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Strength properties and associated mechanisms of magnesium oxychloride cement-solidified urban river sludge
Highlights Eco-friendly magnesium oxychloride cement is innovatively used to stabilize sludge. Magnesium oxychloride cement is proved effective in improving strength of sludge. Strength is affected by molar ratio of MgO/MgCl2, MOC content and curing period. MOC hydration process controls microstructure and strength of solidified sludge. Phase 5 and brucite are identified as micromechanisms for MOC solidified sludge.
Abstract Eco-friendly magnesium oxychloride cement (MOC) is incorporated to reduce the disposal obstacles and mitigate the environmental impacts related to the urban river sludge. Three major factors including MOC content, molar ratio of MgO/MgCl2 and curing time are examined by unconfined compressive strength (UCS) tests. The microscopic effect caused by the MOC-hydration process is identified using X-ray diffraction (XRD), mercury intrusion porosimetry (MIP) and scanning electron microscopy (SEM) technique to reveal the intrinsic mechanisms. The results show that MOC content, molar ratio of MgO/MgCl2 and curing time strongly affects the UCS of MOC-solidified sludge. The suitable parameter values for sludge treatment by MOC turn out to be molar ratio of MgO/MgCl2 of 8–10, MOC content of 10% and curing time of 60 d. The UCS and strength retention coefficient of MOC-solidified sludge present an important decreasing trend with water immersion time due to the gradual decomposition of phase 5 – 5 Mg(OH)2·MgCl2·8H2O into Mg(OH)2 phase, some soluble ions and H2O molecules. The UCS development is directly related to the formation of phase 5 and brucite, which induces a transformation of pore structure and boosts to develop a much stronger interlocking microstructure in solidified matrix. The identification of brucite with a significant volumetric expansion and phase 5 provides an insightful interpretation for the strength evolution of MOC-solidified sludge. Overall, the innovative incorporation of MOC treatment is supposed to be an efficient and sustainable approach on sludge solidification.
Strength properties and associated mechanisms of magnesium oxychloride cement-solidified urban river sludge
Highlights Eco-friendly magnesium oxychloride cement is innovatively used to stabilize sludge. Magnesium oxychloride cement is proved effective in improving strength of sludge. Strength is affected by molar ratio of MgO/MgCl2, MOC content and curing period. MOC hydration process controls microstructure and strength of solidified sludge. Phase 5 and brucite are identified as micromechanisms for MOC solidified sludge.
Abstract Eco-friendly magnesium oxychloride cement (MOC) is incorporated to reduce the disposal obstacles and mitigate the environmental impacts related to the urban river sludge. Three major factors including MOC content, molar ratio of MgO/MgCl2 and curing time are examined by unconfined compressive strength (UCS) tests. The microscopic effect caused by the MOC-hydration process is identified using X-ray diffraction (XRD), mercury intrusion porosimetry (MIP) and scanning electron microscopy (SEM) technique to reveal the intrinsic mechanisms. The results show that MOC content, molar ratio of MgO/MgCl2 and curing time strongly affects the UCS of MOC-solidified sludge. The suitable parameter values for sludge treatment by MOC turn out to be molar ratio of MgO/MgCl2 of 8–10, MOC content of 10% and curing time of 60 d. The UCS and strength retention coefficient of MOC-solidified sludge present an important decreasing trend with water immersion time due to the gradual decomposition of phase 5 – 5 Mg(OH)2·MgCl2·8H2O into Mg(OH)2 phase, some soluble ions and H2O molecules. The UCS development is directly related to the formation of phase 5 and brucite, which induces a transformation of pore structure and boosts to develop a much stronger interlocking microstructure in solidified matrix. The identification of brucite with a significant volumetric expansion and phase 5 provides an insightful interpretation for the strength evolution of MOC-solidified sludge. Overall, the innovative incorporation of MOC treatment is supposed to be an efficient and sustainable approach on sludge solidification.
Strength properties and associated mechanisms of magnesium oxychloride cement-solidified urban river sludge
Wang, Dongxing (author) / Di, Shengjie (author) / Gao, Xiangyun (author) / Wang, Ruihong (author) / Chen, Zhengguang (author)
2020-03-27
Article (Journal)
Electronic Resource
English