The authors gratefully acknowledge financial supports from the National Nature Science Foundation of China (Grant No. 51578208), Hebei Provincial Nature Science Foundation (Grant No. E2017202030 and E2014202178), and Key Project of University Science and Technology Research of Hebei Province (Grant No. ZD2015028).

1. Solenoid Magnetic Field Setup
NOTE: The magnetic field is generated by a solenoid with a hollow chamber. The setup is a polybutylene terephthalate (PBT) board solenoid skeleton coiled with 4-6 layers of enamel insulated copper wire and wrapped with a plastic insulating layer for protection (Figure 1). After connecting the coil to DC, the current in the coil creates a uniform electromagnetic field within the solenoid chamber with a fixed direction and constant magnetic induction intensity. Use the magnetic field to align steel fibers in fresh mortar and prepare the ASFRC specimens. In this study, we prepared 150&#215;150&#215;550 mm prism specimens using a solenoid with a chamber size of 250&#215;250&#215;750 mm.
<ol>
	<li>Correlate the magnetic induction intensity to the electrical current of the solenoid.
	<ol>
		<li>Connect the solenoid to DC and apply current from 0 to 10 A with a step length of 1 A. Measure and record the magnetic induction intensity in the solenoid chamber using a tesla meter.</li>
		<li>Plot the magnetic induction intensity-current curve (Figure 2), which will be used in later steps to determine the necessary current of the solenoid. 
		NOTE: Carefully follow electrical safety procedures when connecting the solenoid to the power source and in all other operation procedures relevant to electrical power.</li>
	</ol>
	</li>
</ol>
2. Workability of Fresh Mortar
<ol>
	<li>Prepare three mortar mixes with steel fiber volume fractions 0.8%, 1.2%, and 2.0%, respectively (Table 1). The three mixes have the same matrix composition with a water to cement to sand ratio of 0.42:1:2. According to the mix ratio, weigh 0.5 kg of cement, 1.0 kg of sand, and 0.21 kg of water for workability tests.</li>
	<li>Add water to the mortar mixer first. Then add the cement. Mix the water and cement for 30 s. Then mix for another 30 s, and during this 30 s of mixing, gradually add sand to the mixer. Then mix for another 60 s.</li>
	<li>Test the sinking depth of the mixture using a sinking depth meter following the Chinese standard for test method of performance on building mortar (JGJ/T70-2009)19.</li>
	<li>Repeat steps 2.2 and 2.3, adjusting the dosage of the superplasticizer until the sinking depth falls into the 50-100 mm range. Record the dosage of the superplasticizer that produces the desired workability and supplement it as part of the mix proportion in Table 1. Also test the specific density of the fresh mortar after the workability is achieved. The optimized dosage of a polycarboxylate superplasticizer from the aforementioned tests is 0.10% (mass ratio to cement), and the specific density of fresh mortar is 2186 kg/m3.</li>
	<li>Test the viscosity of the fresh mortar using a co-axial rotational mortar rheometer (Figure 3). The rheometer has a water bath that can maintain the temperature of the sample container at 20 &#176;C.
	<ol>
		<li>Put 300 mL of fresh mortar mixed within the previous 5 min into the sample container.</li>
		<li>Begin the viscosity test. The probe gradually drops into the fresh mortar in the container, and the container begins to rotate. As the fresh mortar moves within the rotating container, it applies a shear force on the probe. In the process, the rheometer records the shear stress and shear rate and plots the curve of shear stress to shear rate. The slope of the curve is the viscosity of the mortar20,21. In this investigation, the viscosity of the fresh mortar from tests is 0.82 Pas.</li>
	</ol>
	</li>
</ol>
3. Specimen Preparation
<ol>
	<li>Determine the magnetic induction intensity of the magnetic field and the current of the solenoid.
	<ol>
		<li>Using the viscosity of the cement mortar determined in step 2.5.2, calculate the magnetic induction intensity of the magnetic field required for aligning steel fibers in cement mortar using Equation (1):13 
		<img alt="Equation 1" src="/files/ftp_upload/56307/56307eq1v2.jpg" /> (1) 
		where B is magnetic induction intensity,&#160;&#951; is the viscosity of fresh mortar, lf is the length of steel fiber, m is the mass of an individual steel fiber, rf is the radius of steel fibers, &#956; is the permeability of steel fibers, &#956;0 is the permeability of the vacuum, &#916;t is time interval, and &#945;(t+&#916;t) is the angular acceleration at the next time interval. According to the viscosity and the parameters of the steel fiber used in the tests, the required magnetic induction intensity is 9.83 mT.</li>
		<li>Determine the electrical current of the solenoid required to create a sufficient magnetic induction intensity according to Figure 2 or Equation (2):14 
		<img alt="Equation 2" src="/files/ftp_upload/56307/56307eq2v2.jpg" /> (2) 
		where I is the required current, N is the number of solenoid turns, and L is the length of the solenoid. 
		Using Equation (2), the required current is 8.3 A, while from Figure 2 it is about 8.5 A.</li>
	</ol>
	</li>
	<li>Prepare ASFRC specimens
	<ol>
		<li>Use a 15 L mortar mixer to mix fresh mortar. For each batch, mix 7.5 L of mortar according to the mix proportions listed in Table 1. Table 1 denotes the ASFRC mixes as A-Vf, where A indicates that the steel fibers are aligned and Vf indicates the volume fraction of steel fiber. Accordingly, the SFRC mixes are denoted, for comparison, as R-Vf, where R indicates that the steel fibers are randomly distributed. The SFRC mixes are not listed in Table 1 but have the same proportions as ASFRC.</li>
		<li>Weigh the raw materials and mix the steel fiber reinforced cement mortar following routine procedures.</li>
		<li>Pour the fresh mortar into a plastic mold with clear size of 150&#215;150&#215;550 mm. Cast the specimens promptly after mixing to avoid losing workability. It takes around 25 min to cast one ASFRC prism from the contact between cement and water.</li>
		<li>Move the mold onto a compacting table, and switch on the compacting table for 30 s. Add more mortar as needed to ensure that that the mold is completely filled.</li>
		<li>Put the mold into the chamber of the solenoid.</li>
		<li>Switch on the solenoid and compacting table for 50 s. 
		NOTE: For ordinary concrete the reasonable compacting time is around 60-120 s. In this test, it is attempted to control the total compacting time within this range. Longer compacting time may improve the alignment of steel fibers; however, it may cause over compacting and consequently the segregation (the sinking of steel fibers and coarse aggregates if there are). Less compacting time may cause poor alignment of steel fiber and unconsolidated concrete.</li>
		<li>Switch off the compacting table.</li>
		<li>Switch off the solenoid after the compacting table has stopped completely.</li>
		<li>Gently take out the mold from the solenoid and smooth the top surface of the mortar with a trowel. Avoid disturbing the steel fibers near the top surface.</li>
	</ol>
	</li>
	<li>For each mix, prepare three electromagnetically treated specimens (following steps 3.2.2-3.2.9) and three non-electromagnetically treated specimens (following steps 3.2.2-3.2.4 and 3.2.9). In the preparation of non-electromagnetically treated specimens, the total compacting time was 80 s&#8212;the same as that in the preparation of electromagnetically treated specimens.</li>
	<li>Leave the specimens indoors and in their molds for 24 h. Then demold and cure the specimens in a fog room until they are used for mechanical tests.</li>
</ol>
4. Three-Point Bending Test
<ol>
	<li>After 28 days, take out the specimens from the curing room and mark the positions for loading (A), supports (B), mid-span deflection (C), and LVDT fixing points (D) (Figure 4).</li>
	<li>Place the specimen on the three-point bending test rig (Figure 4) of the MTS test machine and fix a LVDT to the mid-span using a LVDT holder on each side surface of the specimen (Figure 4).</li>
	<li>Connect the LVDT to a datalog. Then set the data acquisition frequency on the control PC of the test machine.</li>
	<li>Gradually raise the specimen by raising the bottom supports so that the upper loading cell of the test machine is very close to, but not touching, the top surface of the specimen.</li>
	<li>Zero the initial load, mid-span deflection (LVDT), and displacement (load cell) values.</li>
	<li>Start the test and apply a three-point bending load to the specimen with a displacement control at a speed of 0.2 mm/min. Record the full history of the loading and mid-span deflection of the specimen.</li>
	<li>Watch the load and deformation of the specimen. After peak value, when the displacement is greater than 30 mm, stop the test. Usually, the specimen is cracked and the load is less than 1.0 kN.</li>
	<li>Repeat steps 4.1-4.7 to test all specimens.</li>
</ol>
5. Steel Fiber Orientation Analysis
<ol>
	<li>Count the number of steel fibers on the fractured section.
	<ol>
		<li>Separate the specimens into two portions at the cracked section.</li>
		<li>Measure and record the orientation of the steel fibers on the fractured cross section of the cement mortar specimen. The orientation is the angle between a steel fiber and the axis of the specimen. Because manually measuring the orientations of steel fibers is difficult and can produce inaccurate measurements, orientations can be categorized as one of six angle ranges: 0 - 15 &#176;, 15 - 30 &#176;, 30 - 45 &#176;, 45 - 60 &#176;, 60 - 75 &#176; and 75 - 90 &#176;. Record the number of steel fibers in each group, and then calculate the average fiber orientation efficiency factor of the specimen using Equation (3): 
		<img alt="Equation 3" src="/files/ftp_upload/56307/56307eq3v2.jpg" /> (3) 
		where &#951;&#952; is the average orientation efficiency factor of the steel fibers, lf is the length of an individual steel fiber, n is the total number of steel fibers on the cracked section, and &#952;i is the angle between a steel fiber and direction of the magnetic field applied to the specimen (in the calculation, the middle value of the angle range is adopted for all steel fibers in each group).</li>
	</ol>
	</li>
	<li>Perform X-ray computed tomography analysis.
	<ol>
		<li>Cut a 75 mm cube from each mortar specimen.</li>
		<li>Perform the X-ray scanning of the cube using an X-ray computed tomography system. Place a specimen on the test platform and begin scanning. The specimen rotates 360 &#176; gradually and the machine records the attenuation of the X-rays caused by the specimen at each rotating step. The computed tomography system generates a three-dimensional digital structure of the cube.</li>
		<li>Identify the steel fibers in the digital cube structure by black and white binary processing. Then obtain the digital image describing the distribution of steel fibers.</li>
		<li>Determine the coordinates of all steel fibers by image analysis.</li>
		<li>Calculate the orientation of each steel fiber according to its coordinates.</li>
		<li>Calculate the orientation efficiency factor of the fibers using Equation (3).</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. 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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>

The authors have nothing to disclose.

The electromagnetic solenoid developed in this study has a chamber measuring 250&#215;250&#215;750 mm and cannot accommodate the full size structural elements. Although the size of the chamber limits the application of the setup, the concept and protocol proposed in this paper will inspire the further development of a full size setup for manufacturing ASFRC elements, particularly precast elements.
Achieving an appropriate viscosity of fresh mortar is essential factor for controlling the qualit...

Incorporating steel fibers into concrete is an effective way to overcome the inherent weakness of brittleness and to improve the tensile strength of concrete1. During the past decades, steel fiber reinforced concrete has been extensively investigated and widely used in the field. Steel fiber reinforced concrete is superior to concrete in terms of cracking resistance, tensile strength, fracture toughness, fracture energy, etc.2 In steel fiber reinforced concrete, steel fibers are randomly dispersed, thereby uniformly dispersing the reinforcing efficiency of the fibers in every direction. However, under certain loading conditions, only some of the steel fibers in concrete contribute to the performance of the structural elements because the reinforcing efficiency of the fibers requires that they be aligned with the principle tensile stresses in the structure. For instance, when using steel fiber reinforced concrete containing randomly distributed steel fibers to prepare a beam, some of the steel fibers, especially those parallel to the direction of the principal tensile stress, will make major contribution to reinforcing efficiency, while those perpendicular to the direction of the principal tensile stress will make no contribution to reinforcing efficiency. Consequently, finding an approach to align the steel fibers with the direction of the principal tensile stress in concrete is necessary to achieve the highest reinforcing efficiency of the steel fibers.
The orientation efficiency factor, defined as the ratio of the projected length along the direction of the tensile stress to the actual length of fibers, is usually used to indicate the efficiency of the reinforcement of steel fibers3,4. According to this definition, the orientation efficiency factor of the fibers aligned with the direction of the tensile stress is 1.0; that of the fibers that are perpendicular to the tensile stress is 0. Inclined fibers have an orientation efficiency factor between 0 and 1.0. The analytical results show that the orientation efficiency factor of randomly distributed steel fibers in concrete is 0.4054, while that from tests of ordinary steel fiber reinforced concrete is in the range of 0.167 to 0.5005,6. Evidently, if all the short steel fibers in concrete are aligned and have the same orientation as the tensile stress, the steel fibers will have the highest reinforcing efficiency and the specimens will have the optimum tensile behavior.
Some successful attempts to prepare aligned steel fiber reinforced concrete have been conducted since 1980s. In 1984, Shen7 applied an electromagnetic field to the bottom layer of steel fiber reinforced cementitious composite (SFRC) beams during casting, and X-ray detection analysis revealed that steel fibers were well aligned. In 1995, Bayer8 and Arman9 patented the approach for preparing aligned steel fiber reinforced concrete using a magnetic field. Yamamoto et al.10 considered the orientation of steel fibers in concrete to be mainly influenced by the casting approach and attempted to obtain aligned steel fiber reinforced concrete by keeping fresh concrete flowing into the formwork from a constant direction. Xu11 attempted to align steel fibers in shotcrete by spraying steel fibers from a constant direction. Rotondo and Wiener12 sought to make concrete poles with aligned long steel fibers by centrifugal casting. These experimental studies reveal that aligned steel fiber reinforced concrete has significant advantages over randomly distributed steel fiber reinforced concrete.
Recently, Michels et al.13 and Mu et al.14 have successfully developed a group of aligned steel fiber reinforced cementitious composites (ASFRCs) using electromagnetic fields. In these studies, various solenoids were made to provide a uniform magnetic field for aligning steel fibers in mortar specimens of different sizes. The solenoid has a hollow cuboid chamber, which can accommodate specimens of predefined sizes. When the solenoid is connected to direct current (DC), a uniform magnetic field is created in the chamber with a fixed orientation, which aligns with the axis of the solenoid. According to the principle of electromagnetics15, magnetic fields can drive ferromagnetic fibers to rotate and align in fresh mortar. Appropriate workability of the mortar is critical for allowing steel fibers to rotate in fresh mortar. A high viscosity may cause difficulty in the alignment of the steel fibers in the mortar, while low viscosity may lead to the segregation of fibers.
This paper describes the details of the preparation of ASFRC specimens and tests the flexural properties of ASFRC and SFRC. It is expected that ASFRC has a higher flexural strength and toughness than SFRC. Thus, ASFRC potentially has advantages over SFRC in withstanding tensile stress and resisting cracking if used as cover concrete, pavement, etc.
Using the fractured specimens after flexural tests, the orientation of the steel fibers in the specimens is investigated by observing the fractured cross sections and utilizing X-ray scanning computed tomography analysis16,17,18. The mechanical properties of ASFRCs, including their flexural strength and toughness, are reported and compared with those of non-electromagnetically treated SFRCs.

<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

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 Earth&#39;s magnetic field, for manufacturing a cementitious composite reinforced with aligned steel fibers. Aligned steel fiber reinforced cementitious composites (ASFRC) were prepared by applying a uniform electromagnetic field to fresh mortar containing short steel fibers, whereby the short steel fibers were driven to rotate in alignment with the magnetic field. The degree of alignment of steel fibers in hardened ASFRC was assessed both by counting steel fibers in fractured cross-sections and by X-ray computed tomography analysis. The results from the two methods show that the steel fibers in ASFRC were highly aligned while the steel fibers in non-magnetically treated composites were randomly distributed. The aligned steel fibers had a much higher reinforcing efficiency, and the composites, therefore, exhibited significantly enhanced flexural strength and toughness. The ASFRC is thus superior to SFRC in that it can withstand greater tensile stress and more effectively resist cracking.

The flexural strengths of ASFRCs and SFRCs determined from three-point bending tests are shown in Figure 5. The flexural strengths of ASFRCs are higher than those of SFRCs for all fiber dosages. The flexural strengths of ASFRCs were 88%, 71%, and 57% higher than those of SFRCs at the fiber volume fractions of 0.8%, 1.2%, and 2.0%, respectively. These results imply&#160;that the aligned steel fiber reinforces the cementitious matrix more effectively than rando...

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

This protocol describes an approach for manufacturing aligned steel fiber reinforced cementitious composite by applying a uniform electromagnetic field. Aligned steel fiber reinforced cementitious composite exhibits superior mechanical properties to ordinary fiber reinforced concrete.

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 ...

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11.0K 조회수.  Hebei University of Technology. This protocol describes an approach for manufacturing aligned steel fiber reinforced cementitious composite by applying a uniform electromagnetic field. Aligned steel fiber reinforced cementitious composite exhibits superior mechanical properties to ordinary fiber reinforced concrete.

비디오: 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.

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

연구

공학

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.

폴리머의 내구성 연구 및 동시 Hygrothermo 기계적 자극에 따라 섬유 강화 고분자 복합 재료에 대한 테스트 플랫폼

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.

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.

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.

섬유에 대 한 품질 관리를 향상 시키기 위해 설치 방법 강화 폴리머 스파이크 앵커

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).

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.

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.

DP780 강철의 마찰 교반 점 용접을 통해 랩 조인트 생성

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.

폴리 에스테르 강화 및 폴리 염화 비닐 코팅 기술 직물의 인공 열 노화

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.