Customized Raw Material Performance for Premium Brick & Tile Products

In the brick and tile manufacturing industry, there is a well-recognized industrial axiom: 70% of finished product quality depends on raw materials, and 30% on processing technology. Clay raw materials are the fundamental foundation of brick and tile production, and their physical properties directly affect every production link from green body molding to high-temperature firing. Unstable raw material performance is the primary cause of common defective products such as cracking, deformation, underfiring, and overburning in brick and tile factories.

Why Raw Material Customization Is Indispensable for Brick Production?

The brick and tile production process consists of three critical stages: molding, drying, and firing. Each stage puts forward strict performance requirements for raw clay. During the molding stage, raw materials need sufficient cohesiveness to maintain the integrity of wet green bodies; in the drying process, reasonable shrinkage performance is required to prevent surface cracking; during high-temperature firing, stable thermal expansion and contraction characteristics can avoid product deformation and burning defects.

Conventional raw material detection can only judge basic indicators, while subtle deviations in plasticity, particle gradation and moisture content will trigger batch quality problems. Therefore, professional brick manufacturers must implement raw material customization adjustment. Targeted soil conditioning is adopted to adjust raw material indicators to the optimal controllable range, realizing stable and consistent product quality.

Plasticity: The Core Evaluation Index of Clay Raw Materials

Plasticity is the most critical physical property of brick-making clay. It refers to the ability of clay to produce permanent deformation under external force and maintain a stable shape after the force is removed. Raw materials with excessive plasticity will cause excessive drying shrinkage and cracking; raw materials with insufficient plasticity lead to loose green bodies, edge missing and low molding qualification rate.

The core goal of raw material optimization is to keep clay plasticity within a scientific controllable window. Factories need to adopt targeted plasticizing or plasticity reduction technologies according to the inherent properties of local clay, rather than using a unified production formula for all raw materials. This personalized customization mode is the key to reduce production defects and improve comprehensive production efficiency.

Raw material performance customization is the cornerstone of high-quality brick and tile manufacturing. Only by strictly controlling raw material plasticity and matching the performance indicators with molding, drying and firing processes can manufacturers eliminate common product defects. In the follow-up articles, we will elaborate on practical plasticizing and plasticity reduction techniques to provide a complete raw material optimization solution for brick and tile producers.

The Direct Impact of Stacking on Firing

• Airflow & Velocity: Stacking density directly controls airflow volume. Overly tight settings increase resistance, reducing ventilation and causing incomplete combustion. Loose settings waste heat and increase fuel consumption. Even within a single kiln car, uneven channel sizes create velocity differences, leading to temperature stratification.
• Cross-Section Heat Distribution: Hot air naturally rises, causing faster flow at the top and edges. Without adjusted stacking density, upper and outer bricks underfire while center bricks overfire.
• Fuel Distribution: Stacking patterns act as the blueprint for fuel placement. Misaligned settings lead to hot spots and cold zones, ruining batch consistency.

Our Proven Stacking Optimization Principles

• Control moisture content below 3% before entering the kiln.
• Preheat green bricks to raise temperature before loading.
• Dry, hot bricks fire faster, reduce cracking risk, and save fuel.

• Reduce setting density by 10–15% vs traditional mode.
• Keep uniform gaps between brick columns for smooth hot air flow.
• Avoid blocking airflow; ensure even heating in preheating zone, firing zone, cooling zone.

• Properly open exhaust dampers to speed up flue gas flow.
• Increase fan frequency reasonably to enhance oxygen supply.
• Avoid over-ventilation which causes under-fired bricks.

• Raise firing temperature by 10–15°C (within raw material limits) to shorten cycle.
• Shorten holding time while ensuring sintering quality.
• Increase internal combustion ratio, adopt small & frequent external coal feeding, or switch to natural gas/oil firing for faster, uniform heating.

• Shorten car interval and match zone lengths reasonably.
• Fast, stable pushing ensures continuous mass production.

1. Pre-firing Material Constraints (The "Foundation" Stage)

Collapse often begins before the bricks even enter the kiln if the green body lacks physical integrity.

• Moisture Threshold: The residual moisture content must be kept below 6%. High moisture levels drastically reduce the compressive strength of the bricks, causing the bottom layers to buckle under the weight of the stack.

• Material Aging: Clay requires at least 3 days of aging to ensure uniform plasticity and water distribution. Insufficient aging leads to internal stresses and a fragile structure.

• Mechanical Density: Ensure an extrusion pressure of ≥40kg/cm² to increase the density of the green body, making it more resistant to deformation at high temperatures.

2. Strategic Stacking Techniques (Mechanical Stability)

Stacking is not just about volume; it is about managing gravity and thermodynamics.

• The "Four-Point" Standard: Stacks must be level, stable, vertical, and straight. Any minor deviation in the center of gravity will be amplified as the bricks soften in the heat.

• Airflow Optimization: Follow the principle of "Dense Edges, Sparse Centers" and "Dense Tops, Sparse Bottoms." This balances the temperature across the kiln cross-section, preventing the edges from over-firing while the center remains under-fired.

• Load Management: Due to the high sensitivity of clay, limit the stacking height to 12 layers or fewer. This minimizes the static pressure on the base bricks.

3. Dehumidification in the Preheating Zone (The "Critical" Stage)

This is the most common zone for collapses. If moisture is not evacuated efficiently, the bricks effectively "steam" and lose their rigidity.

• Inlet Temperature Control: Keep the initial drying air below 116°C. Temperatures above this threshold cause the surface to harden too quickly, trapping steam inside and creating internal pressure.

• Heating Rate: Maintain a steady rise of 6–8°C/h. Sudden temperature spikes, especially in winter, can cause thermal shock and structural failure.

• Ventilation and Pressure: Ensure the exhaust fan provides sufficient negative pressure. Poor ventilation causes moisture to linger and re-condense on the bricks, leading to "soggy" bricks that collapse instantly.

4. Firing Zone Temperature Management (Thermodynamic Control)

Once the bricks reach high temperatures, preventing them from entering a pyroplastic state (melting) is vital.

• Anti-Overfiring Measures: Strictly monitor the sintering peak. Exceeding the clay's softening point leads to viscous flow, where the bricks begin to behave like liquid and slump.

• Internal Fuel Ratio: Control the amount of internal additives (coal powder or gangue). Excessive internal fuel generates uncontrollable heat within the stack, causing the bricks to "melt from the inside out."

• Visual Monitoring: Use inspection holes to watch for "white-out" conditions or "shimmering/swaying" stacks, which are immediate warning signs of imminent collapse.

5. Infrastructure and Mechanical Integrity (Environmental Factors)

The physical environment of the kiln must remain consistent to prevent mechanical triggers.

• Track Leveling: Regularly inspect kiln car tracks. Uneven rails cause vibration and jolting, which can topple a stack that is already weakened by heat.

• Kiln Structure Maintenance: Check for sagging roof bricks or protruding exhaust ports. Mechanical obstructions are a frequent cause of "domino-effect" collapses during car movement.