Effect of calcination temperature of shale clay on some characteristics of autoclaved portland-pozzolanic cement.

The ground clay was calcined at 750, 850 and 950 degrees C for 2 hours. The variation in the mineralogical composition of clay due to calcination was studied using XRD. The ordinary portland cement was mixed with the calcined clay in the ratio 80:20 (weight percent), respectively. The pastes were pressed into cylindrical specimens under 250 kg.cm(-2) and autoclaved at 10 atm for 0.5, 2, 6, 12 and 24 hours. The compressive strength and chemically combined water content were determined for the hardened specimens. The strength was correlated with the phase composition which is identified using DTA. It was concluded that the strength increases with calcination temperature.