海洋工程混凝土中钢筋腐蚀自动检测与智能防护的原理与技术

The corrosion of reinforcing steel in concrete cannot be easily detected. Usually, it is too late to repair corroded rebar when its corrosion damage becomes visible from outside by naked eye. Such corrosion damage is particularly severe in marine environments and has become a roadblock in construction in the South China Sea and implementation of the “One-road and One-belt” strategy of China. To detect the corrosion of steel in concrete and protect it from corrosion attack in the very beginning, it is proposed in this application to make magnesium (Mg) into a corrosion probe and also a sacrificial anode based on the unique electrochemical properties of Mg. As a probe, Mg can sensitively exhibit a different potential when the cover concrete becomes aggressive after chloride ingress or carbonation. The variation in potential or current is actually a clear indication of the increased corrosivity of concrete. Mg can also be activated by concrete deterioration, and act as a sacrificial anode, smartly providing an adequate cathodic protection for the steel under corrosion threat according to the steel corrosion potential in the concrete. Based on this principle, an automatic and intelligent corrosion detection and prevention system can be built, which creatively combines an automatic corrosion probe and a smart sacrificial anode into a Mg electrode. Such an electrode system will not over-protect uncorroded passive steel in concrete. Instead, it can sensitively detect the corrosivity of concrete and the initiation of corrosion on steel rebar after the cover concrete is carbonated by carbon dioxide or polluted by chlorides, and smartly give out an adequate current density to protect the steel from corrosion attack in the corrosive concrete. In the proposed project, the response of Mg to chloride ingress and carbonation will be tailored through alloying. After the mechanism of passivation-corrosion transition of Mg alloys in strong alkaline concrete has been systematically investigated and the influence of chloride and pH value on the polarization behavior of the alloys has been comprehensively understood, an intelligent electrode system with automatic corrosion detection and smart corrosion protection functions will be developed. The completion of this project will lead to extension of service life of reinforced concrete structures in marine environments.

混凝土中钢筋腐蚀初期极难发现，等到肉眼观察到时已无法挽救。这种隐蔽破坏在海洋工程中尤为致命，制约着海洋开发和“一路一带”战略的实施。为了尽早检测钢筋腐蚀并及早进行保护，本申请提出利用镁独特的电化学行为，通过它对混凝土中氯离子入侵和二氧化碳碳化的敏感响应，自动检测混凝土的腐蚀性和钢筋的腐蚀；同时利用钢筋的腐蚀和混凝土腐蚀性的变化，激发镁阳极反应，为钢筋提供适当的阴极保护；使混凝土中钢筋在未腐蚀时不受强烈的阴极地保护，避免过保护；在腐蚀开始时就能被立即地检测到，并根据其腐蚀倾向的大小被适当地阴极保护，避免欠保护。本课题将通过镁的合金化，精细地调节它对混凝土中导致钢筋腐蚀的临界氯离子浓度和pH值的响应水平和敏感度，研究镁及其合金在强碱性混凝土中的钝化和腐蚀行为，探明氯离子和pH值的影响机理，优化镁合金自动检测腐蚀和智能牺牲阳极保护这两大功能一体化的系统，实现预警抑制海洋工程钢筋混凝土腐蚀的目标。

混凝土中钢筋腐蚀初期极难发现，后期发现时已无法挽救。这种对海洋结构工程基础设施的隐蔽破坏，极为危险致命，是海洋开发和“一路一带”战略的实施的工程障碍。为了尽早检测钢筋腐蚀并及早进行保护，本课题利用镁独特的电化学行为，通过它对混凝土中氯离子入侵和二氧化碳碳化的敏感响应，自动检测混凝土的腐蚀性和钢筋的腐蚀；同时利用钢筋的腐蚀和混凝土腐蚀性的变化，激发镁阳极反应，为钢筋提供适当的阴极保护；使混凝土中钢筋在未腐蚀时不受强烈的阴极地保护，避免过保护；在腐蚀开始时就能被立即地检测到，并根据其腐蚀倾向的大小被适当地阴极保护，避免欠保护。.经过4年的努力，本课题按计划探明如下规律：混凝土模拟液碱性的增强和合金元素铝的添加，能提高镁的钝性；氯离子在碱性混凝土中，当浓度超过一定水平后，依然能破坏镁及其合金在钝性；提高温度也能促进镁活性的提高。在这些可以预料的机理研究中，通过实验证实了镁自动腐蚀监测和智能保护的设想。在此基础上，本课题进一步探索了合金化对镁智能阳极性能的提升和镁合金阳极的优化。发现含铝17wt.%的铸态镁合金具有较好腐蚀监检测和保护智能水平。如果能消除合金相组织的微观不均匀性，则Mg17Al12相有最佳的腐蚀监检测和保护智能性。随着机理研究的深入，本课题意外地发现，混凝土中钢筋腐蚀可能真正起因于缝隙腐蚀，而不是人们习以为常的点蚀。在一些极端的实际工业环境中，碳化可以很快导致混凝土中钢的腐蚀，而本课题研发的智能镁阳极正可用于这样腐蚀体系的监检测和保护。 此外，为了确保和拓展研究成果的应用，本课题还研发了实验室腐蚀环境模拟设备和可用于钢筋混凝土的绿色缓蚀剂，建立了实验室快速点蚀/缝隙双功能腐蚀评价电解池和现场无参比无辅助的简易单丝腐蚀检测技术。.本项目共资助发表论文20篇，其中与本课题紧密相关的第一标注论文7篇，第二标注1篇，尚有多篇紧密相关的论文待发表；申请相关发明专利2项，都已授权；申请实用新型专利1项，并已授权。项目共培养了2名博士研究生和3名硕士生，其中2名硕士已毕业获得学位，其余在读。