Specification of Required Raw Material for Making Bricks
1. Chemical Composition
Raw material with bigger particle of SiO2 can improve bricks refractoriness,
reduce the shrinkage and sensitivity when drying; Raw material with smaller
particle of SiO2 can let the structure of bricks even and dense.
But if the SiO2 is more than 80%, the final finished bricks are easy expansion
and the bending strength will be reduced. If less than 45%,
the performance of frost resisting is bad.
It effects the color of bricks. If the raw material with bigger particle of Fe2O3,
there will be brown or black spot on (or in) bricks.
It effects the mechanical strength of bricks. If the content of Al2O3 is more than 20%,
the mechanical strength will improve, but the burning temperature will increase;
if it is less than 10%, the mechanical strength will reduce.
It is a kind of co-solvent to reduce the refractory degree.
If the particle size of CaO is more than 1mm, there will be lime crack for bricks.
It is also a kind of co-solvent to reduce the refractory degree.
But it is not obvious like CaO.
The MgSO in raw material can let the bricks occur scum.
It is the weight percent of lost when the dried (in 105-110℃) raw material burning in 1000-1100℃ .
It shows the content of products in gas state (H2O, CO2)
and organic material after the raw material is fired and decomposed,
then judge whether to pre-burn it or not to let the volume of raw material stable.
2. Physical Performance
2.1 Particle composition
The particle size of raw material will effect directly on the plasticity, drying shrinkage, burning shrinkage, void ratio of bricks.
The particle size can be graded into three levels:>0.02mm, 0.02-0.002mm, <0.002mm.
There should be suitable proportion for the three grades particle in raw material to make bricks as follows:
There is no sticky performance
if the particle size is more than 0.02mm.
It has the effect of skeleton
when drying and burning. If less
0.02mm in raw material,
easy to mold, burning temperature low,
but difficult to dry
There is some sticky performance
if the particle size is between 0.02-0.002mm,
it has the effect of skeleton and filling.
There is much sticky performance
if the particle size is less than 0.002mm,
can occur plasticity when meet water.
This part of particle in raw material is
essential but can not be more,
or it will be difficult to dry.
2.2 Physical performance
|Physical performance||Required data||Remarks|
|Plasticity index||7～15%||It is the data (Liquid limit –Plastic limit)|
The shrinkage data will effect the speed of drying, when data is more,
had better to slow down the speed of drying, or the bricks will be easy
to crack to effect the quality of bricks.
The data of plasticity is high, the dried linear shrinkage rate and dried
sensitivity will be high