News detail
Lightweight Insulating Castable: High-Energy-Saving Monolithic Refractory for Industrial Kilns
1. Product Overview
Lightweight insulating castable is a type of unshaped refractory prepared by mixing porous lightweight aggregates, high-purity refractory fine powder, calcium aluminate cement binder and composite functional additives. Its raw materials include mullite hollow spheres, expanded perlite, vermiculite, lightweight chamotte and bubble alumina. A complete product series is available, with bulk density ranging from 0.4 g/cm³ to 1.8 g/cm³.
Different from dense castables used for working linings, this material contains a large number of closed micropores inside the structure, delivering ultra-low thermal conductivity and light weight. It is widely adopted as a back-up thermal insulation layer to replace traditional insulating bricks. The integrated pouring construction can be applied to furnace walls, furnace tops and flues, which simultaneously reduces heat loss and the overall weight of kiln bodies.
We supply customized low-temperature, medium-temperature and high-temperature grades to fit working temperatures from 1100°C up to 1600°C, covering all thermal insulation demands in high-temperature production lines.
2. Core Raw Material & Classification
Raw Material Formula
- Light aggregate: porous mullite, floating beads, lightweight ceramsite, bubble corundum
- Matrix powder: high alumina fine powder, silica fume
- Binding system: pure calcium aluminate cement, low-cement bonding agents
- Functional additives: water reducing agent, anti-shrinkage agent, thermal shock resistance modifier
Classification Standard
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Classified by bulk density
Ultra-lightweight castable features bulk density between 0.4–0.6 g/cm³, suitable for low-load and low-temperature insulation layers. Standard lightweight castable with bulk density of 0.8–1.2 g/cm³ is the universal choice for medium-temperature thermal preservation. Semi-lightweight high-strength castable ranges from 1.3–1.8 g/cm³, designed for high-temperature back-up linings that require slight wear resistance.
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Classified by maximum service temperature
Low-temperature grade can withstand temperatures no higher than 1150°C, ideal for boilers and waste heat recovery channels. Medium-temperature grade works stably at 1200–1350°C, commonly used in ceramic tunnel kilns and heat treatment furnaces. High-temperature bubble alumina grade supports 1400–1600°C, matching glass kilns and non-ferrous metal smelting furnaces.
3. Outstanding Product Advantages
Superior Thermal Insulation & Energy Saving
Its thermal conductivity stays between 0.15–0.75 W/m·K at 1000°C, forming an effective thermal barrier to cut outward heat dissipation of kilns. Practical industrial operation data shows it can reduce energy consumption by 15%–25% compared with ordinary dense refractory linings, significantly lowering long-term fuel and electricity costs for manufacturers.
Light Weight Reduces Structural Load
The low bulk density greatly lowers the total mass of furnace linings. It decreases load-bearing requirements for kiln steel frames and foundations, saving construction investment for newly built kilns and eliminating risks of structural deformation during equipment renovation.
Excellent Construction Performance
Supplied as premixed dry powder, it only needs clean water mixing on site. The material boasts good fluidity and long usable working time. Two construction methods are supported: integral pouring with vibrating formworks, and gunning spraying for narrow flues and irregular structural positions. After curing, it forms a seamless integrated lining that prevents hot gas leakage and improves kiln tightness.
Stable High-Temperature Performance
It has remarkable thermal shock resistance, resisting frequent temperature rise and fall without peeling or cracking. The permanent linear shrinkage is well controlled, with volume change less than -1.5% after firing at 1000°C, avoiding collapse of insulation layers. Its cold crushing strength ranges from 1.5 MPa to 30 MPa to resist mechanical impact during daily operation. Besides, the product is asbestos-free, non-toxic and eco-friendly, complying with global industrial safety regulations.
Low Long-Term Maintenance Cost
Integrally poured linings have far fewer joints than brick masonry, cutting off erosion channels of high-temperature flue gas. The outstanding anti-permeability and anti-corrosion capacity extend lining service life by 30%–40%, reducing frequent production shutdown and relining expenses for factories.
4. Main Industrial Application Scenarios
Metallurgy Industry
Back-up thermal insulation lining for hot blast stoves, carbon roasters, coke ovens, non-ferrous smelting furnaces and annealing furnaces.
Building Material Manufacturing
Middle insulation layer of cement rotary kilns, ceramic tunnel kilns, lime kilns and outer linings of glass melting furnaces.
Energy & Power Equipment
Thermal insulation for boiler walls, lining of waste heat recovery equipment, high-temperature flues, chimneys and incinerators.
Petrochemical & Heat Treatment
Insulation layers for reactors, back-up lining of heat treatment furnaces and atmosphere furnaces, pouring thermal protection for industrial high-temperature pipelines.
Other Application Fields
Heat preservation layers of drying ovens, tunnel furnaces and all thermal equipment with strict weight control limits.
5. Standard Technical Index Reference
Ultra-light grade has a bulk density of 0.4–0.6 g/cm³ after drying at 110℃ for 24 hours, alumina content no less than 25% to 35%, and maximum service temperature of 1100℃. Its cold crushing strength after heat treatment at 1000℃ for 3 hours reaches at least 1.5 MPa, thermal conductivity under 700℃ is no higher than 0.22 W/m·K, and permanent linear change after 1000℃ firing for 3 hours ranges from -1.2% to -0.3%.
Standard light grade owns bulk density of 0.8–1.2 g/cm³ after drying, alumina content above 35% to 42%, and maximum service temperature of 1300℃. Its cold crushing strength after 1000℃ heating is over 5 MPa, thermal conductivity at 700℃ is below 0.40 W/m·K, and permanent linear change falls between -1.0% and -0.2%.
High-strength semi-light grade features bulk density of 1.3–1.8 g/cm³ after drying, alumina content not lower than 42% to 48%, and maximum service temperature up to 1600℃. Its cold crushing strength after heat treatment at 1000℃ for 3 hours exceeds 12 MPa, thermal conductivity under 700℃ is controlled within 0.65 W/m·K, and permanent linear change ranges from -0.8% to 0.
6. Construction & Storage Guidance
On-Site Construction Steps
- Mixing: Add clean tap water according to the recommended water-powder ratio and stir fully within 3 to 5 minutes. Hardened mixed slurry cannot be mixed again for secondary use.
- Casting: Pour the mixture into formworks layer by layer and vibrate evenly with vibrating rods to eliminate internal bubbles. Avoid long-time vibration to prevent aggregate segregation.
- Curing: Complete natural curing for 24 to 48 hours after pouring before demoulding. Slow heating is required during initial baking to drain internal water and prevent lining cracking caused by rapid water vapor expansion.
Storage Requirements
The dry castable powder must be stored in dry, ventilated warehouses with waterproof packaging intact. Keep away from rain, moisture and ground water. Unsealed materials should be used up as soon as possible to avoid moisture absorption that damages construction performance. The valid storage period under dry conditions is 6 months.
7. Service Customization
We provide one-stop customized solutions of lightweight insulating castable for different industrial working conditions. Adjustments can be made on bulk density, alumina content, service temperature and mechanical strength according to clients’ kiln structure, operating temperature and energy-saving targets. Professional technical teams support on-site construction guidance and furnace lining operation consultation for global buyers.
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