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Brick Making Raw Material Analysis

Bricmaker automatic brick making plant could produce bricks from raw materials like clay, waster soil, river silt, shale, construction wastes, tailings, fly ash, gangue, life sludge, loess, etc.

Comprehensive raw materials analysis is the basis of brick making production process design, equipment selection, kiln structure, firing features design, fired bricks quality, and other factors of the brick plants. Raw materials analysis includes chemical composition analysis and physical performance analysis.

  • Chemical Analysis
Chemical composition analysis is usually measured as SiO2, Al2O3, Fe2O3, MgO, CaO, magnesium oxide, sulfur gangue, loss on ignition and etc.
SiO2: Main content, suitable 55-70%, if too much, the plasticity of the green bricks will be lower, although good for fast-drying, however the finished products with low compressive strength.
Al2O3: If less than 12%, the mechanical strength of the products is reduced, if more than 24%, the firing temperature is increase, increasing energy consumption.
Fe2O3: If the content too high, it will reduce the products refractoriness, resulting in low of sintering temperature.
CaO:If presenting in a state of CaCo3 in raw materials, classified as hazardous substances. If the particles larger than 2mm, it is likely to cause crisp brick or burst when burning.
MgO: The less the better, otherwise, products easily growing generate magnesium, causing white hoarfrost.
Sulfur Dagan: Being sulphate in raw material, the content should not exceed 1%. When burning, it will make SO2 and corrode the production equipment and be harmful to workers’ health.

Loss on ignition: Caused by organics in raw materials. If higher loss on ignition, more hole rate on the products.

Chemical composition of brick's raw materials:

Item Suitable content % Available content %
SiO2 55-70 55-80
Al2O3 15-20 10-25
Fe2O3 4-10 3-16
CaO / 0-10
MgO / 0-3
SO3 / 0-1
Loss on ignition / 3-15
Calcareous content <0.5mm 0-25 /
Calcareous content 2-0.5mm / 0-2

  • Physical Performance Analysis

Usually measure particles composition, plasticity, shrinkage, drying sensitivity and sinter ability.

Particle composition:

Particle category Particle diameter Reasonable composition
Plastic particles <0.05mm 35-50%
Filler particles 0.05-1.2mm 20-65%
Skeleton particles 1.2mm-3mm <30%

Plasticity: When plasticity index in 7 ~ 15, most suitable for middle plastic mud extrusion.

Shrinkage: Linear shrinkage <6%, if it is too high to crack products, affecting the quality of brick.
Drying sensitivity: The higher raw material plasticity, the finer of the particles, also the higher of drying sensitivity. Sensitivity coefficient determines the drying process design, too high cause green bricks’ surface cracking.

Relationship of forming moisture content and drying sensitivity:

Green brick molding moisture 20 26
Critical water of green bricks 14 10
Drying sensitivity coefficient 0.76 1.10