考虑絮凝-胶凝作用的磷酸镁/氯氧镁水泥固化淤泥力学性能与微观机制

How to develop low-carbon and environmental friendly binders based on novel cementitious materials and industrial byproducts to replace or partly replace traditional binders such as Portland cement becomes the technical difficulty and key problem in the green and sustainable solidification technology of abandoned sludge. The flocculation-vacuum filtration dehydration device will be developed to establish the sludge-water separation process and consolidation settlement law considering the type and amount of flocculants. By introducing magnesium phosphate/magnesium oxychloride cement and fly ash/slag, the effect of various factors such as binder amount, mix proportion and curing mode on the mechanical property of dehydrated sludge solidified with novel composite magnesia cement will be explored, and the mathematical model of strength-deformation/modulus relationship will be proposed taking into account of flocculation and cementation. The scanning electron microscope, mercury intrusion and X-ray diffraction tests will be applied to investigate the interaction between components including MgO, MgCl2 and KH2PO4 etc., and to reveal the dynamic chemical reaction process, formation of hydration products, phase transition law, pore structure characteristics and micro-mechanism of sludge solidified by magnesia cement. The resistance to freeze-thaw, dry-wet, water immersion and CO2 carbonation will be discussed to study the durability evolution and micro-mechanism of magnesia cement-solidified sludge under simulated complex weather conditions. The suitability and performance of flocculation-cementation jointly treated-sludge reused as roadbed fillings will be systematically evaluated by means of laboratory model test. These research findings can provide a scientific basis for solidification disposal and beneficial reuse of abandoned sludge from water environment treatment and engineering construction.

如何利用新型胶结材料和工业副产物研发低碳环保固化剂以替代或部分替代水泥等传统材料，是开展淤泥绿色可持续固化技术研究的难点和关键。研制絮凝-真空抽滤脱水装置，建立考虑絮凝剂类型和掺量的泥水分离过程和固结沉降规律。引入磷酸镁/氯氧镁水泥和粉煤灰/矿渣，探索水泥掺量、配合比和养护模式等因素对脱水淤泥力学特性影响，发展新型复合镁质水泥固化淤泥强度与变形、模量之间数学关系模型。开展扫描电镜、压汞和X射线衍射试验，明确MgO、MgCl2、KH2PO4等组分间物理化学作用，揭示镁质水泥固化淤泥动态化学反应过程、水化产物形成及相变规律、孔隙结构特征和微观作用机制。运用冻融、干湿、浸水和碳化等试验，研究复杂气候条件下镁质水泥固化淤泥长期稳定性演变规律与内在微观机理。通过室内模型试验，系统评价絮凝-胶凝联合处理淤泥用作路基填料的适宜性及路用性能，为环境治理和工程建设中废弃淤泥固化处理与资源化利用提供科学依据。

高含水率疏浚淤泥处理处置，已成为国内外工程领域共同关注、亟待解决的研究难题和社会问题。如何利用新型胶结材料和工业副产物研发低碳环保固化剂以替代或部分替代水泥等传统材料，是开展淤泥绿色可持续固化技术研究的难点和关键。研制了一套高含水率淤泥真空预压抽滤装置，构建了物化絮凝-真空预压相结合技术，实现了底泥有效固结压缩和快速脱水减容（体积缩小20-37%、含水率降至53%）。创新地将绿色低碳高性能镁质水泥引入淤泥固化领域，提出了工业固废-镁质水泥协同固化淤泥技术，研究了多因素影响下工业固废改性镁质水泥固化淤泥物理力学特性，揭示了诱发淤泥工程性能改良的胶结产物形成和孔隙结构重构的微观驱动机制。明确了镁质水泥基胶凝材料固化淤泥长期稳定性，揭示了外界复杂环境诱发固化淤泥长期服役性能演变的内在机理。开展了室内模型试验和现场工程示范，验证了固化淤泥再生高性能路基填料技术的可行性。发现了MOC固化淤泥抗压强度提升根本原因是5相凝胶体与Mg(OH)2、淤泥颗粒协同作用结果；粉煤灰/矿粉改性MOC固化体主要水化产物是5相凝胶和M/C-S-H-Cl凝胶，共同克服MOC固化淤泥强度倒缩；磷酸和柠檬酸是克服MOC固化淤泥耐水性差的高效添加剂。发现了MKPC固化淤泥抗压强度高达8.31MPa（90d）、钾鸟粪石（MgKPO4·6H2O）为主要水化产物，将未完全反应MgO颗粒胶结包裹形成以MgO颗粒为骨架、水化产物为胶凝体的致密结构，显著提高固化淤泥抗压强度；高钙粉煤灰溶出Ca2+与PO32-发生反应形成磷酸钙（Ca2P2O7·2H2O），硅灰中活性SiO2与Mg2+结合生成硅酸镁盐MgSiO3，上述水化产物作为MKPC固化体系的有效补充，进一步提升固化淤泥力学特性。研究成果可为环境治理等众多工程建设中废弃淤泥固化处理与资源化利用提供科学依据，具有良好的经济效益和社会效益。