锈蚀钢筋-纳米粘土混凝土界面多尺度损伤演化及粘结滑移特性研究

The reinforcing steel corrosion can cause damage of concrete cover, and influence the bond properties. Adequate bond between reinforcing steel and concrete is essential for the performance and durability of reinforced concrete structures. The damage of bonding interface between corroded steel bars and concrete is one of the major reasons that cause the deterioration and failure of reinforced concrete structures. Once the bonding interface properties between corroded steel bars and concrete is improved, higher bond behavior between corroded steel bars and concrete can be achieved. In this research, Nanoclay is applied to improve the engineering properties and durability of the reinforced-concrete structures with the bond properties strengthened. The bond behavior between corroded steel bars and Nanoclay modified concrete will be investigated, and the failure mode and damage mechanism will be examined. Based on the the multi-scale theory, the damage and deterioration of the interface between corroded steel bars and concrete will be investigated during the steel bars corrosion process from a deeper level. A quantitative evalution criterion will be suggested to assess the cracking of Nanoclay modified concrete induced by non-uniform corrosion of steel bars, and a crack width development model of Nano-clay modified concrete will be established. The modification mechanism of Nanoclay to the interface characteristics between corroded steel bars and concrete will be discussed in detail. It is hoped that this work may help to improve the bond properties between corroded steel bars and concrete, and an improved durability of the concrete can be obtained.

钢筋锈蚀引发保护层锈胀开裂造成粘结性能劣化，并将直接导致钢筋混凝土结构承载力退化、耐久性降低，严重影响工程的使用性与耐久性。锈蚀钢筋-混凝土粘结界面的损伤、破坏是钢筋混凝土构件性能下降和失效的主要原因，优化锈蚀钢筋-混凝土界面特性，延缓混凝土锈胀开裂是提高锈蚀钢筋-混凝土粘结性能的关键问题。本项目旨在利用纳米粘土颗粒提高锈蚀钢筋-混凝土粘结性能，增强钢筋混凝土结构的工程性和耐久性；探索锈蚀钢筋-纳米粘土混凝土界面粘结滑移特性，揭示界面粘结失效模式和破坏机制；基于多尺度分析方法从更深层次分析钢筋锈蚀过程钢筋-纳米粘土混凝土界面损伤、劣化规律；深入研究钢筋非均匀锈蚀与纳米粘土混凝土锈胀开裂的关系，建立纳米粘土混凝土裂缝宽度扩展模型；探明纳米粘土改善锈蚀钢筋-混凝土界面特性作用机理；研究成果可为优化锈蚀钢筋-混凝土粘结性能提供借鉴，亦为制备高耐久性混凝土提供参考。

钢筋与混凝土有效粘结是保障钢筋混凝土承载力的关键因素之一；鉴于纳米粘土能够有效阻碍氯离子在混凝土中的渗透，同时纳米粘土混凝土导电性的降低也将延迟同样条件下混凝土内部钢筋电化学锈蚀的发生和发展，从理论上可以预测同样条件下纳米粘土混凝土内部钢筋起锈时刻较普通钢筋混凝土构件有所推迟，即便钢筋发生锈蚀，钢筋锈蚀率增长速度较普通混凝土构件缓慢。本项目对纳米粘土对水泥混凝土性能增强机理进行了深入研究；研究了不同纳米粘土掺量、混凝土强度、钢筋直径、保护层厚度、锚固长度对锈蚀钢筋-纳米粘土混凝土粘结滑移特性影响规律；基于微观、细观、宏观层次，研究不同锈蚀程度钢筋-纳米粘土混凝土粘结界面过渡区结构特性损伤演变过程，建立表征粘结界面多尺度损伤的定量指标，明确损伤指标对锈蚀钢筋-纳米粘土混凝土粘结特性的影响；探索锈蚀钢筋-纳米粘土混凝土界面过渡区水化程度、微观结构、凝胶特性、孔结构特性的演化过程，揭示纳米粘土对锈蚀钢筋-混凝土界面特性改善作用。获得了锈蚀钢筋-纳米粘土混凝土粘结性能劣化过程，明确了纳米黏土混凝土与钢筋粘结增强机理；开展了锈蚀钢筋-纳米粘土混凝土粘结界面损伤多尺度演化过程的试验和理论研究；探明了锈蚀钢筋-纳米粘土混凝土界面多尺度劣化指标与粘结特性的定量关系，建立了基于界面微细、观损伤的锈蚀钢筋-纳米粘土混凝土粘结强度退化模型及粘结滑移本构关系。本项目针对锈蚀钢筋混凝土结构耐久性退化这一世界工程难题，以“可持续发展”为出发点，旨在利用纳米粘土增强钢筋混凝土界面特性，从根本上改善锈蚀钢筋-混凝土粘结滑移性能并探索其中涉及的关键科学问题。本课题对于指导侵蚀环境中钢筋混凝土结构耐久性设计，正确评估实际工程中钢筋混凝土结构服役性能、力学性能，以及经济合理的确定维修加固方案具有重要的理论意义和应用价值。