Thermodilatometry of the Brick Clay

Thermodilatometric analysis (TDA) and differential thermal analysis are performed on brick clay. Various processes (escaping physically bounded water, dehydroxylation of phyllosilicates and their collapse) affect the shape of the curves. Thermodilatometric analysis (TDA) was carried out using the heating/cooling rate 10 degrees C/min and soaking time at the maximum temperature 0, 10, 20, 40, 60 and 90 min. The maximum temperature was 1000 degrees C. A polynomial dependence between final relative contraction versus soaking time for the green samples during firing was found: The correlation coefficient R2 =1 and the dependence is dl/lo = 5.10-8 t4 1.10-5 t3 + 1.10-3 t2 0,0422 t 0,7181, where dl/lo is the relative contraction in % and t is the soaking time in minutes. Relative expansion of fired samples increases with increasing of the soaking time. Higher value of soaking time leads to the higher value of thermal contraction. That means that sample is shrinking also during constant temperature.