氯盐侵蚀与荷载耦合作用下UHTCC修复锈蚀RC梁的劣化机制研究

The efficient repair of corroded reinforced concrete (RC) structures and deterioration mechanism of repaired structure members subjected to coupling multiple factors such as environment, loading etc. are the research hotspots in current. Ultrahigh toughness cementitous composite (UHTCC), characterized by tensile strain-hardening, multiple cracking and fine durability, has become an ideal material for structure repair and strengthening. And the study on the deterioration mechanism of UHTCC-repaired members subjected to combined loading and corrosion of chloride environment is a prerequisite for the durability assessment of retrofitted structures. In the present project, the chloride corrosion experiment of corroded RC beams repaired by UHTCC under different coupling loading levels is performed to explore the influence of loading on the corrosion process. And the degradation behaviors of flexural stiffness and the interface bonding between UHTCC and old concrete are further analyzed. Moreover, the deterioration mechanism of flexural properties, under different coupling loading and rebar corrosion levels, is studied through the bending tests of corroded RC members repaired by UHTCC after corrosion. And then, the effect of combined loading and induced crack on the appearance and mass loss of the corroded rebar is analyzed through destroying RC beams after bending tests. Based on the classic flexural theory and experimental results, the theoretical models for the prediction on the flexural deflection and residual load carrying capacity of UHTCC-repaired beam subjected to corrosion are proposed with considering the effect of combined loading. The present investigation may provide some scientific references for the repair of corroded RC structures with UHTCC and the durability assessment of repaired structures.

锈蚀钢筋混凝土（RC）结构的高效修复以及修复结构在环境、荷载等多因素耦合作用下的劣化机制是当前研究热点。超高韧性水泥基复合材料（UHTCC）以其拉伸应变硬化、多缝开裂及耐久性优良等特征，成为结构修复加固的理想材料，研究UHTCC修复构件在氯盐环境侵蚀与荷载耦合作用下的劣化机制是修复结构耐久性评估的必要前提。本项目拟通过不同耦合荷载水平下UHTCC修复锈蚀RC梁的氯盐腐蚀试验，探究荷载对腐蚀过程的影响机理，分析抗弯刚度及UHTCC与混凝土界面粘结的退化特征。进行腐蚀后UHTCC修复锈蚀RC梁的抗弯试验，研究不同耦合荷载及锈蚀水平下其弯曲性能的退化机制，破损构件探究耦合荷载及其所致裂缝对钢筋锈蚀特征及质量损失的影响。基于经典弯曲理论及试验结果，建立考虑耦合荷载影响的受腐蚀UHTCC修复梁的弯曲挠度及剩余承载能力理论模型。本研究为UHTCC修复锈蚀RC结构，以及修复结构的耐久性评估提供科学依据。

锈蚀钢筋混凝土（RC）结构的高效修复以及修复结构在环境、荷载等多因素耦合作用下的劣化机制是当前重要研究方向。超高韧性水泥基复合材料（UHTCC）以其拉伸应变硬化、多缝开裂及耐久性优良等特征，成为结构修复加固的理想材料，研究UHTCC修复构件在氯盐环境侵蚀与荷载耦合作用下的劣化机制是修复应用的必要前提。本研究先后开展UHTCC与锈蚀钢筋的粘结试验、UHTCC修复锈蚀RC梁的受弯试验，以及氯盐环境与荷载耦合作用下RC/UHTCC复合梁的腐蚀及腐蚀后复合梁受弯试验研究。粘结试验研究表明，基体延性、锈蚀率、保护层厚度和粘结长度等参数对粘结性能均有显著影响，粘结强度随锈蚀率的变化规律与粘结长度和保护层厚度相关，并建立了锈蚀钢筋与UHTCC的粘结滑移本构模型。UHTCC修复梁试验研究表明，UHTCC与旧有混凝土粘结良好，变形符合平截面假定，混凝土宏观裂缝分散为若干细裂缝，屈服前最大裂缝宽度低于0.1 mm。当锈蚀率低于11%时，采用UHTCC修复可恢复其初始承载能力，而锈蚀更为严重时，则需考虑与其它增强筋材复合修复。RC/UHTCC 复合梁的腐蚀及受弯试验研究表明，在持续荷载和收缩裂缝的影响下，锈蚀产物均从横向裂缝中渗出，未出现纵向锈胀裂缝，横向裂缝位置处钢筋锈蚀严重。锈蚀率低于6.7% 时，复合梁的承载能力基本与RC对比梁相当，但锈蚀率高于8.9%时，往往由于横向裂缝处的严重坑蚀而发生钢筋拉断破坏，承载能力和延性显著下降。最后，基于平截面假定和锈蚀后钢筋力学性能退化模型，综合钢筋坑蚀和持载效应等影响，建立了UHTCC修复梁和RC/UHTCC复合梁的受弯承载能力和正常使用阶段弯曲变形理论模型。研究成果为采用UHTCC修复加固土木、水利工程中锈蚀RC结构以及修复加固后结构的耐久性评估提供科学依据，具有重要的科学意义和工程实用价值。