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Testing report
The basic performance of the raw materials
1.  the appearance of raw material
 Soil 1#red, the clay is not purity mix grass roots, tree roots, and small stones, the wet bulk specific gravity is 1.0040g/cm3,the natural water content is 23.55%
Soil 2#: the color are wheat, the wet bulk specific gravity is 1.1120g/cm3 the natural water content is 8.26%
Fly ash: offwhite, finely ground, the dry bulk specific gravity is 0.8800g/cm3
2. The heat of fly ash
  The sample of fly ash without heat, so it couldn’t provide heat as internal combustion.
     3. The chemical analysis of raw materials
Raw material SiO2 Fe2O3 Al2O3 CaO MgO Loss on ignition
Soil 1# 62.03 7.05 9.17 1.08 0.56 10.79
Soil 2# 62.41 1.10 16.13 1.54 2.33 5.20
Fly ash 59.28 6.57 23.30 1.85 1.44 6.57
 The physical property of raw material
1.     The processing of raw material
The soil 1# was selected by screen(the diameter is
  The soil 2# after crushing, also selected by screen (the diameter is
   Fly ash is very fine,it was used directly.
a)Raw material blending
According to plastic limit, the matching rate as following:
mixture   soil 1# :fly ash =7030
soil 1# 100%
b)The physical property of raw material
Liquid limit 
Plastic limit  
 The index of plasticity
 Pfefferkorn test moisture content
 Drying property   
 Coefficient of drying sensitivity Critical moisture content    Drying linear shrinkage rate
 Soil 1#  41.2  25.6  15.6  32.47  1.09  15.5 7.04
 Soil 2#  27.2  19.8  7.4  23.87  0.36  17.6  3.20
 mixture  32.1  21.5  10.6  23.59  0.81  13.0  4.25

    The plastic limit of item reflect the forming performance, according to above chart, the index of plasticity of soil 1# is more than 15,this is high plastic material, can add some low plasticity materials. The index of plasticity of soil 2# and mixture are all more than 7 and less than 15, this is medium plastic material, it was suitable to making clay bricks, but these two materials lack tenacity.

  Regarding drying performance, the coefficient of drying sensitivity of soil 2# and mixture are all less than 1#,we called it low coefficient of drying sensitivity material, this material is not easy to appear crack, it’s suitable to adopt speedy drying,

       2.    Forming

      We use small double stage de-airing extruder to produce sample bricks, the chart show the performance of extrusion as following:  

 Item  Extrusion pressure
Vacuum degree
Moulding moisture
(dried bricks) 
 Soil 2#  8~10  -0.082  20.37  the surface of bricks are smoothly, the bricks are strength but lack tenacity
 Mixture  6~8  -0.082 22.66


   The soil 2# and mixture are all low coefficient of drying sensitive, it’s suitable for speedy drying.
  After nature drying of 24hours,at the speed of 30℃/h come up to 105±5℃,after drying, the sample of bricks without crack,     this is the good result.
4.  Firing
  a)Room temperature——400℃:temperature rise speed at150℃/h;
    400℃——400℃:preserve heat for 20 minutes;
    400℃——800℃:temperature rise speed at 150℃/h;
    800℃——800℃:preserve heat for 20 minutes;
    800℃——1100℃:temperature rise speed at 150℃/h;
    1100℃——1100℃:preserve heat for30 minutes;
 After firing, natural cooling.
This is shrinkage and water absorption for the sample of bricks
the whole progress for firing is in the temperature range of 950~1100℃, along with temperature rise, the Shrinkage is gradually accretion, and water absorption speedy fall and water absorption is low, the bricks are already fired.the Shrinkage of mixture is more speedy than 2#.
According to firing curve, the suitable temperature range of firing bricks is 950~1010℃.
the temperature of two sample of bricks is 950℃
After firing, the bricks color is red, without crack, and high strength. while temperature reach to 950℃,the firing shrinkage of mixture sample of bricks is 2.35%,the total shrinkage is 6.6%;the firing shrinkage of soil 2# is 0.55%,the total shrinkage is 3.75%.

. conclusion and suggestion

a) Soil 1# is high plastic raw material, can add some low plasticity materials, soil 2# is medium plastic raw materials, both are good performance in forming, but lack tenacity, the red bricks are all high strength, it’s good for making clay bricks.
b) Mixture and soil 2# are all low sensitivity, it’s suitable to for speedy drying, the mixture drying linear shrinkage rate is higher, should dry slowly little bit.

c) The sample of fly ash without heat, it’s better to add high calorific value material for provide internal combustion.

d) On the process of firing for mixture, the shrinkage rate change  speedy, it’s important to control the balance and steady of  kiln temperature, so as to improve the quality of bricks.


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