(1) Temperature gradient furnace: small samples (40x20x10mm) is fired in the temperature gradient furnace to measure the firing temperature and temperature range. Firing conditions is as follow:

Heating rate: ＜200℃/hr
Firing cycle: 6 hours
Heat preservation: 30 minutes
Cooling method: cooled to room temperature together with the furnace

Figure 1 Small-sized sintered bricks burned in temperature gradient furnace from 900℃～1150℃

(2) Product firing shrinkage rate and water absorption rate: firing shrinkage rate and water absorption rate are measured on the samples fired in the gradient furnace, and the relationship curves among temperature, water absorption and shrinkage are shown in Fig. 2.

The sample firing system is listed below (table 1) by combing figure 2 (firing curve) and sample firing condition at different temperature.

Table 1 Sample firing system

 (3) High temperature firing furnace: the dried samples were fired in the high temperature furnace according to the regular firing system. Firing conditions were as follow:
Room temperature~firing temperature         150℃/hr
Firing temperature                                        1 hour insulation
Cooled to room temperature together with the furnace

Clay samples: small-scale experimental sintered brick sample fired at 1040℃
The firing temperature for clay sample is determined at 1040℃. After firing, the sample color turns into light yellow, with a clear sound upon tapping. The sample shrinkage ratio while firing is 0.24%.