水化硅酸钙微纳结构及其组成的量化研究

As the main source of strength of cement, C-S-H is concerned by scholars from countries for its chemical composition, structure and performance; and in the academic field, there is no general consensus on the issues such as the complex microstructure. This topic aims at exploring C-S-H’s micro-nano structure quantitation by preparing single minerals (C3S and C2S) using sol-gel method based on the work in the previous two years, manipulating the micro-nano mineral particles using optical tweezers technology and placing them in the micro-reactor with certain size to ensure the number of molecules participated in the reaction, observing hydration process and morphology change of the particles on the ESEM, and analyzing their chemical composition with energy spectrum. Moreover, the content of atomic groups in C-S-H is obtained by XPS and NMR to determine the state of combination, and to reveal the influence of growth space in the microstructure and chemical combining characteristics. C-S-H is distinguished by nano-hardness; their production conditions are analyzed and the association between micro and macro scopic properties is established via the apparent density values. Last but not least, element Al is added into the synthetic mineral to discuss its effect on calcium silicate minerals and their hydration products. All the results can establish new C-S-H microstructure model that is more practical in cement and provide a method for performance improvement of cement. All in all, the subject introduces innovatiovely the optical tweezers technology and micro-reactor, providing the foundation for quantitative tests on structure of C-S-H and supplementation in cement scientific theory.

作为水泥石强度来源，水化硅酸钙（C-S-H）的化学组成、结构及性能是学者们关注热点，学术界对其复杂微观结构等问题尚无共识。本课题以探索C-S-H微纳结构定量化为目标，在前二年工作基础上，采用溶胶凝胶法制备单矿物（C3S、C2S），以光镊技术操控微纳矿物粒子，置于设定空间尺寸微反应器中，保证参与反应分子数量确定；在FESEM上观察粒子水化过程和形貌变化，以能谱分析量化化学组成；凭借XPS和NMR获得C-S-H内基团含量，确定其结合状态，揭示生长空间对微结构和结合特征影响；以纳米硬度差异分类辨别C-S-H的密度差异，分析其产生的条件，与表观密度值类比建立微观-宏观性能的联系；还探索在合成矿物中Al元素存在对硅酸钙矿物及其水化产物的影响；以此构造更符合实际体系的C-S-H微观新模型，为水泥性能改进提供方向。课题创新性引入光镊技术和微型反应器，为定量测试C-S-H结构和充实水泥科学理论奠定了基础。

水化硅酸钙（C-S-H）是决定水泥基材料性能的核心单元，精确揭示其微纳结构并掌握演化规律、进而提出针对性结构调控措施，是水泥基材料低碳制备、长寿命服役的关键环节。但由于C-S-H结构尺寸跨度大、影响因素多、组成不稳定等，导致其微纳结构及其形成过程的精细化表征一直是亟待突破的重点。基于此，本课题综合采用多种先进测试手段，旨从多维度深入弄清C-S-H微纳结构并量化其组成。首次实现了光镊技术对水泥单矿微粒的稳定捕获，为精细化表征C-S-H结构提供了工具支撑；提出了表面增强拉曼光谱（SRES）、拉曼成像扫描电子显微镜（SEM-Raman）、基于原子力显微镜的红外光谱（AFM-IR）及飞行时间二次离子质谱（TOF-SIMS）从样品制备、参数选择、数据采集与结构分析的全过程方法；通过微反应器、紧密堆积等模拟不同限制空间，掌握了生长空间对C-S-H微纳结构及组成的影响，丰富了C-S-H的微纳结构模型；考虑工程应用材料特点，系统研究了环境因素对合成C-S-H的结构与组成的影响规律，弄清了温-湿-压作用下C-S-H微纳结构量化特征及其演变规律；借助共价键和物理吸附两种形式对C-S-H结构进行设计，提出了聚合物调控C-S-H结构的精细化方法，并成功通过端羟基聚二甲基硅氧烷和预糊化淀粉实现了C-S-H微观力学性能提升；进一步研究了Cl-、SO42-、Mg2+等侵蚀离子对C-S-H结构的影响以及介质迁移机制，为高耐久水泥基材料设计与性能优化提供理论支撑。项目的研究成果为深入揭示C-S-H微纳结构提供了方法支撑，丰富了传统水泥化学体系中多尺度相微纳结构的理论模型，为高效、精确调控水泥基材料性能开辟了新的有效路径。