rsrefractorycastable, Author at Rongsheng Refractory Castable Cement for Sale Manufacturer and Supplier

Applications of Several Wear-Resistant Refractory Plastics

January 12, 2026 by rsrefractorycastable

Rongsheng Refractory Materials Manufacturer specializes in the research, development, and production of shaped and unshaped refractories, providing comprehensive life-cycle services for thermal kiln linings, including refractory material configuration, furnace lining optimization, engineering construction, and technical services. Rongsheng also boasts an environmentally friendly, fully automated production line for unshaped refractories, professionally producing various types. Among unshaped refractories, abrasion resistant refractory, those with common refractory and wear-resistant properties include the following:

Ordinary Wear-Resistant Plastic

Ordinary wear-resistant plastic is a high-alumina, corundum-based granular product. Compared with traditional refractory plastics, it has excellent properties such as easy construction, high efficiency, good molding, and high strength. abrasion resistant refractory. This material is composed of adhesive, refractory aggregate, and hardening accelerator. Adding a certain proportion of PA adhesive forms a plastic refractory mortar, facilitating construction in various complex areas. It is an air-hardening material with low-temperature hardening properties, ensuring the wear resistance required for circulating fluidized bed boilers. However, its wear resistance is relatively poor.

1) Application Method: Use a forced mixer to stir the material, adding the accelerator evenly during stirring. After dry stirring for 1 minute, add 4-5% of the adhesive and stir for another 3 minutes. Once the material reaches a certain plasticity, it can be unloaded and used.
2) Applicable Areas: Suitable for high-temperature areas with low friction, such as the boiler bottom air chamber, primary air duct, return riser (material leg), return feeder, return pipe, tail flue furnace wall, slag cooler, and filling of various furnace doors in the tail flue. 3) Storage method. Generally, store in a cool, dark place. Shelf life is about 2 to 3 months.

Micro-Expansion Wear-Resistant Plastic Refractory — Wear-Resistant Plastic Refractory

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Wear-Resistant Refractory Plastic

Abrasion-resistant refractory plastics are made from high-alumina bauxite clinker, corundum, mullite, and silicon carbide as aggregates. They possess excellent wear resistance, strong adhesion, and a high service temperature. Formulated with different binders and additives, they are refractory materials with high strength and wear resistance. They offer advantages such as easy construction, good plasticity, and excellent wear resistance. The applied wear-resistant layer has high strength and wear resistance, fully meeting the performance requirements of wear-resistant refractory materials for boilers.

1) Application Method: The materials and binder are mixed evenly with phosphoric acid before use. Construction is typically carried out using a ramming process.
2) Applicable Areas
- Suitable for construction in thin-thickness areas such as furnace water-cooled walls, mainly used in the dense phase zone of the furnace and in steam-cooled and water-cooled cyclone separators. In this area, the wear-resistant refractory material is designed as a single-layer rammed structure, fixed with wear-resistant pins, and its design thickness is relatively thin, directly applied to the construction surface.
- In the repair of circulating fluidized bed cyclone separators, its superior bonding properties allow for the repair of any irregular wear areas without the need for steel templates or molds. Ignition can be performed immediately after construction, requiring no special curing, thus shortening the construction cycle and saving costs.
3) Storage method. Avoid open-air storage and direct sunlight. Store in a cool, damp place in summer and protect from freezing in winter.

Corundum Wear-Resistant Refractory Plastic

This material belongs to the field of high-temperature wear-resistant refractory materials. The raw materials consist of high-alumina homogeneous material, alumina micropowder, silica micropowder, clay, phosphoric acid, aluminum dihydrogen phosphate solution, and pure calcium aluminate cement. Its key feature is the use of low-water-absorption, low-porosity, and highly uniform synthetic homogeneous materials to replace traditional high-water-absorption, high-porosity, and poorly uniform sintered bauxite clinker natural raw materials or corundum composite raw material systems, producing a homogeneous, high-strength, wear-resistant corundum plastic.

1) Application Method: This material is applied using a tamping process, suitable for thin-thickness applications such as furnace water-cooled walls. The resulting wear-resistant layer exhibits high strength and wear resistance. Unlike castables, this plastic does not require molds and can be applied directly using a smearing and tamping method. The refractory plastic material has good workability, high strength, and good wear resistance, resulting in optimal performance in the field. It helps extend the service life of furnace linings and improve the utilization efficiency of high-temperature kilns.
2) Applicable Areas. It is mainly used in the dense phase zone of the furnace and in steam-cooled/water-cooled/insulated cyclone separators. The wear-resistant refractory material in this area is designed as a single-layer rammed structure and fixed with wear-resistant pins. Its thickness varies, generally 40-60mm (steam-cooled/water-cooled) and 320-350mm (insulated), and it can be directly laid on the construction surface.

Corundum Silicon Carbide Wear Resistant Refractory Plastic — Corundum Silicon Carbide Wear-Resistant Refractory Plastic

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Silicon Carbide Corundum Wear-Resistant Refractory Plastic

Silicon carbide corundum wear-resistant refractory plastic is a high-grade refractory material. It possesses excellent wear resistance, strong adhesion, and a high service temperature. It is also renowned for its simple construction process, short construction period, and the superior characteristic of not requiring furnace drying after construction. In practice, its service life is significantly longer than other wear-resistant refractory materials, and it is widely used in industries such as power, metallurgy, steel, and ceramics.

1) Application Method: This material is applied using a smearing and tamping method. Before application, rigid anchor pins should be fixed to the required locations, with a mesh spacing of approximately 120-150mm (maximum not exceeding 200mm). During application, the plastic is laid evenly on the required areas. The thickness of the smear can be determined according to the design requirements of different furnace types.
2) Applicable Areas: Silicon carbide wear-resistant refractory plastic can be widely used in cyclone separators, thermal radiation materials, and other applications where refractory materials are used. It possesses superior adhesive properties, allowing for easy application and application to any irregular, worn areas, significantly reducing wear. No steel templates or molds are required; it can be ignited immediately after application without special curing, thus shortening the construction cycle and saving costs.
3) Storage Method. Avoid open-air storage and direct sunlight. In summer, store in a cool, damp place; in winter, protect from freezing. The shelf life of the plastic is generally one year, and the accelerator should be replaced after 4-6 months of unused use (if used after one year of storage, the material must be re-cured).

High-Strength Wear-Resistant Refractory Plastics

Rongsheng’s high-strength wear-resistant refractory plastics belong to the high-strength wear-resistant series of refractory plastics. Their materials include high-alumina, corundum, silicon carbide, chromium, and zircon.

High-strength wear-resistant refractory plastics possess strong plasticity and wear resistance. They can be tamped into any shape using the tamping method, making them a quick-repairing material for kiln linings.

High-strength wear-resistant refractory plastics are refractory plastics composed of the above-mentioned materials as the main raw materials, with the addition of binders and additives (shrinkage inhibitors, preservatives, and antifreeze agents).

Commonly used castables include: corundum wear-resistant refractory castables, wear-resistant refractory plastics, non-stick alumina castables, low-cement refractory castables, adjustable-mouth castables, high-strength impermeable low-cement castables, lightweight refractory insulating castables, and steel fiber refractory castables.

Applications of High-Strength Wear-Resistant Plastics:

In the power generation industry: coal unloading trenches, coal hoppers, coal storage bins, dry coal grids, tippers, slag removers, water treatment, etc.
In the chemical industry: corrosion-resistant flooring, pump foundations, etc.
In the coal industry: wear-resistant linings for grinding bins, medium tanks, scraper conveyors, bucket elevators, chutes, underscreen hoppers, etc.; in the steel industry: blast furnace mixing bins, sintering bins, feeders, pelletizing machines, etc.

Lightweight Insulating Castable for Nitrogen Purification Equipment

December 28, 2025 by rsrefractorycastable

High-purity nitrogen is a crucial protective gas required for cold-rolled sheet, hot-dip galvanizing, and silicon steel production lines. The purity of nitrogen significantly impacts product quality. Excessive oxygen content leads to surface oxidation of steel sheets, causing surface elements to react with oxygen and affecting steel quality, resulting in problems such as bare spots in galvanized sheets. Cryogenic air separation units produce nitrogen as a byproduct; due to its relatively low purity and unstable oxygen content, this nitrogen is often referred to as “dirty nitrogen.” Chinese steel mills possess abundant “dirty nitrogen” resources, but due to purity and stability issues, this nitrogen cannot be directly used in cold-rolling production and must be purified before use. Even imported air separation units experience fluctuations in gas production and potential cross-contamination of instrument air. Therefore, imported production lines typically employ terminal purification devices to ensure nitrogen purity and stability. Currently, these nitrogen purification devices commonly use ceramic fiber as an insulation material. However, ceramic fiber has drawbacks, including a short lifespan requiring replacement every two years, difficulty in installation as required, inability to achieve a 1/2 compression ratio, significant environmental hazards, and health risks to construction workers.

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Lightweight Insulating Castable Refractories for Nitrogen Purification Units

Vermiculite is a group of hydrous mica (usually biotite or phlogopite) formed through alteration and weathering in hot aqueous solutions. It is a secondary metamorphic mineral containing magnesium and iron silicates. When raw vermiculite ore or beneficiated ore is heated to above 300℃, it becomes a highly efficient insulating material. The resulting expanded vermiculite possesses properties such as low density, thermal insulation, sound insulation, earthquake resistance, fire resistance, and freeze resistance. Furthermore, since vermiculite is environmentally friendly, it is also an important environmentally friendly material. To address the drawbacks of using ceramic fibers as insulation materials, this paper develops a lightweight insulating refractory castable refractories using vermiculite and calcium aluminate cement as the main raw materials, based on the operating conditions and requirements of nitrogen purification units, aiming to meet the insulation material requirements of nitrogen purification units.

Based on the experimental results, the developed lightweight insulating castable was used as an external insulation material in a field test on two nitrogen purification units at the gas plant of a steel plate company. The results showed that the lightweight insulating castable performed well as the external insulation material for the nitrogen purification units, with no damage observed. Furthermore, the use of this lightweight insulating castable reduced the external temperature of the nitrogen purification units. In actual use, the external temperature remained below 40℃, achieving the goals of reducing heat loss from thermal equipment, improving thermal efficiency, reducing energy consumption, and achieving energy conservation and emission reduction.

In conclusion, the lightweight insulating castable can replace ceramic fiber as the external insulation material for nitrogen purification units, demonstrating excellent performance. It reduces the external temperature of the nitrogen purification units, achieving the goals of reducing heat loss from thermal equipment, improving thermal efficiency, reducing energy consumption, and achieving energy conservation and emission reduction.

Lightweight Insulating Castable

Lightweight insulating castable is an unshaped material with lightweight aggregates and a specific binder as its core, possessing both fire resistance and high-efficiency thermal insulation properties. It is also known as lightweight insulating castable. Aggregates, depending on the service temperature, can include expanded vermiculite, expanded perlite, ceramsite, porous clay particles, corundum, high-alumina mullite, etc. Binders include ordinary silicate cement, alum cement, calcium aluminate cement, dialuminate phosphate, silica sol, alumina sol, etc. It is usually supplied in dry powder or slurry form, and is mixed with water or liquid binder on-site before being applied by pouring, vibration, tamping, etc.

Characteristics of Lightweight Insulating Castable: Lightweight insulation with low bulk density and low thermal conductivity, effectively reducing heat loss. High strength, with certain flexural and compressive strength. Good corrosion resistance; some products are resistant to acidic gas corrosion and can be used in harsh chemical environments. Construction is convenient; it can be cast into various shapes and made into precast blocks as needed, making construction relatively easy. It is suitable for kiln insulation layers, reducing kiln load and improving thermal efficiency, such as kilns in the metallurgical and building materials industries, and acid-resistant pools and tanks in the petroleum, chemical, and non-ferrous metallurgical industries. It is also an ideal material for high-temperature flue ducts and air duct linings in chimneys, effectively improving the airtightness and corrosion resistance of the lining.

Ultra-Lightweight Insulating Castable Series

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Optimization of Low Thermal Conductivity Castable Technology

Low thermal conductivity castables are not simply an extension of the ordinary “lightweight” concept, but rather achieve “three lows and one high” simultaneously under high-temperature service conditions—low bulk density, low thermal conductivity, low linear shrinkage rate, and high refractory strength. This performance combination breaks the traditional rule of “temperature increase → simultaneous increase in bulk density,” enabling simultaneous reduction of equipment weight and strengthening of furnace lining insulation, providing a material basis for further energy saving and consumption reduction in industrial kilns.

Performance Characteristics of Low Thermal Conductivity Castables

Lightweight and High Strength: At the same service temperature level, the bulk density can be lower than that of conventional lightweight insulating castables, while the compressive strength remains at the same or higher level.
Stable Thermal Conductivity: In the 1000 ℃ high-temperature range, the thermal conductivity remains ≤0.35 W·(m·K)⁻¹, significantly reducing heat loss from the furnace wall. 3. Excellent integrity and high plasticity: The material has a uniform porous network structure, allowing for on-site casting, tamping, spraying, or prefabrication. Complex irregular furnace linings can be formed in one piece, and subsequent local repairs do not require furnace shutdown for cooling.
Thermal shock resistance and spalling resistance: The introduction of composite micro-powder and fiber synergistic toughening ensures no through-cracks after more than 50 rapid cooling and heating cycles, extending service life by 1.5 to 2 times.

Raw Materials and Processes for Low Thermal Conductivity Castables

Lightweight Aggregate Selection: Low-iron, high-alumina porous homogeneous aggregates are used, requiring a bulk density ≤1.2 g·cm⁻³ and a compressive strength ≥8 MPa, ensuring “lightweight yet not loose” from the source.
Composite Additives: Expandable minerals are introduced to offset high-temperature sintering shrinkage; reducing water addition while increasing filling rate.
Particle Size Distribution Redesign: The upper limit of critical particle size is relaxed to enhance the aggregate “skeleton” effect, balancing construction flowability and surface smoothness.
Standardized Testing Methods: A “dual-indicator” admission system is established to address regional differences in aggregate testing—measuring both the intrinsic properties of the lightweight aggregate and its high-temperature linear change and thermal conductivity after coupling with additives, ensuring batch stability.

Construction Advantages of Low Thermal Conductivity Castables

After mixing with water, the material has a flow value ≥180 mm, self-leveling with vibration, and can be poured within 30 minutes; initial setting time is 2.5 hours, final setting time is 4 hours, and the baking curve is shortened by 20% compared to traditional materials; no harmful gases are emitted, and there is no corrosion to the furnace shell steel structure.

Energy Saving and Economic Benefits

Field measurements in metallurgical heating furnaces, mechanical heat treatment furnaces, electric circulating fluidized bed furnaces, chemical cracking furnaces, and petrochemical reforming furnaces show that: the average temperature of the furnace lining outer wall decreases by 40-60℃, and heat loss is reduced by 20%-25%. The furnace heating rate increases by 15%, the production cycle is shortened, and the unit consumption of gas or electricity decreases by 8%-12%. Furnace temperature uniformity is improved, the product qualification rate increases by 2-3 percentage points, and the material price difference can be recovered within one year of comprehensive operating costs. Industry Application Differences

Petrochemical kilns, due to their harsh operating conditions (large temperature differences, high permeability of light oils), require low thermal conductivity castables with even lower bulk density and higher chemical stability. Corresponding products require high-purity matrices and special sealants, resulting in prices approximately 20%–30% higher than similar materials used in the metallurgical industry. However, their service life can be extended by more than 3 years, and their total life-cycle cost is still superior to ordinary light materials.

With the continuous advancement of raw material purification and composite modification technologies, the application boundaries of low thermal conductivity castables will further expand from traditional kilns to higher temperatures, more complex, and more demanding extreme operating conditions.

Formulation and Properties of Corundum and High-Alumina Refractory Mortar

December 18, 2025December 13, 2025 by rsrefractorycastable

Refractory mortar is an unshaped refractory material composed of powdered materials and binders, used for preparing slurries. The powdered materials are made from fully sintered clinker (such as high-alumina clinker, calcined silica, magnesia, etc.) or other volume-stable refractory raw materials (such as silica, wax stone).

Rongsheng Refractory Mortar Manufacturer

The powder used to make refractory mortar can be fully sintered clinker and other volume-stable refractory raw materials. The particle size of the powder depends on the application requirements, with a generally limited particle size of less than 1mm, and sometimes less than 0.5mm or even finer. A reasonable particle composition has a significant impact on ensuring the mortar’s workability, as do the binders and admixtures. Ordinary refractory mortars use bonded clay as the binder. However, chemical binders are increasingly widely used. Adding various admixtures to refractory mortar can improve its workability. For example, adding water-retaining agents to extend the water loss time and ensure construction quality; adding plasticizers, even in small amounts, can increase the mortar’s plasticity; adding dispersants to improve the mortar’s fluidity, etc.

Refractory mortars can be classified into hydraulic, thermohardening, and air-hardening refractory mortars based on their binder setting and hardening characteristics. Hydraulic refractory mortars use cement as a binder and can be used at room temperature or in places where they may frequently come into contact with water or moisture. Thermosetting refractory mortars are commonly made with thermosetting binders such as phosphoric acid or phosphates. After hardening, these mortars exhibit high strength at various temperatures, low shrinkage, tight joints, and strong erosion resistance. Air-hardening refractory mortars commonly use air-hardening binders such as sodium silicate. These mortars ensure tight joints in masonry.

Depending on the material of the refractory powder used, commonly used refractory mortars can be classified as: clay-based, silica-based, high-alumina-based, magnesia-based, and insulating. Refractory mortar is mainly used as a contact and surface coating for refractory brick masonry. When used as a jointing material, its quality has a significant impact on the lifespan of the masonry. It can adjust dimensional errors and irregular shapes of bricks, making the masonry neat and load-bearing. It also helps the masonry form a strong and tight whole, resisting external damage and preventing the infiltration of molten metal.

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Corundum Refractory Mortar

The formulation of corundum refractory mortar mainly uses sintered corundum clinker or fused alumina with a diameter of 0.5-0.63 mm and finer. Fused alumina with a diameter of 5-7 μm or industrial alumina with a diameter of less than 5 μm is used as a binder. To ensure the shrinkage of the refractory clay during air and firing, the industrial alumina content in the formulation should not exceed 15%-20%, while the content of ultrafine fused alumina powder should reach 40%-50%. 10% of the refractory mortar is introduced with orthophosphoric acid (density 1.72 g/cm³).

Using corundum clinker and introducing less than 0.1% fermented alcohol waste liquid can improve the plasticity of the slurry and reduce its water content. This refractory mortar has a normal moisture content of less than 19%, a weight loss of 1.8% when heated to 110°C, and an apparent porosity of 26%. As shown in Table 1, the refractory clay has sufficient shear bond strength after firing at 1000-1500°C.

Properties of Corundum Refractory Mortar

Note: Component 1 is a refractory mortar primarily composed of sintered corundum, with particles smaller than 0.5 mm, 10% phosphoric acid, and 0.1% fermented alcohol waste liquid. Component 2 is a refractory mortar primarily composed of industrial alumina, with particles smaller than 30 μm, 5.5% polyphosphoric acid, and 0.1% fermented alcohol waste liquid. Component 3 is a refractory mortar primarily composed of light-burned alumina, bonded with sodium pyrophosphate. Component 4 is a refractory mortar primarily composed of high-alumina clinker, 10% clay, 0.1% fermented alcohol waste liquid, and 0.15% sodium carbonate.

According to Table 1, the shear bond strength of the refractory mortar is related to the final porosity; as porosity increases, the shear bond strength tends to decrease. To maintain the uniformity of the moisture content of the corundum refractory mortar at 2.5%, some dust needs to be removed, and 2.5% CaCl2 needs to be introduced. This increases the moisture content of the slurry to 24%–27%, without reducing the cohesive strength between the refractory mortar and the corundum refractory material. The shear bond strength after firing at 1000°C is 1.4–2.0 MPa, and reaches 10 MPa after firing at 1500°C.

Phosphate-bonded corundum refractory mortar can withstand 40 cycles of repeated water exchange at 1300°C without cracking. Corundum refractory mortar containing approximately 96% alumina has a refractoriness of 2000°C. Reducing the alumina content in the refractory mortar to 90%–91% slightly decreases the refractoriness, and the deformation initiation temperature under a 0.2 MPa load drops to 1580°C.

High Alumina Mortar Material Can Be Used to Fill up Seam — High Alumina Mortar Material of Rongsheng

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High-Alumina Refractory Mortar

The technical properties of high-alumina refractory mortar are shown in Table 2.

Storage and Usage Principles of High-Alumina Mortar

High-alumina mortar is the jointing material for high-alumina refractory bricks, mainly used for bonding bricks. Its storage time affects its performance, and its continued usability can be determined.

Judging the Storage Condition of the Binder

Check the Binder Packaging

First, check if there is a separately packaged binder in the high-alumina refractory mortar. If there is a separately packaged binder, and the storage time exceeds 6 months, it cannot be used and needs to be replaced.

If there is no separately packaged binder, take a small amount of refractory mortar and smell it. If there is an odor, it means that the binder was added to the refractory powder during production; if there is no odor, it means that the binder was not added.

Advantages of No Added Binder

High-alumina mortar without added binder is in its optimal state. It can be remixed with binder and used again, thus ensuring its bonding performance.

Judgment of Refractory Mortar with Added Binder

If the high-alumina refractory mortar has had a binder added directly during production and has been stored for more than 6 months, the following test is required to determine its usability:

Test Preparation

Weigh 1 kg of refractory powder, add 20%-25% drinking water, and stir to form a slurry. Prepare two refractory bricks of the same material.

Test Procedure

Take a portion of the refractory mortar and evenly spread it on one refractory brick, smooth it out, and place the second refractory brick on top. Rub the two refractory bricks back and forth approximately 15 times.

Result Judgment

If the two refractory bricks can bond together, the high-alumina refractory mortar is still usable. If the refractory bricks cannot bond, add an appropriate amount of binder in a reasonable proportion and repeat the above test. If the refractory bricks bond successfully, they can be put into use.

Summary of High-Alumina Refractory Mortar Usage

The binder in high-alumina refractory mortar primarily promotes the adhesion of the mortar. However, the binder will disappear after high-temperature baking. Therefore, high-alumina mortar that has been stored for a long time needs to be assessed for its continued usability using the methods described above. By checking the storage condition of the binder and conducting simple tests, the feasibility of using high-alumina refractory mortar can be effectively determined, avoiding the impact of material issues on the bonding effect and construction quality of refractory bricks.

Preparation and Properties of Porous Spherical Mullite Castables

December 18, 2025November 28, 2025 by rsrefractorycastable

In high-temperature industries such as iron and steel metallurgy, the poor insulation and rapid heat loss of refractory materials used in industrial kiln linings lead to excessively high kiln surface temperatures, resulting in increased energy consumption during ironmaking and steelmaking processes. This not only hinders the lifespan of refractory materials but also affects production schedules and endangers the safety of production personnel.

Low Thermal Conductivity Refractory Materials for High-Temperature Kilns

For example, the high thermal conductivity of refractory materials used in steel ladles leads to accelerated heat loss, which triggers a series of chain reactions during steelmaking:

Rapid heat loss causes excessively high ladle shell temperatures, resulting in severe deformation;
Rapid cooling of molten steel leads to cold forming, nodule formation, and even ladle flow interruption and final pouring.

Therefore, developing low thermal conductivity refractory materials for high-temperature kilns has become an urgent need for major steel mills. The high porosity and low thermal conductivity of lightweight materials offer new insights into the preparation of insulating refractory materials for high-temperature kiln linings. However, the preparation of lightweight refractories is often achieved by changing process conditions or adding additives, which suffers from poor controllability of pore size distribution. Consequently, functionalized refractory raw materials have rapidly developed, such as lightweight mullite, alumina hollow spheres, and gel powder. These raw materials facilitate the preparation of lightweight thermal insulation refractory materials. However, their excessively light weight and high price also limit their industrial application.

Meanwhile, with increasing production requirements, lightweight, high-strength refractory materials suitable for higher temperatures have gradually become the focus. Using microporous lightweight mullite, multiphase hollow spheres, high-alumina bauxite, silica, and alumina micropowder as main raw materials, the effects of lightweight aggregate composition, micropowder composition, bonding system, and pore-forming agent on the performance and structure of lightweight high-alumina castables were studied, and a lightweight high-alumina castable with good high-temperature performance was developed. Using mullite microspheres, α-Al₂O₃ micropowder, and silica micropowder as raw materials, and AlF₃·3H₂O and V₂O₅ as additives, a lightweight, high-strength mullite microsphere thermal insulation refractory material was prepared. Lightweight, high-strength, and highly thermally shock resistant corundum-mullite refractory materials were prepared by using alumina hollow spheres as pore-forming agents and AlF3·3H2O as additives to control the pore characteristics of corundum-mullite and the in-situ formation of mullite whiskers.

Rongsheng Mullite Refractory Castable Manufacturer

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Preparation and Properties of Porous Spherical Mullite Castables

Existing research shows that recent studies on the performance of aluminosilicate materials have largely focused on aggregate substitution or the use of additives. Alumina, a commonly used and relatively inexpensive raw material in aluminosilicate materials, has had its impact on aluminosilicate castables rarely reported.

To prepare a high-temperature kiln insulating refractory material with excellent thermal insulation and mechanical properties, porous spherical mullite-based castables were prepared using porous spherical mullite, fine alumina powder, α-Al₂O₃ micropowder, silica powder, and Secar 71 cement as the main raw materials.
The effects of fine alumina powder content on the mechanical properties, thermal conductivity, erosion resistance, and thermal shock resistance of the porous spherical mullite-based castables were investigated.

The results show that changing the content of fine alumina powder can improve the thermal insulation, thermal shock resistance, and erosion resistance of the porous spherical mullite-based castables while maintaining high mechanical properties.

With increasing bauxite powder content, the mechanical properties of porous spherical mullite-based castables did not change significantly. However, the thermal conductivity decreased slightly, and the erosion resistance showed considerable differences, with thermal shock stability initially increasing and then decreasing. When the bauxite powder content was 28% (mass fraction), the porous spherical mullite-based castable exhibited good mechanical properties, thermal shock stability, and erosion resistance. The thermal conductivity at 1000℃ was 0.905 W·m⁻¹·K⁻¹. The high-temperature flexural strengths of the porous spherical mullite-based castable at 1100℃ and 1400℃ were 22 MPa and 5 MPa, respectively, indicating good thermal insulation performance, high flexural strength, and a certain degree of resistance to ladle slag erosion.

The thermal conductivity of the porous spherical mullite-based castable is lower than that of high-alumina castables used in tundish and ladle permanent layers, making it a viable alternative to high-alumina castables used in tundish and ladle permanent layers to reduce heat loss.

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Application Effects of Lightweight Mullite Castables

Lightweight mullite castables are primarily used as integral linings for regenerators in heating furnaces. This working layer operates continuously at a high temperature of 1350℃, enduring temperature fluctuations within the kiln and the erosion and wear of high-temperature gases. During construction, the casting thickness is 300-400mm, with a water content of 18%-19%. In practical applications, this castable demonstrates advantages such as high workability, high-temperature strength, low thermal conductivity, good insulation, and good thermal shock resistance. Furthermore, its low-cement, micro-powder composite bonding allows for direct contact with the flame.

Energy-saving and environmentally friendly lightweight mullite castables, with their superior workability and high-temperature performance, have become ideal refractory linings for regenerators in heating furnaces. In addition, their application in thermal kilns such as aluminum melting furnaces, fluidized bed boilers, and gasifiers has also seen widespread development.

The Importance of Water Addition in the Fabrication of Precast Refractory Shapes

December 17, 2025November 13, 2025 by rsrefractorycastable

Precast Refractory Shapes are products made according to the shape of the application area to facilitate on-site construction. They are produced by pouring the refractory castable into a mold and vibrating it into various shapes after the refractory castable is produced.

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Water Addition in Precast Refractory Shapes Manufacturing

The amount of water added during the manufacturing process of Precast Refractory Shapes is crucial. Excessive water leads to a sparse particle size, affecting the strength and performance of the finished product. Insufficient water results in a lack of fluidity, making it impossible to form. The water addition amount for each type of precast refractory castable is determined based on the raw materials and binders used in the mixing process.

If the binder, such as high-alumina cement, is used in large quantities, resulting in a high calcium content, the water addition amount will also increase. Currently, most castable products utilize low-cement technology to reduce water addition, shorten drainage time, and enhance product strength. A moderate water addition improves product fluidity and facilitates construction. Furthermore, reduced drainage time results in higher product strength, lower porosity, and consequently, a longer service life for the Precast Refractory Shapes.

Excessive water addition fails to enhance the fluidity of the castable. Moreover, during the manufacturing process, the use of a vibrator can cause water to splash out, quickly rising to the surface while large aggregates sink to the bottom. This also generates a large number of water bubbles, meaning excessive and large pores. This prolongs the demolding cycle of Precast Refractory Shapes, and even if demolding is successful, the product’s strength and usability will suffer from cracking and eventual detachment during use.

The appropriate amount of water added depends on the different raw material matrixes. During mixing, aggregates should be added first, followed by fine powders, then the binder, and finally the appropriate proportion of water. This simplifies the manufacturing process, reduces drainage, increases product strength, and lowers porosity.

Therefore, the amount of water added during the pre-fired Precast Refractory Shapes manufacturing process is crucial and cannot be arbitrarily increased. The principle is to add less rather than more, which enhances the product’s performance and facilitates faster and more convenient construction.

Rongsheng Precast Refractory Shapes Manufacturer

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Can Precast Refractory Shapes be Used Without Baking?

Yes, Precast Refractory Shapes can be used without baking at a certain temperature. However, this requires the addition of explosion-proof fibers to the pre-made process mix to ensure sufficient drainage of crystal water. Alternatively, a long natural drying time can also allow them to be used without baking.

Precast Refractory Shapes are an extension of refractory castables. They are made by mixing raw material granules and powders, binders, and water to form a castable. This mixture is then poured into pre-made molds and undergoes dehydration, baking, and drainage processes before use. Comparatively, precast refractory components that have been baked at 300℃ have a better service life and safety than those that haven’t been baked.

However, if the quantity of precast refractory components used is large and the operating conditions are not demanding, adding explosion-proof materials during production and ensuring sufficient drainage of moisture allows them to be used during the industrial furnace lining baking process as the furnace temperature gradually increases. Unbaked pre-fired refractory precast components, while possessing higher strength, are more prone to breakage during transportation, handling, and construction.

Currently, the proportion of unbaked Precast Refractory Shapes used in the market is higher than that of baked ones. This is due to lower costs, coupled with improvements in castable technology, resulting in performance comparable to products from earlier technologically advanced periods.

However, under harsh operating conditions, such as excessively high furnace lining temperatures and the need for emergency repairs, where the furnace lining temperature rises rapidly, unbaked Precast Refractory Shapes, even those unbaked, offer better performance and a longer service life. Baked precast refractory components, on the other hand, have higher strength, better thermal shock resistance, and are less likely to crack during use.

Basis for Selecting Castable Refractory for Flue Lining

December 16, 2025October 29, 2025 by rsrefractorycastable

The most important consideration for flue lining is the erosion and corrosion caused by acidic gases. Acidic gases necessitate the use of acid-resistant castables or acid-resistant bricks for the lining. However, flues can be vertical or horizontal; for vertical flues, weight must be considered. If they are too heavy or the chimney is too tall, installation and assembly will be extremely difficult.

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Flue Lining Using Castable Refractory

Flue temperatures are not high, but the gas pressure is high, and the flue gas volume is large. The lining is susceptible to acid erosion and water erosion due to the generation of water vapor. Therefore, careful consideration is needed when choosing castable refractory or refractory bricks for the lining.

For example, roasting furnace flues can be vertical or horizontal, and the vertical and horizontal structures are often connected. Therefore, when selecting materials for the lining, both weight and erosion must be considered. If acid bricks are used, the mortar joints will result in poor airtightness. If heavy acid-resistant castable refractory is used, it will be too heavy. If lightweight acid-resistant castable refractory is used, its erosion and scouring resistance is insufficient, which is not suitable for flue lining applications. Furthermore, since the flue lining temperature is not high, insulation is generally not required.

Therefore, semi-heavy acid-resistant castable refractory should be considered. Semi-heavy refractory has a bulk density of around 1.5, which provides resistance to erosion and scouring while also offering some insulation. Another reason is that the weight issue is also alleviated. Currently, considering market conditions and chimney characteristics, semi-heavy acid-resistant castable is an ideal material for flue linings. It is particularly suitable for use in large-diameter flues.

What is the thickness of the castable lining for a chimney?

Fluid ducts typically have small inner diameters. If acid-resistant castable lining is used, the thickness is generally less than 100mm, resulting in a significant weight reduction. However, the small diameter of the lining can cause unnecessary difficulties during construction. For flues with a diameter of less than 2 meters, using a coating material is a better alternative, as semi-heavy coating materials can be 30-50mm thick. This reduces the weight by approximately 50% compared to castable lining. For vertical flues, this further reduces the potential for excessive weight. It also facilitates construction in small-diameter flues. Therefore, semi-heavy acid-resistant coating materials are an ideal choice for small-diameter flues.

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Construction of Flue Lining with Castable Refractory

The construction of flue lining with castable refractory can be carried out after installation or after the lining is installed. When constructing the flue lining with castable refractory, a 3mm gap should be left between each cast section for expansion joints. The process involves applying sealant to adjacent sections of the castable refractory before pouring the next section.

Construction of Flue Lining with Castable Refractory Before Installation

Constructing the lining after installation is generally preferable. Large-diameter flue linings are easier to construct with castable refractory. However, if the large-diameter pipe is heavy, lining before installation will significantly increase the pipe’s weight, increasing installation risk and making component welding difficult. Large-diameter flue linings are best constructed after installation.

The construction of flue lining with castable refractory before installation is suitable for small-diameter flue linings due to its lighter weight. Pre-installation construction reduces the difficulty of high-altitude operations, as the refractory lining is poured on the ground, resulting in lower labor intensity and higher construction efficiency. The disadvantage is that the lining construction cannot be carried out continuously, and expansion joints are difficult to handle.

Safety is the primary concern during construction.

The primary concern in constructing flue linings using refractory lining is safety, followed by the welding of anchors and the refractory pouring method. For large-diameter flues, the anchor nails are welded first, and then the anchors are painted before proceeding with the construction in sections. Sectioning involves constructing two sections within a 180° radius, then rotating the pipe 180° to construct the third and fourth sections. If there is an insulation layer, the insulation refractory lining is constructed first, followed by the working layer of the wear-resistant refractory lining. Additionally, if two types of refractory lining are used, the construction must also be carried out in four sections. However, a 12-hour break must be observed after each section is completed before proceeding to the next section. The lower half is poured first, and then the flue is rotated on the ground to pour the remaining half.

Lining Construction on the Ground

If lining construction is carried out on the ground, pipe openings must be straightened and anti-deformation measures implemented. This is to prevent pipe opening deformation due to weight differences during construction and rotation. Areas prone to deformation during refractory lining construction should not be constructed initially; lining should be applied to these areas after other parts are completed.

For pipe bends, expansion joints, and valves, refractory lining should be applied in sections, with expansion joints reserved in both horizontal and vertical directions. For lower-lying areas, inclined formwork can be used for refractory lining, followed by vibration to ensure compaction, and excess material should be removed tangentially. In areas with limited space or high construction joints, refractory lining should be applied using a flat butt joint, with a 3mm high-temperature resistant ceramic fiber felt sandwiched within the joint before welding.

What Type of Refractory Castable is Best for a Kiln Operating at 1500℃?

When the operating temperature of a kiln is 1500℃, corundum castable should be selected based on the temperature. However, many users don’t understand this and think that because it’s expensive, they should choose general high-alumina castable.

However, if the operating temperature is directly at 1500℃, general high-alumina castable is not suitable. Brown corundum castable is required to meet the requirements. Some users have suggested using steel fiber castable. However, this is also not an option because steel fibers begin to melt above 1300℃. Therefore, steel fiber castable cannot be used.

However, some users suggest using stainless steel, but this is also not suitable. Because the lining only uses rust as an anchor, it does not provide high-temperature resistance or corrosion resistance. Corundum castable is characterized by the highest bulk density, the lowest apparent porosity, and good high-temperature resistance, corrosion resistance, and thermal shock resistance. Moreover, the characteristics of corundum castable are fully realized at 1500℃. If steel fiber castable is used, it cannot withstand temperatures up to 1500°C. General high-alumina castables, however, can be used at temperatures of 1300°C-1400°C.

However, for different kilns with varying gas fields and degrees of corrosion, corundum wear-resistant castables or high-strength wear-resistant castables can be selected. This provides both high-temperature resistance and corrosion resistance. For example, in waste incinerators, the temperature is not high, but the degree of corrosion is strong, sometimes involving both acid and alkali corrosion. In such cases, corundum castable is unsuitable because the temperature is too low for the corundum to be fully utilized. Using clean, wear-resistant castables can resist acid or alkali corrosion. Moreover, they are cheaper than corundum castables, making them cost-effective and suitable for the special conditions of incinerators.

In short, regardless of the material of the refractory castable chosen, it is essential to select the appropriate refractory castable based on the specific kiln, temperature, and degree of corrosion.

Application of Dry Ramming Refractory Material in Electric Furnace Bottom

October 14, 2025 by rsrefractorycastable

Currently, the working layer of high-power and ultra-high-power electric furnaces is commonly constructed using magnesia dry ramming refractory materials. The working layer, made of refractory materials, comes into direct contact with molten steel and slag, bearing the high-temperature heat load and slag erosion. The erosion of molten steel, the mechanical impact of scrap steel, and the high-temperature oxidation and reduction processes within the furnace cause slag to penetrate the furnace floor, resulting in a thinning of the furnace floor. During discontinuous operation, the dicalcium silicate in the slag absorbs atmospheric moisture and disintegrates, reducing the material’s durability and service life.

Magnesia Refractory Ramming Mass Material from Rongsheng — Refractory Ramming Mass Material from Rongsheng

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Common dry ramming refractory materials use high-iron, high-calcium synthetic magnesia and fused magnesia as aggregates, with the synthetic and fused magnesia powders used as fine powders, with a critical particle size of 5-6 mm. C2F (dicalcium ferrite) in the synthetic magnesia is used as a sintering aid, without the addition of any binders, and are produced using a multi-stage batching process. Through vigorous ramming, the resulting density is guaranteed, allowing it to sinter into a solid, integral structure at the appropriate temperature. Its service life is several times longer than that of previous knotting and bricklaying methods. The dry ramming mass used in medium frequency furnaces has higher quality requirements. Some scholars have studied the use of fused corundum, white corundum, plate-shaped corundum, and magnesia as granular materials, magnesia fine powder and corundum fine powder as powder, adding high-temperature sintering agents and boric acid as admixtures. The various raw materials are mixed evenly and the particle size distribution is adjusted to produce dry ramming mass.

Dry Ramming Material for Electric Furnace Bottom Construction

Before applying dry ramming refractory material for electric furnace bottoms, be sure to clean away any foreign matter such as permanent layer residue, dust, wire, and plastic sheeting. Calculate the knot size; the actual knot thickness is the desired knot thickness multiplied by 1.09. Prepare a sufficient amount of ramming material based on the required furnace slope and bottom dimensions. Upon receipt, inspect the ramming material for debris and moisture. Remove any debris and do not use damp material. Prepare ramming tools such as a rammer and jackhammer.

For specific construction steps, refer to the following plan:

After shoveling the material flat and laying it flat, tamp it down with your feet to remove any air. After tamping, insert a steel chisel into the material and shake it repeatedly, then tamp it down further with your feet. The ideal thickness for each layer of ramming refractory material is 150-200mm. Then, use a knotter to tamp the material three times in a spiral motion from the perimeter to the center.

The quality of the knot is usually checked by placing a 5mm diameter round steel bar on the ramming layer and pressing it down with a 10kg pressure to a depth of no more than 30mm. During on-site construction, you can forcefully insert the chisel, but the depth should not exceed 30mm.

The method for knotting the furnace slope is the same as for the furnace bottom: first tamp it down with your feet, then tamp it with a knotter. The maximum angle between the slope and the furnace bottom should not exceed 40°. This is to prevent rolling or collapse caused by excessive slopes.

In areas where molten steel is agitated and eroded, such as the taphole base bricks and the furnace door, ramming should be more vigorous and appropriate thickness may be added to maximize the service life of the refractory material in these damaged areas.

After ramming, a 5-10mm thick steel plate is placed on the ramming refractory material to prevent the scrap from damaging the furnace bottom or piercing the ramming material layer, which could cause steel leakage. If steelmaking cannot be carried out in time, a 100-200mm thick layer of lime is placed on the iron plate to prevent the ramming material from hydrating.

When knotting the ramming material, strict adherence to construction requirements is crucial to ensure its density. Failure to do so will result in significant shrinkage during use, leading to numerous cracks and spalling, shortening its lifespan. The first furnace smelting is crucial. During oxygen decarburization, the oxygen lance must not be inserted too deeply, as this can cause the ramming material to flip upwards and create large pits at the furnace bottom. During the first furnace smelting, a layer of lime can be applied to the furnace bottom. This not only prevents scrap steel from directly impacting the furnace bottom, but also prevents the ramming material from hydrating and prematurely forming slag.

Generally, dry ramming refractory material has a lifespan of over 300 furnaces. This can be extended to 500-600 furnaces through hot repair, with some commercially available products even exceeding 600 furnaces.

Repair of ramming material at the bottom of an electric furnace

After a certain period of use, the ramming refractory material at the bottom of an electric furnace will be damaged to varying degrees due to various reasons. Therefore, the lining should be repaired according to the damage of the lining.

(1) Hot repair is carried out at regular intervals during smelting, but the bottom dynamics must be closely monitored after each batch of steel is discharged. If a pit with a depth greater than 150mm is found, it must be repaired.
(2) Before repairing, use oxygen (immediately after the steel and slag are discharged) to blow the surface to be repaired to completely remove the residual steel and slag in the area.
(3) Hoist the ramming material to the top of the area to be repaired and drop it down. Move the crane to distribute it reasonably.
(4) Hoist iron blocks or other heavy objects and compact them.
(5) It should be emphasized that if a large area of the furnace bottom or furnace slope is hot-repaired, in order to ensure the service life after the repair, shorten the number of repairs, and reduce the consumption of dry ramming refractory material per ton of steel, the first batch of steel after hot repair can be smelted in accordance with the “Operation Requirements for Smelting New Furnaces”.

Bauxite Calcination Process

September 30, 2025 by rsrefractorycastable

We are a professional manufacturer of calcined bauxite aggregate, offering a comprehensive range of products including lumps, aggregates, and fine powders. We process and sell a wide range of aggregates and fine powders (containing 60-90% aluminum) and can also customize them to meet customer needs. Particle sizes include: 0-1mm; 1-3mm; 3-5mm; 5-8mm; 8-15mm; and 80-325 mesh. Our aggregate products are high-quality and competitively priced. Contact us for free samples and a quote.

Calcined Bauxite Aggregate Material Can be Applied to Make Monolithic Refractory — Calcined Bauxite Aggregate Material of Rongsheng

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Bauxite Calcination Process

The bauxite calcination process follows: raw materials entering the factory → crushing → screening → calcination → crushing → finished product delivery.

Equipment for Calcining Bauxite

In the process of producing calcined bauxite aggregate clinker, the calcination of bauxite has a great influence on the quality of the clinker. Therefore, it is very important to choose a kiln for calcining bauxite. The main equipment for calcining bauxite includes downdraft kiln, rotary kiln, tunnel kiln, etc.

(1) Downdraft kiln is an intermittent kiln. Its name is derived from the flow of flame. The flames generated by combustion all rise from the fire nozzle of the combustion chamber to the top of the kiln. Since the kiln top is sealed, the flames cannot continue to rise. In the absence of an air outlet at the top of the kiln, they are pulled downward by the suction force of the chimney. After passing through the gaps in the sagger columns, they enter the branch flue and the main flue from the fire-absorbing hole at the bottom of the kiln and are finally discharged from the chimney. Because hot gases are light in weight and always float on the surface, people are accustomed to calling the flames flowing from bottom to top “shun”. The flames flowing from top to bottom are called “reverse”. This is the origin of the name “downdraft kiln”.

The advantages of the downdraft kiln are that the kiln volume can be large or small, which is flexible in production and can produce high-quality products. The construction investment cost is low and the metal material consumption is low. The disadvantages are that it is intermittent operation and the exhaust gas temperature is very high when it leaves the kiln, so the fuel consumption per unit product is high. The production scale is small and the working conditions are poor. The mechanization level is low, the operation and control are difficult, and the production efficiency is low. The environmental performance is poor. Generally, the thermal efficiency of the downdraft kiln is only 6.48%, while the coal consumption per ton of finished product is as high as 1.456 tons.

Rotary Kiln for Bauxite Calcining Production

(2) The rotary kiln refers to a rotary calcining kiln, which originated in cement production. Rotary kiln equipment is now widely used in many production industries such as building materials, metallurgy, chemical industry, and environmental protection to perform mechanical, physical or chemical treatment on solid materials. Most rotary kilns for calcining bauxite have changed from heavy oil as fuel to coal powder as fuel. The coal consumption for calcining 1 ton of high-bauxite is 200-250kg. The characteristics of rotary kilns are: simple structure, few vulnerable parts, easy to control the production process and high operating rate. It is easy to mass produce and easy to realize automatic control, and the product quality is stable.

(3) Tunnel kilns are modern continuous firing thermal equipment, widely used in the roasting production of ceramic products, and also used in metallurgical industries such as abrasives. Tunnel kilns are mainly used for the firing of products. The refractory industry can be divided into three types according to the different operating temperatures. Low-temperature tunnel kilns are mainly used for roasting skateboard bricks, etc., with a firing temperature of about 1000℃. Medium-temperature tunnel kilns are mainly used for firing ordinary alkaline bricks, clay bricks, high-alumina bricks, silica bricks, etc., with a firing temperature of 1300℃-1650℃. High-temperature tunnel kilns are mainly used for firing mid-range magnesia bricks, high-purity magnesia bricks, magnesia-alumina and corundum products, with a firing temperature greater than 1700℃, generally between 1800℃-1900℃. The labor intensity is high, the production efficiency is low, the heat consumption is high, and it is difficult to realize automatic control.

At present, for calcined bauxite aggregate, large-scale bauxite calcining production systems at home and abroad all use rotary kiln equipment and technology.

Advantages and Disadvantages of Ceramic Aggregates and High-Alumina Aggregates

As two important refractory and construction materials, ceramic aggregates and high-alumina aggregates each possess unique advantages and disadvantages. Below is a detailed comparison of their advantages and disadvantages:

Ceramic Aggregate

Advantages

Reduced Density: Compared to traditional concrete aggregates, ceramic fine aggregate has a lower density, effectively reducing the overall density of concrete, thereby reducing the load on the building itself.
Increased Strength and Durability: Ceramic fine aggregate has higher strength and hardness, effectively improving the compressive strength and durability of concrete, making it stronger and more durable.
Reduced Environmental Pollution: Traditional concrete production produces large amounts of carbon dioxide and other pollutants, while ceramic fine aggregate concrete can effectively reduce environmental pollution and improve production efficiency.

Disadvantages

Higher Cost: Because the production cost of ceramic fine aggregate is higher than that of traditional aggregates, the cost of ceramic fine aggregate concrete is also higher, increasing the overall cost of concrete structure construction.
Difficult Construction: The construction of ceramic fine aggregate concrete is relatively difficult, requiring high technical requirements and construction experience, as well as special construction techniques and equipment.
Poor Seismic Resistance: Due to its lower density, ceramic fine aggregate concrete has inferior seismic performance compared to traditional concrete.

High-Alumina Aggregate

Advantages

High Strength and Hardness: High-alumina aggregates offer high strength and hardness, capable of withstanding high temperatures and mechanical stress, ensuring a stable and safe production process.
High-Temperature Resistance: High-alumina aggregates, calcined bauxite aggregates are primarily made from bauxite calcined at high temperatures. They contain a high proportion of aluminum oxide, resulting in excellent high-temperature resistance.
Chemical Stability: High-alumina aggregates exhibit excellent chemical stability at high temperatures and are resistant to reactions with acids and alkalis, maintaining excellent stability in aggressive media.
Wide Applications: High-alumina aggregates are widely used in ceramics, metallurgy, and the chemical industry. They are an indispensable raw material for applications such as refractory bricks, castables, and gunning mixes.
Thermal Insulation: High-bauxite aggregates are rich in alumina and have low thermal conductivity. They reduce indoor heat loss in winter and block external heat conduction in summer, providing greater building comfort and contributing to energy conservation and environmental protection.
Durability: Due to its high content of alumina, high-alumina aggregates are impervious to deliquescence, moisture, and water erosion, and are also resistant to acid and alkali corrosion. This extends the lifespan of buildings and reduces maintenance costs.

Disadvantages

High Cost. Due to the complex production process and high raw material costs, high-alumina aggregates command a relatively high market price.
High production equipment and processes are required. The production of high-alumina aggregates requires advanced equipment and processes to ensure product quality and performance.

In summary, ceramic aggregates and high-alumina aggregates each have their own unique advantages and applications. Choosing which aggregate to use requires careful consideration based on the specific project requirements and budget.

Monolithic Refractories in Various Shapes, Such as Powder, Granular, Mortar, and Block

September 17, 2025September 15, 2025 by rsrefractorycastable

Monolithic refractories, also known as bulk refractories, are made by mixing refractory aggregates and powders of a specific grade with binders and admixtures. These refractory linings materials are used directly without undergoing forming and firing processes. Rongsheng Castable Refractory Factory, a manufacturer of unshaped refractory materials, operates an advanced, environmentally friendly, fully automatic monolithic refractory production line with an annual output of 80,000 tons. They primarily produce monolithic refractory products, including refractory castables, refractory plastics, refractory ramming materials, refractory clay, high-temperature mortar, refractory cement, and prefabricated refractory blocks. These products provide reliable support for the integral lining of high-temperature industrial furnaces.

Refractory Castables

Refractory castables are a new type of refractory material that exhibits excellent fluidity after mixing with water without calcining. They are an important type of amorphous refractory material. They are a mixture of refractory aggregate, refractory powder, and binder (or admixtures) in a specific proportion. They can be shipped in bulk form or prefabricated.

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The composition of castable refractory is as follows:

Refractory aggregate is the main component of refractory castables and functions similarly to the crushed stone and sand in conventional building concrete. Refractory aggregate can be obtained from calcined clinker of various refractory materials (clay, high-alumina, siliceous, magnesian, etc.) or from various waste bricks that have been crushed to a certain degree. Aggregate particle size significantly impacts product quality. Coarse aggregate (5-20 mm) generally accounts for 35%-45% of the mix, while fine aggregate (0.15-5 mm) accounts for 30%-35%.
Binders: These act as a bonding and hardening agent, imparting a certain strength to the product. Common binders include ordinary Portland cement, alumina cement (high-alumina cement), magnesia cement, water glass, and phosphoric acid. To ensure refractoriness and minimize volume shrinkage during use, the binder dosage should be kept as low as possible, generally 10% to 25%. Furthermore, the binder and aggregate should not form excessive low-melting products.
Admixtures: To improve the physical and chemical properties and workability of refractory castables, appropriate amounts of these additives are often added. These include plasticizers, dispersants, accelerators, retarders, dilution agents, and gelling agents. For refractory castables exposed to high mechanical forces or intense thermal shock, adding an appropriate amount of stainless steel fiber can significantly increase the material’s toughness. Adding inorganic fiber to insulating refractory castables not only enhances toughness but also helps improve thermal insulation.

Refractory Mortar

Refractory mortar, composed of refractory aggregate, binders, and admixtures, is used as a joint material for shaped products. It is delivered in dry or wet form. During construction, a mixing liquid (water or other liquid) is added to the mortar to a specified consistency. Masonry or pouring is then performed using a trowel or specialized machinery (such as a pressure grouting machine).

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Refractory mortar is divided into two categories: heavy and light. Based on the binder, it can be categorized as phosphate slurry, water glass slurry, and organic binder slurry. Based on the material, it can be categorized as clay, high-alumina, magnesia, silica, or carbonaceous slurry. Its components are as follows:

01 Refractory Powder

Refractory powder is typically fine particles of refractory materials such as high-alumina, silica, and magnesia, and determines the basic properties of the refractory mortar.

02 Binder

Binders, such as Portland cement, phosphate, and water glass, are used to allow the refractory mortar to harden and develop a certain strength after application.

03 Admixtures

Admixtures are added according to specific application requirements, such as setting accelerators, setting retarders, and plasticizers.

Performance Characteristics

Excellent Adhesion: Securely bonds refractory bricks and other refractory materials, forming a tight masonry structure and preventing the penetration of high-temperature gases and slag.
High Refractoriness: Remains stable at high temperatures without softening or melting, maintaining masonry stability.
Suitable Plasticity: Facilitates construction and can fill brick joints and irregularities.
Excellent Volume Stability: Minimal volume change at high temperatures, preventing expansion or contraction that could damage the masonry structure.

Refractory Precast Blocks

Precast blocks, which cannot be mass-produced for certain reasons, are typically prefabricated refractory block products composed of refractory aggregate, refractory powder, binders, and admixtures.

Precast Shapes with Refractory Anchor Bricks for Heating Furnace Top — Precast Shapes with Refractory Anchor Bricks for Furnace

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01 Refractory Aggregates

Refractory aggregates, such as high-alumina bauxite, corundum, and mullite, form the primary skeleton of precast blocks. They determine their refractoriness and high-temperature strength.

Refractory powder: Refractory powder has a finer particle size and fills the gaps between aggregates, increasing the density and strength of the precast blocks.

02 Binders

Common binders include cement, phosphate, and water glass. They are used to bind the aggregate and powder together, ensuring sufficient strength after curing under certain conditions.

03 Admixtures

Additional additives, such as accelerators, retarders, and explosion-proofing agents, are added as needed to improve the construction and performance of precast blocks.

Performance Characteristics

Excellent refractory properties: Maintains structural stability in high-temperature environments without softening or melting. High refractoriness and refractoriness under load.
Good mechanical strength: Through a rational formulation and manufacturing process, the precast blocks possess high compressive and flexural strength, capable of withstanding mechanical loads at high temperatures.
High-dimensional accuracy: Prefabricated in the factory, dimensional deviations can be strictly controlled, facilitating installation and ensuring the quality and tightness of the masonry.
Easy and convenient construction: The precast blocks can be transported directly to the construction site for installation, reducing on-site construction time and workload. They are particularly suitable for the construction of complex structures such as large industrial furnaces.
Good thermal stability: They can withstand rapid temperature fluctuations without cracking or flaking, ensuring safety during furnace startup and shutdown.

Refractory Cement

Refractory cement, also known as aluminate cement, is a specialty cement with high refractory properties. It is used as a binder in refractory materials for the production of refractory bricks, refractory castables, and refractory spray coatings. It enables refractory materials to maintain excellent strength and integrity at high temperatures. It is also used in the linings of various industrial furnaces, such as those used in steelmaking, cement, and glassmaking.

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01 Composition

It is primarily composed of calcium aluminate minerals, such as monocalcium aluminate (CaO·Al₂O₃) and monocalcium dialuminate (CaO·2Al₂O₃). It may also contain small amounts of dicalcium silicate (2CaO·SiO₂).

Performance Characteristics

High refractoriness: It maintains structural stability in high-temperature environments, resisting softening and melting. Its refractoriness generally exceeds 1580°C.
Early Strength and Rapid Hardening: It exhibits a high rate of early strength development, achieving high strength in a short period of time, facilitating rapid construction.
Excellent Corrosion Resistance: Strong resistance to corrosive media such as slag and molten salt at high temperatures.
Excellent Thermal Stability: Minimal volume change with temperature fluctuations, making it less susceptible to cracking and flaking.

Can Lightweight Castables Used as Insulation Layers for Industrial Furnaces Reduce Heat Consumption?

August 31, 2025 by rsrefractorycastable

Lightweight castables have lower thermal conductivity than heavy castables and significantly reduce the weight of the furnace lining. The diffusion rate of combustion temperature in industrial furnaces can be reduced by about 30% compared to heavy castables. Therefore, using lightweight insulating castables as insulation layers can effectively reduce the heat loss of industrial furnace linings.

Lightweight Castable Refractory for Furnaces

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Lightweight Castables as Insulation for Industrial Furnaces

Lightweight castables are the first layer of material that adheres to the furnace shell in the kiln lining. High-end lightweight castables, such as hollow alumina sphere castables and lightweight mullite refractory castables, can also be used directly as a working layer on the lining of some lightweight kilns. This reduces furnace weight, lowers heat consumption, and saves energy costs.

The thickness of lightweight castables used as insulation should be 80mm-150mm. Thicknesses below 50mm will result in poor installation and ineffective insulation. Using lightweight castables for lining pipes and chimneys is also a poor choice. Castables with a specific gravity of approximately 1.5 can serve as both an insulation layer and a working layer. This reduces weight while meeting the requirements for chimney and pipe linings.

Lightweight castables are used at different temperatures: low temperatures (600-900°C), medium temperatures (900-1200°C), and high temperatures (1200°C). High-temperature insulation layers require high-quality lightweight materials, such as lightweight mullite and hollow alumina sphere castables. Commonly used materials include vermiculite, perlite, and ceramsite. These materials have an operating temperature of approximately 1000°C and cannot be used at high temperatures. Lightweight mullite and corundum-mullite castables can be used at temperatures between 1350°C and 1500°C, allowing for direct use in the working layer.

Lightweight castables lack the refractoriness, compressive strength, and flexural strength of heavier castables. However, their low thermal conductivity provides excellent insulation. Choosing the right lightweight material for different temperatures and kiln linings can effectively insulate and reduce energy consumption.

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Significant Features of Low Thermal Conductivity Castables

Low thermal conductivity castables are unique refractory materials that maintain low bulk density and low thermal conductivity even at high temperatures, while also offering excellent thermal insulation. Unlike conventional lightweight castables, whose bulk density increases with increasing temperature, low thermal conductivity castables maintain a low bulk density even at high temperatures. Their light weight effectively reduces the weight of equipment, which is crucial for the installation and operation of large-scale industrial equipment. Furthermore, their excellent thermal insulation properties ensure more uniform furnace temperature distribution, thereby saving energy and reducing production costs.

In terms of technical performance, low thermal conductivity castables offer the dual advantages of low bulk density and high refractory strength, a true innovation in themselves. They offer strong overall performance, excellent spalling resistance, a long service life, and can be repaired and processed into various shapes as needed. They can also be used to construct integral furnace linings, greatly facilitating the maintenance and construction of industrial furnaces.

Wide Application Areas and Energy-Saving Advantages

Low thermal conductivity castables have a wide range of applications across numerous industries. They are widely used in industrial furnaces and thermal equipment in industries such as metallurgy, machinery, power generation, chemicals, and petroleum. Compared to conventional lightweight castables, using low thermal conductivity castables can achieve energy savings of over 20%, a significant saving for energy-intensive industries. Especially in applications such as petroleum and petrochemical furnaces, where material performance requirements are more stringent, low thermal conductivity castables require a lower bulk density and adhere to stricter quality standards. Therefore, compared to lightweight castables used in other industries, low thermal conductivity castables for petroleum and petrochemical furnaces are of higher quality and relatively higher price. However, the energy-saving benefits and equipment protection they provide are well worth the effort.

Easy Construction

Low thermal conductivity castables are relatively easy to apply. Manufacturers carefully select the aggregate particle size. An appropriate particle size helps enhance the compressive strength of lightweight castables. Excessively large particle sizes can negatively impact the construction process. By optimizing the particle size, low thermal conductivity castables can be constructed more smoothly, reducing difficulties and problems during construction, improving construction efficiency, and ensuring construction quality.

Considerations for Lightweight Castable Pipe Installation

Lightweight castables provide insulation. For pipe use, their bulk density generally must be no less than 1.2 kg/m³. Specific gravity of 1.5 is more common. When used in pipes, installation is limited by the pipe diameter, making it difficult for workers to work within the pipe.

1. Pay attention to the insulation layer.

Applying the insulation layer to the insulation is also challenging. The pipe insulation in the image above is applied irregularly, and the anchors are not suitable for use. Anchors must be painted. If not, plastic caps must be placed on them. Otherwise, rust will occur, shortening their lifespan.

If this occurs, there is a remedy: apply a layer of plastic film to the surface of the insulation. This prevents moisture from penetrating the insulation during baking after the lightweight castable is applied. If moisture seeps into the insulation, even after drying, the insulation’s effectiveness will be reduced.

2. Pay attention to the proportions added during construction.

When applying lightweight materials, the water ratio must be carefully considered. If too little water is added, some of the base materials, due to their light weight, will be difficult to apply and will not set easily. Adding too much water will affect the strength of the material in the final application.

3. Mix the aggregate and powder before construction.

During on-site construction, first mix the aggregate and powder, then add the binder. Then, strictly follow the manufacturer’s water ratios and mix the lightweight castable. After mixing, verify that the castable has good fluidity before vibrating. Generally, the water content for lightweight castables is 15-17%. Some manufacturers, due to the light weight of the lightweight castable, may sprinkle some water during production to facilitate production control.

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Optimization of Low Thermal Conductivity Castable Technology

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High-Alumina Refractory Mortar

Storage and Usage Principles of High-Alumina Mortar

Judging the Storage Condition of the Binder

Judgment of Refractory Mortar with Added Binder

Summary of High-Alumina Refractory Mortar Usage

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Low Thermal Conductivity Refractory Materials for High-Temperature Kilns

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Preparation and Properties of Porous Spherical Mullite Castables

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Application Effects of Lightweight Mullite Castables

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Water Addition in Precast Refractory Shapes Manufacturing

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Can Precast Refractory Shapes be Used Without Baking?

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Flue Lining Using Castable Refractory

What is the thickness of the castable lining for a chimney?

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Construction of Flue Lining with Castable Refractory

Construction of Flue Lining with Castable Refractory Before Installation

Safety is the primary concern during construction.

Lining Construction on the Ground

What Type of Refractory Castable is Best for a Kiln Operating at 1500℃?

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Dry Ramming Material for Electric Furnace Bottom Construction

Repair of ramming material at the bottom of an electric furnace

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Bauxite Calcination Process

Equipment for Calcining Bauxite

Advantages and Disadvantages of Ceramic Aggregates and High-Alumina Aggregates

Ceramic Aggregate

High-Alumina Aggregate

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Refractory Castables

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Refractory Mortar

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Performance Characteristics

Refractory Precast Blocks

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Performance Characteristics

Refractory Cement

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Performance Characteristics

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Lightweight Castables as Insulation for Industrial Furnaces

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Significant Features of Low Thermal Conductivity Castables

Wide Application Areas and Energy-Saving Advantages

Easy Construction

Considerations for Lightweight Castable Pipe Installation