I. Four Core Matching Rules
1. Consistent Acid-Base Properties The refractory mortar shall share the same material and acid-base property as the bricks. Dissimilar materials tend to form low-melting substances at high temperatures, leading to crack formation, erosion and spalling of brick joints.
2. Compatible Physical & Chemical Indexes The mortar shall have a refractoriness matching furnace temperature, slightly lower alumina content than bricks and a similar thermal expansion coefficient, balancing construction workability and high-temperature performance.
3. Binder Matched with Service Conditions Water-based mortar for low-temperature drying equipment; phosphate mortar for high-temperature zones with frequent thermal shock; magnesium halide mortar for alkaline smelting kilns; lightweight insulating mortar for thermal insulation layers.
4. Particle Size Matching Joint Width Mortar particle size shall not exceed 30% of the brick joint thickness to ensure dense joints.
II. On-site Application Notes
1. Use separate tools for different mortars; don’t add extra water to initially set mortar for re-use.
2. Select separate mortars for the working lining and insulation layer of kilns.
3. Store magnesium mortar in sealed moisture-proof packaging; test trial laying to confirm water mixing ratio before construction.
III. Common Selection Misconceptions
1. Higher alumina content equals better performance: High-alumina mortar has poor plasticity and loose joints; graded matching is required.
2. One mortar fits all high-alumina bricks: Bricks with different alumina contents have distinct properties and require dedicated supporting mortar.
3. Pairing magnesia bricks with high-alumina mortar: Acid-base reaction occurs, causing rapid lining damage.
4. Using dense mortar for insulating bricks: Raises thermal conductivity and increases energy consumption.
Compliance with the four matching rules of consistent material properties, compatible technical indexes, applicable working conditions and reasonable particle size distribution can effectively extend kiln service life and reduce later maintenance costs.
