In industrial kilns, boilers, flues, and other high-temperature equipment, besides the use of shaped refractory bricks, there is another indispensable material—refractory cement. It serves both as a jointing agent for refractory bricks and can be mixed with aggregates to produce refractory castables, which can be directly cast into linings of any shape. It is particularly suitable for irregular parts, emergency repair projects, and the construction of monolithic furnace linings.

What is Refractory Cement?

Refractory cement, also known as high-temperature cement or aluminate cement, is a hydraulic cementitious material made primarily from bauxite and limestone, which are calcined and then ground. Its core characteristic is a refractoriness of no less than 1580℃, allowing it to maintain structural stability in extreme high-temperature environments.

Unlike ordinary Portland cement, the main mineral component of refractory cement is calcium aluminate. This unique chemical structure not only gives it binding capability but also allows it to be combined with refractory aggregates (such as corundum and calcined bauxite) to produce refractory concrete capable of withstanding temperatures above 1700℃.

Core Advantages of Refractory Cement

1. Flexible Construction and Arbitrary Shaping
   When mixed with aggregates, refractory cement becomes fluid or plastic, allowing it to be cast into furnace linings of any shape. It is especially suitable for irregular parts like kiln arches, pipe bends, burner bricks, and furnace doors, avoiding the mold costs and waiting periods associated with shaped bricks.
2. Excellent Integrity with No Weak Brick Joints
   Monolithic cast linings have no brick joints, eliminating the risk of joint cracking and gas leakage due to thermal expansion and contraction. Their sealing and spalling resistance are superior to brick-laid structures.
3. Rapid Hardening and Short Construction Periods
   Refractory cement can be demolded within 4 to 24 hours after the addition of water at room temperature, requiring no prolonged curing. This makes it especially suitable for emergency repairs and projects with tight maintenance schedules.
4. Repairability
   For damaged linings, repair materials prepared with refractory cement can be used for spraying, troweling, or casting repairs, extending kiln life and reducing losses from production stoppages.

How to Select High-Quality Refractory Cement?

• Chemical Composition: Does the Al₂O₃ content meet the standard? Are impurities like Fe₂O₃ and SiO₂ excessive? For high-quality CA-50 cement, Al₂O₃ should be ≥50%, and for CA-70, it should be ≥68%.
• Fineness (Specific Surface Area): Fineness affects hydration activity and early strength. Typically, the residue on a 0.088mm sieve should be ≤10%.
• Setting Time: Initial setting time should be ≥30 minutes, and final setting time should be ≤24 hours. Too fast affects construction, while too slow prolongs the project.
• Refractoriness: Tested according to the national standard (GB/T 3001), it should meet the requirements for the intended service temperature.
• Cold Crushing Strength: The strength of cured samples should be ≥40 MPa (for CA-50) or ≥60 MPa (for CA-70).
• Packaging and Storage: Refractory cement is highly susceptible to moisture and失效 (becoming ineffective). It must be packaged in moisture-proof composite bags and has a storage life of no more than 6 months.

Special Note: Refractory cement must not be mixed with ordinary Portland cement, as this will cause a sharp decline in high-temperature performance and may even lead to lining failure.

Refractory cement is an indispensable “adhesive” and “shaping agent” in modern high-temperature industries. Correctly selecting and using refractory cement not only simplifies construction and shortens project timelines but also enhances the integrity and service life of furnace linings, bringing significant economic benefits to enterprises.