作者感谢中国国家自然科学基金 (51578208 号赠款)、河北省自然科学基金 (批准号:) 的财政支持。E2017202030 和 E2014202178), 河北省大学科技研究重点项目 (批准号:ZD2015028)。

1. 电磁磁场设置
注: 磁场是由一个空心腔的螺线管产生的。该装置是一个聚对苯二甲酸 (PBT) 板螺线管骨架盘绕4-6 层搪瓷绝缘铜线和包装的塑料绝缘层保护 (图 1)。将线圈连接到直流后, 线圈中的电流在螺线管腔内产生一个均匀的电磁场, 具有固定方向和恒定的磁感应强度。使用磁场将钢纤维与新鲜砂浆对齐, 并准备 ASFRC 试样。在这项研究中, 我们准备了150×150×550毫米棱镜标本, 使用的电磁阀室大小的250×250×750毫米。
<ol><li>将磁感应强度与电磁线圈的电流相关。<ol>
<li>将螺线管连接到 DC, 并将电流从0到 10 a 与步骤长度 1 a 测量并记录电磁室中的磁感应强度, 使用特斯拉计。</li>
		<li>绘制磁感应强度-电流曲线 (图 2), 将在以后的步骤中使用, 以确定螺线管的必要电流。 注: 在将螺线管连接到电源和所有其他与电力有关的操作程序时, 小心地遵循电气安全程序。</li>
	</ol>
</li>
</ol>2. 新鲜砂浆的实用性
<ol><li>准备三砂浆与钢纤维体积分数分别0.8%、1.2% 和2.0% 混合 (表 1)。三混合有相同的基质组成与水水泥砂比为 0.42:1: 2。根据混合比, 重0.5 公斤水泥, 1.0 公斤沙子和0.21 公斤水为可加工性测试。</li>
	<li>先把水加入砂浆搅拌机。然后加入水泥。三十年代混合水和水泥。然后再混合三十年代, 在这个三十年代的混合, 逐渐增加了沙子的搅拌机。然后再混合六十年代。</li>
	<li>根据中国建筑砂浆性能试验方法标准 (JGJ/T70-2009)19, 用下沉深度计测试混合料的下沉深度。</li>
	<li>重复步骤2.2 和 2.3, 调整减水剂的用量, 直到下沉深度降到50-100 毫米范围。记录生产所需的可行性的减水剂的用量, 并在表 1中补充它作为混合比例的一部分。还可以在可加工性达到后, 测试新鲜砂浆的特定密度。在上述试验中, 聚羧酸系高效减水剂的最佳用量为 0.10% (与水泥质量比), 新鲜砂浆的比重为2186公斤/米3。</li>
	<li>使用共轴旋转砂浆流变仪测试新鲜砂浆的粘度 (图 3)。流变仪有一个水浴, 可以保持样品容器的温度在20摄氏度。<ol>
<li>将300毫升的新鲜砂浆混合在前5分钟内, 放入样品容器中。</li>
		<li>开始粘度测试。探头逐渐滴入容器中的新鲜砂浆, 容器开始旋转。当新的砂浆在旋转容器内移动时, 它会在探针上应用剪切力。在该过程中, 流变仪记录了剪切应力和剪切速率, 并将剪切应力曲线绘制为剪切速率。曲线的斜率是灰浆的粘度20,21。在本研究中, 新鲜砂浆的粘度为0.82 失礼</li>
	</ol>
</li>
</ol>3. 标本准备
<ol><li>确定磁场的磁感应强度和电磁线圈的电流。<ol>
<li>利用阶梯2.5.2 中确定的水泥砂浆粘度, 计算用方程对钢纤维在水泥砂浆中的磁场感应强度 (1):13 <img alt="Equation 1" src="/files/ftp_upload/56307/56307eq1v2.jpg">(1) 凡B是磁感应强度, η是粘度的新鲜砂浆, lf 是钢纤维的长度, m是单个钢纤维的质量, rf 是钢纤维的半径, μ是钢纤维的渗透性, μ0是真空的透气性, Δt为时间间隔, α(t + Δt) 是下一次间隔时的角加速度。根据试验所用钢纤维的粘度和参数, 所需的磁感应强度为 9.83 mT。</li>
		<li>根据图 2或方程 (2) 确定所需电磁线圈的电流, 以产生足够的磁感应强度:14 <img alt="Equation 2" src="/files/ftp_upload/56307/56307eq2v2.jpg">(2) 在我所要求的电流中, N是电磁线圈的数目, 而L是螺线管的长度。 使用等式 (2), 所需的电流是 8.3 a, 而从图 2它是大约 8.5 a。</li>
	</ol>
</li>
	<li>准备 ASFRC 标本<ol>
<li>使用15升砂浆搅拌机混合新鲜砂浆。对于每批, 根据表 1中列出的混合比例混合7.5 升砂浆。表1表示 ASFRC 混合物为 Vf, 其中 a 表示钢纤维对齐, Vf表示钢纤维的体积分数。因此, 钢纤维混凝土的混合物被表示, 作为比较, r-Vf, 其中 r 表明, 钢材是随机分布。钢纤维混凝土混合物没有列在表 1 , 但有相同的比例 ASFRC。</li>
		<li>根据常规程序, 对原材料进行称量, 混合钢纤维增强水泥砂浆。</li>
		<li>将新鲜的砂浆倒入塑料模中, 150×150×550的尺寸清晰. 混合后迅速浇铸试样, 避免失去可加工性。从水泥和水的接触中铸造一 ASFRC 棱镜需要大约25分钟。</li>
		<li>将模具移动到压实表上, 然后在压缩工作台上打开三十年代. 根据需要添加更多砂浆, 以确保模具完全填充。</li>
		<li>把模具放进螺线管的腔内。</li>
		<li>开关在五十年代的电磁线圈和压实表。 注: 对于普通混凝土, 合理的压实时间约为60-120 秒。在此测试中, 尝试控制此范围内的总压缩时间。较长的压实时间可改善钢纤维的对准;然而, 它可能导致过度压实和因此离析 (如果有的话, 钢纤维和粗骨料的下沉)。压缩时间越小, 钢纤维和疏松混凝土的线形就越差。</li>
		<li>关掉压实表。</li>
		<li>在压实表完全停止后, 关掉电磁线圈。</li>
		<li>轻轻地从螺线管中取出模具, 用铲子将砂浆的顶面光滑。避免干扰顶部表面附近的钢纤维。</li>
	</ol>
</li>
	<li>对于每个混合, 准备三电磁处理标本 (以下步骤 3.2. 2-3. 2.9) 和三非电磁处理标本 (以下步骤 3.2. 2-3 和 3.2.9)。在非电磁处理标本的制备中, 总压实时间为八十年代--与制备电磁处理试样时相同。</li>
	<li>将标本留在室内, 并在其模具中24小时。然后脱模和治疗雾室中的标本, 直到它们被用于机械测试。</li>
</ol>4. 三点弯曲试验
<ol><li>28天后, 取出固化室中的标本, 并标记装货位置 (A)、支撑 (B)、中跨偏转 (C) 和 LVDT 固定点 (图 4)。</li>
	<li>将试样放在 MTS 测试机的三点弯曲试验台 (图 4) 上, 并用试样的每一侧表面的 LVDT 保持架固定 LVDT 到中跨 (图 4)。</li>
	<li>将 LVDT 连接到数据记录。然后设置测试机控制 PC 上的数据采集频率。</li>
	<li>通过提高底部支撑来逐步提高试样的承载力, 使试验机上部加载单元非常接近, 但不接触试样的顶端表面。</li>
	<li>零初始负载、中跨偏转 (LVDT) 和位移 (加载单元) 值。</li>
	<li>开始测试并将三点弯曲载荷应用于具有位移控制的试样, 其速度为0.2 毫米/分钟. 记录试样的荷载和中跨挠度的完整历史。</li>
	<li>观察试样的载荷和变形。峰值后, 当位移大于30毫米时, 停止测试。通常, 试样开裂, 载荷小于 1.0 kN。</li>
	<li>重复步骤 4.1-4.7 测试所有标本。</li>
</ol>5. 钢纤维取向分析
<ol><li>计算断裂截面上钢纤维的数量。<ol>
<li>把标本分成两部分在破裂的部分。</li>
		<li>测量和记录钢纤维在水泥砂浆试样断裂断面上的定位。方向是钢纤维和试样轴线之间的夹角。由于手工测量钢纤维的方向是困难的, 可能产生不准确的测量, 方向可以归类为六个角度范围: 0-15 °, 15-30 °, 30-45 °, 45-60 °, 60-75 °和 75-90 °。记录每组钢纤维的数量, 然后用方程计算试样的平均纤维取向效率系数 (3): <img alt="Equation 3" src="/files/ftp_upload/56307/56307eq3v2.jpg">(3) ηθ 是钢纤维的平均取向效率系数, lf 是单个钢纤维的长度, n是裂纹截面上钢纤维的总数量, 而θi 是钢纤维与磁场方向的夹角 (在计算中, 每个组的钢纤维采用角度范围的中间值)。</li>
	</ol>
</li>
	<li>执行 X 射线计算机断层扫描分析。<ol>
<li>从每个迫击炮标本中剪下一个75毫米的立方体。</li>
		<li>使用 x 射线计算机层析成像系统对立方体进行 x 射线扫描。将标本放在测试平台上, 开始扫描。试样逐渐旋转360°, 机器记录每个旋转步骤中试样引起的 X 射线的衰减。计算机断层扫描系统生成立方体的三维数字结构。</li>
		<li>用黑白二进制处理技术识别数字立方体结构中的钢纤维。然后获得了描述钢纤维分布的数字图像。</li>
		<li>用图像分析法确定所有钢纤维的坐标。</li>
		<li>根据其坐标计算各钢纤维的方向。</li>
		<li>用方程 (3) 计算纤维的取向效率系数。</li>
	</ol>
</li>
</ol>

<ol>
	<li>Zollo, R. F. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Fiber-reinforced+concrete:+an+overview+after+30+years+of+development.">Fiber-reinforced concrete: an overview after 30 years of development.</a> Cem. Concr. Compos. 19 (2), 107-122 (1997).</li><li>Bentur, A., Mindess, S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=.">.</a> Fiber reinforced cementitious composites. , (2014).</li><li>Deeb, R., Karihaloo, B. L., Kulasegaram, S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Reorientation+of+short+steel+fibres+during+the+flow+of+self-compacting+concrete+mix+and+determination+of+the+fiber+orientation+factor.">Reorientation of short steel fibres during the flow of self-compacting concrete mix and determination of the fiber orientation factor.</a> Cem. Concr. Res. 56 (1), 112-120 (2013).</li><li>Soroushian, P., Lee, C. D. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Distribution+and+orientation+of+fibers+in+steel+fiber+reinforced+concrete.">Distribution and orientation of fibers in steel fiber reinforced concrete.</a> ACI Mater. J. 87 (5), 433-439 (1990).</li><li>Sebaibi, N., Benzerzour, M., Abriak, N. E. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Influence+of+the+distribution+and+orientation+of+fibres+in+a+reinforced+concrete+with+waste+fibers+and+powders.">Influence of the distribution and orientation of fibres in a reinforced concrete with waste fibers and powders.</a> Constr. Build. Mater. 65 (1), 254-263 (2014).</li><li>Lee, C., Kim, H. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Orientation+factor+and+number+of+fibers+at+failure+plane+in+ring-type+steel+fiber+reinforced+concrete.">Orientation factor and number of fibers at failure plane in ring-type steel fiber reinforced concrete.</a> Cem. Concr. Res. 40 (5), 810-819 (2010).</li><li>Shen, R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Effect+of+compaction+methods+on+fibre+orientation,+flexural+strength+and+toughness+of+steel+fiber+reinforced+concrete.">Effect of compaction methods on fibre orientation, flexural strength and toughness of steel fiber reinforced concrete.</a> J. of the Chinese Ceramic Society. 12 (1), 21-31 (1984).</li><li>Bayer, A. G. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Process+for+producing+a+prepreg+with+aligned+short+fibres.">Process for producing a prepreg with aligned short fibres.</a> US patent. , (1988).</li><li>Arman, E. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Building+material,+especially+concrete+or+mortar,+contains+magnetically+or+electrically+aligned+parallel+fibers.">Building material, especially concrete or mortar, contains magnetically or electrically aligned parallel fibers.</a> US patent. , (1975).</li><li>Yamamoto, T., Gasawara, N., Ohashi, T. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+construction+method+and+directional+dispersion+of+steel+fiber+reinforced+concrete.">The construction method and directional dispersion of steel fiber reinforced concrete.</a> Advances in Science and Technology of Water Resource. (4), 188-197 (1983).</li><li>Xu, X. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+new+type+of+steel+fiber+reinforced+concrete.">A new type of steel fiber reinforced concrete.</a> Architecture Technology. 20 (4), 240-241 (1993).</li><li>Rotondo, P. L., Weiner, K. H. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Aligned+steel+fibers+in+concrete+poles.">Aligned steel fibers in concrete poles.</a> Con. Int. 8 (12), 22-27 (1986).</li><li>Michels, J., Gams, M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Preliminary+study+on+the+influence+of+fibre+orientation+in+fibre+reinforced+mortars.">Preliminary study on the influence of fibre orientation in fibre reinforced mortars.</a> Gradevinar. 68 (8), 645-655 (2016).</li><li>Mu, R., Li, H., Qing, L., Lin, J., Zhao, Q. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Aligning+steel+fibers+in+cement+mortar+using+electro-magnetic+field.">Aligning steel fibers in cement mortar using electro-magnetic field.</a> Constr. Build. Mater. 131 (1), 309-316 (2017).</li><li>Jones, D. S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=.">.</a> The theory of electromagnetism. , (1964).</li><li>Liu, J., Li, C., Liu, J., Cui, G., Yang, Z. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Study+on+3D+spatial+distribution+of+steel+fibers+in+fiber+reinforced+cementitious+composites+through+micro-CT+technique.">Study on 3D spatial distribution of steel fibers in fiber reinforced cementitious composites through micro-CT technique.</a> Constr. Build. Mater. 48 (2), 656-661 (2013).</li><li>Schnell, J., Schladitz, K., Schuler, F. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Direction+analysis+of+fibres+in+concrete+on+basis+of+computed+tomography.">Direction analysis of fibres in concrete on basis of computed tomography.</a> Betonund Stahlbetonbau. 105 (2), 72-77 (2010).</li><li>Wuest, J., Denari&#233;, E., Br&#252;hwiler, E., Tamarit, L., Kocher, M., Gallucci, E. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Tomography+analysis+of+fiber+distribution+and+orientation+in+ultra+high-performance+fiber+reinforced+composites+with+high+fiber+dosages.">Tomography analysis of fiber distribution and orientation in ultra high-performance fiber reinforced composites with high fiber dosages.</a> Experimental Techniques. 33 (5), 50-55 (2009).</li><li>. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=.">.</a> JGJ/T70-2009 Chinese standard for test method of performance on building mortar. , (2009).</li><li>Roussel, N. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=.">.</a> Understanding the Rheology of Concrete. , (2012).</li><li>Roussel, N. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Steady+and+transient+flow+behaviour+of+fresh+cement+pastes.">Steady and transient flow behaviour of fresh cement pastes.</a> Cem. Concr. Res. 35 (9), 1656-1664 (2005).</li></ol>

作者没有什么可透露的。

本研究开发的电磁螺线管有一室测量250×250×750毫米, 不能容纳全尺寸结构元素。虽然会议厅的大小限制了设置的应用, 本文提出的概念和协议将激励进一步开发一个完整的尺寸设置, 制造 ASFRC 元素, 特别是预制元件。
达到适当粘度的新鲜砂浆是控制 ASFRCs 质量的关键因素, 因为钢纤维的对准是由需要克服新砂浆粘性阻力的磁力驱动的。粘性电阻受新砂浆粘度的制约。砂浆的粘度...

钢纤维掺入混凝土是克服脆性的固有弱点, 提高混凝土抗拉强度的有效途径1。在过去的几十年中, 钢纤维混凝土已被广泛的研究和广泛应用于该领域。钢纤维混凝土在抗裂性、抗拉强度、断裂韧性、断裂能等方面优于混凝土2在钢纤维混凝土中, 钢纤维随机分散, 从而均匀分散纤维在各个方向的增强效率。然而, 在一定的荷载条件下, 混凝土中只有部分钢纤维对结构构件的性能有贡献, 因为纤维的增强效率要求它们与主拉应力在结构。例如, 当钢纤维混凝土中含有随机分布的钢纤维来制备梁时, 某些钢纤维, 特别是与主拉应力方向平行的钢筋, 将对提高效率, 而垂直于主拉应力方向的那些将不会对提高效率作出贡献。因此, 寻找一种将钢纤维与混凝土主要拉应力方向相对准的方法, 是实现钢纤维最高加固效率的必要条件。
定位效率因子, 定义为沿拉伸应力方向的投影长度与纤维实际长度的比值, 通常用来表示钢筋纤维3、4 的增强效率..根据这一定义, 与拉伸应力方向一致的纤维取向效率系数为 1.0;与拉伸应力垂直的纤维是0。倾斜纤维在0和1.0 之间有一个取向效率因素。分析结果表明, 混凝土中随机分布钢纤维的取向效率系数为 0.4054, 而普通钢纤维混凝土的试验范围为0.167 到 0.5005,6.显然, 如果混凝土中的短钢纤维对齐, 并且与拉伸应力方向相同, 则钢纤维将具有最高的加固效率, 试样的拉伸性能最佳。
自二十世纪八十年代以来, 一些成功的尝试准备对齐钢纤维钢筋混凝土。在 1984年, 沈7在铸钢纤维增强水泥基复合材料 (纤维混凝土) 梁的底层应用了一个电磁场, x 射线检测分析表明, 钢纤维的排列良好。在 1995年, 拜耳8和 Arman9获得专利的方法, 以制备对齐钢纤维钢筋混凝土使用磁场。山本等。10考虑了钢纤维在混凝土中的取向主要受铸造方法的影响, 并试图通过保持新混凝土从恒定方向向模板流动的方式获得对齐钢纤维混凝土。徐11试图将钢纤维从一个恒定的方向喷出, 使其在喷射混凝土中保持一致。圣乔瓦尼罗和维纳12试图用离心铸造的方式使长钢纤维的混凝土极。试验研究表明, 钢纤维混凝土与随机分布的钢纤维混凝土相比具有明显的优越性。
最近, 米歇尔斯等。13和亩等。14已成功开发了一组采用电磁场的排列钢纤维增强水泥基复合材料 (ASFRCs)。在这些研究中, 各种螺线管被用来提供一个统一的磁场, 使钢纤维在不同尺寸的砂浆试样中进行对准。螺线管有一个空心长方体室, 可以容纳预定大小的样品。当电磁线圈连接到直流 (DC), 一个统一的磁场是在腔内创建一个固定的方向, 这与螺线管的轴对齐。根据电磁15原理, 磁场可以驱动铁磁纤维在新鲜砂浆中旋转和对准。砂浆的适当的可加工性对于允许钢纤维在新鲜砂浆中旋转是至关重要的。高粘度可能会导致砂浆中钢纤维的对准困难, 而低粘度可能导致纤维的离析。
本文介绍了 ASFRC 试样的制备细节, 并对 ASFRC 和钢纤维混凝土的弯曲性能进行了试验研究。预计 ASFRC 比钢纤维混凝土具有更高的抗弯强度和韧性。因此, ASFRC 有可能比钢纤维混凝土在抗拉应力和抗裂性能方面具有优越性, 如用作覆盖混凝土、路面等.
利用弯曲试验后的断裂试样, 通过观测裂隙剖面, 利用 X 射线扫描计算机层析分析16、17 , 研究了试样中钢纤维的取向。,18. 报告了 ASFRCs 的力学性能, 包括其弯曲强度和韧性, 并与非电磁处理的 SFRCs 进行了比较。

<table border="1" fo:keep-together.within-page="1" fo:keep-with-next.within-page="always">
	<tbody>
		<tr >
			<td >Cement</td>
			<td >Tangshan Jidong Cement Co., Ltd.</td>
			<td >P&#215;O 42.5</td>
			<td >Oridnary Portland Cement</td>
		</tr>
		<tr >
			<td >Sand</td>
			<td ></td>
			<td >River sand</td>
			<td>Fineness modulus is 2.4</td>
		</tr>
		<tr >
			<td >Superplasticizer</td>
			<td >Subote New Materials Co., Ltd.</td>
			<td >PCA-III</td>
			<td>Polycarboxylated type, water reducing ratio is 35%</td>
		</tr>
		<tr >
			<td >Steel fiber</td>
			<td >Tianjin Hengfeng Xuxiang New Metal Materials Co., Ltd.</td>
			<td >Round straight</td>
			<td>Diameter 0.5mm, length 25mm</td>
		</tr>
	</tbody>
</table>

preparation of aligned steel fiber reinforced cementitious composite and its flexural behavior

这项工作的目的是提出一种方法, 灵感的方式, 罗盘针保持一致的方向, 在地球的磁场的作用下, 制造的水泥基复合材料加强了对齐钢纤维。将均匀的电磁场应用于含短钢纤维的新鲜砂浆中, 通过将短钢纤维与磁场相对准, 使钢纤维增强水泥基复合材料 (ASFRC) 制备。通过对断裂剖面中钢纤维的计数和 X 射线计算机断层分析, 对钢纤维在硬化 ASFRC 中的对准程度进行了评价。这两种方法的结果表明, ASFRC 中的钢纤维高度排列, 而非磁处理复合材料中的钢纤维是随机分布的。所对的钢纤维具有更高的增强效率, 因此复合材料的抗弯强度和韧性明显增强。因此, ASFRC 比钢纤维混凝土更优越, 它能承受较大的拉应力, 更有效地抵御开裂。

由三点弯曲试验确定的 ASFRCs 和 SFRCs 的弯曲强度如图 5所示。ASFRCs 的抗弯强度高于所有纤维用量的 SFRCs。ASFRCs 的抗弯强度分别为0.8%、1.2%、2.0% 纤维体积分数的88%、71% 和57% 以上的 SFRCs。这些结果意味着, 对齐钢纤维比随机分布的钢纤维更有效地加强胶凝基体。
图 6显示?...

Watch this Scientific Journal Video about Preparation of Aligned Steel Fiber Reinforced Cementitious Composite and Its Flexural Behavior at JoVE.com

Preparation of Aligned Steel Fiber Reinforced Cementitious Composite and Its Flexural Behavior

本协议描述了一种采用均匀电磁场制造对齐钢纤维增强水泥基复合材料的方法。对钢纤维增强水泥基复合材料具有优异的力学性能。

定向钢纤维增强水泥基复合材料的制备及其弯曲性能研究

The aim of this work is to present an approach, inspired by the way in which a compass needle maintains a consistent orientation under the action of the ...

preparation-aligned-steel-fiber-reinforced-cementitious-composite-its

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10.9K 次观看.  Hebei University of Technology. 本协议描述了一种采用均匀电磁场制造对齐钢纤维增强水泥基复合材料的方法。对钢纤维增强水泥基复合材料具有优异的力学性能。

视频: Preparation of Aligned Steel Fiber Reinforced Cementitious Composite and Its Flexural Behavior

Mechanical Expansion of Steel Tubing as a Solution to Leaky Wellbores

Wellbore cement, a procedural component of wellbore completion operations, primarily provides zonal isolation and mechanical support of the metal pipe (casing), and protects metal components from corrosive fluids. These are essential for uncompromised wellbore integrity. Cements can undergo multiple forms of failure, such as debonding at the cement/rock and cement/metal interfaces, fracturing, and defects within the cement matrix. Failures and defects within the cement will ultimately lead to fluid migration, resulting in inter-zonal fluid migration and premature well abandonment. Currently, there are over 1.8 million operating wells worldwide and over one third of these wells have leak related problems defined as Sustained Casing Pressure (SCP)1. 
The focus of this research was to develop an experimental setup at bench-scale to explore the effect of mechanical manipulation of wellbore casing-cement composite samples as a potential technology for the remediation of gas leaks. 
The experimental methodology utilized in this study enabled formation of an impermeable seal at the pipe/cement interface in a simulated wellbore system. Successful nitrogen gas flow-through measurements demonstrated that an existing microannulus was sealed at laboratory experimental conditions and fluid flow prevented by mechanical manipulation of the metal/cement composite sample. Furthermore, this methodology can be applied not only for the remediation of leaky wellbores, but also in plugging and abandonment procedures as well as wellbore completions technology, and potentially preventing negative impacts of wellbores on subsurface and surface environments.

This article reports on a laboratory scale investigation of an existing field procedure and its adaptation for sealing of leaky wellbores. It consists of mechanical expansion of metal pipe, which results in an improved metal/cement bond, ultimate sealing of hydraulic pathways and prevention of gas leaks caused by the presence of a microannular channel.

钢管机械性扩张为解决井眼漏

Wellbore cement, a procedural component of wellbore completion operations, primarily provides zonal isolation and mechanical support of the metal pipe ...

科研

工程学

A Testing Platform for Durability Studies of Polymers and Fiber-reinforced Polymer Composites under Concurrent Hygrothermo-mechanical Stimuli

The durability of polymers and fiber-reinforced polymer composites under service condition is a critical aspect to be addressed for their robust designs and condition-based maintenance. These materials are adopted in a wide range of engineering applications, from aircraft and ship structures, to bridges, wind turbine blades, biomaterials and biomedical implants. Polymers are viscoelastic materials, and their response may be highly nonlinear and thus make it challenging to predict and monitor their in-service performance. The laboratory-scale testing platform presented herein assists the investigation of the influence of concurrent mechanical loadings and environmental conditions on these materials. The platform was designed to be low-cost and user-friendly. Its chemically resistant materials make the platform adaptable to studies of chemical degradation due to in-service exposure to fluids. An example of experiment was conducted at RT on closed-cell polyurethane foam samples loaded with a weight corresponding to ~50% of their ultimate static and dry load. Results show that the testing apparatus is appropriate for these studies. Results also highlight the larger vulnerability of the polymer under concurrent loading, based on the higher mid-point displacements and lower residual failure loads. Recommendations are made for additional improvements to the testing apparatus.

The durability of polymers and fiber-reinforced polymer composites in service is a critical aspect for their designs and condition-based maintenance. We present a novel low-cost laboratory testing platform for the investigation of the influence of concurrent mechanical and environmental loadings, and may help design more efficient yet safer composite structures.

一个测试平台为聚合物的耐久性研究，并在同期Hygrothermo机械刺激纤维增强聚合物复合材料

The durability of polymers and fiber-reinforced polymer composites under service condition is a critical aspect to be addressed for their robust designs ...

Strain Sensing Based on Multiscale Composite Materials Reinforced with Graphene Nanoplatelets

The electrical response of NH2-functionalized graphene nanoplatelets composite materials under strain was studied. Two different manufacturing methods are proposed to create the electrical network in this work: (a) the incorporation of the nanoplatelets into the epoxy matrix and (b) the coating of the glass fabric with a sizing filled with the same nanoplatelets. Both types of multiscale composite materials, with an in-plane electrical conductivity of ~10-3 S/m, showed an exponential growth of the electrical resistance as the strain increases due to distancing between adjacent functionalized graphene nanoplatelets and contact loss between overlying ones. The sensitivity of the materials analyzed during this research, using the described procedures, has been shown to be higher than commercially available strain gauges. The proposed procedures for self-sensing of the structural composite material would facilitate the structural health monitoring of components in difficult to access emplacements such as offshore wind power farms. Although the sensitivity of the multiscale composite materials was considerably higher than the sensitivity of metallic foils used as strain gauges, the value reached with NH2 functionalized graphene nanoplatelets coated fabrics was nearly an order of magnitude superior. This result elucidated their potential to be used as smart fabrics to monitor human movements such as bending of fingers or knees. By using the proposed method, the smart fabric could immediately detect the bending and recover instantly. This fact permits precise monitoring of the time of bending as well as the degree of bending.

The integration of conductive nanoparticles, such as graphene nanoplatelets, into glass fiber composite materials creates an intrinsic electrical network susceptible to strain. Here, different methods to obtain strain sensors based on the addition of graphene nanoplatelets into the epoxy matrix or as a coating on glass fabrics are proposed.

基于多尺度复合材料的增强与石墨烯纳米片应变传感

The electrical response of NH2-functionalized graphene nanoplatelets composite materials under strain was studied. Two different manufacturing methods are ...

Preparation and High-temperature Anti-adhesion Behavior of a Slippery Surface on Stainless Steel

Anti-adhesion surfaces with high-temperature resistance have a wide application potential in electrosurgical instruments, engines, and pipelines. A typical anti-wetting superhydrophobic surface easily fails when exposed to a high-temperature liquid. Recently, Nepenthes-inspired slippery surfaces demonstrated a new way to solve the adhesion problem. A lubricant layer on the slippery surface can act as a barrier between the repelled materials and the surface structure. However, the slippery surfaces in previous studies rarely showed high-temperature resistance. Here, we describe a protocol for the preparation of slippery surfaces with high-temperature resistance. A photolithography-assisted method was used to fabricate pillar structures on stainless steel. By functionalizing the surface with saline, a slippery surface was prepared by adding silicone oil. The prepared slippery surface maintained the anti-wetting property for water, even when the surface was heated to 300 &#176;C. Also, the slippery surface exhibited great anti-adhesion effects on soft tissues at high temperatures. This type of slippery surface on stainless steel has applications in medical devices, mechanical equipment, etc.

Slippery surfaces provide a new way to solve the adhesion problem. This protocol describes how to fabricate slippery surfaces at high temperatures. The results demonstrate that the slippery surfaces showed anti-wetting for liquids and a remarkable anti-adhesion effect on soft tissues at high temperatures.

不锈钢滑面的制备及高温抗粘接性能研究

Anti-adhesion surfaces with high-temperature resistance have a wide application potential in electrosurgical instruments, engines, and pipelines. A ...

Installation Method to Enhance Quality Control for Fiber Reinforced Polymer Spike Anchors

Fiber reinforced polymer (FRP) anchors are a promising way to enhance the performance of externally-bonded FRPs applied to existing structures, as they can delay or even prevent debonding failure. However, a major concern faced by designers is the premature failure of the anchors due to stress concentration. Poor installation quality and preparation of the clearance holes can result in stress concentration that provokes this premature failure. This paper deals with an installation method that aims to reduce the impact of the stress concentration and to provide a proper quality control of the preparation of the drill hole. The method involves three parts: the drilling and cleaning of the holes, the smoothing of the hole edges with a customized drill bit, and the installation of the anchor itself, including the impregnation of the anchor dowel and its insertion. Anchor fans (the free length of the spikes) are then bonded to the external FRP reinforcement. For the end anchorage, and in the case of reinforcements with multiple plies, it is recommended that the anchor fan be inserted between two plies to assist the stress-transfer mechanism. 
The proposed procedure is complemented with a design approach for spike anchors, based on an extensive database. It is proposed that the design follow a number of steps, namely: selection of the anchor diameter and subsequent tensile strength of the connector (that is to say, the anchor before fanning out the free end), evaluation of the reduction in the tensile strength due to bending, provision of enough embedment to prevent slippage failure, and consideration of the number and spacing of anchors for a given reinforcement. In this sense, it should be noted that further research is needed in order to obtain a general expression for the contribution of spike anchors to overall bond strength of FRP reinforcements.

This manuscript presents a method for controlling the quality of installation for spike anchors designed to delay delamination of externally bonded fiber reinforced polymers. The protocol includes the preparation of the drill hole and the insertion process. The most influential parameters on the efficiency of the anchors are discussed.

提高纤维增强聚合物穗锚质量控制的安装方法

Fiber reinforced polymer (FRP) anchors are a promising way to enhance the performance of externally-bonded FRPs applied to existing structures, as they ...

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 ...

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 ...

Generating Lap Joints Via Friction Stir Spot Welding on DP780 Steel

Friction stir spot welding (FSSW), a derivative of friction stir welding (FSW), is a solid-state welding technique that was developed in 1991. An industry application was found in the automotive industry in 2003 for the aluminum alloy that was used in the rear doors of automobiles. Friction stir spot welding is mostly used in Al alloys to create lap joints. The benefits of friction stir spot welding include a nearly 80% melting temperature that lowers the thermal deformation welds without splashing compared to resistance spot welding. Friction stir spot welding includes 3 steps: plunging, stirring, and retraction. In the present study, other materials including high strength steel are also used in the friction stir welding method to create joints. DP780, whose traditional welding process involves the use of resistance spot welding, is one of several high strength steel materials used in the automotive industry. In this paper, DP780 was used for friction stir spot welding, and its microstructure and microhardness were measured. The microstructure data showed that there was a fusion zone with fine grain and a heat effect zone with island martensite. The microhardness results indicated that the center zone exhibited a greater degree of hardness compared with the base metal. All data indicated that the friction stir spot welding used in dual phase steel 780 can create a good lap joint. In the future, friction stir spot welding can be used in high-strength steel welding applied in industrial manufacturing processes.

Here, we present a friction stir spot welding (FSSW) protocol on dual phase 780 steel. A tool pin with high-speed rotation generates heat from friction to soften the material, and then, the pin plunges into 2 sheet joints to create the lap joint.

通过 DP780 钢上的摩擦搅拌点焊生成圈接头

Friction stir spot welding (FSSW), a derivative of friction stir welding (FSW), is a solid-state welding technique that was developed in 1991. An industry ...

Artificial Thermal Ageing of Polyester Reinforced and Polyvinyl Chloride Coated Technical Fabric

Architectural fabric AF9032 has been subjected to artificial thermal ageing to determine changes of the material parameters of the fabric. The proposed method is based on the accelerated ageing approach proposed by Arrhenius. 300 mm x 50 mm samples were cut in the warp and fill directions and placed in a thermal chamber at 80 &#176;C for up to 12 weeks or at 90 &#176;C for up to 6 weeks. Then after one week of conditioning at ambient temperature, the samples were uniaxially tensioned at a constant strain rate. Experimentally, the parameters were determined for the non-linear elastic (linear piecewise) and viscoplastic (Bodner&#8211;Partom) models. Changes in these parameters were studied with respect to the ageing temperature and ageing period. In both cases, the linear approximation function was successfully applied using the simplified methodology of Arrhenius. A correlation was obtained for the fill direction between experimental results and the results from the Arrhenius approach. For the warp direction, the extrapolation results exhibited some differences. Increasing and decreasing tendencies have been observed at both temperatures. The Arrhenius law was confirmed by the experimental results only for the fill direction. The proposed method makes it possible to predict real fabric behavior during long term exploitation, which is a critical issue in the design process.

Here, we simulate accelerated thermal ageing of technical fabric and see how this ageing process influences the mechanical properties of the fabric.

聚酯增强和聚氯乙烯涂层技术织物的人工热老化

Architectural fabric AF9032 has been subjected to artificial thermal ageing to determine changes of the material parameters of the fabric. The proposed ...

Advanced Self-Healing Asphalt Reinforced by Graphene Structures: An Atomistic Insight

Graphene can improve the self-healing properties of asphalt with high durability. However, the self-healing behaviors of graphene-modified asphalt nanocomposite and the role of incorporated graphene are still unclear at this stage. In this study, the self-healing properties of pure asphalt and graphene-modified asphalt are investigated through molecular dynamics simulations. Asphalt bulks with two crack widths and locations for graphene are introduced, and the molecular interactions among asphalt components and the graphene sheet are analyzed. The results show that the location of graphene significantly affects the self-healing behaviors of asphalt. Graphene near the crack surface can greatly accelerate the self-healing process by interacting with the aromatic molecules through &#960;-&#960; stacking, while graphene at the top area of the crack tip has a minor impact on the process. The self-healing process of asphalt goes through the reorientation of asphaltene, polar aromatic, and naphthene aromatic molecules, and the bridging of saturate molecules between crack surfaces. This in-depth understanding of the self-healing mechanism contributes to the knowledge of the enhancement for self-healing properties, which will help to develop durable asphalt pavements.

Graphene-modified asphalt nanocomposite has shown an advanced self-healing ability compared to pure asphalt. In this protocol, molecular dynamics simulations have been applied in order to understand the role of graphene in the self-healing process and to explore the self-healing mechanism of asphalt components from the atomistic level.