High Alumina Castables

How to Distinguish the Quality of High-Aluminum Castables?

There are many types of high-aluminum castables. It is necessary to choose high-aluminum refractory castables of different quality when used under different linings and different temperatures and erosion conditions. So, how can we distinguish the quality of high-aluminum castables?

High-Alumina Refractory Castables
High-Alumina Refractory Castables
  • First, distinguish the grade of the material from the aluminum content. The higher the aluminum content, the better the quality of the castable. If it exceeds the quality of refractory castable and contains 80% aluminum content, it is called corundum castable. Under normal circumstances, high alumina castables have 55%, 60%, 65%, 70%, 75% alumina content.
  • Secondly, it is distinguished from the bulk density. The higher the bulk density, the denser the castable and the better the quality.
  • Then, it is distinguished from the flexural strength at room temperature. Flexural resistance is a measure of the degree of bending that the castable can withstand. The higher the flexural resistance, the better the performance of the material.
  • Also, it is distinguished from the compressive strength. Compressive strength is the ultimate load that the castable can withstand without being destroyed. The greater the strength, the stronger the wear resistance and impact resistance.
  • It can also be distinguished from the softening temperature under load. The load softening temperature is the ability of the castable to resist the effects of both high temperature and load. Therefore, the load softening temperature can best explain the quality of the castable.
  • From other aspects, we can also distinguish the grade and quality of high-aluminum castables, such as alkali resistance and wear resistance. The high-aluminum castable used in cement rotary kilns and boiler walls will be eroded by alkaline gas or flue gas in the kiln. Therefore, when purchasing high-aluminum castables, it is necessary to test the alkali resistance and wear resistance of the castables. Alkali resistance and abrasion resistance are the ability of castables to resist alkaline erosion at high temperatures.

In short, no matter from the above aspect to distinguish the quality of the high alumina refractory castables. During use, if poor quality castables are selected under high-temperature conditions, the life cycle of the furnace lining will be affected, causing the trouble of replacing the furnace lining back and forth. If the temperature is low, choosing high-quality high-aluminum castables will not only increase the use cost of the furnace lining but also may not necessarily receive a good use effect. Regarding how to choose high-quality high-aluminum refractory castables, it is still necessary to choose the quality grade of the castables according to the use of their own furnace lining.

To purchase high-alumina refractory castables, please choose refractory castables manufacturers. A strong refractory castable manufacturer not only guarantees product quality but also provides comprehensive customer service. Powerful manufacturers of refractory materials have their own advantages in the types and formulations of refractory castables and can customize solutions for refractory castable refractory linings according to their production needs. To learn more about the product knowledge of monolithic refractory linings, please continue to pay attention to our blog.

Refractory Castables

What are the Selection Techniques for Using Refractory Castables?

With the increasing use of refractory castables, how to choose suitable materials or refractory castables with certain special properties for refractory linings requires certain methods and skills.

Construction of Castable Refractory Lining
Construction of Castable Refractory Lining

Selection skills of refractory castables

Refractory castables are divided into neutral, acidic, alkaline, and heavy and light. Heavy-weight refractory castables are generally used in the working layer, while light-weight castables are used in the insulation layer for heat preservation.
If it is a neutral high-aluminum refractory castable, the castable of which index is used is determined according to the temperature and erosion of the furnace lining. If the temperature is below 1200°C, use clay castables; if the temperature exceeds 1250°C, use high-alumina castables. If the use temperature exceeds 1350℃, corundum refractory castable is used. If it is extremely corrosive, chromium corundum castable should be used. If the wear is severe, wear-resistant refractory castables are used. The storage time of neutral materials is 6 months, so we must pay attention to the separate opening of raw materials and binders.
If it is a castable used in an acidic atmosphere, an acidic castable should be used. There are two combinations of acidic castables, one is water glass combination and the other is phosphoric acid combination. If it is an acidic atmosphere with a temperature not exceeding 1250°C, the acidic castable combined with water glass can be used. If the temperature is too high, choose acid-resistant castable combined with phosphoric acid.
If it is a castable used in an alkaline atmosphere, magnesia refractory castable should be used. In the case of erosion and wear resistance, use magnesia-aluminum refractory castables or magnesia-chromium castables. If the temperature is too high, magnesia castables with high specific gravity or high content magnesia castables can be used. However, the preservation of magnesia castables must be paid attention to, and they cannot be stored in the open air. Because the magnesia castable cannot see water, otherwise it will pulverize.
If it is a castable for the insulation layer, it also depends on the temperature. If the temperature is low, general light-weight insulation castables can be used. If the temperature is too high, use lightweight high-aluminum or alumina hollow sphere lightweight castables as the insulation layer. The storage of lightweight castables must also be paid attention to, and it should not be placed with materials that are too corrosive, otherwise it will cause damage to the lightweight castables.
If the furnace shell requirements are low, double-layer insulation should be used to solve the problem. It is possible to first use ceramic fiber and then light-weight thermal insulation castable, or directly use ceramic fiber blocks to solve the problem. But if there is a weight requirement in the insulation area, use a specific gravity of 0.6-0.8 as the insulation layer. If the flue is directly used in the thermal insulation castable of the working layer, a lightweight castable with a specific gravity of 1.3-1.5 is used as the lining. If it is acid-resistant atmosphere, it is necessary to choose to use light acid-resistant castable as the lining.
In short, no matter what refractory castable is selected, the castable must be selected according to the use situation, the lining atmosphere, and the temperature.

Tips: What is the relationship between the performance of high-alumina castables and the cement content?
High-aluminum castables often have a higher proportion of cement content, but this also causes a series of performance declines in high-alumina castables. So, what is the relationship between the properties of high-alumina castables and the cement content?

high-alumina castables
high-alumina castables

1. In order to fully hydrate the cement, excessive water (10%~15%) is needed when mixing. This is easy to cause ceramic refractory castables to show high porosity and decrease density.
2. Calcium aluminate hydrate has a strong dehydration and recrystallization effect in the middle temperature stage. This destroys the structure of the hard spots in the castable, and makes the strength of the refractory castable drop sharply in the middle temperature stage.
3. The cement binder brings more calcium into the castable. This leads to a decrease in the softening temperature of the ceramized high-alumina refractory castable under load, and a decrease in the thermal shock stability performance index.
To learn more about refractory castables, please continue to pay attention to our blog. To purchase high-quality refractory castables, please choose a strong refractory manufacturer.

Refractory Castables · Refractory Concrete

Is the Refractory Concrete the same as Refractory Castable?

Refractory concrete is an unshaped refractory material that is prepared by adding water or other liquids to refractory aggregates, powders, and cement and is used directly without calcination. Also known as refractory castable, generally, most of this material is constructed by pouring. So it is also called refractory castable. It can be divided into the following types. ① Ordinary refractory concrete. The aggregates used are high alumina, clay, siliceous, alkaline materials (magnesia, chromite, dolomite, etc.) or special materials (carbon, silicon carbide, zircon, etc.). Several combinations of refractory aggregates can also be used. ②Insulation refractory concrete. It is mainly formulated with refractory light aggregate. The light aggregates used include expanded perlite, vermiculite, ceramsite, porous clay clinker, hollow alumina balls, and so on. It can also be combined with several refractory lightweight aggregates, or combined with refractory aggregates. The cement used in refractory concrete includes high alumina cement, phosphate cement, water glass cement, clay, and so on.

Kinds of Refractory Concrete for the Thermal Furnace Lining
Kinds of Refractory Concrete for the Thermal Furnace Lining

Advantages of Refractory Concrete

Refractory concrete (https://refractorycastablecement.com/high-heat-refractory-concrete/) is a non-burning product, with a simple production process and energy saving. It can be shaped according to needs, the integrity is better than the brick lining, suitable for mechanized construction, and the life of the lining can be prolonged when it is reasonably used. Refractory concrete is mainly used in industrial kilns such as metallurgy, petroleum, chemical industry, building materials, and machinery. The general use temperature is 1300~1600°C. The refractory concrete whose service temperature is lower than 900°C is called heat-resistant concrete, which is mainly used in the foundations of thermal equipment, chimneys, flues, and other structures.

Performance Comparison of Refractory Concrete and Refractory Bricks

  1. The refractoriness is similar to that of refractory bricks of the same material. However, because the refractory concrete (castable) is not sintered, it shrinks greatly during the initial heating, so the load softening point is slightly lower than that of refractory bricks. Nevertheless, in general, the performance is better than refractory bricks.
  2. Refractory concrete is superior to low-temperature cementitious materials and has higher compressive strength at room temperature. At the same time, because the integrity of the masonry is good, the furnace is airtight and not easily deformed. Therefore, the outer furnace shell steel plate can be eliminated, and the furnace has better resistance to mechanical vibration and impact than brick masonry. For example, it is used on the sidewall of the soaking furnace. The mechanical abrasion and collision at this place are relatively severe, and the life span is several times longer than that of bricks.
  3. Good thermal stability. Most of all of the aggregate are clinker, and the expansion is offset by the shrinkage of the cement. Therefore, the thermal expansion of the masonry is relatively smaller than that of the brick, and the temperature stress is also smaller. Moreover, there are various network, needle, and chain crystal phases in the structure. Strong resistance to low-temperature stress. For example, it is used for pouring the furnace mouth and furnace cover of the soaking furnace, and the service life is extended to one and a half years.
  4. The production process is simple, and the complicated brick-making process is eliminated. It can be made into a variety of prefabricated blocks and can be mechanized for construction, which greatly accelerates the furnace building speed and increases the efficiency of bricklaying by more than ten times. You can also use waste bricks as aggregates to turn waste into profit.

To learn more about refractory concrete, please continue to follow our blog.

Refractory Concrete

What is Lightweight Refractory Concrete?

The material, composition, and ingredients of refractory concrete are very similar to refractory castables and are non-burning products. The production process is simple, energy-saving, and can be shaped as required. Refractory concrete is divided into high alumina concrete, fireclay concrete, siliceous concrete, and magnesia concrete. There are also light and heavy quality points. Combination of heavy and refractory aggregates. Lightweight expanded perlite, vermiculite, ceramsite, porous clay clinker, hollow alumina balls, etc. The binders used include high alumina cement, phosphate cement, water glass cement, and so on. Next, let’s learn more about what is lightweight refractory concrete?

Lightweight Insulating Refractory Concrete
Lightweight Insulating Refractory Concrete

Lightweight Insulation Refractory Concrete

Buy lightweight heat-insulating refractory concrete(https://refractorycastablecement.com/buy-refractory-concrete/) is an unshaped heat-insulating material prepared from lightweight refractory aggregates, admixtures, and cementing materials. The casting method is usually used for construction, and sometimes spraying or spraying method is used for construction. Therefore, it is also called lightweight insulating refractory castable and lightweight refractory spray coating or lightweight unshaped refractory. Because the lightweight heat-insulating refractory concrete has the advantages of convenient and rapid construction, especially for inner villages with complex shapes and structures, the construction is easier, and it has many advantages such as energy saving. It has been widely used as heat insulation material in many high-temperature projects. Lightweight refractory concrete is usually named after its lightweight aggregates, such as expanded vermiculite concrete, expanded perlite concrete, etc. The performance of lightweight refractory concrete mainly depends on the performance of lightweight aggregates and cementitious materials.

(1) Lightweight refractory aggregate

The selection of lightweight aggregates to prepare lightweight heat-insulating refractory concrete mainly depends on the temperature of the concrete. Generally, expanded vermiculite, expanded perlite, or diatomite is used when it is used below 800~100℃. When used in the temperature range of 1100~1400℃, light clay aggregate is used. When used at higher temperatures, high-grade thermal insulation aggregates such as alumina hollow balls are used.

(2) Cementing material

Lightweight insulating refractory concrete usually uses aluminate cement, water glass, and phosphate as cementing materials. The nature of the cementitious material has a great influence on the lightweight heat-insulating refractory concrete.

(3) Thermal conductivity of lightweight heat-insulating refractory concrete

The thermal conductivity of lightweight heat-insulating refractory concrete depends on the type of lightweight aggregate. Factors such as cementing material and bulk density.

In practical applications, due to the temperature gradient at the cross-section of the lightweight heat-insulating refractory concrete lining, different physical and chemical changes occur in different parts, thus affecting the thermal conductivity.

For example, the lightweight heat-insulating refractory concrete combined with calcium aluminate cement, before being heated, the entire inner lining is completely combined with cement hydration products. When the furnace is heated, a temperature gradient is generated along the section of the furnace lining. When the thermal temperature is heated to above 480°C, the chemically bound water begins to drain. When heated at 980~1090°C, sintering and ceramic bonding begin to occur. When the furnace lining reaches thermal equilibrium, a zoned structure is produced in the refractory concrete.

The first layer is the area near the cold surface of the furnace shell, and the highest temperature is lower than 480°C. Refractory concrete still maintains the original hydrated state and has high thermal conductivity. The second layer is the dehydration decomposition zone. The hydrate bond and chemical bond are partially destroyed, but the temperature has not reached the high temperature required to form a ceramic bond. Due to the higher porosity, the thermal conductivity of this layer becomes lower. The third layer is a sintered zone, that is, a high-temperature zone, near the end of the working face. When the temperature exceeds 1090℃, high-temperature chemical reaction and sintering take place, forming a strong ceramic bond. The thermal conductivity of this layer is higher than that of the middle layer. Learn more from Rongsheng Refractory Castable Manufacturer.

Refractory Concrete

What are the Advantages and Applications of Refractory Concrete?

Refractory concrete is a special kind of concrete prepared by proper cementing materials, refractory aggregates, admixtures, and water in a certain proportion. It can maintain the required mechanical properties under the long-term action of high temperatures above 900℃. Its properties depend on the materials and proportions of all aggregates, admixtures, and cementitious materials. Its material, composition, and ingredients are similar to refractory castables. Through communication with experienced refractory practitioners, refractory concrete is another name for refractory castables. So what are the advantages and applications of refractory concrete? Refractory Castable Cement Manufacturers will give us a more comprehensive answer.

Refractory Concrete
Refractory Concrete

Classification of Refractory Concrete

Refractory aggregates can be heavy slag, crushed refractory bricks, basalt, bauxite clinker, sintered magnesia, etc. According to the cementing materials used, it can be divided into Portland cement refractory concrete, aluminate cement refractory concrete, sodium silicate refractory concrete, phosphate refractory concrete, magnesia refractory concrete, etc.

High-Quality Refractory Concrete
High-Quality Refractory Concrete

Advantages and Applications of Refractory Concrete

The material, composition, and ingredients of refractory concrete are very similar to refractory castables. It is a non-burned product, a simple production process, energy-saving, and can be shaped as required. The granular and powdery materials in refractory concrete are called aggregates and admixtures, respectively. The concrete mixture can be formed by pouring, vibrating, or ramming. According to the hardening characteristics of the cementitious material (such as air hardness, hydraulic hardness, thermal hardness, etc.), corresponding measures are adopted to promote its hardening.

Refractory concrete is divided into high alumina concrete, clay concrete, siliceous concrete, and magnesia concrete. There are also light and heavy quality points. The heavyweight is combined with refractory aggregates, and the lightweight has expanded perlite, vermiculite, ceramsite, porous clay clinker, hollow alumina balls, etc. The binders used are high alumina cement, phosphate cement, water glass cement, and so on.

Refractory concrete is superior to low-temperature cementitious materials and has higher compressive strength at room temperature. At the same time, because of the good integrity of the masonry, the airtightness of the furnace is good and it is not easy to deform. The outer furnace shell steel plate can be eliminated. The resistance of the furnace to mechanical vibration and impact is better than that of brick masonry. Especially the mechanical wear and collision parts are used, and the service life is several times longer than that of bricks.

Heat-resistant concrete has good thermal stability, and clinker is used as aggregate during production, and the expansion and shrinkage of cementitious material are offset. Therefore, the thermal expansion of the masonry is relatively smaller than that of the brick, and the temperature stress is also smaller. Moreover, there are various net-like, needle-like, and chain-like crystal phases in the structure, which have a strong resistance to low-temperature stress. If it is used for pouring soaking furnace mouth and furnace cover, the service life is extended to one and a half years.

Refractory concrete is mainly used in the bottom and wall of blast furnaces, hot blast furnaces, and industrial kilns in metallurgy, petroleum, chemical, machinery, etc., to construct the overall lining of industrial kilns and make prefabricated blocks. The refractory concrete whose service temperature is lower than 900℃ is called heat-resistant concrete, which is mainly used in the foundation, chimney, flue, and other structures of industrial kilns and thermal equipment.

To purchase high-quality refractory concrete, please contact the refractory manufacturer. The price is cheap and the quality is reliable.

Refractory Mortar

What Should I do if the High Alumina Refractory Mortar Dries too Fast during Construction?

High alumina refractory mortar (KHLN-55) is prepared from high alumina bauxite clinker, binding agent, and admixture. It is usually delivered in bulk and dry, and it is mixed with water during use. [Solemn reminder] Refractory mortar is different from refractory cement. Refractory mortar is mainly used as the joint material or brick joint material for the construction of refractory bricks. The adjusted refractory mortar is also called refractory mortar. Refractory cement is used as a binder for making refractory castables or refractory plastics. Refractory cement is also called high alumina cement or aluminate cement.

Refractory Mortar for Sale
Refractory Mortar for Sale

Use of High Alumina Refractory Mortar

The high-alumina refractory mortar is correctly configured according to the material of the refractory bricks. Usually, it is mainly used for laying high alumina bricks and corundum bricks.

How to Use High Alumina Refractory Mortar

The refractory slurry used for refractory bricks is made of powdered refractory materials. It should have good masonry performance and high-temperature performance to bond the refractory bricks into a dense overall furnace lining.

The masonry performance of mud refers to the work performance of refractory mortar that helps to ensure the quality of masonry during the masonry process. If there are good fluidity and plasticity. It has a certain water retention performance and can maintain a uniform state without segregation and precipitation. It has proper consistency and viscosity during masonry and does not dry out during the brick kneading time to achieve the required thickness of the brick joints, and the mortar in the brick joints is full.

The chemical composition similar to that of refractory bricks should be taken into consideration when selecting fire clay. The thermal expansion of the mud is consistent with the thermal expansion of the refractory bricks to ensure that the masonry can be reliably bonded.

The Use of Wet Refractory Mortar for Sale
The Use of Wet Refractory Mortar for Sale

What should I do if the high alumina refractory mortar dries too fast during construction?

Can refractory clay fail to condense or dry too fast on the construction site and cannot be built with refractory bricks? The answer is yes.

What if this situation is reproduced on the construction site? It is necessary to add an admixture, otherwise, the https://refractorycastablecement.com/high-alumina-mortar/ refractory mortar will dry too quickly and affect the construction. So, what is the proportion of joining? Many construction companies are very clear, some say an increase of 1%, and some say 0.5%. There is no clear regulation on this amount of addition, it depends on the construction site.

RS High-Alumina Refractory Mortar for Sale
RS High-Alumina Refractory Mortar for Sale

The role of high alumina refractory mortar additives

The soft clay is added to the high alumina refractory mortar to improve workability, such as spreading and adhesion. Using soot silica powder instead of soft clay can lower the sintering temperature. Additives mainly include precipitation agents, stabilizers, plasticizers, and anti-shrinking agents. The role of the precipitation agent is to reduce the amount of water added. The stabilizer prevents the solid-liquid separation phenomenon of the adjusted refractory mortar during the standing process. Adding plasticizers improves the spreadability of the mud and prevents flow. The anti-shrinking agent is to prevent cracks or peeling caused by volume shrinkage after sintering.

  • Refractory material itself is an applied science, and it depends on the situation during use. If the construction is cold in winter, add 2%, if it is hot in summer, add 0.5-1%.
  • In the construction process of refractory mortar, drinking water must be added at a ratio of 25-30%. Can’t add too much, it depends on site usage.
  • Add yellow dextrin and methylcellulose, add powder. Yellow dextrin is a yellow-white powder, and it is easily soluble in water, and it has strong viscosity when dissolved in water. At a certain temperature, it will be decomposed by heat.
  • If at the construction site, yellow dextrin and methylcellulose add one of them, it can also play a sticky effect.
  • If the refractory mortar https://refractorycastablecement.com/refractory-mortar-for-sale/ is the phosphoric acid refractory mortar and the construction site appears to dry too fast, yellow dextrin or methylcellulose must be added to adjust it. The added bonding agent has evaporated after high temperature and will not affect the later use.

To learn more about the precautions for the use of unshaped refractory materials and the solutions to various problems, please visit our website: https://refractorycastablecement.com/.

Wear-Resistant Castable

How to Choose a Suitable Wear-Resistant Castable?

Wear-resistant castable is a refractory castable commonly used in high-temperature industrial kilns. In the high-temperature working environment, how to choose the refractory castable lining mainly focuses on the following points. For example, high-temperature resistance, wear resistance, thermal shock resistance, chemical resistance, etc. Different use environment, different choice of refractory castable. This article mainly introduces how to choose suitable wear-resistant castables with so many kinds of wear-resistant castables.

Wear Resistant Castable
Wear Resistant Castable

Introduction of Wear-Resistant Castable

Wear-resistant castable is an unshaped refractory that can resist high-temperature solid particles and airflow. The main performance of wear-resistant castables is strong wear resistance. Wear resistance mainly refers to the ability of refractory castable lining to resist the friction and wear (grinding, friction, impact, etc.) of hard materials or gases (containing solid particles) without being damaged, or the characteristics of low wear rate. It is an important indicator to predict whether it can be used in abrasion and erosion environments. Generally, the higher the bulk density, the higher the compressive strength and the stronger the wear resistance.

Corundum Self-flowing Wear Resistant Castable
Corundum Self-flowing Wear Resistant Castable

Main Application Parts of Wear-Resistant Castables

The use environment of wear-resistant castables is mainly aimed at various feed ports, discharge ports, various flue linings, etc. These parts have high requirements on the wear resistance of the lining material. In order to prolong the service life of the lining, it is necessary to choose high-quality wear-resistant castables.

Wear-resistant castables are classified according to different materials. Such as high-strength wear-resistant castable, high-alumina wear-resistant castable, steel fiber wear-resistant castable, corundum wear-resistant castable, etc. The wear-resistant castables selected for different parts of use are different. Such as:

The materials selected for the feed port and the discharge port must not only have to wear resistance but also have thermal shock resistance. When feeding or discharging, the temperature fluctuates greatly and the thermal stress is strong. It is not enough to only choose to have abrasion resistance, but also to have excellent thermal shock resistance. The steel fiber wear-resistant castable can be selected as the inner lining, and the use effect is better.

Corundum High Strength Wear Resistant Castable
Corundum High Strength Wear Resistant Castable

Wear-Resistant Castable for Power Plant Boiler

In the furnace lining of power plant boilers, not only the scouring of various high-temperature gases and materials but also the characteristics of high-temperature resistance and chemical corrosion resistance are required. At this time, corundum wear-resistant castable lining or high alumina wear-resistant castable with an alumina content of about 75% can be used. The current circulating fluidized bed boilers have high thermal efficiency and low pollution emissions, and most of them are used in thermal power plants and heating projects. The furnace lining temperature is 800℃~1100℃ after long-term strong dust erosion. Therefore, higher requirements are put forward for the wear resistance of the castable at the location. Manufacturers producing wear-resistant castables are also constantly adjusting the process, correspondingly reducing the addition of fine particles, so that the wear resistance is continuously improved.

To sum up,

The flue of various high-temperature kilns is mainly damaged by various air currents and chemical erosion, and the use temperature is different. At this time, there is no need to choose corundum wear-resistant castable for sale. According to the analysis of the specific use temperature and corrosive medium, it is more appropriate to choose high-alumina wear-resistant castables that are resistant to wear and acid and alkali.

Refractory Castables

Application Characteristics of High-quality Lightweight Mullite Castables

Lightweight mullite castables are a type of main material used in heating furnaces. It not only requires good high-temperature performance but also requires a smaller bulk density and thermal conductivity. Lightweight mullite castable is a refractory material with excellent high-temperature performance and a good thermal insulation effect. Because it uses high-quality synthetic raw materials and is combined in the form of low cement or micro-powder, it can be directly applied to high-temperature parts in contact with the flame.

Lightweight Insulating Castable
Lightweight Insulating Castable

Application Characteristics of High-quality Lightweight Mullite Castables

  • (1) Choose high-quality lightweight mullite aggregate as the main raw material. Adding an appropriate amount of fine powder and using low cement bonding can produce high-quality lightweight mullite castables. This castable can be directly applied to the high-temperature part of the heating furnace.
  • (2) Lightweight aggregates with different bulk densities have a greater impact on the index of the castable, and which grade of raw material should be used carefully.
  • (3) It can be proved by using that this castable has better flow properties. Peeling resistance and heat preservation performance, suitable for application in high-temperature parts of the heating furnace. It has obvious effects on improving the service life of the furnace body, reducing the thermal conductivity of the heating furnace body, and improving the thermal efficiency.

Structural Composition of Lightweight Mullite Castable

1: Selection of lightweight mullite aggregate

As the main component of the castable, lightweight mullite aggregate has a vital influence on the performance of the castable, and its selection should be carried out carefully. Properly increasing the critical particle size of the aggregate is beneficial to enhance the compressive strength of the castable, but if the critical particle size is too large, it will have an adverse effect on the construction performance of the material. Through experiments, we determined that the critical particle size is 12mm. The ratio of particles to a fine powder should be controlled at 65%~70%, or 32%~40% is more appropriate.

2: The choice of cement

Because this castable is used in the high-temperature part of the heating furnace, the use temperature is about 1350°C. Therefore, pure calcium aluminate cement with excellent performance should be selected, and its AL2O3 content should generally be greater than 70%. If the cement has a high impurity content, it will easily react with the castable at high temperatures to produce low-melting substances, which will affect the high-temperature performance of the castable. The dosage is generally controlled at 5%~10%. If the dosage is too large, it will reduce the medium temperature strength of the castable. At high temperatures, it will adversely affect the high-temperature strength and spalling resistance of the castable.

3: Choice of micro powder

Compared with compact castables, lightweight castables have lower fluidity. Especially for this kind of castable used in high-temperature parts, due to the restriction of use conditions, the added amount and variety of some subdivisions are restricted to a certain extent. In order to enhance the flow properties of this castable, the form of adding composite micro-powder is adopted. After comparative tests, it is believed that it is difficult to achieve good fluidity and performance of this castable by adding only a single alumina powder or silica powder. For this reason, two kinds of micro powders are selected for compounding. In order to improve the construction performance and high-temperature strength index of the castable, we increased the amount of superfine powder added. Considering comprehensively, it is more appropriate to control the total amount of superfine powder at 10%-18%.

4: Determination of the amount of kyanite added

Because the compactness of lightweight castable aggregates is poor, if the proportion is not properly controlled, it is easy to cause the high-temperature linear shrinkage of the castable to increase. The castable is prone to cracks and peeling when used at high temperatures, which seriously affects the high-temperature performance of the castable. For this reason, we add an appropriate amount of kyanite to control the linear change of the castable, and the appropriate amount is 4%~6%.

Factors Affecting the Performance of Castables

1: Lightweight aggregates with a larger bulk density of raw materials of the same variety have higher compressive strength and flexural strength for their refractory castables. Different manufacturers have different production processes, and the strength of the lightweight aggregate itself is also quite different. The choice of raw materials should be determined by inspecting test blocks.

2: Increasing the amount of cement added will obviously increase the normal temperature strength of the castable. However, because calcium aluminate cement contains more silica, it can make the castable produce more crystal phases such as CA6 and CAS2 at high temperatures. It is easy to have a negative impact on the medium temperature, high-temperature strength, and peeling resistance of the castable. Therefore, the amount of cement should be 5%~10%.

Get more information about the Advantages and Applications of Lightweight Insulating Castables: https://refractorycastablecement.com/advantages-and-applications-of-lightweight-insulating-castables/.

Refractory Castables

Application of Self-flowing Refractory Castable in Kiln Repair

Self-flowing refractory castables are used in narrow parts of the kiln lining, or when repairing damage to various kilns. Self-flowing castables are characterized by high-temperature and hot self-flow pouring.

Self-flowing Refractory Castable

Self-flowing refractory castable material is a kind of refractory castable that has fluidity, filling property and stability, and can rely on self-flow to form a dense lining. In general, the self-flow rate of self-flowing material is controlled between 50% and 100%. If the self-flow value is too small, the material fluidity is poor, and the castable cannot fill the model during construction, forming a dense lining. If the self-flow value is too large, materials may segregate during construction.

Application of Self-flowing Refractory Castable in Kiln Repair

Due to the characteristics of the self-flowing refractory castable, it is convenient to be used for repairing the furnace. In most impressions, the maximum particle size of the self-flowing castable is 5mm. Because this facilitates the flow of the castable. Different types of refractory aggregates used in self-flowing refractory castables have different degrees of self-flowing. It is also based on different temperatures to determine the different materials used for self-flowing castables.

Rongsheng Self-flow Refractory Castable for Sale

White corundum, brown corundum, alumina-based corundum and high alumina are used as refractory aggregates. When the proportion of various materials and the proportion of water are the same, the self-flow rate of the castable is different. Because the bulk density of the raw materials of self-flowing refractory castables is large, the water absorption rate is low and the impurities are few are the biggest factors of fluidity.

Factors Affecting the Quality of Self-flowing Castables

1. Reasonable aggregate particles and aggregate gradation. Refractory aggregates generally use spherical, low water absorption raw materials, with a particle size of 5-8mm. The ratio of aggregate to powder is 6:4, and the ratio of coarse, medium and fine aggregate is 20:45:30.

2. Suitable binding agent and water reducing agent. Choose reasonable binding agent and water reducing agent.

3. Proper water consumption. Strictly control the water consumption, too much water can reduce viscosity and improve fluidity.

For self-flowing refractory castables, the selection of critical particle size is very important. However, in recent years, with the continuous improvement and research of castable manufacturers, the addition of large particles in the particles has increased the strength of the self-flowing castable. Moreover, the castable flows uniformly and does not sink, which makes the self-flowing castable have a longer service life in repairing the furnace lining. Learn more about the refractory castables for the kiln lining, https://refractorycastablecement.com/.