Calcination and hydration characteristics of carbonaceous shale - Limestone mixes

The lime-rich clays are the most important raw materials available for building technology. Carbonaceous shale from Sinai and Sammalout limestone were used as new raw materials in this work. Different mixes are calcined from 700 up to 1000 degreesC and then hydrated for one, 3, 7, 28 and 90 days. The residual time and combined water were used as a degree of hydration characteristics. It is found that, the calcination temperature 700degreesC is insufficient for complete calcination of the different mixes. The free lime content decreases with firing temperature from 700 degreesC up to 1000 degreesC due to the reaction of lime with the aluminosilicate constituents. On the other side, the free time content of the hydrated mixes decreases and the combined water increases with firing temperature. Therefore, the calcination at 900-1000 degreesC is the suitable temperature and the mix 60-70/40-30 carbonaceous shale / limestone is the suitable mix.