sand is slightly higher, and its chemical and thermal stability is good.Pottery sand is mainly used to replace natural river sand or mountain sandLight aggregateConcrete, lightweightmortar, can also be used as acid resistantHeat resistant concreteFine aggregate.The main varieties areClayPottery sand shale pottery sand andFly ashPottery sand, etc.The purpose of using pottery sand is also to reduce the dead weight of buildings.Pottery sand can also be used for soilless cultivation and industrial filtration.
Ceramsite is a kind of lightweight aggregate produced by foaming in rotary kiln.It has a spherical shape, smooth and hard surface, honeycomb inside, small density, low thermal conductivity, and high strength.In the refractory industry, ceramsite is mainly used as aggregate for thermal insulation refractory.
The stacking density of ceramsite is less than 1100kg/mthree, generally 300~900kg/mthree。Take ceramsite asaggregateThe density of produced concrete is 1100 ～ 1800kg/mthreeThe corresponding compressive strength of concrete is 30.5~40.0Mpa.The biggest feature of ceramsite is that it has a hard surface and many micropores inside.These micropores endow ceramsite with light quality.200 # fly ashCeramsite concreteWith a density of 1600kg/mthreeabout.Ceramsite sand in China is mainly used as oil proppant, which is also one of the largest demand ceramsite sand varieties, also known as oil fracturing proppant ceramsite sand.
Ceramsite has excellent properties, such as low density, high cylinder compression strengthporosityHigh,Softening coefficientHighFrost resistanceGood, excellent alkali resistant aggregate reactivity, etc.In particular, due to the small density of ceramsite, porous inside, uniform shape and composition, and certain strength and solidity, the ceramsite has multi-function characteristics such as light weight, corrosion resistance, frost resistance, earthquake resistance and good isolation.With these excellent properties, ceramsite can be widely used in building materials, gardening, food and beverage, fire resistanceThermal insulation material, chemical, petroleum and other sectors, with more and more applications, are still expanding.
At the beginning of the invention and production of ceramsite, it was mainly used in the field of building materials. Due to the continuous development of technology and people's deeper understanding of the properties of ceramsite, the application of ceramsite has already exceeded the traditional scope of building materials, expanding its new application fields.The application of ceramsite in building materials has declined from 100% to 80%, and in other areas, it has accounted for 20%.With the continuous development of new quality and new uses of ceramsite, its proportion in other aspects will gradually increase.
performance
The reason why ceramsite has been developed rapidly in the world is that it has many excellent properties that other materials do not have, which makes it irreplaceable.These excellent performances include the following aspects.
Thermal insulation
The ceramsite provided by Chinese ceramsite has good thermal insulation due to its porous interior. The concrete prepared with itThermal conductivityGenerally 0.3~0.8W/(m · k)ordinary concrete 1~2 times lower.Therefore, ceramsite buildings have good thermal environment.
Excellent fire resistance
Common fly ashCeramsite concreteOr the flyash ceramsite block integrates thermal insulation, earthquake resistance, frost resistance, fire resistance and other properties, especially the fire resistance is more than 4 times that of ordinary concrete.For the same fire resistance cycle, the plate thickness of ceramsite concrete is 20% thinner than that of ordinary concrete.In addition, fly ash ceramsite can also be used to prepareRefractory concrete。At 650 ℃, ceramsite concrete can maintain 85% of the strength at room temperature.Ordinary concrete can only maintain 35%~75% of the strength at room temperature.
Good seismic resistance
Ceramsite concreteDue to light weight, low elastic modulus and good deformation resistance, it has good seismic performance.In the 1976 Tangshan earthquake, the four ceramsite concrete slab buildings built in Tianjin were basically intact and could be used as usual.A considerable number of brick and concrete buildings around it were damaged to varying degrees.Although this is different frombuilding structureHowever, the excellent seismic performance of ceramsite concrete is also an important reason.In 1976, a strong earthquake of magnitude 9 occurred in the Ferruli region of Italy. Statistical data showed that the damage rate of brick concrete buildings reached 40%~60%, and the clay of frame structuresHollow brickThe building damage rate is 33%, while the ceramsite concrete building damage rate is only 5%.The seismic performance of ceramsite can be seen from this.
Low water absorption, good frost resistance and durability
Ceramsite concreteAcid and alkali corrosion resistance and frost resistance are better thanordinary concrete 。No. 250Fly ash ceramsiteFor concrete, the strength loss of 15 freeze-thaw cycles shall not be greater than 2%.In 1976, relevant departments measured ceramsite concrete projects built in China since 1985. The results showed that the reinforcement contained in both prefabricated and cast-in-place, indoor and outdoor was not corroded. The measured carbonation depth was generally not more than 30mm, and the strength could continue to increase in the later period.It can be seen that ceramsite concrete is an excellent building material and should be vigorously promoted.
Excellent impermeability
According to many tests,Ceramsite concreteIs better thanordinary concrete 。Taking 20MPa ceramsite concrete and ordinary concrete as an example, after many tests and comparisons, the impermeability index of ordinary concrete is B6, while ceramsite concrete can reach B18 to B25.In 1970, Tianjin built an air defense passage with 20 MPa ceramsite concrete (3 m deep, 0.9 m underground water level), but no leakage was found during the inspection in 1980.Two 20MPa ceramsite concrete bunkers (with a load capacity of 80t) built in Ningbo have been operating on water for 13 years without any leakage.Therefore, ceramsite concrete is one of the excellent building materials for making dams and underground works.
The main components of concrete are cement and aggregate.Aggregate includes crushed stone and sand. If the stone and sand are dolomite, limestone or other aggregates containing SiOtwoThe alkali in cement will react with these aggregates to cause the disintegration of rock minerals or the expansion of concrete to crack and collapse, resulting in building damage.This is the alkali aggregate reaction.Every year, a large number of buildings at home and abroad are damaged due to the alkali aggregate reaction of concrete.In the 1980s, the United States counted 500000 highway bridges nationwide, of which 200000 were damaged to varying degrees due to alkali aggregate reaction.The annual loss caused by alkali aggregate reaction in the world can reach hundreds of billions of dollars.
Since ceramsite does not contain these igneous rock components and its alkali content is very low, it will not occur with cement during useAlkali aggregate reaction。Domestic and foreignCeramsite concreteBuilding, no case of alkali aggregate reaction has been found.Facts have shown that ceramsite has excellent resistance to alkali aggregate reaction, which can increase safety to a certain extent and extend the service life of buildings.
Strong adaptability
It has been proved by decades of production practices at home and abroad that clay, shale, fly ash or other solid wastes can be used to produce ceramsite according to different resource conditions in different regions.According to different uses and market needs, we can produce ceramsite products with different stacking density and particle size (ultra light ceramsite, ceramsite for structural insulation, ceramsite for structural insulation), as well as ceramsite with special uses, such as high-temperature resistant ceramsite, acid resistant ceramsite, flower ceramsite, etc.
When using ceramsite, different types of ceramsite can be used to prepare sand free large holes, full light, ultra light reinforcement or prestressed concrete with different densities and strength grades according to actual needs.It can be prefabricated into various types of wall products and building components, and can also be used for filling, cast-in-place, slip form and other construction operations.It can be applied to various building systems, such as frame filled or self bearing block buildings, one formwork with three plates, fully assembled large plates, internally cast and externally hung, and fully cast slip form buildings.Walls (blocks, exterior wall panels, interior partition slats), floors, roof slabs, beams and columns, and some foundations in any building can be usedCeramsite concreteIt is incomparable to any other new wall.[1]
It is mainly made of high-quality bauxite, coal and other raw materials through multiple processes such as crushing, fine crushing, grinding, granulating and high-temperature sintering. It is characterized by high temperature resistance, high pressure, high strength, strong conductivity and corrosion resistance. It is mainly used for downhole support of oil fields to increase oil and gas production. It is an environmental protection product.yesNatural quartz sandSubstitutes of medium and low strength proppants such as glass balls and metal balls have good effects on increasing oil and gas production.
（2）Clay ceramsite
Clay ceramsite is a kind of light coarse aggregate with a particle size of more than 5mm, which is made from clay, sub clay, etc. through processing, granulation and sintering.
(3) Shale ceramsite
It is also called expanded shale.Shale ceramsite refers to the light coarse aggregate with a particle size of more than 5mm formed by crushing, screening, or grinding clay shale, slate, etc.According to the process method, shale ceramsite can be divided into: ordinary shale ceramsite formed by crushing, screening and burning;Spherical shale ceramsite is grinded, balled and burnt.
Clay ceramsiteFly ash ceramsiteShale ceramsite is suitable for thermal insulation and structural thermal insulationLightweight aggregate concreteIt can also be used for lightweight aggregate concrete for structure.The main use of shale ceramsite is to produce lightweight aggregate concrete small hollow blocks andLight partition board。
(4) Garbage ceramsite
With the continuous development and expansion of the city, more and more urban garbage will be disposedcity waste, has become an increasingly prominent problem.
Rubbish ceramsite isMunicipal domestic wasteAfter treatment, sintered ceramsite is produced by granulation and roasting.Or add garbage cinderscementGranulation and natural conservation can produce unburned waste ceramsite.Garbage ceramsite is characterized by sufficient raw materials, low cost, low energy consumption, light weight and high strength.In addition to making new wall materials such as wallboard, block and brick, garbage ceramsite can also be used for thermal insulation, floorLightweight concrete, water treatment and purification, and has a broad market.
(5) Gangue ceramsite
Coal gangue is black waste rock with less carbon content discharged during coal mining, which is the largest solid waste in China. Its discharge and accumulation not only occupy a large amount of farmland, but also cause great pollution to the surface and atmosphere.The chemical composition of coal gangue is similar to that of clay. The coal gangue contains high carbon and sulfur and has a large loss on ignition.Only in a certain temperature range can a sufficient amount of melt with appropriate viscosity be produced, which has expansion property.According to its characteristics, China has developed coal gangue ceramsite.
Gangue ceramsite is produced by crushing, preheating, swelling, cooling, grading and packaging the gangues that meet the requirements of swelling.The quality of ceramsite products obtained completely conforms to the national standards, and some technical indicators exceed the national standards, reaching the quality of similar products abroad. The product is innovative, first in progress, and environmentally friendly.
(6) Biological sludge ceramsite
The sewage treatment plant produces a large amount of biological sludge after sewage treatment. Some biological sludge is made into agricultural fertilizer, some is directly used for greening, and some is discharged into the sea or burned, which will cause secondary ecological environment pollution.The ceramsite made of biological sludge as the main raw material by drying, grinding, balling and sintering is called sewage treatment biological sludge ceramsite.Using biological sludge instead of some clay to burn ceramsite not only saves clay, but also protects farmland, and also plays a certain role in environmental protection.
(7) River bottom clay ceramsite
A large number of rivers and lakes formed a lot of sediment after years of sedimentation.The haydite made from river bottom mud instead of clay through dredging, natural drying, raw meal balling, preheating, roasting and cooling is called river bottom mud haydite.Using river bottom mud to make ceramsite will not only reduce the competition between building materials manufacturing industry and agricultural land, but also find a reasonable way for river bottom mud, solve the secondary pollution problem of river bottom mud, and achieve the goal of waste recycling.
With solid waste as the main raw material, a certain amount of cement and water are added, processed into balls, sintered and expanded or naturally cured, and the light coarse aggregate with a particle size of more than 5mm is called fly ash ceramsite for short.
Classification by strength
Ceramsite can be divided into high-strength ceramisite and ordinary ceramisite according to strength.
(1) High strength ceramsite
According to the new standard (Light aggregate and its test methods) GB/T 17431.1-1998, high-strength ceramsite refers to structural light coarse aggregate with strength grade not less than 25MPa.Its technical requirements are the same as those of ultra light and ordinary ceramsite except that there are specific indicators such as density grade, cylinder pressure strength, strength grade and water absorption rate.When producing high-strength ceramsite, the output is low, the energy consumption is high, and the added value is high. The sales price is about 50% higher than that of ultra light ceramsite and ordinary ceramsite.Preparation of high grade and prestress with high-strength ceramsiteLightweight aggregate concreteIt must be homogeneous.
(2) Ordinary ceramsite
According to the new standard of Light Aggregate and Its Test Methods (GB/T 17431.1-1998), ordinary ceramsite refers to light coarse aggregate for structure with strength grade less than 25MPa.Ordinary ceramsite is widely used and has great market potential.
Classification by density
According to the density, ceramsite can be divided into three types: ordinary density ceramsite, ultra light density ceramsite and extra light density ceramsite.
(1) Ordinary density ceramsite
Ordinary density ceramsite refers to the density greater than 500kg/mthreeCeramic grains.Its strength is generally relatively high, and it is mostly used for structureThermal insulation concreteorhigh-strength concrete 。
(2) Ultra light density ceramsite
Ultra light density ceramsite generally refers to 300-500kg/mthreeCeramic grains.This kind of ceramsite is generally used for thermal insulation concrete and its products.
(3) Extra light density ceramsite
Extra light density ceramsite refers to less than 300kg/mthreeCeramic grains.Its thermal insulation performance is very excellent, but its strength is poor.It is generally used to produce extra light thermal insulation concrete and its products.
Sort by shape
According to the shape, ceramsite can be divided into crushed stone ceramsite, spherical ceramsite and cylindrical ceramsite.
(1) Gravelly ceramsite
Crushed stone ceramsite is generally produced with natural ores. The stones are crushed, roasted, and then screened;Natural and artificial light materials such as pumice, volcanic slagcoal cinder, natural or calcined coal gangue, directly crushed and screened.
(2) Spherical ceramsite
Spherical ceramsiteDisc Pelletizer Production.First, the raw materials are ground, and then water is added to granulation, which is made into balls and then baked or cured.Most ceramsites in China are of this variety.
(3) Cylindrical ceramsite
Cylindrical ceramsite is generally molded by plastic extrusion.First make mud strips, and then cut them into cylindrical shapes.This kind of ceramsite is suitable for clay materials with high plasticity, and its output is relatively low.If the cylindrical billet is baked in a brick kiln, the cylinder will roll into an ellipse in the kiln.
Classification by performance
(1) High performance ceramsite
High performance ceramsite refers to roasted or unfired ceramsite with high strength, low water absorption and low density.Light aggregate is rich in resources and various in varieties.It is divided into natural light aggregate, solid waste light aggregate and artificial light aggregate.According to their generation conditions and performance, they can be used to preparehigh performance concrete Only specially processed high-performance ceramsite is available.It is generally called high-performance lightweight aggregate abroad, and can also be called high-strength ceramsite in China.
High performance ceramsite is a kind of artificial lightweight aggregate with different density grades, high strength, low porosity and low water absorption, which is made of suitable raw materials and special processing technology.Some properties of this lightweight aggregate are similar to those of ordinary dense aggregate, and its performance is superior to that of ordinary lightweight aggregate.
(2) Ordinary performance ceramsite
Ordinary ceramsite is relative to high-performance ceramsite.That is, its strength is slightly lower than that of high-performance ceramsite.The porosity is slightly higher and the water absorption is also high.However, its comprehensive performance is still better than that of ordinary aggregate.[2]
productionFly ash ceramsiteDouble drum rotary kiln should be adopted, that is, the preheating section and drying section of the kiln body can control its rotational speed separately, and Ningbo Huawen can control the ceramsite produced by its preheating time according to the state of raw materials.In recent years, clay ceramisite has been banned from production and use in some areas due to the limitation of land resources.However, in some areas, river silt and waste mountain soil can be used for production.The technological process is: raw material mixing - granulation - screening - sintering - stacking - transportation (bagging).
During operation, attention shall be paid to lookout to prevent materials from agglomerating in the kiln and affecting the quality.
The production equipment of ceramsite in China isIndustrial rotary kiln。The cylindrical main kiln body is placed on the supporting roller at an angle of about 3 ° to the horizontal.The materials enter the kiln at the high end. Under the action of the rotary movement of the kiln body, the materials roll down from the high (kiln tail) to the low (kiln head). At the same time, at the kiln head, the high-pressure fan injects pulverized coal (or natural gas and other fuels) into the kiln and fully burns it. The heat generated causes physical and chemical changes in the materials, resulting in expansion. After cooling, the materials become ceramsite.
Production equipment
The main equipment for ceramsite production mainly includes: raw material storage bin, dust chamber, induced draft fan, main kiln body, coal injection system, control cabinet, etc.Among them, the feeder at the lower part of the raw material bin, the kiln body speed and the amount of arch coal are all stepless speed regulation, so as to adjust its process parameters and obtain the maximum output on the premise of ensuring product quality.
The auxiliary equipment for shale ceramisite production includes: crusher, screening machineBelt conveyor, feeding machine, discharging machine, etc.
The auxiliary equipment for the production of fly ash and clay ceramsite include: wheel rollerBiaxial mixer, granulator, screening machine, feeding belt conveyor, etc.
During operation, attention should be paid to the matching relationship between the feeding amount, coal feeding amount, kiln body speed and air volume, so that they can be adjusted to the best process state.
Using fly ash and other industrial waste residue to produce ceramisite is a subject developed by many people concerned for many years.High strength and light weightFly ash ceramsiteIt has been successfully launched, and all performance indicators are better than shale and clay ceramsite.In addition to mastering the process requirements, additives are also the main reasons affecting its performance.Admixtures mainly include adhesives, expansion agents and mineralizers.The admixtures of fly ash with different compositions are also different.[3]
purpose
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building material
Ceramsite concreteIt has been widely used in various types of prefabricated components andcast-in-place concreteIn engineering (such as prestressed and non prestressed, load-bearing structure or enclosure, thermal insulation or impermeability, static load or dynamic load).Ceramsite can also be used for pipe insulation, furnace body insulation, cold insulation, sound insulation and other building materials;It can also be used as soilless bed material and water filtering material in agriculture and gardens.
Greening materials
Because ceramsite has a special structure of porous, light weight and high surface strength, its use in landscaping and indoor greening not only meets the needs of plant water, but also meets the requirements of air permeability, especially its characteristics of no dust and light weight have been increasingly applied to the breeding of indoor ornamental plants.
Food hygiene materials
In addition to porous, light and heavy, high surface strength and other physical properties, ceramsite also has certain active substances in the production process, so it has begun to be used in drinking water, bathing and other aspects related to daily life, such as filtering drinking water by placing it in the water dispenser, increasing the activity of water by placing it in the handle of the shower, and so on.
Industrial filter material
The active material of ceramsite is also widely used in industry.BiologicalCeramsite filter materialIt can be used as biological membrane carrier of industrial wastewater high load biological filter material pool, micro polluted water source of tap water, pre-treatment biological filter, coarse-grained material of oily wastewater, ion exchange resin cushion, and microbial dry storage;It is suitable for advanced treatment of drinking water. It can adsorb harmful elements, bacteria and mineralized water in the water body. It is the best filter material for active biological degradation of harmful substances, and the best biofilm carrier in the biofilter.[4]
