الفهرس 
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Abstract
Larger quantities of solid wastes are produced from several chemical industries. These solid wastes represent a severe environmental problem as a result of accumulation in the industrial plants which cause a big air pollution in the surrounding atmosphere. This pollution problem shows the utmost necessity of utilization of these solid wastes in the production of low cost building materials for environmental protection and environmental development.
This investigation deals with the utilization of granulated blast-furnace slag (solid waste of big iron industry) and lime-rich sludge (solid waste of acetylene gas industry) in the production of autoclaved building products having reasonable physico-chemical and mechanical properties.
Four initial dry mixtures were autoclaved at a pressure of 8 atm. of saturated steam for different times of hydrothermal curing (0.5, 2,6,12 and 24 hours), these are:
Mix I: sludge (20%) – granulated slag (80%).
Mix II: sludge (30%)- granulated slag (30%)- gorund sand (40%)
Mix III: sludge (30%)- granulated slag (50%)-ground sand (20%).
Mix IV: sludge (20%) – granulated slag (40%)- ground sand (40%)
The autoclaved specimens, thus obtained, were characterized by means of their compressive strength, hydration kinetics and phase composition of the formed hydroration products. Hydration kinetics of the hydrothermal reactions were studied by the determination of chemically-combined water, free lime and free silica contents at the various ages of autoclaving. The phase composition of the formed hydrates was studied by means of x-ray diffraction (XRD) analysis and differential scanning calorimetry (DSC).
from the results of the present investigation of the following conclusions could be derived.
1. The compressive strength of autoclaved granulated slag (GBFS) lime rich sludge (LRS) specimens of Mix I increases during the early ages of autoclaving (0.5-2 hours), then decreases after 6 hours and followed by an increase up to the final age of autoclaving (24 hours); a result which is mainly attributed to the well crystallization of the initially formed CSH phases and/or their partial transformation into hydrogarnet-like hydrates (C3 ASH4) as indicated from XRD and DSC studies.
2. The free lime content of the hydrothermally hardened GBFS-LRS pastes of Mix I decreases with increasing age of autoclaving; meanwhile, the chemically combined water content increases with increasing age of the hydrothermal reaction.
3. The strength results of autoclaved GBFS-LRS-Sand specimens made of Mix II increases with increasing age of autoclaving up to 6 hours; this was followed by a regression (a slight decrease) after 12 hours with a further increase in the strength after 24 hours of the hydrothermal process. The results of combined water content follows the same trend (similar compressive strength) with increasing age of autoclaving.
4. Both of the free lime and free silica contents are decreased with increasing age of autoclaving.
5. The compressive strength values obtained for the autoclaved GBFS-LRS-Sand pastes made of Mix III show the same variations observed for Mix II with increasing age of autoclaving.
6. The free lime and free silica contents of autoclaved pastes of Mix III are decreased with increasing age of autoclaving; while the combined water content increases continuously on progressive autoclaving.
7. The compressive strength of autoclaved GBFS-LRS-Sand specimens of Mix IV increases markedly with increasing age of autoclaving. The combined water content increases until the free lime and free silica contents decreases with increasing age of autoclaving.
8. In all GBFS-LRS-Sand mixes, the main hydration products identified are calcium silicate hydrates with varying degrees of crystallinity.