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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.