Name: detecting the water-soluble chloride distribution of cement paste in a high-precision way
Uploaded: 2017-11-21T13:00:00.000+00:00
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Description: Watch this Scientific Journal Video about Detecting the Water-soluble Chloride Distribution of Cement Paste in a High-precision Way at JoVE.com

作者赞赏中国国家基础研究项目 (973 项目) 在合同 No. 2015CB655105、自然科学基金合同 No. 51308262、江苏省自然科学基金的资助下根据合同 No。BK20131012

注意: 在测试过程中使用的几种化学物质, 如硝酸银、铬酸钾和浓硫酸, 都具有剧毒和腐蚀性。使用时请采取适当的安全措施, 包括安全眼镜、手套、实验室大衣、等的佩戴。
1. 膏体试样的制备
<ol><li>
模具的制备
	<ol>
<li>使用刷子清理模具尺寸 70 mm x 70 mm x 70 mm, 确保模具的内表面无杂质。</li>
		<li>用另一笔刷子在模具的内表面上均匀地刷脱模柴油。</li>
	</ol>
</li>
	<li>
成型膏样
	<ol>
<li>使用电子天平将1000克水称量成1500毫升塑料杯和2000克水泥, 放入3000毫升的塑料盆中。</li>
		<li>依次将1000克水和2000克水泥加入 5 L 混合罐中。水的水灰比是0.5。</li>
		<li>把搅拌锅放在水泥浆搅拌机的底座上, 将其调到搅拌位置后再固定。</li>
		<li>混合在 65 rpm 九十年代。</li>
		<li>让混合物坐三十年代。在此期间, 用刮刀将锅内壁上的浆糊刮掉, 并将其混入锅中的其余部分。混合在 130 rpm 六十年代。</li>
		<li>从搅拌机中取出混合罐。将混合的水泥糊倒入模具中。用刮刀将水泥浆铲起, 振动模具几秒钟, 将膏体压紧在振动台上。</li>
		<li>填充模具后, 用保鲜膜密封模具表面, 防止水份蒸发。在23±2° c 的成型中, 让 24 h 坐。</li>
	</ol>
</li>
	<li>
固化
	<ol>
<li>从模具中取出硬化的粘贴试样。</li>
		<li>将硬化膏样放置在23±2° c 和95% 相对湿度为 60 d 的固化室中。</li>
	</ol>
</li>
	<li>
切割
	<ol>
<li>60 d 后从固化室取出标本。</li>
		<li>将试样固定在高精度切割机上, 从无模表面切割20毫米。经过处理的尺寸为70毫米 x 70 mm x 50 mm 的试样将会在事后受到氯 ingression 的照射。</li>
	</ol>
</li>
	<li>
环氧树脂密封
	<ol>
<li>以切口表面作为曝光表面, 用刷子密封其他五表面 (70 毫米 x 70 毫米 x 50 毫米) 与环氧树脂。每个标本的环氧树脂用量约30毫升。通过空气接触硬化环氧树脂24小时。 注: 在环氧树脂硬化后, 准备用于氯 ingression 暴露的试样。</li>
	</ol>
</li>
</ol>2. 循环润湿和干燥
<ol><li>将0.35 公斤的盐和9.65 公斤的去离子水添加到一个15升的塑料桶中, 盐解决方案的质量比为 3.5%. </li>
	<li>当曝光面朝下时, 将试样放在塑料盒中 (50 厘米 x 30 cm x 20 厘米), 在底部放置两个大括号。支架可以是不锈钢钢筋或塑料网格板。大括号的存在使曝光表面需要大约1.0 厘米的空间的底部的框。</li>
	<li>将3.5% 盐溶液慢慢倒入塑料盒中, 当液面在曝光表面上方约1.0 厘米时停止. 用塑料薄膜封箱 (约0.25 毫米厚度), 以防止蒸发引起的浓度变化。然后, 把塑料盒放在一个室温为23±2° c 和湿度65±2% 的房间里。</li>
	<li>从浇注氯化钠溶液的时间开始, 浸泡试样24小时用于润湿过程。</li>
	<li>在润湿 24 h 后取出溶液中的标本, 轻轻地用毛巾擦拭残留溶液, 并将其放在相同的恒温恒湿室中 6 d, 这是干燥过程。</li>
	<li>干燥 6 d 后, 再将标本放回盐溶液中。</li>
	<li>重复步骤2.5 和 2.6 (7 d 为一个润湿干燥周期) 总共12周期。</li>
</ol>3. 研磨粉样品
<ol><li>经过12干湿循环, 在高精度计算机数控 (CNC) 磨床的基础上, 将原刀具与钛合金刀具进行更换, 从铣床上进行改造。</li>
	<li>在开始研磨前, 将粉体纸放在研磨机底座的试样周围。</li>
	<li>启动高精度数控磨床, 等待系统加载。</li>
	<li>按下 "零" 按钮和随后的 "X→0"、"Y→0"、"Z→0" 按钮, 使操作台和铣刀自动返回到坐标原点。</li>
	<li>按 "手动数据输入 (MDI)", 双击 "程序", 输入 "N3S1000", 然后点击 "输入", 然后按 "循环启动" 来启动主轴。请注意, "N3S1000" 指的是轴的旋转速度是设置在 1000 rpm。</li>
	<li>加载主磨削程序: 按 "MDI", 点击 "程序" 反复查找 "程序 (目录)" 页面, 并选择相应的程序。接下来, 单击 "编辑", 然后按 "输入" 来加载主程序。 注: 主程序可根据具体磨削要求进行个性化, 包括总磨削深度、层数、每层厚度、研磨两层之间的时间间隔等设置。该协议的总磨削深度为10毫米, 层数为 20;每层的磨削厚度为0.5 毫米;研磨层间的时间间隔为六十年代。查看有关程序细节的信息。</li>
	<li>设置铣刀位置: 首先, 单击 "手动操作", 然后 "主轴前进" 以旋转主轴。接下来, 单击 "手轮", 并手动将刀具调整到 ready-to-grind 位置 (通常在试样前左表面的三分之一处)。最后, 依次单击 "设置" 和 "X"、"输入"、"Y"、"输入"、"Z" 和 "输入" 按钮。将相对坐标记录为 "完成刀具设置" 的原始空间坐标。</li>
	<li>启动主磨削程序: 按 "开始", 然后单击 "自动" 和 "循环启动" 按钮随后。机器开始自动研磨为预编程。 注: 在研磨过程中, 在机器底座 pre-spread 的收集纸上会堆积粉末。研磨后的每一个层, 铣刀将上升远离标本和保持静止在 X, Y, Z 方向为六十年代的编程。在六十年代的休息期间收集粉末样品, 并 re-spread 收集的纸张。 注意: 虽然铣刀在 X、Y、Z 方向上停止移动, 但仍在旋转。应注意避免接触铣刀与任何身体部位, 以避免伤害。此外, 由于磨削过程中产生的粉尘, 需要使用口罩和手套。</li>
	<li>完成研磨后关闭机器。</li>
</ol>4. 检测氯化物含量7
<ol><li>
溶液的制备
	<ol>
<li>
铬酸钾溶液
		<ol>
<li>在20毫升去离子水中溶解5克铬酸钾。加入10毫克硝酸银。摇匀, 让我们坐24小时。 注意: 铬酸钾和硝酸银是有毒的。使用时必须戴上橡皮手套和口罩。</li>
			<li>将溶液过滤成漏斗和滤纸的圆锥烧瓶, 并将其移动到100毫升的容积烧瓶中。添加去离子水, 直到达到100毫升校准标记。得到了5% 浓度的铬酸钾指示剂。</li>
		</ol>
</li>
		<li>准备0.5% 酚酞溶液: 在75毫升的乙醇中溶解0.5 克酚酞。加入25毫升去离子水, 摇匀。</li>
		<li>制备稀硫酸: 将5毫升浓硫酸 (98.3%) 溶于100毫升的去离子水中。 注意: 浓硫酸具有很强的腐蚀性。使用时必须戴上橡皮手套、口罩和护目镜。</li>
		<li>
盐标准解决方案
		<ol>
<li>加热约2克的纯氯化钠在 200-300 ° c 以下的坩埚与电炉, 并搅拌与玻璃棒在过程中, 直到有没有盐开裂的声音 (缺乏水)。</li>
			<li>在干燥冷却后, 采取1.169 克盐晶体, 溶解在1000毫升的体积烧瓶与100毫升去离子水。添加去离子水, 直到达到1000毫升校准标记。得到了 0.02 M 的氯化钠标准溶液。用以下公式计算氯化钠标准溶液的浓度: <img alt="Equation 1" src="/files/ftp_upload/56268/56268eq1.jpg"> 其中, C氯化钠是氯化钠溶液的标准浓度, 摩尔/L;V是解决方案的体积, L;M是氯化钠的摩尔质量, 58.45 克/摩尔;m是氯化钠的质量, g。</li>
		</ol>
</li>
		<li>
硝酸银溶液
		<ol>
<li>在100毫升去离子水中溶解1.7 克硝酸银, 200 毫升断路器。移动到一个1000毫升棕色体积烧瓶和添加去离子水高达1000毫升校准标记。</li>
			<li>吸管三10毫升 (V1) 单位的0.02 米标准盐溶液成三圆锥烧瓶。加入10滴铬酸钾指示剂, 每个用滴管。</li>
			<li>滴定从台阶4.1.5.2 与制备的银硝化4.1.5.1。当溶液变红时停止, 红色不会褪色。记录消耗的银硝化溶液的体积 (V2)。用下面的公式计算出银硝化溶液的标准浓度, 并取三测试结果的平均值。 <img alt="Equation 2" src="/files/ftp_upload/56268/56268eq2.jpg"> 其中, CAgNO3 是硝酸银溶液的浓度, 摩尔/L;V1 是氯化钠溶液的体积, 10 毫升;V2 是所消耗的硝酸银溶液的体积, mL。</li>
		</ol>
</li>
	</ol>
</li>
	<li>
水溶性氯化物含量
	<ol>
<li>将3节中获得的每一个样品磨碎, 直到可以通过80µm 筛筛分。在105° c 的烤箱中加热和烘干2小时的过滤样品。</li>
		<li>取2克的每一个干样品, 把它们放在100毫升塑料瓶, 添加50毫升 (V3) 的去离子水与50毫升测量吸管, 并密封瓶的瓶盖。剧烈摇动瓶子, 以保证样品和去离子水混合。</li>
		<li>将塑料瓶固定在自动振动器上, 并振动24小时, 以从样品中溶解水溶性氯化物。</li>
		<li>用漏斗和滤纸在振动24小时后用瓶子过滤溶液。吸管的两个10毫升 (V4) 单位的过滤溶液从每个瓶子变成两个圆锥烧瓶。</li>
		<li>在每个圆锥烧瓶中加入两滴酚酞溶液, 使溶液呈现紫红色。用稀硫酸中和溶液为无色。</li>
		<li>在无色溶液中加入10滴铬酸钾指示剂, 立即用硝酸银溶液滴定。在滴定期间, 手动摇动圆锥烧瓶, 以确保氯离子与硝酸银反应迅速而彻底。当溶液变红时停止滴定, 红颜色不会褪色。记录消耗的硝酸银溶液的体积 (V5)。</li>
		<li>用下面的公式计算水溶性氯化物的含量, 取两个试验结果的平均值。 <img alt="Equation 3" src="/files/ftp_upload/56268/56268eq3.jpg"> 其中, Cw是在糊样中水溶性氯化物的含量,% 水泥;ms 是粉末样本的质量, 2 克;V3 是用于溶解样品的去离子水的体积, 50 毫升;V4 是在每次硝化时提取的过滤溶液的体积, 10 毫升;V5 是每个硝化时所消耗的硝酸银溶液的体积;Mcl 是 cl 的摩尔质量, 35.5 克/摩尔。</li>
		<li>在不同深度的膏样中获得氯含量后, 绘制水溶性氯化物剖面图。</li>
	</ol>
</li>
</ol>5. 磨削厚度精度试验
<ol><li>设置五研磨厚度: 1.0 毫米, 0.5 毫米, 0.2 毫米, 0.1 毫米, 和0.05 毫米的主要研磨程序。每厚度研磨五次。</li>
	<li>在磨削(h1)和研磨(h2) 后, 用游标卡尺测量试样的厚度, 并用下面的公式计算实际磨削厚度。在测量过程中不要从机器上取标本, 以保证测量的可靠性。 <img alt="Equation 4" src="/files/ftp_upload/56268/56268eq4.jpg"> 其中, P 是实际磨削厚度, mm;H1 是在研磨前试样的厚度, mm;H2 是磨削后试样的厚度, mm。</li>
</ol>

<ol>
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作者没有什么可透露的。

高精度数控铣床的磨削误差控制在 0.04 mm 以内, 标准偏差小于 0.03 mm (表 1)8。结果表明, 该铣削方法在氯化物含量的测量中具有很高的精度和稳定性, 是一种深度函数, 有助于更好地说明试样中的实际氯化物分布情况。
当测试间隔为 0.5 mm 时, 随着曝光表面的深度增加, 氯化物含量 (图 1) 中有一个最大点。当测试间隔为 2.0 mm 时...

氯离子对钢筋的腐蚀是破坏受攻击环境 (e. g、海洋环境或除冰盐环境) 的钢筋混凝土结构使用寿命的主要原因之一。氯离子分布可用于对氯离子渗透率、钢腐蚀量和寿命预测的研究。因此, 精确的氯离子分布对混凝土结构耐久性研究具有重要意义。
multi-mechanisms 的机制或联合行动负责在具体环境下的氯离子运输1。在海洋结构的淹没部分, 纯扩散是推动氯离子侵入的唯一机制2, 导致氯含量随深度的增加而降低。混凝土是在一个饱和状态3当受到湿润干燥环境, 如海洋潮汐带或冰盐环境。在这种情况下, 氯离子的侵入过程变得非常复杂, 扩散和毛细管吸力都在氯化物运输中操作4。因此, 在湿润干燥条件下, 氯化物的分布可能比淹没条件下的更复杂。因此, 在循环湿润干燥条件下, 氯化物的分布需要更精确地研究。
在水泥基材料中氯化物的分布通常由氯化物剖面来表示。氯化物剖面的准确度主要取决于两个方面: 氯化物含量的准确度和沿深度氯分布的准确度。关于氯化物含量测试, 基本原理是基于 (Cl-) 和 (Ag+)5、6之间的化学反应, 但不同的标准需要不同的特定操作。只要遵循特定的操作, 就可以获得确切的氯化物含量。但是, 氯离子沿深度分布的准确度主要取决于取样位置的准确度。在试样的不同深度获得动力样品的方法是电钻、普通磨床和型材磨床。不幸的是, 当磨削厚度或取样间隔很小时, 它们都有一个缺点, 即精度较低。因此, 在循环湿润干燥条件下, 对试样表层的氯离子分布进行研究的要求是不符合的。因此, 需要一个新的方法来允许较小的采样间隔 (例如, 小于 0.5 mm) 并将错误减少到最小 (例如, 小于 0.05 mm)。
这里的详细的协议提供了一个更准确的方法, 以获得一个氯化物剖面, 提高精度的氯分布沿深度。

<table><tbody><tr><td>Cement</td><td>Jiangnan Xiaoyetian</td><td>P.II. 52.5</td><td></td></tr><tr><td>Potassium chromate, 99.7%</td><td>Tianjin Kemiou</td><td>HG391887</td><td>Toxic</td></tr><tr><td>Ethyl alcohol</td><td>Sinopharm</td><td>XK10009257</td><td></td></tr><tr><td>Silver nitrate, 99.8%</td><td>Sinopharm</td><td>7761888</td><td>Toxic</td></tr><tr><td>Phenolphthalein, 99.5%</td><td>Tianjin Fuchen</td><td>XK1301100017</td><td></td></tr><tr><td>Concentrated sulfuric acid, 98.3%</td><td>Shanghai Lingfeng</td><td>XK1301100085008</td><td>Highly corrosive</td></tr><tr><td>Sodium chloride, 99.7%</td><td>Xilong Scientific</td><td>XK1320100153</td><td></td></tr><tr><td>Diesel oil</td><td>China Petroleum</td><td>0#</td><td></td></tr><tr><td>Epoxy resin</td><td>Yifeng Chemical</td><td>E44-6101</td><td></td></tr><tr><td>Deionized water</td><td>Beijing Liyuan</td><td>PUW-10N</td><td></td></tr><tr><td>CNC Milling meachine</td><td>Foshan Xiandao Digital Technology</td><td>C31E</td><td></td></tr><tr><td>Cement paste mixer</td><td>Wuxi Construction and Engineering</td><td>NJ160</td><td></td></tr><tr><td>High precision cutting machine</td><td>Buehler</td><td>2215</td><td></td></tr><tr><td>Mixing spot</td><td>Wuxi Construction and Engineering</td><td>JJ-5</td><td></td></tr><tr><td>Scraper knife</td><td>Jinzheng Building Materials</td><td>CD-3</td><td></td></tr><tr><td>Cling film</td><td>Miao Jie</td><td>65300</td><td></td></tr><tr><td>Mold (70mm&amp;times;70mm&amp;times;70mm)</td><td>Jingluda</td><td>ABS707</td><td></td></tr><tr><td>Plastic box</td><td>Fangao Household</td><td>32797</td><td></td></tr><tr><td>Stainless steel brace</td><td>An Feng</td><td>316L</td><td></td></tr><tr><td>Paper</td><td>Deli</td><td>A4</td><td></td></tr><tr><td>Oven</td><td>Shanghai Huatai</td><td>DHG-9070A</td><td></td></tr><tr><td>Automatic vibrator</td><td>Lichen</td><td>HY-4</td><td></td></tr><tr><td>Vibrating table</td><td>Jianyi</td><td>GZ-75</td><td></td></tr><tr><td>plastic film</td><td>Miao Jie</td><td>65303</td><td></td></tr><tr><td>Vernier caliper</td><td>Links</td><td>601-01</td><td></td></tr><tr><td>Electronic balance</td><td>Setra</td><td>BL-4100F</td><td></td></tr><tr><td>Plastic bottle</td><td>Lining Plastic</td><td>454</td><td></td></tr><tr><td>Brush</td><td>Huoniu</td><td>3#</td><td></td></tr><tr><td>Mask</td><td>UVEX</td><td>3220</td><td></td></tr><tr><td>Gloves</td><td>Ammex</td><td>TLFGWC</td><td></td></tr><tr><td>Plastic cup</td><td>Maineng</td><td>MN4613</td><td></td></tr><tr><td>Desiccator</td><td>Shenfei</td><td>GZ300</td><td></td></tr><tr><td>Filter paper</td><td>Hangzhou Wohua</td><td>9614051</td><td></td></tr><tr><td>Dropper</td><td>Huaou</td><td>1630</td><td></td></tr><tr><td>Breaker</td><td>Huaou</td><td>1101</td><td></td></tr><tr><td>Funnel</td><td>Huaou</td><td>1504</td><td></td></tr><tr><td>Measuring cylinder</td><td>Huaou</td><td>1601</td><td></td></tr><tr><td>volumetric flash</td><td>Huaou</td><td>1621</td><td></td></tr><tr><td>Conical flash</td><td>Huaou</td><td>1121</td><td></td></tr><tr><td>Pipette</td><td>Huaou</td><td>1633</td><td></td></tr><tr><td>Burette</td><td>Huaou</td><td>1462</td><td></td></tr><tr><td>Mortar</td><td>Huaou</td><td>YBMM254</td><td></td></tr><tr><td>80&amp;micro;m sieve</td><td>Shanghai Dongxing</td><td>KJ-80</td><td></td></tr><tr><td>Crucible</td><td>Oamay</td><td>GYGG</td><td></td></tr><tr><td>Electric furnace</td><td>Tyler</td><td>SX-B06</td><td></td></tr></tbody></table>

detecting the water-soluble chloride distribution of cement paste in a high-precision way

为了提高水泥浆在循环干湿条件下的氯离子分布的准确度, 提出了一种高精度氯化物剖面的新方法。首先, 粘贴试样成型, 固化, 并暴露在循环湿干燥条件。然后, 在接触年龄达到时, 研磨不同试样深度的粉末样品。最后, 用硝酸银滴定法测定了水溶性氯化物的含量, 并绘制了氯化物剖面图。提高氯离子沿深度分布精度的关键是排除 powderization 中的误差, 这是检验氯化物分布的最关键步骤。基于上述概念, 本协议中的磨削方法可用于研磨粉末样品, 从表面自动分层, 并应注意到极薄的磨削厚度 (小于 0.5 mm), 最小误差小于 0.04 mm获得。通过这种方法获得的氯化物剖面更好地反映了试样中的氯化物分布, 这有助于研究人员捕捉经常被忽略的分布特征。此外, 该方法还可用于水泥基材料领域的研究, 要求高的氯化物分布精度。

收集了有关磨削厚度精度的原始数据和统计结果 (表 1)8。平均值和误差用于反映精度和标准偏差 (SD) 用于反映此方法的一致性。
使用下面的公式收集测试间隔 0.5 mm (图 1) 和 2.0 mm (图 2) 和相应的扩散系数D的水溶性氯化物, 称为菲克第二定?...

Watch this Scientific Journal Video about Detecting the Water-soluble Chloride Distribution of Cement Paste in a High-precision Way at JoVE.com

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

提出了一种利用高精度铣削法获得水溶性氯化物剖面的协议。

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 ...

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Unit 1

Introduction to Concrete

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9.5K 次观看.  Southeast University. 提出了一种利用高精度铣削法获得水溶性氯化物剖面的协议。

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

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 ...

科研

化学

Measurement of Ion Concentration in the Unstirred Boundary Layer with Open Patch-Clamp Pipette: Implications in Control of Ion Channels by Fluid Flow

Fluid flow is an important environmental stimulus that controls many physiological and pathological processes, such as fluid flow-induced vasodilation. Although the molecular mechanisms for the biological responses to fluid flow/shear force are not fully understood, fluid flow-mediated regulation of ion channel gating may contribute critically. Therefore, fluid flow/shear force sensitivity of ion channels has been studied using the patch-clamp technique. However, depending on the experimental protocol, the outcomes and interpretation of data can be erroneous. Here, we present experimental and theoretical evidence for fluid flow-related errors and provide methods for estimating, preventing, and correcting these errors. Changes in junction potential between the Ag/AgCl reference electrode and bathing fluid were measured with an open pipette filled with 3 M KCl. Fluid flow could then shift the liquid/metal junction potential to approximately 7 mV. Conversely, by measuring the voltage shift induced by fluid flow, we estimated the ion concentration in the unstirred boundary layer. In the static condition, the real ion concentrations adjacent to the Ag/AgCl reference electrode or ion channel inlet at the cell-membrane surface can reach as low as approximately 30% of that in the flow condition. Placing an agarose 3 M KCl bridge between the bathing fluid and reference electrode may have prevented this problem of junction potential shifting. However, the unstirred layer effect adjacent to the cell membrane surface could not be fixed in this way. Here, we provide a method for measuring real ion concentrations in the unstirred boundary layer with an open patch-clamp pipette, emphasizing the importance of using an agarose salt-bridge while studying fluid flow-induced regulation of ion currents. Therefore, this novel approach, which takes into consideration the real concentrations of ions in the unstirred boundary layer, may provide useful insight on the experimental design and data interpretation related to fluid shear stress regulation of ion channels.

Mechanosensitive ion channels are often studied in terms of fluid flow/shear force sensitivity with patch-clamp recording. However, depending on the experimental protocol, the outcome on fluid flow-regulations of ion channels can be erroneous. Here, we provide methods for preventing and correcting such errors with a theoretical basis.

开放补丁夹具移液器测量未搅拌边界层中的离子浓度: 流体流动对离子通道控制的启示

Fluid flow is an important environmental stimulus that controls many physiological and pathological processes, such as fluid flow-induced vasodilation. ...

生物化学

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

The aging of reinforced concrete infrastructure in developed countries imposes an urgent need for methods to reliably assess the condition of these structures. Corrosion of the embedded reinforcing steel is the most frequent cause for degradation. While it is well known that the ability of a structure to withstand corrosion depends strongly on factors such as the materials used or the age, it is common practice to rely on threshold values stipulated in standards or textbooks. These threshold values for corrosion initiation (Ccrit) are independent of the actual properties of a certain structure, which clearly limits the accuracy of condition assessments and service life predictions. The practice of using tabulated values can be traced to the lack of reliable methods to determine Ccrit on-site and in the laboratory.
Here, an experimental protocol to determine Ccrit for individual engineering structures or structural members is presented. A number of reinforced concrete samples are taken from structures and laboratory corrosion testing is performed. The main advantage of this method is that it ensures real conditions concerning parameters that are well known to greatly influence Ccrit, such as the steel-concrete interface, which cannot be representatively mimicked in laboratory-produced samples. At the same time, the accelerated corrosion test in the laboratory permits the reliable determination of Ccrit prior to corrosion initiation on the tested structure; this is a major advantage over all common condition assessment methods that only permit estimating the conditions for corrosion after initiation, i.e., when the structure is already damaged.
The protocol yields the statistical distribution of Ccrit for the tested structure. This serves as a basis for probabilistic prediction models for the remaining time to corrosion, which is needed for maintenance planning. This method can potentially be used in material testing of civil infrastructures, similar to established methods used for mechanical testing.

We propose a method to measure a parameter that is highly relevant for corrosion assessments or predictions of reinforced concrete structures, with the main advantage of permitting testing of samples from engineering structures. This ensures real conditions at the steel-concrete interface, which are crucial to avoid artifacts of laboratory-made samples.

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 ...

工程学

Expression of Cementitious Pore Solution and the Analysis of Its Chemical Composition and Resistivity Using X-ray Fluorescence

The goal of this method is to determine the chemical composition and electrical resistivity of cementitious pore solution expressed from a fresh paste sample. The pore solution is expressed from a fresh paste sample using a pressurized nitrogen gas system. The pore solution is then immediately transferred to a syringe to minimize evaporation and carbonation. After that, assembled testing containers are used for the X-ray fluorescence (XRF) measurement. These containers consist of two concentric plastic cylinders and a polypropylene film which seals one of the two open sides. The pore solution is added into the container immediately prior to the XRF measurement. The XRF is calibrated to detect the main ionic species in the pore solution, in particular, sodium (Na+), potassium (K+), calcium (Ca2+), and sulfide (S2-), to calculate sulfate (SO42-) using stoichiometry. The hydroxides (OH-) can be calculated from a charge balance. To calculate the electrical resistivity of the solution, the concentrations of the main ionic species and a model by Snyder et al. are used. The electrical resistivity of the pore solution can be used, along with the electrical resistivity of concrete, to determine the formation factor of concrete. XRF is a potential alternative to current methods to determine the composition of pore solution, which can provide benefits in terms of reduction in time and costs.

This protocol describes the procedure to express fresh pore solution from cementitious systems and the measurement of its ionic composition using X-ray fluorescence. The ionic composition can be used to calculate pore solution electrical resistivity, which can be used, together with concrete electrical resistivity, to determine the formation factor.

胶孔溶液的表达及其化学成分和电阻率的 X 射线荧光分析

The goal of this method is to determine the chemical composition and electrical resistivity of cementitious pore solution expressed from a fresh paste ...

Fabrication of a Dipole-assisted Solid Phase Extraction Microchip for Trace Metal Analysis in Water Samples

This paper describes a fabrication protocol for a dipole-assisted solid phase extraction (SPE) microchip available for trace metal analysis in water samples. A brief overview of the evolution of chip-based SPE techniques is provided. This is followed by an introduction to specific polymeric materials and their role in SPE. To develop an innovative dipole-assisted SPE technique, a chlorine (Cl)-containing SPE functionality was implanted into a poly(methyl methacrylate) (PMMA) microchip. Herein, diverse analytical techniques including contact angle analysis, Raman spectroscopic analysis, and laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS) analysis were employed to validate the utility of the implantation protocol of the C-Cl moieties on the PMMA. The analytical results of the X-ray absorption near-edge structure (XANES) analysis also demonstrated the feasibility of the Cl-containing PMMA used as an extraction medium by virtue of the dipole-ion interactions between the highly electronegative C-Cl moieties and the positively charged metal ions.

The fabrication protocol of a dipole-assisted solid phase extraction microchip for the trace metal analysis is presented.

水样中偶极辅助固相萃取Microchip的痕量金属分析的制作

This paper describes a fabrication protocol for a dipole-assisted solid phase extraction (SPE) microchip available for trace metal analysis in water ...

生物工程

Quantification of Metal Leaching in Immobilized Metal Affinity Chromatography

Contamination of enzymes with metals leached from immobilized metal affinity chromatography (IMAC) columns poses a major concern for enzymologists, as many of the common di-and trivalent cations used in IMAC resins have an inhibitory effect on enzymes. However, the extent of metal leaching and the impact of various eluting and reducing reagents are poorly understood in large part due to the absence of simple and practical transition metal quantification protocols that use equipment typically available in biochemistry labs. To address this problem, we have developed a protocol to quickly quantify the amount of metal contamination in samples prepared using IMAC as a purification step. The method uses hydroxynaphthol blue (HNB) as a colorimetric indicator for metal cation content in a sample solution and UV-Vis spectroscopy as a means to quantify the amount of metal present, into the nanomolar range, based on the change in the HNB spectrum at 647 nm. While metal content in a solution has historically been determined using atomic absorption spectroscopy or inductively coupled plasma techniques, these methods require specialized equipment and training outside the scope of a typical biochemistry laboratory. The method proposed here provides a simple and fast way for biochemists to determine the metal content of samples using existing equipment and knowledge without sacrificing accuracy.

We present an assay for easy quantification of metals introduced to samples prepared using immobilized metal affinity chromatography. The method uses hydroxynaphthol blue as the colorimetric metal indicator and a UV-Vis spectrophotometer as the detector.

金属浸出在固定金属亲和力色谱中的定量

Contamination of enzymes with metals leached from immobilized metal affinity chromatography (IMAC) columns poses a major concern for enzymologists, as ...

An Assay for Real-Time Monitoring of Extracellular pH in Dental Biofilms

Source: Schlafer, S., et al. <a href="https://app.jove.com/v/53622">Ratiometric Imaging of Extracellular pH in Dental Biofilms.</a> J. Vis. Exp. (2016)
This video demonstrates a real-time assay for monitoring extracellular pH in dental biofilms using a pH-sensitive ratiometric probe. When an in situ-grown bacterial biofilm is exposed to glucose, a reduction in extracellular pH near the bacterial biomass protonates the probe, leading to its increased concentration inside the bacteria. The disparity in emission wavelength between the protonated and unprotonated probe is utilized to calculate the pH across the extracellular matrix of the biofilm and track pH changes over time.

一种用于实时监测牙科生物膜中细胞外 pH 值的检测方法

All procedures involving sample collection have been performed in accordance with the institute&#39;s IRB guidelines.
1. Collection of In Situ Grown ...

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Immunology

Immunodiagnostics

Specialized Assays

Porosity in Cement Paste

The porosity of concrete is a measure of the void spaces within its structure. These spaces impact its strength and durability significantly. When water and cement interact, a chemical reaction called hydration creates a semi-solid paste. This paste includes combined water, making up approximately 23% of the cement&#39;s dry mass, and gel water, which fills minuscule voids known as gel pores, accounting for about 28% of the cement gel volume.
The balance of water to cement in the mix is critical&#8212;it influences the extent of hydration and, thereby, the porosity and strength of the cured concrete. In an ideal hydration process, extra space not occupied by solid hydration products forms capillary pores, representing around 18.5% of the original cement volume. As the concrete cures, continuous hydration can fill the capillary pores with hydration products, increasing the density of the material.
For complete hydration and optimal strength, the curing process must be managed carefully. It allows for additional hydration, reducing porosity by filling the capillary spaces with more stable hydration products and, as a result, densifying the paste. This meticulous process is crucial for achieving durable, high-quality concrete that is less susceptible to environmental and mechanical degradation.

水泥浆中的孔隙率

As fresh cement paste sets, it transitions from a fluid state to a solid mass, entrapping water in various forms, such as gel water, capillary water, and ...

教育

Strength of Concrete

KEY TERMS AND CONCEPTS

Soundness of Cement

The soundness of cement refers to the ability of cement paste to retain its volume after setting. Unsound cement can lead to expansion and structural damage due to the presence of free lime, magnesia, and calcium sulfate. Free lime hydrates very slowly, expanding and causing unsoundness, which is difficult to detect because it intercrystallizes with other compounds. Magnesia also reacts with water, forming crystals that can disrupt the cement&#39;s structure. Calcium sulfate can create ettringite, which leads to expansion if not adequately consumed during the setting process.
The standard tests for cement soundness are Le Chatelier&#39;s and autoclave tests. Le Chatelier&#39;s test primarily detects unsoundness from free lime, and the autoclave test measures the unsoundness from free lime and magnesia. If expansion is more than 0.8% of the original length after autoclaving, the cement may be considered unsound. Unsoundness from free lime is rare, with magnesium-related issues more prevalent in US-produced cement due to the raw materials used.

水泥的坚固性

Occasionally, after the cement paste sets, the free lime, magnesia, and calcium sulfate may hydrate, causing a destructive expansion in the hardened ...

高精度水泥浆水溶氯分布的检测

摘要

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此视频中的章节

氯离子的动态电化学测试

开放补丁夹具移液器测量未搅拌边界层中的离子浓度: 流体流动对离子通道控制的启示

测定钢筋混凝土结构试样腐蚀的氯化物阈值的试验规程

胶孔溶液的表达及其化学成分和电阻率的 X 射线荧光分析

水样中偶极辅助固相萃取Microchip的痕量金属分析的制作

金属浸出在固定金属亲和力色谱中的定量

一种用于实时监测牙科生物膜中细胞外 pH 值的检测方法

水泥浆中的孔隙率

水泥的坚固性

水泥的坚固性