纳米SiO2改性轻骨料混凝土性能
Properties of nano-SiO2 modified lightweight aggregate concrete

纳米SiO2（NS）具有极强火山灰活性、晶核作用和填充效应，因此用NS改善水泥基材料性能成为众多学者研究的热点。本课题对不同掺量的NS对轻骨料混凝土强度及耐久性的改性效果进行了研究。通过测试轻骨料混凝土的力学性能（抗压和抗折）和氯离子渗透性能及利用SEM和EDS测试分析了NS对混凝土宏观和微观结构的影响。研究结果表明：在适当的掺量下，NS能够有效地提高轻骨料混凝土的力学性能，其中28 d的抗压强度和抗折强度比空白组混凝土分别提高了21.6%和46.2%。氯离子渗透的结果表明，轻骨料混凝土的抗氯离子渗透性能随着掺量的增加而呈线性增强。混凝土界面过渡区（ITZ）也发生了显著变化，其厚度减小，形貌也更加致密。ITZ的钙硅比随着NS掺量增加而减小，说明该区域内水化产物C-S-H凝胶增多，Ca（OH）2被消耗，从而形成致密的过渡区，有利于强度提高。 Nano-SiO2(NS) has very strong pozzolanic activity, nucleation effect and filling effect, so using nano-SiO2 to improve the performance of cement-based materials has become a hot research topic of many scholars. This topic studied the effect of different dosage of NS on the strength and durability of lightweight aggregate concrete. The effects of NS on the macrostructure and microstructure of concrete were summarized and analyzed by testing the mechanical properties (compressive and flexural resistance) and chloride ion permeability of lightweight aggregate concrete, as well as the SEM and EDS test methods. The results show that NS can effectively improve the mechanical properties of lightweight aggregate concrete at appropriate dosage. The compressive strength and flexural strength of 28 d were 21.6% and 46.2% higher than that of the blank group concrete respectively. The results of chloride ion penetration show that the resistance to chloride ion permeability of lightweight aggregate concrete increases linearly with the increase of the content of nano-SiO2. Concrete interface transition zone (ITZ) has also undergone significant changes, its thickness decreases, the morphology is also more dense. The ratio of calcium to silicon in ITZ decreases with the increase of the amount of NS, which indicates that the C-S-H gel of hydration product increases and Ca(OH)2 is consumed in this region, resulting in a dense transition zone, which is conducive to the increase of the strength. 国家自然科学基金（51678367