喷射混凝土单层衬砌微裂缝遇水自修复材料及其性能研究

Although shotcrete single shell lining technology is applied to different fields in varying degrees all over the world, the anti-cracking problem of the lining structure is always one of the most important factors that prevents it from moving forward. The applicant and many other researchers has already yielded many positive results in the shotcrete anti-cracking technology, but because of the micro-fractures existed inside, the anti-cracking problem of shotcrete lining structure during still exists in use. And just on the basis of this breakthrough point, the self-repairing polymer materials and performance of shotcrete single shell lining micro-fractures encountering water are studied in this project. Based on the investigation on self-repairing concrete technology at home and abroad, combining with component testing of shotcrete cementing material and analysis of formation and influence on the stability of ettringite and expansion characteristic of delayed ettringite, it is proposed in this project that, on the premise of modified cementing material, the method for self-healing polymer of micro-fractures encountering water in shotcrete single shell lining can be achieved, by means of delay control of formation time、production and distribution of ettringite in cementing material and making full use of the hydrophilic expansion characteristic. Besides, the formulation for self-healing polymer cementing material of micro-fractures in shotcrete single shell lining structure, under multiplied coupling conditions, is introduced in hopes that it can contribute to the application and extension of the shotcrete single shell lining technology.

喷射混凝土单层衬砌技术在世界许多国家的不同领域已有不同程度的应用，但喷射混凝土单层衬砌结构的抗渗裂问题一直是阻碍该项技术全面推广的重要原因之一。尽管申请者及其他学者在实验室对喷射混凝土的抗渗技术取得了一定的研究成果，但喷射混凝土作为结构在服役过程中由于其内部存在的微裂缝仍存有渗漏问题。本项目即以此为切入点，对喷射混凝土单层衬砌微裂缝遇水的自修复材料及其性能进行研究。在调研国内外混凝土自修复技术的基础上，通过对喷射混凝土胶凝基材组分测试、钙矾石形成机理、胶凝基材微观环境对钙矾石稳定性及延迟钙矾石膨胀的影响分析，提出以改性胶凝基材为前提，利用钙矾石的遇水膨胀特性，通过控制延迟钙矾石的生成时间、生成量以及在胶凝基材中的分布形态，来实现喷射混凝土单层衬砌微裂缝遇水自修复的方法；并配置出多性能耦合条件下用于喷射混凝土单层衬砌遇水微裂缝自修复的胶凝材配方，服务于喷射混凝土单层衬砌技术的推广应用。

喷射混凝土单层衬砌结构的抗渗问题一直是阻碍该技术全面推广的重要原因之一，本项目以此为切入点，对喷射混凝土微裂缝在遇水条件下的自修复技术展开研究。研究中，以改性喷射混凝土胶凝基材为前提，以控制钙矾石的生成量为重点研究对象，以硅粉、粉煤灰和矿粉作为主要掺和料，采用压汞法和低场核磁共振法对不同龄期下复合胶凝材硬化浆体的孔隙特征进行测试，通过Rietveld全谱拟合定量分析水化产物中钙矾石的含量变化，研究了复合胶凝材硬化浆体的孔隙特征与钙矾石含量的相互关系，并结合对应的强度指标，选出了孔隙特征和强度更优的胶凝材配合比，进一步实现喷射混凝土在遇水条件下的自修复。通过研究得到：（1）粉煤灰和矿粉对形成钙矾石有利，硅粉对钙矾石的形成基本没有影响，但掺入硅粉可提高胶凝基材的密实性，有利于提高结构的整体抗渗性；（2）复合胶凝材料水化产物中的钙矾石含量与硬化浆体的平均孔径、孔隙率的相互关系表现为：钙矾石含量主要分布在0~3%的范围内，对应的孔隙率则集中分布在15%~30%之间，平均孔径集中分布在14nm~30nm之间；（3）以复合胶凝材硬化浆体中，更高的强度指标、更小的平均孔径和孔隙率作为评判依据，确定了单一掺和料时复合胶凝材的最优掺量范围：硅粉6%左右，粉煤灰4%~8%之间，矿粉12%左右；多掺和料复合胶凝材的优化掺量范围：硅粉6%左右，粉煤灰7.5%以下，矿粉4%~8%左右。