A Concise Guide to Brick Making Raw Material Matching and Proportioning

A Concise Guide to Brick Making Raw Material Matching and Proportioning

I. Core Raw Material Roles

Cement: The core binder, like "glue." It's responsible for binding various materials into a strong whole. Ordinary construction silicate cement is sufficient, commonly graded 32.5 or 42.5.

Aggregates: The main skeleton, providing strength and volume. Divided into:

Fine aggregates: Such as river sand and manufactured sand, determining the density and surface smoothness of the brick blank.

Coarse aggregates: Such as crushed stone and small stones (particle size usually less than 10 mm), used to enhance the compressive strength of load-bearing bricks.

Waste residue: Functional filler, which can partially replace cement or aggregates to achieve cost reduction, performance improvement, or environmental protection.

Fly ash (power plant waste): Improves the fluidity of raw materials during mixing and enhances the later strength and durability of bricks.

Slag powder (steel plant waste): Highly reactive, can replace part of the cement, enhancing the final strength.

Recycled building materials: Concrete and brick particles after crushing and screening, which can replace natural aggregates.

Tailings sand (mining waste): Similar in fineness to sand; ensure it is free of harmful substances before use.

II. Key Points for Mixing Proportions of Different Machine Models

(I) Vibratory Brick Press (Most Widely Used)

Machine Characteristics: Relies on vibration to compact raw materials, requiring good flowability and a certain degree of viscosity.

General Reference Proportion (by weight):

Cement: 15% - 20%

Aggregate (sand + stone chips): 70% - 80%

Waste residue (e.g., fly ash): 5% - 10%

Water: Appropriate amount (Judgment standard: can be formed into a ball by hand, but crumbles upon impact).

Adjustment Direction:

For load-bearing bricks: Use the upper limit of the cement ratio, and add 30%-50% coarse aggregate (stone chips) to the aggregate.

For non-load-bearing/filler bricks: Use the lower limit of the cement ratio, and increase the waste residue content to 20%-30%. (II) Hydraulic Static Press Brick Machine

Machine Features: Relies on immense static pressure for molding, producing high-density, high-strength bricks. It has relatively low requirements for raw material moisture content (slightly dry).

General Reference Mix Ratio (by weight):

Cement: 18% - 25%

High-Quality Aerated Aggregate (Good Coarse-Fine Mixture): 75% - 82%

Water: Less (for dry, hard materials).

Adjustments:

For high-strength paving bricks/permeable bricks: Use the upper limit of the cement ratio, strictly screen aggregate gradation, and add a small amount of water-reducing agent (0.2%-0.5%) to reduce water usage and increase strength.

For ordinary bricks: The mix ratio can refer to that of a vibratory brick press, but the moisture content needs to be reduced.

(III) Small Manual/Semi-Automatic Brick Machine

Machine Features: Lower pressure, relies on the plasticity of the raw materials.

Key Techniques: The cement ratio can be increased by 2%-5% compared to vibratory press models.

It is recommended to use only fine sand (particle size less than 3 mm) as aggregate. A small amount (less than 5%) of clay can be added to enhance the plasticity of the raw materials and facilitate molding.

Moisture control needs to be more precise; slightly moist conditions are beneficial for compaction.

III. Special Precautions for Using Waste Residue

Fly ash: High-quality fly ash with a light color and fine texture can replace 10%-15% of cement; dark-colored fly ash with coarse particles is mainly used as filler, and its dosage should not exceed 30% of the total aggregate.

Recycled construction waste: Must be crushed, screened (to control the maximum particle size), and impurities (such as wood blocks and plastics) removed. It is recommended that the proportion replacing natural aggregate should not exceed 50%, and an initial trial of 30% can be conducted.

Tailings sand: Must be tested before use to ensure that safety indicators such as radioactivity meet standards. Due to its generally fine particles, it needs to be used in combination with coarse sand to optimize the gradation; it is recommended that it account for 20%-40% of the total aggregate.