| Raw material | SiO2 | Fe2O3 | Al2O3 | CaO | MgO | Loss on ignition |
| Sample 1 | 62.03 | 7.05 | 9.17 | 1.08 | 0.56 | 10.79 |
| Sample 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 |
|
Item |
Liquid limit |
Plastic limit |
The index of plasticity |
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 |
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# is more than 7 and less than 15, this is medium plastic material, it was suitable to making clay bricks.
Regarding drying performance, the coefficient of drying sensitivity of soil sample 2 is 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
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 (bar) |
Vacuum degree (Mpa) |
Moulding moisture (dried bricks) |
Extrusion |
| Soil 1 | 2~4 | -0.082 | 20.37 |
the surface of bricks are smoothly, the bricks are strength but lack tenacity |
| Soil 2 | 4~6 | -0.082 | 22.66 |
Drying
Firing
Conclusion and Suggestion
Soil Sample 1 is high plastic raw material, can add some low plasticity materials, soil sample 2 is medium plastic raw materials, both are good performance in forming, the red bricks are all high strength, it's good for making clay bricks.