多重复材混合修复滨海劣化混凝土结构的高效增强机理与耐久性研究

Marine structures made from reinforced concrete (RC) can be subject to a number of deterioration processes, the most important of which are associated with corrosion of embedded steel reinforcement, which can dangerously affect the service life of the structures. In order to avoid catastrophic structural failure caused due to reinforcing steel corrosion, one has to use appropriate tools to repair these weakened, damaged or deteriorated RC structures. The aim of this proposal is to develop innovative, high-efficient and sustainable repair systems by combining conventional fibre reinforced polymer (FRP) as external strengthening with recently developed engineered cementitious composite (ECC) as internal replacement of damaged concrete to prevent further deterioration of damaged RC structures and extend their service life and improve their performance. The use of FRP can increase the structural performance; whereas the use of ECC can improve the ductility and prevent the development of large cracks in repaired structure, which is expected to completely solve the critical problem of intermediate crack (IC) debonding in FRP-strengthened concrete structures and thus highly improve the strengthening effectiveness. This proposal also aims to improve the durability of the repaired RC structures by taking and further increasing the well-recognized high resistance to chloride permeability ability of ECC so that the corrosion induced-deterioration problem can be solved once and for all. The work will first develop more suitable and durable ECC that can fits effectively with both FRP and remaining concrete in the damaged RC structures. Secondly, the bond behaviours between ECC and steel bars and that between ECC and concrete will be investigated. Thirdly, the interface behaviour between FRP and ECC and the strengthening effectiveness of using ECC in preventing intermediate crack-induced debonding will be investigated. Next, the chloride penetration in ECC and corresponding durability of ECC materials as concrete cover in protecting the reinforcing steel from corrosion will be experimentally studied. Finally, the performance and durability of repaired RC beams using FRP as external strengthening and ECC as internal replacement of damaged concrete will investigated to developed design guidelines. This project addresses one of the most difficult problems in infrastructure. The proposed project will make a significant contribution to our society by developing innovative, sustainable and robust repairing and maintenance methods which use modern technology and not only can improve the durability of the treated structures, but also improve their sustainability and make concrete repair easy, fast, reliable and last longer.

针对由钢筋锈蚀引发的滨海混凝土结构性能劣化问题，本项目拟开发一种快速、高效、可抑制结构二次劣化的多重复材修复体系，即外部采用外贴纤维增强复合材料（简称FRP）增强混凝土结构力学性能，内部采用超高韧性水泥基复合材料（简称ECC）替换锈蚀钢筋周边开裂剥落的混凝土；ECC浇筑或喷射于既有混凝土上并直接与 FRP（布/格栅）粘结，实现三者协同工作。本项目拟通过提升ECC的抗氯离子性能以抑制钢筋的再度锈蚀、解决结构二次劣化问题，和依靠ECC密集细小的裂缝消除FRP粘结界面裂缝尖端的应力集中、以求解决FRP加固混凝土结构由裂缝引起的界面剥离。本项目拟从材料层面研发一种可喷射、可粘结、高耐久的ECC，系统地研究ECC-混凝土、ECC-锈蚀钢筋及ECC-FRP三大界面的粘结性能以及FRP-ECC修复体系的协同工作、剥离控制、性能提升与抗二次锈蚀机理，建立FRP-ECC修复滨海锈蚀钢筋混凝土结构的设计方法。

FRP加固钢筋混凝土结构仍然存在耐久性问题。钢筋的锈蚀导致混凝土保护层的开裂、损伤，从而降低FRP-混凝土界面的协同工作效率。项目提出了一种新型、快速、高效、可持续的滨海钢筋混凝土结构性能修复与保障体系，即外部采用外贴FRP增强混凝土结构力学性能，内部采用ECC替换锈蚀钢筋周边已开裂剥落的混凝土；ECC直接浇筑或喷射于既有混凝土上，以对钢筋形成致密的新保护层，并传递复合修复体系的界面应力、实现FRP与既有混凝土的高效协同工作，形成FRP-ECC修复体系，系统地研究了FRP-ECC修复体系的协调变形工作机理、剥离控制机理及耐久性。.完成了如下的研究目标：.1) 研制了可喷射、超轻质与超高韧性的ECC，获得其材料设计方法及相关力学性能指标。.2) 优化了ECC材料设计，揭示并提升了ECC材料的耐久性；揭示了不同环境参量与疲劳应力状态下ECC的氯离子扩散系数及其扩散规律，研制了高耐久性ECC。.3) 揭示了钢筋锈蚀程度对锈蚀钢筋-ECC界面粘结性能的影响，建立了锈蚀钢筋-ECC粘结滑移本构；分析了ECC厚度及其材料组成对FRP-ECC粘结性能的影响及FRP-ECC界面应力传递机制，构建了FRP-ECC界面粘结滑移关系。.4) 分析了FRP-ECC修复锈蚀钢筋混凝土梁板构件的协同机理，揭示了FRP-ECC界面应力传递规律，建立FRP-ECC修复锈蚀钢筋混凝土梁的设计方法与理论。.5) 分析了ECC护筋性能对修复后锈蚀钢筋混凝土梁长期性能的影响，揭示了修复锈蚀钢筋混凝土受弯构件性能演化规律，建立基于长期性能的设计方法。.6）发表了SCI论文35篇，授权发明专利4项；培养硕士研究生7名（5名毕业，2名在读）。