纳米SiO2对硫酸盐与水泥混凝土作用的调控及其机理

Sulfate is a key factor that influences the durability of concrete structure, and it can both regulate the setting and hardening of concrete and corrode it. Based on the previous results that nanoSiO2 can benefit the reaction between sulfate and cement concrete, in this proposal, the modification of the surface of nanoSiO2 is studied to improve its property enhancement effects with the aid of ultrasonication etc. Based on the study of the influence of SiO2 on the hydration and hardening process of cement clinker, the content and distribution of SO42- are studied, the influence law of SO42- on the reaction law of aluminate minerals, as well as its reaction kinetics with sulfate, and evolution characteristics of reaction products are revealed, and the the content of sulfate is optimized. The composition and structure of cement are controlled and the ingression of sulfate from outside is decreased by the synergizing use of SiO2 and other commonly-used supplementary cementious materials. Combining the results of microanalysis, the equivalent relation of micro-nano materials is estabilished based on their effects on sulfate corrosion resistance. The study of the sulfate crystallization pressure which is tested through built-in strain gauge or optical fiber, together with the analysis of the solid phase and the pore structure, will be used to illustrate the mechanism of nano-SiO2 modification on the physical attack resistance. It is hoped that this work may help to optimize the interaction between sulfate and cement concrete so as to reduce the corrosion risk, and may also serve as an example of the use of the ultrafine particles in cement and concrete to improve the durability.

硫酸盐是影响混凝土耐久性的重要组分，既调控混凝土凝结硬化，又可能对其产生侵蚀。本申请根据纳米SiO2调控水泥水化硬化有望显著优化硫酸盐与水泥混凝土作用的前期研究基础，对纳米SiO2表面改性，结合超声分散等措施优化其对混凝土性能的调控效果。在探究纳米SiO2对熟料矿物水化硬化影响基础上，分析液相硫酸盐含量和分布特性，揭示纳米SiO2对铝酸盐矿物与硫酸盐反应的动力学和产物演变特征的影响规律，优化硫酸盐作用效果。协同纳米SiO2与辅助胶凝材料调控水泥石组成和结构，降低外部硫酸盐的侵入，在阐明协同改性对抗硫酸盐化学侵蚀性影响基础上，结合微观分析结果，建立两者改性等效关系。通过内置应变片/光纤测定水泥基材料硫酸盐结晶膨胀压，结合固液相、孔结构分析，揭示纳米SiO2影响混凝土抗硫酸盐物理侵蚀的作用机理。以期通过本研究为优化硫酸盐作用、降低侵蚀风险提供借鉴，亦为利用超细微粉提高混凝土耐久性研究提供参考。

硫酸盐是影响混凝土耐久性的重要组分，既调控混凝土凝结硬化，又可能对其产生侵蚀。本申请根据纳米SiO2调控水泥水化硬化有望显著优化硫酸盐与水泥混凝土作用的前期研究基础，对纳米SiO2表面改性，结合超声分散等措施优化其对混凝土性能的调控效果。在探究纳米SiO2对熟料矿物水化硬化影响基础上，分析液相硫酸盐含量和分布特性，揭示纳米SiO2对铝酸盐矿物与硫酸盐反应的动力学和产物演变特征的影响规律，优化硫酸盐作用效果。协同纳米SiO2与辅助胶凝材料调控水泥石组成和结构，降低外部硫酸盐的侵入，在阐明协同改性对抗硫酸盐化学侵蚀性影响基础上，结合微观分析结果，建立两者改性等效关系。在自然基金委支持下，具体开展了纳米硅对C3A/C3S体系水化影响及机理探究；纳米硅调控对体系硫酸盐作用的调控；纳米硅和SCMs对水泥基材料抗硫酸盐侵蚀性的宏观作用效果；纳米硅和SCMs对水泥基材料硫酸盐侵蚀性的微观分析，等方面的研究。通过本研究，取得突出研究成果，研究揭示了纳米硅调控水泥Al相水化的表面电荷控制机制，厘清纳米硅对水泥中硫酸盐组分作用优化特征，明确了其与铝硅质辅助性胶凝材料协同优化抗硫酸盐侵蚀的作用规律。在行业顶级期刊发表SCI论文14篇，获得了包括建筑材料联合会基础研究1等奖在内的省部级奖项。相关成果培养研究生4人，项目执行期内，主持人在国内外重要学术会议上积极与国内外学者进行交流，先后访问了美国、英国、德国、印度等 10 余所高等学校，参加国际会议 5 次，国内外重要学术会议报告 10 余次。