同步辐射法对侵蚀环境下现代水泥基材料微结构演变机制研究

Supplementary cementitious materials (SCMs) are one of the most important components for improving the durability of concrete. To reveal the microstructural evolvement of SCMs-cement materials is not only the theoretical basis for improving erosion resistance in concrete, but also is the key to optimize the application of SCMs. Based on the previous studies about the microstructural evolvement on hydrated C3S and C3A with synchrotron radiation (STXM, μXRD, etc), which provide the basis and the inspiration for in-situ study in this proposal. After investigating the effect of fly ash (FA) and granulated blast furnace slag (GBFS) on the characteristics of hydration and setting, the in-situ development of local atomic structure on hydration products will be studied using synchrotron radiation, and the characteristics of content and distribution of composites in cement-based materials will be analyzed comprehensively. The modifying mechanism of microstructure of hydration products in clinkers and FA/GBFS-blended cement are revealed, and the effect of FA and GBFS is optimized. Synchrotron radiation is used to the in-situ study for microstructural evolvement mechanism of hydrated FA/GBFS-blended cement undergoing chemical erosion media (SO42- & Cl-), and analyze the content and distribution of SO42- and Cl-. Both X-ray 3D imaging are used to study 3-dimmensional visualization of pore structure in SCM-cement and concrete in presence of SO42- and Cl-, and synchrotron-radiation methodology is used to reveal the capture mechanism of SO42- and Cl-. It is expected that this proposal may help to provide theoretical basis for optimizing the modification effect of FA and GBFS and lowering the risk of erosion in cement and concrete, and present the new techniques and new methods for characterizing the microstructure of modern cement-based materials at nano- and sub-micron scale.

辅助胶凝材料（SCMs）是提高混凝土耐久性的关键组分，揭示SCMs-水泥基材料微观结构演变机制既是提高混凝土抗侵蚀性的基础，又是优化SCMs应用的关键。本申请前期研究是基于同步辐射法探究熟料单矿水化产物微观结构的影响规律，为本项目的研究提供了基础和研究启示。在探究粉煤灰、矿渣对熟料矿物水化硬化影响基础上，基于同步辐射法研究其水化产物原子结构的局部演变规律，分析组分含量与分布特性，揭示矿渣、粉煤灰对水泥水化产物微观结构的改性机理，优化粉煤灰和矿渣作用效果。基于同步辐射法原位探究侵蚀介质（SO42-和Cl-）下SCM-水泥材料水化产物微结构的演变机制，分析侵蚀介质含量和分布特性，结合X射线三维成像及可视化孔结构分析，揭示粉煤灰、矿渣对侵蚀介质的捕捉机制。以期通过本研究为优化粉煤灰和矿渣改性作用、提高抗侵蚀性提供基础理论，亦为在纳米、亚微米尺度上现代水泥基材料微结构研究提供新方法和新手段。

辅助胶凝材料（SCMs）是提高混凝土耐久性的关键组分，揭示粉煤灰/矿渣与水泥基材料微观结构演变机制既是提高混凝土抗侵蚀性的基础，又是优化SCMs应用的关键。本项目采用了同步辐射法 STXM/NEXAFS、μXRD等先进技术，通过本研究为优化粉煤灰和矿渣改性作用、提高抗侵蚀性提供基础理论，亦为在纳米、亚微米尺度上现代水泥基材料微结构研究提供新方法和新手段。.采用扫描透射X射线显微技术(STXM)，结合近边X射线吸收精细结构吸收谱(NEXAFS)，研究了Cl-对C3S水化产物微观结构的影响。C-S-H作为C3S水化反应的主要产物，CaCl2和Na2SO4的存在并未改变C-S-H凝胶结构中Ca原子的配位对称性，是非对称的七配位；.采用高能X射线衍射技术深入研究了Cl-对C-S-H(I) (钙硅比为1.0)微观结构特征的影响，避免了C3S水化产物氢氧化钙的干扰，发现随着CaCl2的浓度的增加，C-S-H(I)中Si-O键长(1.64 Å)保持不变，Si原子的配位数均为4，而Ca原子的配位数从7下降到6，C-S-H(I)结构从类Tobermorite结构逐渐转变为类jennite结构，而层间距由~12 Å增大至~14.5 Å，Cl-可能通过物理吸附于C-S-H层间结构中，是导致水泥后期力学性能降低的主要原因之一。.采用扫描透射X射线显微技术(STXM)，结合近边X射线吸收精细结构吸收谱(NEXAFS)和XRD等手段，揭示了Cl-与单硫型硫铝酸钙的键合作用机理，发现根据Ca L3,2-edge NEXAFS吸收谱的特征，可以有效地区分AFt相和AFm相(单硫型硫铝酸钙、Kuzel盐和Friedel盐)：单硫型硫铝酸钙>Kuzel盐>Friedel盐。Cl-的存在使得C3A的水化产物C3AH6、钙矾石(AFt)或单硫型硫铝酸钙(AFm)均无法稳定存在，AFt和AFm的结构层间SO42-不断被Cl-所替代，进而形成Kuzel盐和Friedel盐。.此外，探明了粉煤灰/矿渣分别在Cl-和SO42-侵蚀条件下水泥基材料组分及微结构的演变机制，分析了组分含量与分布特性，揭示了矿渣、粉煤灰对水泥水化产物微观结构的改性机理，优化粉煤灰和矿渣作用效果揭示了水化产物对侵蚀介质的捕捉机制。