CRTSⅠ型CA砂浆有害孔结构形成机理及其可控制备

The object of this study is to find the formation mechanism and evolution rule of harmful pore structure including the surface peeling, bubble interlayer and the surface bubbles pit in CRTS I type CA mortar. In this study, we will explore the mechanism underlying the formation and stability of air bubbles in the fresh mortar. Except that, the interaction of air bubbles with cement particle and fine aggregate will be studied. All these are to find the inner relationship between the formation of air bubbles and emulsified system. By studying the mechanisms, we will expect mastering the methods by which harmful pore structure can be controlled so that we can build ideal pore structure model of CA mortar. In addition, we will study the mechanism underlying the formation of the connected pore structure in CA mortar of the non-woven infusion bag and the effect of it on volume stability and durability. Thus, it is possible to avoid the formation of harmful pore structure by optimizing emulsion formula, composition of materials, preparation and filling process of CRTS I type CA mortar. Of course, it is easy to find the harmful pore structure by checking the plate of CA mortar. The study will provide the technologies for the application of ballastless track filling of CRTS type I, II, or III, CA mortar and self-compacting concrete in China. At the same time, this study will improve ballastless track system of Chinese high speed railway. It is of great significance in theory and practice for enriching material science.

本项目研究板式无砟轨道CRTSⅠ型CA砂浆中有害孔结构（表面起皮、中间气泡夹层和表面气泡坑）的形成机理与演变规律，探明新拌砂浆中气泡体系形成、稳定机理及其与水泥颗粒、细骨料的相互作用机制，弄清其与乳化体系的内在关系，掌握其有害孔结构的调控方法，建立CA砂浆的理想孔结构模型；研究板下无纺布灌注袋中CA砂浆连通孔结构的形成机理，及其对体积稳定性与耐久性的影响规律，在此基础上，通过乳化配方、材料组成优化，结合制备与灌注工艺调整，通过施工现场CA砂浆揭板检查，指导或验证有害孔结构的研究。研究成果可为我国无砟轨道CRTSⅠ、CRTSⅡ型CA砂浆和CRTSⅢ型充填层自密实混凝土研究应用提供技术借鉴，推动我国高速铁路无砟轨道技术体系的完善发展，对于丰富材料学理论与实践意义重大。

本课题在新拌砂浆气泡体系的影响因素与分布、体系流变特性、砂浆凝结硬化过程演变及其孔结构形成、长期体积稳定性与施工质量控制等方面进行了系统研究，结果显示，低温环境、原材料质量与有害孔聚集病害相关性良好，是CA砂浆有害孔形成的主因； CA砂浆硬化形成沥青和水泥水化产物互穿网络结构、孔隙与砂分布在硬化体网络结构中；板下袋注CA砂浆渗水动力来源于内部铝粉膨胀，渗出水量随时间延长而逐渐降低，30min后趋稳，其固体物含量对砂浆配比影响可忽略；板下CA砂浆内部孔结构细化，90d电通量随厚度增加逐渐降低，54mm厚试样电通量低于500C，其抗渗性和耐久性提升显著；CA砂浆干燥收缩与其自身相对湿度线性相关，在工程实践中采取袋口挤浆、减少用水量等措施可有效减少板角离缝，提升施工质量；本研究弄清了CRTSⅠ型CA砂浆有害孔结构的形成机理，实现了其可控制备，完善了我国高速铁路无砟轨道技术体系。