Low cement castable:What it is & Where it’s Used

　　Ultra-low cement castable (ULCC) is a specialized type of refractory monolithic material that contains an extremely low amount of calcium aluminate cement (CAC) as a binder. The CAC content in ULCC is typically less than 3% by weight, significantly lower than conventional low cement castables (LCC) that contain around 3-8% CAC.

　　The main features and benefits of ultra-low cement castables include:

　　1. Reduced Cement Content: The ultra-low cement content results in a significant reduction in porosity and permeability compared to conventional castables. This enhances the density, strength, and overall performance of the refractory lining.

　　2. Enhanced High-Temperature Performance: ULCC exhibits improved resistance to thermal spalling, thermal shock, and erosion at high temperatures. The reduced cement content allows for increased mullite formation, which contributes to better thermal stability and mechanical properties.

　　3. Excellent Strength and Load-Bearing Capacity: ULCC offers higher hot strength and superior load-bearing capacity at elevated temperatures compared to conventional castables. This makes them suitable for applications where structural integrity under heavy loads or thermal cycling is crucial.

　　4. Improved Resistance to Chemical Attack: The reduced cement content in ULCC lowers the potential for reactions between refractory aggregates and corrosive chemicals in the environment. This provides enhanced resistance to chemical attack and can extend the service life of the refractory lining.

　　5. Lower Water Requirement: ULCC requires less water for installation, resulting in improved densification and reduced drying time. This minimizes the risk of cracking during heat-up and enhances the overall performance of the refractory lining.

　　6. Easy Installation: ULCC has good flowability and workability, making it easier to handle and install. It can be poured, gunned, or troweled into place, allowing for flexibility in shaping and forming complex geometries.

　　1. Low cement content: Compared with traditional refractory castables, the main feature of low cement castables is that they contain a lower proportion of aluminum silicate cement (Calcium Aluminate Cement, CAC). Typically, low cement castables have a cement content of less than 8%, while traditional castables may contain 10-20% cement. The low cement content reduces the overall porosity and permeability of the castable, improving the compactness and fire resistance of the material.

　　2. High temperature performance: low cement castable has excellent high temperature performance. The lower cement content reduces the material's tendency to crack and provides better resistance to thermal shock and spalling. This allows low cement castables to have better stability and durability in high temperature environments.

　　3. Strength and load-bearing capacity: low-cement castables exhibit high strength and good load-bearing capacity. Compared with traditional castables, its lower cement content can promote the formation of more mullite phases, which improves the thermal strength and bearing capacity of the material. This makes low-cement castables suitable for applications that need to withstand heavy loads or thermal cycling loads at high temperatures.

　　4. Reduced water demand: Low cement castables require less water during construction, which helps to improve the compactness of the material and shorten the drying time. This reduces the risk of cracking during drying and improves the overall properties of the material.

　　5. Good chemical corrosion resistance: Low cement castables are usually added with additional additives and binders to improve their chemical corrosion resistance. This makes low cement castables suitable for applications with alkali metal attack, slag attack or chemical corrosion requirements.

　　6. Construction flexibility: low-cement castables have good fluidity and operability, and are easy to handle and install. It can be applied by pouring, spraying or scraping, providing high flexibility and suitable for applications where complex structures are formed.

　　1. Excellent refractory performance: low-cement castables are composed of high-quality refractory aggregates, powdery materials and a small amount of cement matrix. It has excellent high temperature resistance and can withstand operating temperatures as high as 1500°C.

　　2. Lower cement content: Compared with traditional castables, the cement content of low cement castables is significantly reduced. This means less water is required during preparation, reducing the risk of shrinkage and cracking during drying and curing, and improving the overall compactness and strength of the refractory.

　　3. High strength and durability: low cement castable has high compressive strength, flexural strength and wear resistance. It has stable mechanical properties at high temperatures, is not prone to deformation and fracture, and can maintain the integrity and stability of the structure for a long time.

　　4. Good chemical corrosion resistance: low-cement castables have good resistance to acids, alkalis and other chemicals. It can remain stable in chemically corrosive environments, free from corrosion and dissolution, extending the service life of equipment.

　　5. Construction flexibility: low-cement castables have low fluidity and can be constructed by vibrating or compacting. It can adapt to the pouring of complex shapes and structures, fill irregular voids, and be closely combined with existing refractory materials.

　　6. Fast curing and drying time: Compared with high cement content castables, low cement castables have faster curing and drying times. This makes the construction process more efficient and enables quick return of equipment to service.

　　The thermal conductivity of low cement castables is usually between 0.5 W/(m K) and 1.5 W/(m K), depending on the formulation and material composition. The following is a detailed introduction to the factors affecting the thermal conductivity of low cement castables:

　　1. Cement content: Compared with traditional castables, low cement castables have lower cement content. Generally, cement has a higher thermal conductivity than other refractory particles, so low-cement castables help reduce overall thermal conductivity while reducing cement content.

　　2. Refractory particles: The main component of low-cement castables is refractory particles, such as alumina, mullite, silicate, etc. These refractory particles generally have a low thermal conductivity and play an important role in reducing the overall thermal conductivity.

　　3. Binders and fillers: A certain proportion of binders and fillers may be added to low-cement castables, such as Portland cement, silicate microspheres, etc. These materials generally have low thermal conductivity, which can further reduce the thermal conductivity of the castable.

　　4. Particle gradation and pore structure: The particle gradation and pore structure of low-cement castables will also affect its thermal conductivity. Reasonable particle gradation can reduce the connectivity of pores, thereby reducing the heat conduction path; at the same time, controlling the pore structure, such as increasing the closed pore rate or adopting a fine pore structure, also helps to reduce the thermal conductivity.