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Abstract This study deals with the utilization of some industrial solid wastes in the production of autoclaved building units for environmental protection and development. These include granulated blast-furnace slag and lime-rich sludge wastes. Four autoclaved mixes were studied hydrothermally at a pressure of 8 atm. of saturated steam for different times of autoclaving of 0.5, 2, 6, 12 and 24 hours, these are: (i) lime sludge (20%)-granulated slag (80%), (ii) lime sludge (30%)-granulated slag (30%)- ground sand (40%), (iii) lime sludge (30%)- granulated slag (50%)- ground sand (20%) and (iv) lime sludge (20%)- granulated slag (40%)- ground sand (40%) which are designated as mixes I, II, III and IV, respectively. At each autoclaving age, the hydrothermally hardened specimens were tested for their compressive strength, free lime contents and free silica contents; the phase composition of the formed hydration products was studied by means of x-ray diffraction analysis and differential scanning calorimetry. The variations of compressive strength values with increasing age of autoclaving could be explained in terms of the amount and type of hydration products. The results of free lime and free silica contents indicated a continuous decrease with increasing age of autoclaving, while the chemically combined water content increases continuously with increasing age of the hydrothermal treatment. The strength results of all autoclaved specimens made of the four mixes could be related as such as possible to the distinct phases produced during the hydrothermal treatment of the four blends used in this investigation. |