Effect of calcination temperature on the clay-limestone mixes

Clays are composed basically of clay minerals such as kaolinite, montmorillonite and illite in addition to variable amounts of non-clay materials, e.g. quartz sand, feldspars. micas, iron compounds, gypsum and organic material. When clay minerals are subjected to high temperature. they are activated due to physical and chemical changes which alter their properties. Belbeis-clay and Sammalout-limestone are used in this work. The aim of this work is to study the effect of firing temperature from 700 degrees up to 1 000 degrees C on the clay as well as clay limestone mixes. The results illustrate that the clay shows a very slight increase of weight loss from 700 degrees up to 1 000 degrees C and soaking time From 2 up to 6 hours. The calcination of mix 50/50 clay: limestone is occurred at 800 degrees C whereas the other two mixes are nearly dissociated at 700 degrees C for 1 hours. The ignition loss is in agrreement with the values of free lime. The XRD patterns of the fired mix 60/40 clay:limestone with firing temperature revealed that the gehlenite is formed at 800 degrees C with Ca(OH)(2) and quartz. The gehlenite increases with firing temperature whereas the Ca(OH)(2) is completely consumed in the formation of gehlenite.