【作者】 张琳；

【导师】 柯国军；

【作者基本信息】 南华大学 ， 土木工程， 2018， 硕士

【摘要】 发展越来越迅速的海洋工程结构一般都服役于各种离子及碳化侵蚀的多因素环境下,其耐久性能的问题更加突出。其中,氯离子是引发混凝土中钢筋锈蚀的主要原因。目前来说以吸附或交换阴离子为角度改善混凝土耐久性能的研究未见系统报道。水滑石类层状化合物具有较大的比表面积和孔径,易接受客体分子,常被用作吸附剂。因此,开发并研究能够抑制混凝土外部有害介质侵蚀的新型功能改性材料(水滑石类层状化合物)有着重要的理论与实际意义。本研究采用简单的水热法制备了不同形貌的镁铝碳酸根水滑石,完成了其结构和形貌表征。研究了不同形貌的水滑石在水溶液中对氯离子的吸附性能,并优选吸附性能良好的焙烧水滑石探究了其在水溶液中吸附氯离子过程的热力学和动力学并探究了不同p H、焙烧温度、吸附剂的用量、吸附温度对焙烧镁铝水滑石吸附氯离子的影响。使用氯离子内掺法评价了水滑石材料在水泥浆体中固化氯离子能力,考察了焙烧水滑石在水泥浆体中固化氯离子性能。实验结果表明:(1)采用水热法可成功制备镁铝水滑石。不同的添加剂对制备的水滑石材料的形貌产生了影响,并影响其吸附氯离子性能。水滑石焙烧之后失去层间水和阴离子,层状结构被破坏,在水溶液中重新吸收阴离子之后经过结构重组可以恢复其层状结构,但重建后的水滑石结晶度下降。(2)吸附热力学表明,焙烧镁铝水滑石吸附氯离子的规律符合Langmuir吸附等温方程,理论最大吸附容量为130.97 mg/g,表明了其高效吸附氯离子能力。吸附动力学过程符合准二级动力学方程,焙烧水滑石吸附氯离子的过程以化学吸附为主,化学吸附是焙烧水滑石吸附氯离子的速率控制步骤。(3)与普通水泥净浆相比,掺入焙烧水滑石,固化氯离子能力更强。掺入了焙烧水滑石的水泥浆体重建了水滑石的层状结构,并且生成了不规则的形状,水泥基环境对焙烧水滑石恢复层状结构并没有影响。研究以其在水泥浆体中固化氯离子能力为基础,预测该类材料应用于混凝土中以提高耐久性的应用前景,借此为实现钢筋混凝土的耐久性的提高探索出一种新方法,以推动水滑石在混凝土中的广泛应用。更多还原

【Abstract】 The rapid development of concrete structures in ocean engineering are often served under the environment with multiple factors including ion erosion.The durability problem become more prominent,and the chloride ionsare the main reason for the steel corrosion in concrete.For the present,the research improving concrete durability from the angle of adsorbing or exchanging anions have not been systematic reported.Hydrotalcite-like compounds with larger specific surface area and pore size which can easily accept the objects are often used as adsorbent.Therefore,it has theoretical and practical significance to develop a new modified material to control the external erosion of concrete.The research synthesized different morphologies of Mg-Al-CO3 layered double hydroxides by hydrothermal method,characterized the structure and morphology.The adsorbability of different morphologies of Mg-Al layered double hydroxides of chloride ions in aqueous solution was investigated.The adsorption equilibriumand adsorption kinetic and thermodynamics of the best adsorption performance of LDHs on the adsorbent were studied.The influence of different p H,roasting temperature and the dosage of the adsorbent,adsorption temperature on the binding capability were also studied.The binding capability of LDHs was evaluated by introducing chloride ions into the in cement paste to investigate the binding performance.The results showed that the Mg-Al LDHs could be synthesized by hydrothermal method.Different additives had influence on the morphology and adsorption capability.LDHs calcined within a certain temperature range have been shown to recover their original layered structure in the presence of appropriate anions,with the lower crystallinity.The equilibrium isotherm showed that the uptake of chloride ion by LDO was consistent with the Langmuir equation.The maximum uptake capacity of LDO for chloride ion was 130.97 mg/g,showing its high chlorine ion adsorption capacity.It was also found that the preudo-second-order kinetics model could be used to describe the uptake process satisfactorily,which was controlled by the rate of reaction rather than diffusion.Compared with the ordinary cement paste,the paste added into LDO had a better adsorption capacity of chloride ion.LDO admixed in the cement matrix reconfigured itself with anions in the layered structure.The edges of the reformed LDH in the cement paste were more irregular than those of the raw LDO and the cementitious environment had no effect on the reformed structure of LDHs.Based on the binding capability of chloride ion in cement paste,the LDHs have enormous potential in the concrete to improve durability,which provide a new way that can push the LDHs widely used in concrete.更多还原