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

钢筋混凝土结构暴露在海水或除冰盐中，由于氯离子的进入，很容易受到埋入的钢筋的腐蚀。这种腐蚀会导致结构的劣化，降低结构的使用寿命，给国民经济带来负担。尽管进行了广泛的努力，我们目前的腐蚀防护方法仍然要么过于昂贵，要么无法防止腐蚀行为。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为化学试剂，可以抑制混凝土结构中的钢筋腐蚀。这样的环境可持续解决方案对于维护大规模、广泛和耐用的基础设施至关重要--基础设施是经济增长的关键驱动力。为了支持这些目标，这项研究在加州大学洛杉矶分校和佐治亚理工学院培养了一支多元化的技术队伍：博士后科学家、博士、本科生和高中生。这两个大学小组在层级和职能上相互交叉培训，以促进合作和交流保存基础设施清单所需的科学进步。这项工作的多学科性质将使年轻研究人员接触到与可持续发展有关的交叉知识概念，并将新技术推向市场。这项研究利用二氧化钛纳米颗粒的光活性行为，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。水泥水化过程中产生的单硫酸盐相具有在其结构中插入阴离子的能力，其偏好描述为：chloridenitratenitritecarbonatesulfatehydroxide.因此，可以对水泥进行调整，以最大限度地形成AFM，并捕获侵入混凝土的氯物种。此外，暴露在阳光下，二氧化钛可以将氮氧化物形式的大气污染物转化为用作阳极腐蚀缓蚀剂的硝酸盐/亚硝酸盐水离子。当相互配合使用时，这些工艺可以将侵入的氯离子捕获在AFM相中，同时将硝酸盐/亚硝酸盐离子(先前存储在AFM中)释放到孔溶液中，以确保对钢铁的腐蚀抑制。针对这些目标，本研究：(1)合成可见光活性二氧化钛，(2)优化水泥化学，使AFM相的产量最大化，(3)模拟亚硝酸盐/硝酸盐/氯化物在混凝土中的传输，以最大限度地抑制钢筋腐蚀。这项工作的智力成果包括：缓蚀方法的新进展，这些方法利用光催化行为、热力学选择性和离子交换偏好作为设计混凝土基础设施的可再生和可调腐蚀防护系统的手段。

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.