海洋环境下高耐久FRP筋海水海砂混凝土材料与结构设计基础理论研究

Marine engineering construction are facing some difficult problems, such as the corrosion of common reinforced concrete, the shortage of river sand and fresh water etc. This project proposes to replace rebars with fiber reinforced polymers (FRP) bars which are highly resistant to the corrosion of chloride salt, and also to replace ordinary concrete with sea-water sea-sand concrete in order to obtain highly durable FRP bar reinforced sea-water sea-sand concrete materials and structures, which are suitable for marine environment. This project will study the hydration dynamics of sea-water sea-sand concrete, and reveal the microstructure formation and development rules. The design method for the composition of sea-water sea-sand concrete will be established; and its deformation characteristics and constitutive relationships will be obtained in order to control its microstructure and optimize the performance of sea-water sea-sand concrete. This research will also reveal the coupling mechanism of moisture, heat and chloridion, and establish a response model of internal micro-environment within the sea-water sea-sand concrete in marine environment. The micro-structure evolution and performance degradation process of FRP bars, the interface of FRP bar and sea-water sea-sand concrete in the corrosive marine environment will be investigated, and the corresponding deterioration mechanisms will be to revealed. A long-term performance monitoring method and service life prediction model of FRP bar reinforced sea-water sea-sand concrete will be developed, and a durability evaluation system will be built. The performance of FRP bar reinforced sea-water sea-sand concrete structural members (beam, column and slab) and key connection joints under different loadings will be investigated, and calculation methods and design theories of the highly durable FRP bar reinforced sea-water and sea-sand concrete structure will be proposed. The outcome of this research will develop a new highly durable structural material for marine structures, and provide a scientific guidance for the design, construction, maintenance and long-term service performance evaluation of FRP bar reinforced sea-water sea-sand concrete structure, which has great theoretical value and practical significance.

海洋工程建设面临钢筋混凝土易腐蚀、河砂和淡水匮乏等难题。本项目提出以高耐氯盐腐蚀的纤维增强复合材料（FRP）筋取代钢筋，以海水海砂混凝土取代普通混凝土来制备高耐久FRP筋海水海砂混凝土材料与结构。将研究海水海砂混凝土水化动力学行为，揭示微结构形成和发展规律，建立组成设计方法，得到变形特性和本构关系，实现微结构调控与性能优化。揭示湿-热-氯离子耦合作用机制，建立海水海砂混凝土内部微环境响应模型；研究海洋环境下FRP筋、FRP筋-海水海砂混凝土界面微结构演变与性能劣化过程和机制；发展长期性能监测方法与服役寿命预测模型，构建耐久性评估体系。研究不同荷载作用下FRP筋海水海砂混凝土构件（梁、柱、板）和关键节点的受力性能，提出计算方法和设计理论。本研究将为海洋工程提供一种高耐久结构材料，为FRP筋海水海砂混凝土结构的设计、建造、维修以及长期服役性能评估提供科学指导，具有重大理论价值和实践意义。

本项目围绕海洋环境下高耐久复材筋增强海水海砂混凝土材料与结构的三个关键科学问题“海水海砂混凝土的水化动力学行为与微结构形成”、“海洋环境下复材筋增强海水海砂混凝土性能退化与识别”和“海洋环境下复材筋增强海水海砂混凝土构件的设计理论”开展了系统的试验与理论研究。具体成果如下：（1）分析了海水海砂混凝土的水化动力学行为与微结构形成过程，揭示了海水海砂混凝土水化微结构演变对其宏观性能的影响机理，基于胶凝体系调控设计制备了低碱度海水海砂混凝土；阐明了了海水海砂混凝土中氯离子溶出与迁移机制，研发了低收缩、强氯离子结合海水海砂混凝土；建立了不同强度等级（普通、高强和超高性能）海水海砂混凝土配合比设计及胶凝体系组成优化方法，建立其力学本构关系，得到了其强度发展规律以及抗冻融等耐久性能。（2）通过室内加速老化试验和真实海洋环境暴露试验，揭示了海洋环境下复材筋、复材筋-混凝土界面的静、动态力学性能劣化演变规律；基于拉拔试验和分子动力学模拟阐明了复材筋-混凝土界面粘结力劣化机制，得到了腐蚀环境下纤维-环氧树脂粘结力演变规律，建立了基于无损与非接触检测技术的复材筋、复材筋-海水海砂混凝土界面的劣化损伤识别方法；研发了基于纳米材料改性基体和纤维混杂设计的高耐久复材筋。（3）揭示了海洋腐蚀环境下复材筋增强海水海砂混凝土梁构件静、动态力学性能和破坏模式演化规律，得到了腐蚀时间、温度、干湿循环、筋材强度、混凝土强度与碱度等因素对其力学性能的影响规律，完善了复材筋增强海水海砂混凝土梁构件的正截面抗弯和斜截面抗剪设计理论；建立了复材筋增强海水海砂混凝土柱的轴压承载力计算修正模型和设计方法，提出了通过调控海水海砂混凝土的碱度提升构件长期力学性能的新方法，初步构建了海洋环境下高耐久复材筋增强海水海砂混凝土结构设计理论和方法。发表SCI论文42篇，EI论文18篇，培养国家杰出青年基金获得者1名，博士后2名，博士生9名（在读8名）、硕士生26名（在读10名）。所取得的成果为高耐久FRP增强海水海砂混凝土在海工结构和岛礁基础设施中的应用提供了重要的理论基础和技术支撑。