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采用水热合成技术制备蒸压加气混凝土砌块、板材等是高效利用废弃物的有效手段,然而建筑废弃物中多元、复杂的化学组成限制了相关技术的应用。本文针对废弃物中常见的氧化镁、氧化钙、氧化硅和氧化铝等氧化物的反应顺序,从热力学角度研究了CaO-SiO_2-Al_2O_3-MgO-H_2O体系在水热条件下的反应机理,结果表明:在CaO-SiO_2-Al_2O_3-MgO-H_2O体系中,MgO优先于Al_2O_3反应生成Mg_3Al_2(SiO_4)_2(OH)_4;Mg~(2+)反应完全后,剩余的Al_2O_3继续与CaO及SiO_2富集区生成的水化硅酸钙反应生成水化铝酸三钙,当Mg~(2+)过量时,Mg~(2+)还会促进C-S-H的生成和托贝莫来石的转变。
The preparation of autoclaved aerated concrete blocks and plates by hydrothermal synthesis is an effective way to utilize waste efficiently. However, the diverse and complicated chemical composition of construction waste limits the application of related technologies. In this paper, the reaction mechanism of CaO-SiO_2-Al_2O_3-MgO-H_2O system under hydrothermal conditions was studied thermodynamically for the reaction order of the oxides such as magnesia, calcia, silica and alumina commonly found in wastes. The results show that MgO preferentially reacts with Al_2O_3 to form Mg_3Al_2 (SiO_4) _2 (OH) _4 in CaO-SiO_2-Al_2O_3-MgO-H_2O system. After the reaction of Mg 2+ is completed, the remaining Al_2O_3 continues to react with CaO and SiO_2 The hydrated calcium silicate formed in the catchment area reacts to form hydrated tricalcium aluminate. When Mg 2+ is in excess, Mg 2+ also promotes the formation of CSH and the transformation of tobaco mullite.