This experimental paper to investigate autoclaved specimens the prepared Ordinary Portland cement clinker (OPCC) contain a ground granulated blast-furnace slag and meta kaolin. The dry mixtures were prepared by thermal activation with the same initial water/solid cement ratios of about 0.28 for 3 minutes. Cylindrical specimens were moulded at a pressure of 50 kg.cm-2. The determination free lime and chemically combined water contents at the different autoclaved ages up to 24 hours studied the kinetics of the hydrothermal hardening processes and microstructural characteristics of the autoclaved specimens were studied via differential scanning calorimetery (DSC) and the scanning electron microscope (SEM). Results showed that the autoclaved specimens made of the neat OPCC (mix- A0) have the higher strength values. This could be mainly attributed to the formation of calcium silicate hydrates (CSH), which possess stronger hydraulic character at all ages of autoclaving. The lower compressive strength values of the specimens made of OPCC-GGBFS blend (mix-AI) is mainly due to the formation of hydration products having weaker hydraulic properties. However compressive strength values of the specimens made of OPCC-GGBFS-MK blend(mix-AII) reported higher than (mix-AI )because of formation of calcium silicate hydrates (CSH) . Key