这里描述的工作部分由瑞士联邦路办公室 (研究项目 AGB2012/010) 资助。我们非常感谢财政支持。

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</ol>

作者没有什么可透露的。

为确定C暴击而建议的实验协议的成功最关键的步骤是包括为防止假腐蚀引发和其他钢筋末端效果而采取的措施。在这方面, 对各种方法进行了测试, 其中发现这里所报告的协议能产生最好的结果28。在进一步的测试中, 这种方法允许将假起始率降低到10% 以下。一方面, 这是由于涂层的边界面积的暴露在混凝土表面与环氧树脂, 这增加了运输的长度, 通过混凝土到钢筋两端的钢棒结束。另一方面, 用高密度、高碱性的胶凝浆代替钢筋的两端的原混凝土, 大大提高了这些地区的耐蚀性。这种系统,即, 涂层钢筋结束与一层高分子改性胶凝材料, 已证明成功也在其他研究29,30。
另一个重要的方面是腐蚀起始的标准。此标准基于 RILEM 技术委员会 TC-235, 其目的是建议在实验室31中制造的样本中测试C暴击的检测方法。其基本原理是众所周知, 埋在混凝土中的偏振钢的腐蚀可能会在很长一段时间内发生, 而不是一个定义良好的即时3032。钢可能开始腐蚀在相对地低氯化物集中, 但, 如果这些不能够承受腐蚀过程, 钝化将发生, 变得明显由一个潜在的增量回到最初的被动水平。此类钝化钝化事件通常在类似的研究中观察30,33,34。在稳定腐蚀时测定的氯化物浓度比从被动水平上的潜在偏差的最初迹象变得明显的时间更切合实际。使用所建议的标准, C暴击代表了腐蚀引发的氯化物浓度, 并且稳定地传播。
该方法的一个限制是样本相对较小, 这可能会对结果产生影响35,36。为了抵消这一点, 建议使用相对较高的样本数 (理想情况下为 10)。置信度取决于实际测试区域中的C暴击的统计分布。有关这方面的详细信息, 请参阅参考36。另外一个限制是, 实验室暴露的水分条件可能与实际结构不同。最后, 在潜在的一般为负的情况下, 如在矿渣水泥或其他含硫化物的粘合剂中, 对腐蚀起始的检测可能是困难的。
尽我们所知, 这是第一个在腐蚀开始前的阶段在工程结构中C暴击的方法。对比经验从结构, 是由定义在腐蚀开始以后获得, 这个方法可以用于测量C暴击为具体结构或结构成员在腐蚀之前发生的退化;这样的结果可以用来评估 (未来) 腐蚀的风险, 并预测剩余的腐蚀起始时间 (使用寿命模型)。因此, 这种方法有可能用于材料测试, 类似于用于机械测试的既定方法 (压缩强度,等)
该方法目前适用于瑞士的许多不同的混凝土基础设施。这将扩大对结构中C暴击的统计分布的严重限制的5知识。此外, 它将揭示不同的因素, 如结构的年龄, 使用的建筑材料,等的影响, 从而为土木工程师和 decision-makers 的基础设施管理提供重要的信息。

钢筋在混凝土中的腐蚀, 由氯化物通过混凝土的渗透引起, 是钢筋混凝土结构过早退化的最常见原因之一, 因此在土木工程1,2,3,4。工业化国家通常有大量的老化混凝土基础设施的库存, 建于上个世纪下半叶, 因此有几十年的历史, 暴露于海洋气候或道路上使用的除冰盐。能够可靠地评估这些结构的状况,即, 腐蚀的风险, 构成了规划维护工作和基础设施管理的基础。
在混凝土中氯离子腐蚀的管理工程中建立的方法是基于氯化物阈值 (也称为临界氯含量, C暴击)1,5,6. 根据这个概念, 在钢表面的混凝土中氯化物浓度超过了C暴击阈值时, 就认为会发生腐蚀萌生。因此, 评估现有结构的状况和估计剩余的使用寿命通常依赖于确定不同深度的混凝土中的氯化物含量, 特别是在埋入钢筋的深度。有许多可靠和标准化的方法来测量混凝土样品中的氯化物浓度7,8。将结果与C暴击进行比较, 为评估腐蚀风险提供依据, 并对修复措施的类型和范围进行规划。但是, 此方法需要了解C暴击。
不同的国际标准和建议, 以及教科书, 规定的值为C暴击1,3,9,10,11。这些典型地是大约0.4% 氯化物由水泥的重量, 根据长期经验或早期的研究12,13。然而, 众所周知, 对某一结构或结构成员的C的暴击的实际电阻受到使用的材料、结构的年龄和曝光历史和条件的强烈影响1,5. 因此, 人们普遍认为, 一个结构的经验只应谨慎地适用于其他结构。
尽管如此, 使用表格式的C暴击值是常见的工程实践, 与实际结构无关。这可以通过文献中的C暴击的巨大散布来解释, 也没有可靠的方法来确定c暴击on-site 和实验室中的5。在耐久性评估中使用列表阈值的方法与在老化混凝土结构的状态评估中的结构考虑因素是不同的。在后一种情况下, 有许多标准化的测试方法, 以确定机械性能, 如材料的强度, 在结构 (混凝土, 钢筋), 用于计算的结构行为。
在这项工作中, 提出了一个实验协议来确定从工程结构中抽取的样本的C暴击。该方法是基于钢筋混凝土的钻孔芯, 在混凝土结构部分的腐蚀尚未启动。这些样品被转移到实验室, 在那里他们受到加速腐蚀试验, 以便研究腐蚀起始的条件。所提出的方法的主要优点是, 样本从结构中产生, 从而在许多已知的参数中表现出真实的条件, 而这很大程度上影响了C暴击, 不能代表性在实验室生产的样品中模仿。这包括混凝土的类型和年龄 (年轻实验室混凝土与成熟工地生产的混凝土), 建筑时使用的钢筋的类型和表面条件, 以及一般钢-混凝土的性能接口14。与实验室测量方法的准确性一起, 此方法允许对特定结构或结构成员的C暴击进行可靠的确定。
建议的协议在工程实践中的应用将-与使用C暴击的常量值的一般做法相比, 可以提高条件评估的准确性和模型的预测能力, 以分析剩余的使用寿命。在未来的几十年里, 我们所建造的基础设施的维修工程预计将有强劲的增长15 , 这就迫切需要在腐蚀基础设施工程方面进行这种改进。

<table><tbody><tr><td>Stranded wire</td><td></td><td></td><td>cross section at least 0.50 mm&amp;sup2;; ideally copper wire, tin plated</td></tr><tr><td>Self-tapping metal screw</td><td></td><td></td><td>any suitable self-tapping screw, typically of length 4 - 5 mm and diameter around 2.5 mm</td></tr><tr><td>Ring cable lug</td><td></td><td></td><td>suitable to connect screw and cable</td></tr><tr><td>SikaTop Seal-107</td><td>Sika</td><td></td><td>two-part polymer modified cementitious waterproof mortar slurry</td></tr><tr><td>Epoflex 816 L</td><td>Adisa</td><td></td><td>epoxy coating</td></tr><tr><td>Exposure tank</td><td></td><td></td><td>any suitable tank (&lt;em&gt;e.g.&lt;/em&gt; rako box) with a lid;&amp;nbsp; sufficiently large for exposing the samples</td></tr><tr><td>Reference electrode</td><td></td><td></td><td>Any stable reference electrode suitable for continuous immersion in sodium chloride solution</td></tr><tr><td>Tap water</td><td></td><td></td><td></td></tr><tr><td>Sodium chloride</td><td></td><td></td><td></td></tr><tr><td>Data logger</td><td></td><td></td><td>any device able to monitor the potentials of all samples vs. the reference electrode at the specified interval (input impedance &gt;10E7 Ohm)</td></tr></tbody></table>

experimental protocol to determine the chloride threshold value for corrosion in samples taken from reinforced concrete structures

发达国家钢筋混凝土基础设施的老化, 迫切需要对这些结构的状况进行可靠评估的方法。钢筋锈蚀是最常见的降解原因。众所周知, 结构耐腐蚀的能力在很大程度上取决于使用的材料或年龄等因素, 但通常的做法是依赖标准或教科书中规定的阈值。这些阈值的腐蚀启动 (C暴击) 是独立于特定结构的实际属性, 这清楚地限制了条件评估和使用寿命预测的准确性。使用列表值的做法可以追溯到缺乏可靠的方法来确定C暴击on-site 和实验室。
这里给出了一个用于确定单个工程结构或结构构件的C暴击的实验协议。从结构中抽取了一些钢筋混凝土试样, 并进行了实验室腐蚀试验。该方法的主要优点是, 它确保了有关参数的真实条件, 而这是众所周知的非常影响C暴击的, 如钢-混凝土界面, 不能代表性模仿实验室生产的样品。同时, 实验室的加速腐蚀试验允许在测试结构的腐蚀开始之前, 可靠地确定C暴击;这是一个主要的优势比所有的通用条件评估方法, 只允许估计的条件, 腐蚀后启动,即, 当结构已经损坏。
该协议生成测试结构的C暴击的统计分布。这是一个基础的概率预测模型的剩余时间, 以腐蚀, 这是需要的维修规划。这种方法有可能用于民用基础设施的材料测试, 类似于用于机械测试的既定方法。

图 7显示了在实验室氯化物暴露期间监测到的典型钢电位。这两个例子都表明, 电位可能在很短的时间内明显下降, 但腐蚀过程可能还没有稳定传播, 这变得明显通过增加潜在的初始被动水平。在本协议中, 腐蚀起始时间、即、停止曝光的时间和C暴击是由有标记的潜在下降定义的, 后跟10天的负电位 (请参见3.5.2 和讨论有关详细信息)。
这是常见的, 它可能需要几个月, 直到稳定的腐蚀引发发生。这也取决于从结构中抽取样品时, 混凝土中已经存在的初始氯化物含量。到目前为止, 在某些情况下进行的实验, 它花了超过1年, 直到腐蚀开始。
图 8显示了一个C暴击的例子, 该示例是在瑞士阿尔卑斯山的40年以上的公路隧道中采集的11样本中进行测量的。所有这些样本都是从 1-2 m2的区域中抽取的, 因此可能相同地产生和暴露。在这个例子中, 在取样时钢表面的氯化物含量是微不足道的。此外, 碳化锋仍然远离钢表面。
图 9显示了两个例子, 当接触到无氯溶液时, 钢势会明显降低。在其中一个具体事例, 它是在随后 (破坏性) 检查样品发现了混凝土在钢深度已经是碳酸的。当水到达钢表面时, 腐蚀过程便立即开始。在另一种情况下, 在其中一个钢筋末端发生了假腐蚀。
<img alt="Figure 1" class="xfigimg" src="/files/ftp_upload/56229/56229fig1.jpg"> 
图 1.从结构中抽取的样品的示意图, 并在实验室中处理: (一个) 与嵌入的钢筋的混凝土芯;(b) 通过水冷式金刚石切割减少外露侧和背面的混凝土保护层;(c) 钢棒端面保护, 方法是将钢筋周围的一些混凝土拆除, 并用密实的水泥浆/砂浆和随后的环氧涂层代替;以及 (d) 在外露混凝土表面的侧面和端面上的环氧涂层。<a href="//ecsource-jove-com.remotexs.ntu.edu.sg/files/ftp_upload/56229/56229fig1large.jpg" target="_blank">请单击此处查看此图的较大版本.</a>
<img alt="Figure 2" class="xfigimg" src="/files/ftp_upload/56229/56229fig2.jpg"> 
图 2.实验室中腐蚀试验装置的示意图。这显示了样品在曝光槽中的位置。垫片用于确保接触到暴露溶液从底部样品表面。所有样品都连接到一个数据记录器, 测量每个样品与暴露溶液中所放置的参考电极的电位。<a href="//ecsource-jove-com.remotexs.ntu.edu.sg/files/ftp_upload/56229/56229fig2large.jpg" target="_blank">请单击此处查看此图的较大版本.</a>
<img alt="Figure 3" class="xfigimg" src="/files/ftp_upload/56229/56229fig3.jpg"> 
图 3.示意图绘制了可能的时间演变的钢势, 说明了腐蚀起始的标准.在1点, 从初始 "被动电平" 发生的电位下降小于 150 mV;在点 2, 一个潜在的下降, 至少 150 mV 发生, 其次是钝化;在点 3, 一个潜在的下降至少 150 mV 发生 (在最大的5天内) 和达到负电位水平持续超过10天。在tini中, 从暴露解决方案中撤回该示例。<a href="//ecsource-jove-com.remotexs.ntu.edu.sg/files/ftp_upload/56229/56229fig3large.jpg" target="_blank">请单击此处查看此图的较大版本.</a>
<img alt="Figure 4" class="xfigimg" src="/files/ftp_upload/56229/56229fig4.jpg"> 
图 4.示意图说明了在检测到腐蚀引发后混凝土试样的切割和劈裂.首先, 一条 "沟槽" 从后侧切入, 与钢筋平行。通过插入凿子或类似的工具, 沟槽可以用来分割样品, 如箭头所示。<a href="//ecsource-jove-com.remotexs.ntu.edu.sg/files/ftp_upload/56229/56229fig4large.jpg" target="_blank">请单击此处查看此图的较大版本.</a>
<img alt="Figure 5" class="xfigimg" src="/files/ftp_upload/56229/56229fig5.jpg"> 
图 5.照片说明了腐蚀开始后的样品分析。(a) 拆分后试样的两个半部分, (b) 腐蚀开始后在钢表面可见锈迹。来自不同样品的照片。<a href="//ecsource-jove-com.remotexs.ntu.edu.sg/files/ftp_upload/56229/56229fig5large.jpg" target="_blank">请单击此处查看此图的较大版本.</a>
<img alt="Figure 6" class="xfigimg" src="/files/ftp_upload/56229/56229fig6.jpg"> 
图 6.示意图说明在腐蚀引发后氯化物分析的取样: (a) 拆分混凝土芯的环氧涂层部分 (紫色 = 切割面);(b) 将混凝土保护层从钢表面移除2毫米 (紫色 = 切割平面);(c) 磨削深度间隔为 2 mm 的钢筋覆盖深度 (红色 = 取样体积)。<a href="//ecsource-jove-com.remotexs.ntu.edu.sg/files/ftp_upload/56229/56229fig6large.jpg" target="_blank">请单击此处查看此图的较大版本.</a>
<img alt="Figure 7" class="xf alt="Figure 7" class=""></img alt="Figure 7" class="xf>igimg "src ="/文件/ftp_upload/56229/56229fig7. jpg 
图 7.已测量的潜在与时间曲线的代表性示例.通常发出的潜在的下降, 随后可能会增加 (钝化), 直到稳定的腐蚀开始根据建议的标准, 最终启动。(a) 显示了在负水平上可能稳定的情况, 并且 (b) 是一个示例, 在10天的研究期间, 潜在的持续下降。<a href="//ecsource-jove-com.remotexs.ntu.edu.sg/files/ftp_upload/56229/56229fig7large.jpg" target="_blank">请单击此处查看此图的较大版本.</a>
<img alt="Figure 8" class="xfigimg" src="/files/ftp_upload/56229/56229fig8.jpg"> 
图 8.示例C暴击在瑞士阿尔卑斯山的40年以上的公路隧道中, 从一个小的混凝土区域内抽取的11样本中进行测量.<a href="//ecsource-jove-com.remotexs.ntu.edu.sg/files/ftp_upload/56229/56229fig8large.jpg" target="_blank">请单击此处查看此图的较大版本.</a>
<img alt="Figure 9" class="xfigimg" src="/files/ftp_upload/56229/56229fig9.jpg"> 
图 9.当暴露在无氯溶液中时, 有明显电位的例子会立即减少.在一个案例中, 混凝土在钢的深度已经碳化, 因此, 当水到达钢表面, 腐蚀过程立即开始, 导致急剧下降的潜力。在另一种情况下, 在一个钢筋端部发生了假腐蚀, 这导致了一个更渐进的电位下降。<a href="//ecsource-jove-com.remotexs.ntu.edu.sg/files/ftp_upload/56229/56229fig9large.jpg" target="_blank">请单击此处查看此图的较大版本.</a>

Watch this Scientific Journal Video about Experimental Protocol to Determine the Chloride Threshold Value for Corrosion in Samples Taken from Reinforced Concrete Structures at JoVE.com

Experimental Protocol to Determine the Chloride Threshold Value for Corrosion in Samples Taken from Reinforced Concrete Structures

我们提出了一种方法来测量的参数, 这是高度相关的腐蚀评估或预测钢筋混凝土结构, 主要优势, 允许测试的样品从工程结构。这确保了在钢-混凝土界面的实际条件, 这是至关重要的, 以避免实验室制造的样品的工件。

测定钢筋混凝土结构试样腐蚀的氯化物阈值的试验规程

The aging of reinforced concrete infrastructure in developed countries imposes an urgent need for methods to reliably assess the condition of these ...

experimental-protocol-to-determine-chloride-threshold-value-for

Nanyang Technological University

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Permeability of Concrete

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15.3K 次观看.  ETH Zurich. 我们提出了一种方法来测量的参数, 这是高度相关的腐蚀评估或预测钢筋混凝土结构, 主要优势, 允许测试的样品从工程结构。这确保了在钢-混凝土界面的实际条件, 这是至关重要的, 以避免实验室制造的样品的工件。

视频: Experimental Protocol to Determine the Chloride Threshold Value for Corrosion in Samples Taken from Reinforced Concrete Structures

Potentiodynamic Corrosion Testing

Different metallic materials have different polarization characteristics as dictated by the open circuit potential, breakdown potential, and passivation potential of the material. The detection of these electrochemical parameters identifies the corrosion factors of a material. A reliable and well-functioning corrosion system is required to achieve this.
Corrosion of the samples was achieved via a potentiodynamic polarization technique employing a three-electrode configuration, consisting of reference, counter, and working electrodes. Prior to commencement a baseline potential is obtained. Following the stabilization of the corrosion potential (Ecorr), the applied potential is ramped at a slow rate in the positive direction relative to the reference electrode. The working electrode was a stainless steel screw. The reference electrode was a standard Ag/AgCl. The counter electrode used was a platinum mesh. Having a reliable and well-functioning in vitro corrosion system to test biomaterials provides an in-expensive technique that allows for the systematic characterization of the material by determining the breakdown potential, to further understand the material's response to corrosion. The goal of the protocol is to set up and run an in vitro potentiodynamic corrosion system to analyze pitting corrosion for small metallic medical devices.

Here, we present a protocol to set up and run an in vitro potentiodynamic corrosion system to analyze pitting corrosion for small metallic medical devices.

动电位腐蚀试验

Different metallic materials have different polarization characteristics as dictated by the open circuit potential, breakdown potential, and passivation ...

科研

环境科学

Dynamic Electrochemical Measurement of Chloride Ions

This protocol describes the dynamic measurement of chloride ions using the transition time of a silver silver chloride (Ag/AgCl) electrode. Silver silver chloride electrode is used extensively for potentiometric measurement of chloride ions concentration in electrolyte. In this measurement, long-term and continuous monitoring is limited due to the inherent drift and the requirement of a stable reference electrode. We utilized the chronopotentiometric approach to minimize drift and avoid the use of a conventional reference electrode. A galvanostatic pulse is applied to an Ag/AgCl electrode which initiates a faradic reaction depleting the Cl&#713; ions near the electrode surface. The transition time, which is the time to completely deplete the ions near the electrode surface, is a function of the ion concentration, given by the Nernst equation. The square root of the transition time is in linear relation to the chloride ion concentration. Drift of the response over two weeks is negligible (59 &#181;M/day) when measuring 1 mM [Cl&#713;]using a current pulse of 10 Am-2. This is a dynamic measurement where the moment of transition time determines the response and thus is independent of the absolute potential. Any metal wire can be used as a pseudo-reference electrode, making this approach feasible for long-term measurement inside concrete structures.

Dynamic measurement of chloride ions is presented. Transition time of an Ag/AgCl electrode, during a chronopotentiometric technique, can give the concentration of chloride ions in electrolyte. This method does not require a stable conventional reference electrode.

氯离子的动态电化学测试

This protocol describes the dynamic measurement of chloride ions using the transition time of a silver silver chloride (Ag/AgCl) electrode. Silver silver ...

化学

Metal Corrosion and the Efficiency of Corrosion Inhibitors in Less Conductive Media

Material corrosion can be a limiting factor for different materials in many applications. Thus, it is necessary to better understand corrosion processes, prevent them and minimize the damages associated with them. One of the most important characteristics of corrosion processes is the corrosion rate. The measurement of corrosion rates is often very difficult or even impossible especially in less conductive, non-aqueous environments such as biofuels. Here, we present five different methods for the determination of corrosion rates and the efficiency of anti-corrosion protection in biofuels: (i) a static test, (ii) a dynamic test, (iii) a static test with a reflux cooler and electrochemical measurements (iv) in a two-electrode arrangement and (v) in a three-electrode arrangement. The static test is advantageous due to its low demands on material and instrumental equipment. The dynamic test allows for the testing of corrosion rates of metallic materials at more severe conditions. The static test with a reflux cooler allows for the testing in environments with higher viscosity (e.g., engine oils) at higher temperatures in the presence of oxidation or an inert atmosphere. The electrochemical measurements provide a more comprehensive view on corrosion processes. The presented cell geometries and arrangements (the two-electrode and three-electrode systems) make it possible to perform measurements in biofuel environments without base electrolytes that could have a negative impact on the results and load them with measurement errors. The presented methods make it possible to study the corrosion aggressiveness of an environment, the corrosion resistance of metallic materials, and the efficiency of corrosion inhibitors with representative and reproducible results. The results obtained using these methods can help to understand corrosion processes in more detail to minimize the damages caused by corrosion.

The testing of processes associated with material corrosion can often be difficult especially in non-aqueous environments. Here, we present different methods for short-term and long-term testing of corrosion behavior of non-aqueous environments such as biofuels, especially those containing bioethanol.

金属腐蚀与腐蚀抑制剂在低导电介质中的效率

Material corrosion can be a limiting factor for different materials in many applications. Thus, it is necessary to better understand corrosion processes, ...

Determining the Chemical Composition of Corrosion Inhibitor/Metal Interfaces with XPS: Minimizing Post Immersion Oxidation

An approach for acquiring more reliable X-ray photoelectron spectroscopy data from corrosion inhibitor/metal interfaces is described. More specifically, the focus is on metallic substrates immersed in acidic solutions containing organic corrosion inhibitors, as these systems can be particularly sensitive to oxidation following removal from solution. To minimize the likelihood of such degradation, samples are removed from solution within a glove box purged with inert gas, either N2 or Ar. The glove box is directly attached to the load-lock of the ultra-high vacuum X-ray photoelectron spectroscopy instrument, avoiding any exposure to the ambient laboratory atmosphere, and thus reducing the possibility of post immersion substrate oxidation. On this basis, one can be more certain that the X-ray photoelectron spectroscopy features observed are likely to be representative of the in situ submerged scenario, e.g. the oxidation state of the metal is not modified.

A protocol to avoid the oxidation of metallic substrates during sample transfer from an inhibited acidic solution to an X-ray photoelectron spectrometer is presented.

确定缓蚀剂/金属界面的化学成分与XPS:最小化后浸入氧化

An approach for acquiring more reliable X-ray photoelectron spectroscopy data from corrosion inhibitor/metal interfaces is described. More specifically, ...

Detecting the Water-soluble Chloride Distribution of Cement Paste in a High-precision Way

To improve the accuracy of the chloride distribution along the depth of cement paste under cyclic wet-dry conditions, a new method is proposed to obtain a high-precision chloride profile. Firstly, paste specimens are molded, cured, and exposed to cyclic wet-dry conditions. Then, powder samples at different specimen depths are grinded when the exposure age is reached. Finally, the water-soluble chloride content is detected using a silver nitrate titration method, and chloride profiles are plotted. The key to improving the accuracy of the chloride distribution along the depth is to exclude the error in the powderization, which is the most critical step for testing the distribution of chloride. Based on the above concept, the grinding method in this protocol can be used to grind powder samples automatically layer by layer from the surface inward, and it should be noted that a very thin grinding thickness (less than 0.5 mm) with a minimum error less than 0.04 mm can be obtained. The chloride profile obtained by this method better reflects the chloride distribution in specimens, which helps researchers to capture the distribution features that are often overlooked. Furthermore, this method can be applied to studies in the field of cement-based materials, which require high chloride distribution accuracy.

A protocol for obtaining a water-soluble chloride profile by using a high precision milling method is presented.

高精度水泥浆水溶氯分布的检测

To improve the accuracy of the chloride distribution along the depth of cement paste under cyclic wet-dry conditions, a new method is proposed to obtain a ...

工程学

Applicability Analysis of Assessment Methods for Morphological Parameters of Corroded Steel Bars

The irregular and uneven residual sections along the length of a corroded steel bar substantially change its mechanical properties and significantly dominate the safety and performance of an existing concrete structure. As a result, it is important to measure the geometry and amount of corrosion of a steel bar in a structure properly to assess the residual bearing capacity and service life of the structure. This paper introduces and compares five different methods for measuring the geometry and amount of corrosion of a steel bar. A single 500 mm long and 14 mm diameter steel bar is the specimen that is subjected to accelerated corrosion in this protocol. Its morphology and the amount of corrosion were carefully measured before and after using mass loss measurements, a Vernier caliper, drainage measurements, 3D scanning, and X-ray micro-computed tomography (XCT). The applicability and suitability of these different methods were then evaluated. The results show that the Vernier caliper is the best choice for measuring the morphology of a non-corroded bar, while 3D scanning is the most suitable for quantifying the morphology of a corroded bar.

This paper measures the geometry and the amount of corrosion of a steel bar using different methods: mass loss, calipers, drainage measurements, 3D scanning, and X-ray micro-computed tomography (XCT).

钢筋形态参数评价方法的适用性分析

The irregular and uneven residual sections along the length of a corroded steel bar substantially change its mechanical properties and significantly ...

Determining Tribocorrosion Rate and Wear-Corrosion Synergy of Bulk and Thin Film Aluminum Alloys

The increasing complexity and severity of service conditions in areas, such as aerospace and marine industries, nuclear systems, microelectronics, batteries, and biomedical devices, etc., impose great challenges on the reliable performance of alloys exposed to extreme conditions where mechanical and electrochemical attack co-exist. Finding ways for alloys to mitigate the combined attack of wear and corrosion (i.e., tribocorrosion) under such extreme conditions is thus highly critical for improving their reliability and service lifetime when used in such conditions. The challenge lies in the fact that wear and corrosion are not independent of each other, but rather work synergistically to accelerate the total material loss. Thus, a reliable method to evaluate the tribocorrosion resistance of metals and alloys is needed. Here, a protocol for measuring the tribocorrosion rate and wear-corrosion synergy of Al-based bulk and thin film samples in a corrosive environment under room temperature is presented.

Here, we present a protocol to measure the tribocorrosion rate and wear-corrosion synergy of thin film and bulk Al alloys in simulated sea water at room temperature.

Tribocorrosion 和薄膜铝合金的磨损与腐蚀协同性测定

The increasing complexity and severity of service conditions in areas, such as aerospace and marine industries, nuclear systems, microelectronics, ...

Tests on Fresh Concrete

Source:&#160;Roberto Leon, Department of Civil and Environmental Engineering, Virginia Tech, Blacksburg, VA
Concrete consists of two phases, a cement paste phase comprised of cement, water, and air, and an aggregate phase comprised of coarse and fine aggregates. There are two key considerations when designing a concrete mix. First, the concrete must be workable and easy to cast in the forms in its fresh condition, even when the forms are packed with steel reinforcement. In this condition, it is the rheology of concrete that is important. Second, the mix must produce a hardened concrete of specified strength at 28 days (or similar specified time) that is durable and provides good serviceability.
In this laboratory exercise, a method of concrete mixture proportioning, named the trial batch method, will be explored. The concrete produced will be used in conducting typical tests to determine the principal characteristics of fresh concrete, including slump, flowability, air content, and density. The trial batch method is a simple, empirical approach to mixture design.
The objectives of this experiment are fourfold: (1) to use the trial batch mix method to determine optimum proportions of aggregates, cement, and water for concrete to meet specified slump requirements, (2) to learn concrete mixing practice in a laboratory environment, (3) to observe the characteristic properties of fresh concrete, and (4) to prepare 4&#34;x8&#34; concrete cylinders for subsequent evaluation.

Testing Fresh Concrete by the Trial Batch Method

新鲜混凝土试验

Source:&#160;Roberto Leon, Department of Civil and Environmental Engineering, Virginia Tech, Blacksburg, VA
Concrete consists of two phases, a cement ...

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结构工程

Tests of Hardened Concrete in Tension

Source:&#160;Roberto Leon, Department of Civil and Environmental Engineering, Virginia Tech, Blacksburg, VA
In a previous laboratory focused on concrete in compression, we observed that concrete can withstand very large stresses under uniaxial compressive forces. However, the failures observed were not compressive failures but failures along shear planes where maximum tensile forces occur. Thus, it is important to understand the behavior of concrete in tension and particularly its maximum strength as that will govern both its ultimate and service behavior. From the ultimate standpoint, combinations of tension and shear stresses will lead to cracking and immediate and catastrophic failure. For that reason, concrete is seldom if ever used in an unreinforced condition in structural applications; most concrete members will be reinforced with steel so that these cracks can be stopped and the crack widths limited. The latter is important from the serviceability standpoint because controlling crack widths and distribution is the key to durability, as this will impede deicing salts and similar chemicals from penetrating and corroding the reinforcing steel.
The objectives of this experiment are threefold: (1) to conduct tensile split cylinder tests to determine concrete tensile strength, (2) to conduct beam tests to determine concrete tensile strength, and (3) to demonstrate the influence of steel reinforcement on behavior by comparing the behavior of lightly reinforced beam with an unreinforced one.

Split Tension Test and Beam Tension Test for Hardened Concrete

硬化混凝土的拉伸试验

Source:&#160;Roberto Leon, Department of Civil and Environmental Engineering, Virginia Tech, Blacksburg, VA
In a previous laboratory focused on concrete ...

Corrosion of Reinforcement

The corrosion of steel reinforcement within concrete is a process influenced by the material&#39;s inherent properties and external factors. The high pH level of around 13, provided by calcium hydroxide present in concrete, initially protects the steel reinforcement by promoting the formation of a passive iron oxide layer on its surface.
However, over time and under certain conditions like carbonation, chloride ingress, and cracking this protective state can be compromised. Steel has areas with different electrochemical potentials, known as anodic and cathodic regions. The hydrated cement paste, containing salts, acts as an electrolyte that connects these regions. At the anodic regions, iron from the steel dissolves as positively charged ions into the electrolyte, while at the cathodic regions, electrons are consumed in reactions that involve water and oxygen from the surrounding concrete to produce hydroxyl ions.
These hydroxyl ions combine with the dissolved iron to create ferric hydroxide, which further oxidizes to become rust. The presence of chloride ions exacerbates this process, leading to localized pitting corrosion by forming hydrochloric acid that attacks the protective iron oxide layer. This corrosion can expand the steel, causing the concrete to crack and spall.
Preventative measures against the corrosion of steel reinforcement include using protective coatings such as epoxy or zinc on the steel itself or improving the concrete&#39;s quality to reduce its permeability, thereby hindering the ingress of corrosive agents.

钢筋腐蚀

Inside a concrete mass, high alkalinity of calcium hydroxide with a pH of around 13 shields steel reinforcement from corrosion by creating a protective ...