基于三元微生物体系的混凝土裂缝自修复过程及机理研究

Microbial-induced self healing of concrete damage has been proved to be an effective technology. However, some aspects such as evaluation of microbial mineralization capability, establishment of protective vector, supply of oxygen for bacteria introduced into the concrete, and the mechanism of trigger and repairing of the self healing process still need further study. Therefore, in terms of inner concrete microenvironment, our program firstly attempts to set up a practical evaluation system on microbial mineralization capacity. Via this system, alkaliphilic bacteria with high mineralization capacity will be screened and isolated, and the effects on microbial mineralization capacity will be investigated and optimized. Secondly, a ternary microbial self-healing system will be developed including bacterial spores, nutrients and controlled-releasing oxygen agent, and a kind of suitable microcapsule vector will be explored to provide protection to the microbial self-healing system before its introduction into the concrete. Finally, by means of the methodology in the field of biology, materials and civil engineering, the microbial-induced calcium carbonate precipitation and its influential factors, the effect of physical property of microcapsule on the strength property of concrete material, the trigger mechanism of the ternary microbial self-healing system encapsulated in microcapsule upon the occurrence of concrete crack, and the evaluation and optimization of microbial-induced self healing process will be comprehensively studied. The program can hopefully provide theoretical and experimental foundation for the industrial application of microbial-induced self healing technology in concrete materials.

利用环境中的矿化微生物对混凝土的内部损伤进行自修复已被证明具有良好的应用前景，但目前在微生物的矿化性能评价、保护载体构建、微生物置入混凝土内部后氧的提供、自修复过程的触发及作用机制等方面研究还不够深入。本项目拟依据混凝土内部微环境的特点构建一个普适的微生物矿化性能评价体系，利用该体系从环境中筛选高矿化性能的耐碱菌，并对影响细菌矿化能力的因素进行调控优化；制备适宜的氧缓释剂构建包含细菌芽孢、营养物质和氧的三元微生物自修复体系，并研制合适的微胶囊载体为微生物修复体系提供必要的保护；结合生物学、材料学和土木工程学的手段和方法对微生物在混凝土环境中的碳酸钙诱导沉积及相关影响因素、微胶囊的物理性质对混凝土材料力学性能的影响、微胶囊在混凝土结构出现裂缝时的破裂机制、微生物对混凝土裂缝自修复过程的调控和评价等方面进行系统深入的研究。本研究可为实现混凝土材料微生物自修复技术的应用提供科学理论和实验依据。

建立了一种新型高通量细菌分离策略筛选获得用于修复混凝土裂缝的高钙沉积活性（calcium precipitating activity, CPA）细菌，开发了一种基于不溶性钙检测的细菌CPA评价方法——迷你试管法，利用该方法从红树林沉积物中分离筛选获得数株具有高CPA的嗜碱矿化菌株，经鉴定均属于芽孢杆菌属。探索了各种环境因素和营养可利用性对矿化菌诱导钙沉积的影响，对碳源、氮源、钙源、芽孢发酵与萌发以及pH等因素进行了调控优化，实现了细菌矿化性能的最大化。在以上实验结果的基础上，为提高混凝土内部深层裂缝的微生物自修复效率，提出了在内部裂缝原位供氧的策略，进一步研究了释氧剂和有机酸对释氧曲线的影响，确定最佳释氧剂组分，并验证了释氧剂对芽孢萌发、呼吸作用及矿化活性的促进作用。在过氧化钙供氧条件下，探索了有机酸种类及含量、芽孢浓度、碳源种类及浓度，氮源种类及浓度等因素对细菌矿化的影响，确定了供氧条件下的最佳矿化条件。为实现对微生物芽孢的保护，我们设计了一种新型的水泥基材料外壳，通过优化制备工艺参数（如水泥外壳水灰比、水泥外壳预固化时间、隔离层物质种类及含量）实现壁材与混凝土基体间牢固的粘结，保证水泥外壳随裂缝形成而开裂，制备了水泥外壳包覆的三元微生物自修复剂。通过裂缝面积修复率、修复深度、水渗速率和微观表征综合评价矿化菌-氧-营养三元微生物自修复体系的裂缝修复效果，结果表明三元微生物体系能够成功实现裂缝自修复。