Castozytte 39 lightweight binder for Ceramics and Refractories. Castozytte39 is a registered brand of Mehran Ceramics.

Lightweight Castozytte 39 is a proprietary, cement free, lightweight pumpable refractory product intended for application by pouring, pumping, or pneumatic shotcreting. For pouring/pumping placement, Lightweight Castozytte39 is supplied as a two component system, including the colloidal silica binder plus instant settings, a special chemical accelerant utilized to induce rapid material setting. The patented colloidal silica binder system provides a very fluid, self leveling refractory slurry that allows rapid material placement by pumping onto either hot or cold substrates, or by shotcreting, utilizing the accelerant that is injected into the pneumatic slurry propellent, that results in minimal rebound waste. Lightweight Castozytte39 exhibits excellent adhesion characteristics to refractory and metal substrates and develops strong bonding to itself or to other refractories with no laminations, even if applied during multiple, independent placements, regardless of the time intervals between placements. After heat up, Lightweight Castozytte39 forms very strong bonding to virtually all undeteriorated refractory materials and requires minimal dry out time, which reduces component downtime and increases availability and in service, exhibits excellent insulating and exceptional strength properties.

Application

Lightweight Castozytte 39 is recommended for new lightweight refractory linings or hot or cold repair or replenishment of existing lightweight refractory linings, including in the blast furnace and similar metallurgical process vessel applications, whenever a lightweight, insulating castable/ pumpable/shotcretable product is required.

Castozytte 99. A lightweight binder for Ceramics and Refractories. Registered brand of Mehran Ceramics

Lightweight Castozytte 99 is a proprietary, cement free, lightweight pumpable refractory product intended for application by pouring, pumping or pneumatic shotcreting. For pouring/ pumping placement, Lightweight Castozytte 99 is supplied as a two component system, including a colloidal silica binder, or for application by shotcreting, is supplied as a three component system, including the colloidal silica binder plus instant setters, a special chemical accelerant utilized to induce rapid material setting. The patented colloidal silica binder system provides a very fluid, self leveling refractory slurry that allows rapid material placement by pumping onto either hot or cold substrates, or by shotcreting, utilizing the accelerant that is injected into the pneumatic slurry propellant,
that results in minimal rebound waste. Lightweight Castozytte 99 exhibits excellent adhesion characteristics to refractory and metal substrates and develops strong bonding to itself or to other refractories with no laminations, even if applied during multiple, independent placements, regardless of the time intervals between placements. After heat up, Lightweight Castozytte 99 forms very strong bonding to virtually all undeteriorated refractory materials and requires minimal dry out time, which reduces component
downtime and increases availability and in service, exhibits exceptional strength properties.

Application

Lightweight Castozytte 99 is recommended for new lightweight refractory linings or hot or cold repair or replenishment of existing lightweight refractory linings, including in the blast furnace and similar metallurgical process vessel applications, whenever a lightweight castable/pumpable/ shotcretable product is required.

Refractory Cements and Raw Materials Information.

Refractory cements and raw materials are hard, heat resistant materials that are suitable for applications which require high temperature strength, wear resistance, electrical or thermal insulation, or other specialized characteristics. Refractory cements are used to patch or line furnaces and bond bricks or joints in high temperature applications. Most refractory cements consist of a mixture of a binder or clinker and a coarser aggregate. Clinker is a fused mineral or mineral mixture, such as alumina or bauxite and lime, which is crushed into a fine powder. Aggregates are coarser, granular materials that are added to mortar, grout, and cement to impart special properties such as refractoriness and erosion or oxidation resistance. Refractory raw materials include products such as alumina ceramics, fire clay, bricks, pre-cast shapes, aluminate cement, and monolithics. Monolithic refractories are liners fabricated without joints by ramming, gunning or casting refractory cements in place. 
Types

There are many types of refractory cements and raw materials. Mineral aggregates consist of crushed rock, stone, or sand and require thermal processing. Castable products are poured into forms or cavities to fabricate refractory liners. Coatings and sealants can be sprayed or brushed onto surfaces such as furnace walls. Dry refractories are supplied as a dry powder that is applied and fired in place. Granular fill such as vermiculite is loaded into a cavity to provide insulation and remains in a loose, unbonded condition. Gunning mixes are powdered products that are loaded with a gun into a form or onto a furnace wall to create an insulating layer. Investment refractory cements and raw materials consist of a refractory powder with a plaster or phosphate binder. Potting compounds and encapsulants are used to provide electrical insulation. Wet rams are refractory cements with enough plasticity to allow the wet mix to be rammed or formed into place in a furnace or a form. Refractory mortars, rigidizers, and synthetic aggregates are also available. 
Selection

Selecting refractory cements and raw materials requires an analysis of material types and bonds. Material types include alumina, alumina-zirconia, aluminum silicate or sillimanite, calcium aluminate, calcium silicate, carbon or graphite, chromia or chromite, dolomite, kaolin or fire clay, magnesia or magnesite, magnesium silicate or forsterite, mullite, porcelain, silicon carbide, silica or fused silica, spinel, titania or titanate, yttria, zircon, and zirconia. Cement bond and set types include calcium aluminate, calcium silicate, phosphate, silicate, and sulfur or sulfate. Polycrystalline ceramics or aggregate-based refractories that use chemical, hydraulic, or thermal bonds are also available. Organic or polymer resin binders hold refractories together until firing. Some resins are designed to burn out. Others are converted to carbon.
 
Refractory cements and raw materials differ in terms of cement properties and material features. Cement properties include maximum use temperature, thermal conductivity, modulus of rupture (MOR) or flexural strength, compressive strength, particle or aggregate size, density, and shrinkage. Material features indicate whether refractory cements and raw materials are acidic, alkaline, or neutral; fiber-reinforced or binder-free; or suitable for corrosive environments or electrical applications. Composite materials consist of a matrix material reinforced with a stronger or higher modulus second phase.  The matrix may consist of a ceramic, metal, or polymeric material. The second phase may be in the form of particulates, chopped fibers or continuous fibers. 

Binders for Ceramic Bodies:

General
Description

An overview of the major types of organic and inorganic binders used in various different ceramic industries.

Article
Binders are substances that improve the mechanical strength of green ceramic bodies so they can pass through production steps, before firing, without breakage. In many cases, binder additions to bodies are essential (without them some production processes would be impossible). For instance, in the pressing process of powders, adding organic binders makes possible a forming method that is independent of the plasticity).

There are a wide variety of binders used in traditional ceramics, including natural products, like cellulose or clays, and synthetic products, like polyacrylates or polyvinyl alcohol.

A normal body binder must have several characteristics:

It must leave a minimal amount of ash after firing
It must easily burn out at low temperature
It cannot be abrasive
It must improve the mechanical strength of dry pieces
It does not cause bodies to stick to molds
Its dispersion must be easy
It cannot be toxic
It does not affect the glazing stage of manufacturing
It must be as inexpensive as possible.
Inorganic Binders
Inorganic binders have a couple of very important characteristics: they are inexpensive and are not subject to attack by microorganisms. Another big bonus is that they never cause black coring.

Sodium Silicate
Its main use is in slip deflocculation. However it also improves the mechanical strength of dry pieces when employed in pressing and extruding operations. Behavior does change according to chemical composition of sodium silicates but, in the case of pressed tiles, often it is the best when the properties range toward some tendency to black core.

Magnesium Aluminum Silicates
Available products have different compositions because they are obtained from extremely plastic natural minerals (called smectites). Particles are off-white with colloidal sizes. When we add these binders to slips in the range 0.5-5% the mechanical strength of pieces proportionally increases. These binders are less effective than others but they have an important characteristic: they don t migrate during drying so we have less problem during glazing procedures.

Bentonite
This is a very plastic natural material mineralogically known as montmorillonite. It is used in the range 0.5-3.0% however it raises the viscosity of slips during milling (the maximum allowed percentage depends on characteristics of the material and on the permissible viscosity value). It improves mechanical strength of green and dry bodies and it also does not migrate during drying.

Organic Binders
Often organic binders are made from polymers with more or less long chains where polar groups are present. Most organic binders are soluble in water and behavior is like a surfactant (it improves contact between liquid and solid phases). Short chain binders are adsorbed on the surface of particles and during drying water elimination from hydroxyl groups produces tridimensional hydrogen bonds (among the molecules of binder distributed on the surface of the particles). The development of chemical bonds contributes to a stronger tridimensional structure and mechanical strength improves proportionally to the amount of organic binder. Long chain binders have poor solubility in water but are emulsifiable. During drying they are not absorbed at the surface of particles but they are able to form tridimensional hydrogen bonds.

Usually organic binders do not improve the strength of green pieces before drying. Drying strength rises proportional to the added amount of binder (actually it can even reach values 30% higher). Theoretically, organic binders burn off on firing at low temperatures with minimal residue. Nevertheless, these binders are increasing the organic matter content in bodies, experience has shown that pressed tiles employing organic binders are quite subject to black coring problems.

Often organic binders are decomposed by bacteria and we have to add an anti-bacterial agent to stabilize slips. Organic binders are also used in glazes and engobes to ensure good adhesion to the ceramic surface, prevent sedimentation and improve rheological properties.

The most popular are:

Polyvinyl Alcohol
Usually it is used as a binder for glazes, during glazing operations, before the screen printer (a water solution of polyvinyl alcohol is sprayed on the surface to be decorated). It is a strong surfactant and binding power is connected to its ability to wet particles (products having a low molecular weight exhibit low viscosities and they have a minimal effect on the viscosity of glazes or body slips). It is stable because it does not ferment. Usually suppliers propose water solutions of polyvinyl alcohol.

Starches
Starches are powdered forms of a group of carbohydrates producing colloidal emulsions in water having strong binding properties (however some times modified starches are supplied as liquids).

Often they are not fully soluble in water because of their high molecular weight (this characteristic prevents migration during drying). It is possible to mix starch and dry ceramic powders (after which the mix can be wetted, formed and dried). Starches quickly ferment. Chemical derivatives have properties like esters of cellulose but are not stable against bacteria.

Carboxymethylcellulose
It is a white-yellow powder soluble in water. It can migrate during drying (thus the distribution in the body matrix may not be uniform). There are different types with different molecular weights. Carboxymethylcellulose products with medium or high molecular weights are stronger binders but they increase viscosity of slips so they cannot be used above certain percentages (thus not fully developing their binding properties). These products improve the plasticity and mechanical strength of dry bodies and completely burn out during firing, however they are expensive.

Dextrin
A yellowish powder obtained by treating certain starches with small amounts of acid. Dextrin is a strong binder and is some times used to prepare glaze grains for dry application or as a "glue" for glaze slips to improve adherence to the ceramic body. Dextrin also improves the plasticity of clay slips.

Wax Emulsions
Wax emulsions behave like inter-particle lubricants when bodies are wet and like binders when dry. They are widely used for the production of technical alumina components.

Polyethylene Glycols
Polyethylene glycols having low molecular weights are viscous liquids often used as plasticizers or lubricants. Those having high molecular weights are waxy solids that are used as binders and plasticizers in pressing. They are water soluble and often used as basic mediums for the preparation of printing colors.

Lignosulfonates
Lignosulfonates are yellowish powders having variable compositions and also variable molecular dimensions (because they are polymers that can be modified by the addition of organic or inorganic groups to the molecule). They are anionic derivatives of lignin, water soluble and surfactants. Lignosulfonates are very effective in increasing mechanical green and dry strength in ceramic pieces. In addition, they act as lubricants during extrusion or pressing operations. Additions of lignosulfonates to ceramic slips can vary from 0.1 to 2.0% and they are relatively inexpensive. For pressed tiles, 1% lignosulfonate can double mechanical strength (however often a black core appears). Lignosulfonates are often used to reduce shrinkage yet maintain after-forming mechanical strength (because reduced amounts of plastic clays are needed).

Methylcellulose
A derivative of cellulose (when treated with methylene chloride and alkali under pressure). The composition is variable depending on the length of chains and methylcelluloses are non-ionic polymers, water soluble at low temperature. They are very stable against microorganisms but they have tendency to form foam. Methylcelluloses have different viscosities in water (depending the length of chains) and strong deflocculating properties. Often methylcelluloses are used as temporary binders in refractory production and other technical ceramics because they are at the same time lubricant and wetting agents and plasticizers. Hydroxyethilcellulose is a similar product having less tendency to form foam.

Paraffins
Mixtures of paraffins and carnauba wax are widely used as binders for the production of special pieces obtained by cold isostatic or normal pressing. The nature of mixtures is determined by the dimensional tolerance needed and the shapes of edges. Mixtures as liquid emulsions are blended for specific purposes and they also have binding, plasticizing and lubricating properties.

Polyacrylates
Sodium and ammonium salts of polyacrylate acid are water soluble and they are mainly used as strong deflocculants. They can also act like binders but their cost curtails usage for this purpose. Polyacrylate esters are not soluble but they have a similar behavior.

Refractory linning for the kiln burners.

Abrasion caused by high temperature impact clinker dust and chemical influences causing kiln burners to not reach expected lifespan. This influences production and frequent repairs with high cost on burner refractory material.
Mehran Ceramics the leader in refractory installations and pre-cast products in the cement and lime industry has developed a method to line kiln burner pipes that will exceed lifespan of 12 months on refractory. It is common for cement producers to lose refractory life on their burners within 6 months.
Refractory suppliers around the world have tried many different methods and techniques ranging from anchor types, spacing and high abrasion materials. Mehran Ceramics had the opportunity to work with many refractory suppliers over the years, with experience to different lining procedures.
 
The Group’s Precast Division has taken a different approach irrespective of the refractory material, anchor spacing and expansion allowance present. Mehran Ceramics believes that the key in extending burner lifetime lies in a common procedure that consists of the elements, discussed below.

The installation of refractory material gets installed incorrectly therefore is it important to allow the correct mixing times, right amount of water and sufficient vibrating frequencies. The anchor welding procedure is just as important for the burner refractories as the correct mixing procedure.
 
This is the method that should be followed on any kiln refractory burner and is common to all installation procedures, but the best refractory lining with the best anchors possible would not resolve burner lifetime issues. Mehran Ceramic's answer for the success on burner lifetimes lies within the heat up procedure. What is required is a precast facility that has the capacity to dry out complete burner pipes and not just the burner tip. The process requires increasing the temperature by 10 degrees Celsius per hour till it reaches a 100 degrees Celsius. Thereafter holding the temperature at a 100 degrees Celsius for 16 Hours, and then increasing the temperature by 10 degrees Celsius per hour until it reaches 450 degrees Celsius. Next, maintain the temperature at 450 degrees Celsius for a minimum of 12 hours. This allows you to get rid of all excess moist and water within the refractory lining. The second part of the manufacturing process is cooling the burner down by gradually decreasing the temperature with 10 degrees Celsius per hour from 450 degrees Celsius to room temperature. This will eliminate cracking on refractory lining caused by thermal shock.
 
More innovative precast techniques on refractory lining in cement and lime plants could be gathered from Mehran Ceramics. Visit our website on www.mehranceramics. com

Bauxite grinding machine into the refractory material.

In recent years, the market alumina underlying outbreak influenced by various factors, fluctuation fluctuates development type, but in recent years the development of the industry in market share and speed Development there are some other mineral resources may be comparable with. In recent years the sector of industry and refractory casting accuracy, we can say that the bright spring days a year. From an internal perspective, sustainable development ore bauxite mine bauxite in sales, is the largest power of the rapid growth of the mineral resource industry; from an international perspective, one aspect is the need for the international investment casting market development, on the other hand, is also China's bauxite reserves in overall proportion is very important. Consequently, overall sales unpopular in recent years, it is reasonable.

LUM Ultrafine vertical roller mill

Industry character relevant mining equipment says, the beginning of this year of the new mining industry must combine the development of mining bauxite grinding machine and business development, and strive to develop the market in urgent need of equipment in more convenient for mining needs, the company has developed more in line with superfine grinding machine equipment at home and abroad construction applications , its use of advanced technology very complete.

LUM vertical roller mill

Bauxite by mill after processing can be used for a plurality of high-end industry:

(1) aluminum smelting industry. Used in national defense, aviation, automobile, electric appliance, chemical industry, daily necessities etc.

(2) precision casting. Bauxite clinker by superfine grinding machine processed into fine powder and made into mold. Used in military, aerospace, communications, instrumentation, machinery and medical equipment department.

(3) for refractory products. High alumina bauxite refractory degree is up to 1780 DEG C, high chemical stability, good physical properties.

Ultrafine vertical roller mill

(4) of aluminium silicate refractory fibre. Has the advantages of light weight, high temperature resistance, good thermal stability, low thermal conductivity, heat capacity and has the advantages of small resistance to mechanical shock. For the iron and steel, nonferrous metallurgy, electronics, petroleum, chemical, aerospace, atomic energy, defense and other industries. It is the high alumina clinker into the melting temperature of about 2000 ~ 2200 degrees of arc furnace, by high temperature melting, high speed air or steam injection, cooling, became cotton, aluminium silicate refractory fibre white. It can be pressed into brick fiber blanket, board or woven into cloth instead of smelting, chemical, glass and other industrial high temperature furnace lining. Firefighters used refractory fiber cloth made clothes.

(5) with magnesia and bauxite as raw material, adding appropriate binder, used for pouring ladle integral barrel liner effect is very good.

(6) manufacture of alumina cement, abrasive materials, ceramic industry and chemical industry in a variety of aluminum compounds. Unique design with we a superfine grinding machine. Host the grinding cavity, the pressure device 1500kg2000kg design in the upper plum frame, the same power, yield increase of 10-30%, the pressure roller grinding device for material is increased by 800-1500kgf, the fine fineness can reach 1000 mesh. And the material has strong applicability, can be for a variety of material Mohs hardness below level 9.3. The dust removal effect can reach the national standard. In the building products, we adopt world-class manufacturing processes, selection of material for making the most high-end, strict testing means of transformation of innovation of machinery.

MEDIUM AND HIGH PURITY INSULATING CASTABLES. Various.

Castables is a dry materials that can be combined with water to form a homogenous mass which can be cast in formwork similar to concrete.

Castable refractories can be classified into four major groups - dense castables, lightweight or insulative castables, gunning castables, and special purpose castables - sometimes these classifications can be combined, such as lighhtweight gunning castables, or dense gunning castables.

Dense castables are designed for strength, abrasion and corrosion resistance and are primarily used as the working hot face.Lightweight insulating castables provide low thermal conductivity values behind dense castables, or in certain conditions as working hot face linings.Gunning castables are modified versions of the above castables that allow them to be effectively placed using pneumatic guns. Some grades are dual purpose, allowing both casting and gunning without change.Special duty castables feature specifically enhanced properties over conventional castables, such as the modern range of low cement castables and castables with less conventional binders.
As part of our range of materials we are able to offer a range of castables to complement most applications. The dense castable range of materials we supply are made from selected raw material, aggregates and cements. The careful selection of raw material provide goods in this range with a range of properties and characteristics.

Standard Dense Castables are ues in range of material to cover the range of temperatures from 1400 C to 1800 C. These products are the most suitable for a wide range of applications ranging from boiler work, general furnace applications, burner blocks to specialty muffle furnaces. As part of this range we carry 1450, 1600 and 1650 grades for the majority of general castables work.

Gunning Castables are selected of specialty raw material is used to produce a range of Gunning Refractory. This material is mixed with water at the nozzle of the gunning equipment to enable easy placement of castable. This method is very suitable for placement of bulk material in applications where conditions make formwork unpractible or too time consuming. The temperature range varies from 1400C to 1800C to suit most applications.

Low Cement Castables has range of castables with lower cement content than standard dense castables. Varying in Alumina content these products have excellent physical properties. Low porosity, high strength and good abrasion resistance are features of low cement castables. Generally these products require controlled installation including mixing, water addition and high frequency vibration placement.

Abrasion Resistant Castables are use where conditions are extreme a range of Abrasion resistant dense castables are available. These castables are available as Gunning and Low Cement as well as in the Conventional style of castable.

Insulating Castables as the name describes we supply a range of castables with specialty materials and low densities. These products range from materials with temperatures of 1000C and densities of 400kg/m3 up to 1750C with densities up to 1850 kg/m3. Insulating castables are used as either a back up lining or for hot face work. As a back up lining they can be found behind brick work or behind dense castables where protected they help to reduce the overall density of the lining or to reduce the cold face temperature to something suitable for people to work near. As a hot face they are used in areas where wear and tear is not generally a problem. There low density generally means that the insulating range of castables have only low to medium strength making them not suitable to abrasion or particle attack. As a hot face they are used in boilers and furnaces where they are not subjected to punishment.

This Castable is suited for Medium Castable Insulation, High Castable Insulation. This Castable is use by the Fire Bricks for constructing of the Kiln, Furnaces, Ovens, Tunnel Kiln, Shuttle Kiln, Oil Fired Furnaces etc and all types of Reractories and Refractory lining. Castable is also use for patching of certain area from where hot air can be sealed. Castable is also used in a place of Insulation. This all the Products are been Manufacturer, Export, Wholesale, Supply, with many Dealers.

Refractory bricks.

Refractory bricks
Some important refractory bricks

Alumina bricks (or) Fire clay bricks (Acidic refractories)
Alumina bricks contain 50% or more of Al2O3. They are generally manufactured by mixing calcined bauxite (Al2O3 ) with clay binder.

Manufacture
1. Grinding and mixing
The raw materials (calcined bauxite & SiO2 ) and grog (calcined fire clay ) are ground to fine poeder and mixed and mixed with required amount of water to convert it into pasty material.

2. Moulding
The pasty material is converted into bricks by the general moulding technique like machine pressing or slip casting.

3.Drying and Firing
The bricks after moulding is dried slowly to remove the moisture and then fired in continuous kiln or tunnel kiln to about 1200-1400 for 6-8 days.

Properties
(i) Alumina bricks are acidic refractories.
(ii) They posses very low coefficient of expansion.
(iii) They also posses high porosity, and high temperature load-bearing capacity.
(iv) They are also very stable to both in oxidizing and reducing conditions.
(v) Then posses better resistance to thermal to thermal spalling than silica bricks.

Uses
1. Medium-duty bricks (containing 50 to 60% Al2O3)
It is used in lining of cement rotary kilns soaking pita, reheating furnaces, hearts and walls, etc., which are subjected to high abrasion.

2. High-dury bricts (containing 75% Al2O3)
It is used in hottest zone of cement rotary kilns, lower parts of soaking pits, brass melting reverberatories, aluminium melting furnaces, etc.,

3. Fire clay refractories are larely using in steel industries
Magnesite bricks (Basic refractories )
Mangesite bricks contain mainly MgO. They are generally manufactured by mixing calcined magnesite with caustic magnesia or iron oxide as binding material.

Manufacture
1. Grinding and mixing
The raw materials (calcined magnesite) and binding materials (caustic magnesia) are ground to fine powder and mixed with water to a pasty material.

2. Moulding
Moulding is usually done by machine pressing to a required shape.

3. Drying and firing
Drying is carried out at ordinary temperature to remove the moisture. Firing is done in a kiln at 1500oC for 8 hours and then cooled slowly.

Properties
1. Magnesite bricks are basic refractories.
2. They can be used upto 2000oC without load and upto 1500oC Under a load of 3.5 kg/cm2.
3. They have good resistance to basic slags, but combine with H2O and CO2
4 . They possess good strength, little shrinkage and have lot of spalling.
5. They have poor resistance to abrasions.

Uses
1. They are used where high temperature is required to be maintained, together with great resistance to basic materials.
2. They are used in steel industry for the lining of basic converters and and open –hearth furnaces.
3. They are also used in hot mixer linings, copper converters and reverberatory furnaces.

Zirconia bricks ( Neutral refractories)
Manufacture
They are prepared by mixing zirconite mineral (ZrO2 ) with colloidal zirconia or alumina as binder and finally heated to 1700oC. Small amount of MgO or Cao is added as stabilizer because mineral zirconite undergoes volume changes on hearting and cooling.

Properties
1. Zirconia bricks are neutral refractories.
2. Though zirconia bricks are neutral, they are affected by acidic slags.
3. They can be used upto 2000oC and upto 1500oC under a load of 3.5 kg/cm2 .
4. They are also quie resistant to thermal shocks.
5. Their thermal expansion is low.

Uses
They are used only where very high temperature is maintained, e.g., high – frequency electric furnaces.

General methods of manufacture of refractories.

General methods of manufacture of refractories

The manufacture of refractories involve the following steps.
1. Grinding
Raw materials crushed and ground to fine powder using crushers, pulveriser, ball mills.

2. Mixing
In order to alter the chemical properties of the refractories, two or more powdered raw materials are thoroughly mixed with a suitable binding material, which makes moulding easier.

3. Moulding
Moulding can be done either manually or mechanically by application of high pressure.
Hand-moulding produces refractories of low strength and low density. Mechanical-moulding produces refractories of high strength and high density

4. Drying
Drying is carried out slowly to the moisture from refractories.

5. Firing
It is done at a temperature as high as or higher than their use temperature . Firing is generally carried out in kilns.

The refractories are fired,
(i) to stabilize and strengthen their structures.
(ii) to remove water of hydration.
(iii) to facilitate development of stable mineral to form the finished products.