Understanding High Alumina Refractory Castable

This is the most core property of high alumina refractory castable. Its long-term service temperature can reach 1200-1550℃, and the ultra-high alumina type (Al₂O₃ ≥ 85%) can even withstand high temperatures above 1600℃. It can maintain structural integrity and stable performance in the high-temperature environment of industrial kilns, without melting, deformation or collapse. For example, in the sintering zone of cement rotary kilns with temperatures up to 1400-1500℃, high alumina refractory castable can effectively resist high-temperature erosion and ensure long-term stable operation of the kiln.
2. Erosion Resistance & Wear Resistance

High alumina refractory castable has a dense structure, low porosity (usually ≤ 18%), and good resistance to molten slag, molten metal, acid-base gas and other corrosive media. In the smelting process of non-ferrous metals, it can resist the erosion of molten copper, aluminum and acidic gases (SO₂, Cl₂), with an erosion rate of ≤ 0.5mm/year, which is more than 3 times that of ordinary refractory materials. At the same time, by adding corundum (Al₂O₃) or silicon carbide (SiC) hard phases, its wear resistance can be further improved, and the wear loss can be controlled within 3cm³/500 revolutions (tested according to ASTM C704 standard), which is suitable for equipment parts with serious material scouring such as cement raw meal mills and coal gasifiers.

3. Thermal Shock Resistance

Industrial kilns often face frequent temperature changes (such as start-up, shutdown and load adjustment), which easily cause thermal stress inside the refractory lining and lead to cracking and peeling. High alumina refractory castable has excellent thermal shock resistance, and the number of cold and hot cycles (850℃ water cooling) can reach more than 15 times. The high-alumina castable modified with magnesia-alumina spinel can even reach more than 20 times, effectively extending the service life of the lining.

4. Mechanical Strength & Volume Stability

After curing and baking, high alumina refractory castable has high room-temperature and high-temperature mechanical strength. Its room-temperature compressive strength is generally ≥ 40MPa, and the high-strength type can reach 100-120MPa. The compressive strength retention rate at 1100℃ is ≥ 85%, which can bear the weight of equipment and the impact of materials. At the same time, its linear change rate after firing at 1400℃ is controlled within ± 0.5%, with good volume stability, avoiding structural damage caused by thermal expansion and contraction during high-temperature service.

5. Construction Flexibility

Compared with refractory bricks, high alumina refractory castable has strong construction flexibility. It can be poured into linings of various shapes and sizes according to the structure of thermal equipment, especially suitable for complex-shaped parts such as furnace tops, flues and tapholes. It can also be made into prefabricated parts for on-site installation, which greatly improves the construction efficiency and the integrity of the lining. In addition, it can be constructed by spraying, which is suitable for the maintenance and renovation of old kilns without supporting formwork, saving construction time and cost.

Classification of High Alumina Refractory Castable

1. Classified by Binder Type
- Aluminate Cement Bonded High Alumina Castable: It is the most commonly used type, with fast hardening and high strength. It can be cured at room temperature, and its maximum service temperature is 1400-1500℃. It is widely used in general industrial kilns and thermal equipment, such as heating furnaces and boiler linings.

- Low-Cement/Ultra-Low-Cement High Alumina Castable: The CaO content is controlled at 1%-2.5% (low cement) and less than 1% (ultra-low cement). It has the characteristics of high density, low porosity, high strength and good high-temperature performance. It is suitable for high-temperature and high-pressure working conditions such as blast furnaces and cement rotary kiln sintering zones.

- Chemical Bonded High Alumina Castable: It uses water glass, phosphoric acid or phosphate as binders, with excellent corrosion resistance and high-temperature stability. It is suitable for harsh working environments such as acidic gas corrosion and high-temperature molten slag erosion, such as non-ferrous metal smelting furnaces and chemical reactor linings.

Applications of High Alumina Refractory Castable

1. Metallurgical Industry (Largest Application Field)
In the metallurgical industry, high alumina refractory castable is mainly used for the lining of blast furnaces, converters, electric furnaces, heating furnaces, soaking pits and other equipment. For example, the blast furnace lining needs to bear the erosion of molten iron (1350-1450℃) and slag (1200-1300℃) and the impact of charging. After using high alumina castable modified with magnesia-alumina spinel, the service life of the lining can be extended from 10 years to 15 years, reducing the consumption of refractory materials by about 300 tons per year. In addition, it is also used for the lining of flue gas furnaces and horizontal hot blast stoves in steel plants, effectively solving the problems of cracking and collapse of traditional refractory brick linings.

except  above application, it can also be used into  Building Materials Industry,Electric Power Industry and so on.

Construction Techniques of High Alumina Refractory Castable

The performance of high alumina refractory castable can only be fully exerted through scientific construction.

1. Pre-Construction Preparation

Material Inspection-Equipment Cleaning:-Anchoring Nail Installation-Formwork Support:

2. Mixing Process

2.1 Use a forced mixer for mixing-

2.2 add clean drinking water (or specified binder) and stir for 3-5 minutes.

2.3  add 6%-8% drinking water  of the material weight

Note : The mixed material should be in a paste state, which can form a ball when held by hand but not leak slurry.  The mixed material must be used up within 30 minutes, and secondary water addition or re-stirring of returned materials is strictly prohibited.

3. Pouring & Vibrating

4. Curing & Demolding

5. Baking Process