Collaborative Research: Using sunlight to reduce air pollution and ensure corrosion resistant of concrete infrastructure.

暴露在海水或除冰盐中的钢筋混凝土结构由于氯离子的进入而容易受到嵌入式钢的腐蚀。这种腐蚀导致劣化，降低结构的使用寿命，并对国民经济造成负担。尽管付出了大量的努力，我们目前的腐蚀保护方法仍然要么太昂贵，要么无法防止腐蚀作用。这项研究开发了一种新的策略，利用可见光将空气污染物分解成化学试剂，可以抑制混凝土结构中的钢筋腐蚀。这种环境上可持续的解决方案对于维持大规模、广泛和持久的基础设施至关重要？经济增长的关键驱动力。为了支持这些目标，该研究培训了不同层次的技术劳动力：博士后科学家，博士。以及加州大学洛杉矶分校和格鲁吉亚理工学院的本科生和高中生。这两个大学集团在层次和功能上相互交叉培训，以促进合作和交流保护基础设施库存所需的科学进步。这项工作的多学科性质将使青年研究人员接触到与可持续发展有关的跨领域知识概念，并将新技术推向市场。这项研究利用了二氧化钛纳米颗粒的光活性行为，并利用可见光和水泥化学的操纵来防止钢筋混凝土中的钢筋腐蚀。在水泥水化过程中产生的单硫酸盐（AFm）相具有在其结构中插入阴离子的能力，其优先顺序描述为：氯硝铵硝酸盐碳酸盐硫酸盐氢氧化物。因此，可以调整水泥以最大化AFm形成，并捕获侵入混凝土的氯化物物质。此外，在暴露于光时，二氧化钛可以将氮氧化物形式的大气污染物转化为硝酸根/亚硝酸根离子水溶液，其用作阳极腐蚀抑制剂。当相互结合应用时，这些过程可以将侵入的氯离子捕获在AFm相中，同时将硝酸根/亚硝酸根离子（先前储存在AFm中）释放到孔隙溶液中，以确保钢铁腐蚀抑制。为了实现这些目标，本研究：（1）合成可见光活性二氧化钛，（2）优化水泥化学，以最大限度地提高AFm相的产量和（3）模拟混凝土中的亚硝酸盐/硝酸盐/氯化物运输，以最大限度地抑制钢筋腐蚀。这项工作的智力成果包括：在腐蚀抑制方法的新进展，利用光催化行为，热力学选择性和离子交换偏好作为一种手段，对设计再生和可调腐蚀保护系统的混凝土基础设施。

Reinforced concrete structures exposed to sea water or de-icing salts are susceptible to the corrosion of embedded steel, due to the ingress of chloride ions. Such corrosion results in deterioration, reduces the service-life of structures, and poses a burden to the national economy. In spite of extensive efforts, our current methods of corrosion protection remain either: too expensive, or unable to prevent corrosion actions. This research develops a new strategy that utilizes visible light to decompose air pollutants into chemical agents that can suppress steel corrosion in concrete structures. Such environmentally sustainable solutions are critical to maintain large, widespread and durable infrastructure?a critical driver of economic growth. To support these goals, the research trains a diverse technical workforce at the levels of: post-doctoral scientists, Ph.D. and undergraduate students and high-schoolers at both University of California-Los Angeles and Georgia Tech. Both university groups cross-train with each other, hierarchically and functionally to foster collaboration and exchange scientific advancements needed to preserve infrastructure inventories. The multidisciplinary nature of the work will expose young researchers to cross-cutting intellectual concepts relevant to sustainable development and propelling new technologies to the marketplace. This research exploits the photoactive behavior of titanium dioxide nanoparticles, and uses visible light, and manipulations of the cement chemistry, to prevent steel corrosion in reinforced concrete. Monosulfate (AFm) phases produced during cement hydration have the ability to intercalate anions in their structure in a preference described as: chloridenitratenitritecarbonatesulfatehydroxide. Thus, cements can be tuned to maximize AFm formation, and capture of chloride species intruding into concrete. Further, up on exposure to light, titanium dioxide can convert atmospheric pollutants in the form of nitrogen oxides to aqueous nitrate/nitrite ions which serve as anodic corrosion inhibitors. When applied in conjunction with each other, these processes work to trap intruding chloride ions within the AFm phase while simultaneously releasing nitrate/nitrite ions (previously stored in the AFm) into the pore solution to ensure steel corrosion inhibition. Towards these objectives this research: (1) synthesizes visible light active titanium dioxide, (2) optimizes cement chemistry to maximize the yield of AFm phases and (3) simulates nitrite/nitrate/chloride transport in concrete to maximize steel corrosion inhibition. The intellectual outcomes of this work include: novel advancements in corrosion inhibition methods which exploit photocatalytic behavior, thermodynamic selectivity and ion exchange preference as a means towards designing regenerative and tunable corrosion protection systems for concrete infrastructure.