Name: expression of cementitious pore solution and the analysis of its chemical composition and resistivity using x-ray fluorescence
Uploaded: 2018-09-23T13:00:00
Duration: 6 min 27 s
Description: Watch this Scientific Journal Video about Expression of Cementitious Pore Solution and the Analysis of Its Chemical Composition and Resistivity Using X-ray Fluorescence at JoVE.com

The authors would like to acknowledge partial financial support from the Kiewit Transportation Institute and the Federal Highway Administration (FHWA) through DTFH61-12-H-00010. All of the laboratory work presented herein was performed at the Kiewit Transportation Institute at Oregon State University.

1. Pore Solution Expression13
<ol>
	<li>Make sure the individual components of the pore solution extractor are clean and dry.</li>
	<li>Use a new cellulose filter (with an average pore diameter of 0.45 &#181;m) for each expression.</li>
	<li>Assemble the pore solution extractor, as shown in Figure 1.</li>
	<li>Check that there are no visible deformations in the cellulose filter.</li>
	<li>Add the fresh cementitious paste into the main chamber, leaving it empty for at least 1 cm from the top. 
	NOTE: The term fresh paste indicates any cementitious paste still in a plastic state. Cementitious pastes are generally made by mixing cement, supplementary cementitious materials, water, and chemical admixtures. The volume ratios of these constituents can vary depending on the properties desired.</li>
	<li>Connect the pore solution extractor to the nitrogen source and seal the main chamber.</li>
	<li>Align the expression device with the plastic canister to temporarily collect the extracted pore solution.</li>
	<li>Open the valve of the nitrogen tank and regulate the pressure using the pressure regulator, so that a pressure of approximately 200 kPa is applied to the paste inside the main chamber. 
	NOTE: For safety, a pressure regulator must be utilized.</li>
	<li>Maintain constant pressure for a period of 5 min, during which the pore solution will be collected in the plastic canister.</li>
	<li>After 5 min from the start of the expression, close the main valve so that the pressure inside the main chamber drops to atmospheric pressure.</li>
	<li>Remove the canister from under the extractor and transfer the pore solution to a 5-mL syringe, making sure not to suck in any air bubbles in the process.</li>
	<li>Seal the syringe with its needle cap and move it inside a 5 &#177; 1 &#176;C chamber to be stored till the time of testing.</li>
	<li>Wait until the pressure gauge shows that there is no additional pressure inside the main chamber and, then, disassemble the pore solution extractor.</li>
	<li>Clean the pore solution extractor parts using deionized water and paper towels.</li>
	<li>Discard the cellulose filter.</li>
</ol>
2. Assembly of the Solution Containers
<ol>
	<li>Make sure that the plastic cylinders are clean and dry.</li>
	<li>Place the polypropylene film (commercially available with 0.4-&#181;m thickness, 90 mm in diameter) flat on top of the larger cylinder (commercially available with a 35-mm diameter).</li>
	<li>Insert the smaller cylinder (commercially available with a 32-mm diameter) completely on top of the larger cylinder, pushing down and pressing the film in-between both cylinders to create a plastic container with a polypropylene film base.</li>
	<li>Ensure that the film is smooth and has no tears or deformations.</li>
</ol>
3. XRF Application Development and Solution Calibration
<ol>
	<li>Create an application file on the XRF software. The application has to be for solution samples and has to be able to detect the main ionic species in pore solution: sodium (Na+), potassium (K+), calcium (Ca2+), and sulfide (S2-).</li>
	<li>Calibrate the solution application with solutions of known concentrations.
	<ol>
		<li>Prepare the standard solutions using varying concentrations of &#62; 99% pure sodium chloride (NaCl), potassium chloride (KCl), calcium chloride (CaCl2), and aluminum sulfate (Al2[SO4]3) to accurately quantify the element studied. 
		NOTE: The concentrations of the standards can vary depending on the materials of interest. As an example, it has been observed that the concentrations of Na+ varied between 0 and 0.5 mol/L, the concentrations of K+ between 0 and 0.9 M, the concentrations of Ca2+ between 0 and 0.05 M, and the concentrations of S2- between 0 and 0.25 M; however, exceptions that exceed these limits might occur depending on the system14. The elements defined and measured in the calibration of the application must include all elements used in the calibration standards: sodium (Na+), potassium (K+), calcium (Ca2+), sulfide (S2-), calcium (Cl-), and aluminum (Al3+).</li>
		<li>For each calibration solution, measure 6 g of that solution inside the assembled testing container.</li>
		<li>Seal the container with the corresponding lid.</li>
		<li>Leave the testing container with the standard solution on a paper towel for 2 min to ensure that the film has no leaks that could potentially damage the XRF device.</li>
		<li>Place the sealed testing containers with the standard solutions inside the XRF sample holders and close the XRF.</li>
		<li>Measure each standard solution using the XRF. The intensities of characteristic fluorescent X-rays of elements from each of the solutions, measured in counts per minute (cpm), are detected by the XRF. 
		NOTE: Varying conditions sets for different groups of elements are needed. Refer to a previously published article for parameters such as measuring time and excitation energies6.</li>
		<li>Note the concentration in parts per million (ppm) of each element in each standard solution as defined in the software and related to the intensity in counts per minute (cpm) measured by the XRF.</li>
		<li>After the standard solutions are measured, use a matrix correction model from the XRF software used (linear, alphas, fundamental parameters (FP)) that will yield the minimum relative RMS (%) for each element in the calibration to create the best linear fit for the calibration.</li>
		<li>Verify that the application yields accurate results by testing solutions of known concentrations of sodium hydroxide (NaOH), potassium hydroxide (KOH), calcium hydroxide (Ca[OH]2), and aluminum sulfate (Al2[SO4]3) at different concentration levels within the calibration range. 
		NOTE: The application should yield accurate results if the error is within 5%.</li>
	</ol>
	</li>
</ol>
4. XRF Analysis
<ol>
	<li>Inject at least 2 g of the pore solution sample in the assembled testing container.</li>
	<li>Seal the container with the corresponding lid.</li>
	<li>Leave the container with the solution on a paper towel for 2 min to ensure that the film has no leaks that could potentially damage the XRF device.</li>
	<li>Place the testing containers with the solutions inside the XRF sample holders and close the XRF.</li>
	<li>On the XRF software, select the XRF application that was previously developed.</li>
	<li>Use the application interface on the software to select the XRF sample holders that are going to be subjected to the X-ray fluorescence analysis. 
	NOTE: It is recommended to name the new file for each selected sample holder based on the solution being tested.</li>
	<li>Start the XRF application to measure the ionic concentrations of the solutions. 
	NOTE: The results from the XRF analysis will show the concentration of sodium (Na+), potassium (K+), calcium (Ca2+), and sulfide (S2-).</li>
</ol>
5. Ionic Concentration Calculation
<ol>
	<li>Use stoichiometry to calculate the concentration of sulfate (SO42-) using equation 2. 
	<img alt="Equation 4" src="/files/ftp_upload/58432/58432eq04.jpg" style="opacity: 0.9;" />&#160; (2) 
	Here, 
	<img alt="Equation 5" src="/files/ftp_upload/58432/58432eq05.jpg" />&#160;= the measured ionic concentration of sulfide ions from XRF in ppm; 
	<img alt="Equation 6" src="/files/ftp_upload/58432/58432eq06.jpg" />&#160;= the molecular weight of sulfide in g/mol; 
	<img alt="Equation 7" src="/files/ftp_upload/58432/58432eq07.jpg" />&#160;= the measured ionic concentration of sulfate ions from XRF in ppm; 
	<img alt="Equation 8" src="/files/ftp_upload/58432/58432eq08.jpg" />&#160;= the molecular weight of sulfate in g/mol.</li>
	<li>Use a charge balance to calculate the concentration of hydroxides (OH-) using equation 3. 
	<img alt="Equation 9" src="/files/ftp_upload/58432/58432eq09.jpg" style="opacity: 0.9;" />&#160; (3) 
	Here, 
	<img alt="Equation 10" src="/files/ftp_upload/58432/58432eq10.jpg" />&#160;= the hydroxide ions concentration in ppm; 
	<img alt="Equation 11" src="/files/ftp_upload/58432/58432eq11.jpg" />&#160;= the sodium ions concentration in ppm; 
	<img alt="Equation 12" src="/files/ftp_upload/58432/58432eq12.jpg" />&#160;= the potassium ions concentration in ppm; 
	<img alt="Equation 13" src="/files/ftp_upload/58432/58432eq13.jpg" />&#160;= the calcium ions concentration in ppm; 
	<img alt="Equation 14" src="/files/ftp_upload/58432/58432eq14.jpg" />&#160;= the sulfate ions concentration in ppm.</li>
	<li>Convert the ionic concentrations from ppm to mol/L using equation 4 and assuming a density (&#961;) of 1,000 g/L. If desired, more accurate density information may be obtained from textbooks15 or thermodynamic software and used. 
	<img alt="Equation 15" src="/files/ftp_upload/58432/58432eq15.jpg" />&#160; (4) 
	Here, 
	<img alt="Equation 16" src="/files/ftp_upload/58432/58432eq16.jpg" />&#160;= the ionic concentration of a single ionic species in mol/L; 
	<img alt="Equation 17" src="/files/ftp_upload/58432/58432eq17.jpg" />&#160;= the ionic concentration of a single ionic species in ppm obtained from XRF; 
	<img alt="Equation 18" src="/files/ftp_upload/58432/58432eq18.jpg" />&#160;= the density of the solution in g/L; 
	<img alt="Equation 19" src="/files/ftp_upload/58432/58432eq19.jpg" />&#160;= the molecular weight of a single ionic species in g/mol; 
	<img alt="Equation 20" src="/files/ftp_upload/58432/58432eq20.jpg" />&#160;= a single ionic species.</li>
</ol>
6. Resistivity Calculation
<ol>
	<li>Use the model developed by Snyder et al.16, expressed in equations 5 - 7, to calculate the electrical resistivity of the pore solution. 
	<img alt="Equation 21" src="/files/ftp_upload/58432/58432eq21.jpg" />&#160;(5) 
	<img alt="Equation 22" src="/files/ftp_upload/58432/58432eq22.jpg" />&#160; (6) 
	<img alt="Equation 23" src="/files/ftp_upload/58432/58432eq23.jpg" style="opacity: 0.9;" />&#160; (7) 
	Here, 
	<img alt="Equation 24" src="/files/ftp_upload/58432/58432eq24.jpg" />&#160;= electrical resistivity of the solution in &#8486;m; 
	<img alt="Equation 25" src="/files/ftp_upload/58432/58432eq25.jpg" />&#160;= the equivalent conductivity of a single ionic species in cm2 S/mol; 
	<img alt="Equation 26" src="/files/ftp_upload/58432/58432eq26.jpg" />&#160;= the valence concentration of a single ionic species; 
	<img alt="Equation 17" src="/files/ftp_upload/58432/58432eq17.jpg" />&#160;= the molar concentration of a single ionic species in mol/L; 
	<img alt="Equation 27" src="/files/ftp_upload/58432/58432eq27.jpg" />*&#160;= the equivalent conductivity of ionic species at infinite dilution in cm2 S/mol; 
	<img alt="Equation 28" src="/files/ftp_upload/58432/58432eq28.jpg" />*&#160;= the empirical conductivity coefficient of a single ionic species in (mol/L)-1/2; 
	<img alt="Equation 29" src="/files/ftp_upload/58432/58432eq29.jpg" />&#160;= the ionic strength (molar basis) in mol/L; 
	<img alt="Equation 20" src="/files/ftp_upload/58432/58432eq20.jpg" />&#160;= a single ionic species. 
	Empirical values can be found in Table 1. 
	NOTE: The formation factor can then be estimated as the ratio of the electrical resistivity of concrete and the electrical resistivity of pore solution (equation 1)3. As the formation factor is a fundamental descriptor of the concrete microstructure, the determination of the formation factor is an important step in moving a traditionally prescriptive industry toward performance-based specifications. The formation factor has been linked to various transportation phenomena, such as diffusion, absorption, and permeability, and could be used to predict concrete service life1,2,4,5,17,18.</li>
</ol>

<ol>
	<li>Snyder, K. A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Relationship+between+the+formation+factor+and+the+diffusion+coefficient+of+porous+materials+saturated+with+concentrated+electrolytes:+theoretical+and+experimental+considerations.">Relationship between the formation factor and the diffusion coefficient of porous materials saturated with concentrated electrolytes: theoretical and experimental considerations.</a> Concrete Science and Engineering. 3, 216-224 (2001).</li><li>Dullien, F. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=.">.</a> Porous Media: Fluid Transport and Pore Structure. , (1992).</li><li>Archie, G. E. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+electrical+resistivity+log+as+an+aid+in+determining+some+reservoir+characteristics.">The electrical resistivity log as an aid in determining some reservoir characteristics.</a> Society of Petroleum Engineers. 142 (1), 54-62 (1942).</li><li>Spragg, R., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Factors+that+influence+electrical+resistivity+measurements+in+cementitious+systems.">Factors that influence electrical resistivity measurements in cementitious systems.</a> Transportation Research Record: Journal of the Transportation Research Board. 2342, 90-98 (2013).</li><li>Spragg, R. P., Bu, Y., Snyder, K. A., Bentz, D. P., Weiss, J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Electrical+Testing+of+Cement-Based+Materials:+Role+of+Testing+Techniques,+Sample+Conditioning,+and+Accelerated+Curing.">Electrical Testing of Cement-Based Materials: Role of Testing Techniques, Sample Conditioning, and Accelerated Curing.</a> Joint Transportation Research Program Technical Report. , (2013).</li><li>Tsui-Chang, M., Suraneni, P., Isgor, O. B., Trejo, D., Weiss, W. J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Using+X-ray+fluorescence+to+assess+the+chemical+composition+and+resistivity+of+simulated+cementitious+pore+solutions.">Using X-ray fluorescence to assess the chemical composition and resistivity of simulated cementitious pore solutions.</a> International Journal of Advances in Engineering Sciences and Applied Mathematics. 9 (3), 136-143 (2017).</li><li>Caruso, F., Mantellato, S., Palacios, M., Flatt, R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=ICP-OES+method+for+the+characterization+of+cement+pore+solutions+and+their+modification+by+polycarboxylate-based+superplasticizers.">ICP-OES method for the characterization of cement pore solutions and their modification by polycarboxylate-based superplasticizers.</a> Cement and Concrete Research. 38, 52-60 (2016).</li><li>Capacho-Delgado, L., Manning, D. 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R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=.">.</a> CRC Handbook of Chemistry and Physics. , (2018).</li><li>Snyder, K. A., Feng, X., Keen, B. D., Mason, T. O. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Estimating+the+electrical+conductivity+of+cement+paste+pore+solutions+from+OH-,+K++and+Na++concentrations.">Estimating the electrical conductivity of cement paste pore solutions from OH-, K+ and Na+ concentrations.</a> Cement and Concrete Research. 33 (6), 793-798 (2003).</li><li>Weiss, J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Relating+transport+properties+to+performance+in+concrete+pavements.">Relating transport properties to performance in concrete pavements.</a> CP Road MAP. , (2014).</li><li>Weiss, W. J., Spragg, R., Isgor, O. B., Ley, T. M., Van Dam, T., Hordijk, D. A., Lukovic, M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Toward+Performance+Specifications+for+Concrete:+Linking+Resistivity,+RCPT+and+Diffusion+Predictions+Using+the+Formation+Factor+for+Use+in+Specifications.">Toward Performance Specifications for Concrete: Linking Resistivity, RCPT and Diffusion Predictions Using the Formation Factor for Use in Specifications.</a> , 2057-2065 (2017).</li><li>Andersson, K., Allard, B., Bengtsson, M., Magnusson, B. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Chemical+composition+of+cement+pore+solutions.">Chemical composition of cement pore solutions.</a> Cement and Concrete Research. 19 (3), 327-322 (1989).</li><li>Barneyback, R., Diamond, S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Expression+and+analysis+of+pore+fluids+from+hardened+cement+pastes+and+mortars.">Expression and analysis of pore fluids from hardened cement pastes and mortars.</a> Cement and Concrete Research. 11 (2), 279-285 (1981).</li><li>Nicoleau, L., Schreiner, E., Nonat, A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Ion-specific+effects+influencing+the+dissolution+of+tricalcium+silicate.">Ion-specific effects influencing the dissolution of tricalcium silicate.</a> Cement and Concrete Research. 59, 118-138 (2014).</li><li>Rajabipour, F., Sant, G., Weiss, W. 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The authors have nothing to disclose.

Since this is a sensitive chemical analysis method, it is imperative to have laboratory practices that prevent contamination. For this method, it is critical that the calibration standards are specifically performed with high-purity chemicals (&#62; 99%). When transferring the pore solution into the syringe, make sure that no visible cement grains are present in the solution to avoid any changes in the pore solution. When stored in a sealed syringe at a constant temperature of 5 &#177; 1 &#176;C, the pore solution has been observed to maintain an unaltered chemical composition for up to 7 days.
One of the main limitations of this protocol is that the method of expression outlined can only be used for fresh paste specimens and is not suitable for later age samples. For later age or hardened samples, a method of expression using a high-pressure extraction die20 is needed. Another limitation is that a minimum amount of 2 g of solution is needed to test in the XRF since an amount less than 2 g does not provide a constant sample height that can cover the entire bottom face of the container. This last limitation applies to the particular set-up that was used in this study. A different set-up would probably allow a reduction in the minimum amount of pore solution required for the testing. Another limitation is that the model is not likely applicable to systems containing slag-rich cements since species such as bisulfide (HS-) may be present, as discussed by Vollpracht et al.14.
Since XRF is a commonly used technique in the cement industry, this method could potentially enable cement manufacturers to use a tool already at their disposal to provide more information about the cementitious pore solution, such as the chemical composition and resistivity for numerous applications and at a lower cost and testing time than conventional methods. For example, when comparing sample preparation and testing time between ICP (a commonly used testing method for pore solution composition), the testing time is reduced from 50 min per sample to 8 min per sample using XRF. This method could extend the applications for XRF and could potentially be implemented fairly quickly in the industry.
XRF can be used to determine the main elemental concentrations in the pore solution. This suggests the use of XRF for applications such as (i) determining the composition of pore solutions to study the dissolution kinetics of cementitious phases21 or (ii) determining the effect of chemical admixtures22. Early age pore solution and concrete resistivity measurements could be used as a measure of the water-to-cement ratio of concrete, which could potentially be used in quality control.

The transport properties of concrete are determined by its formation factor, which is a fundamental measure of the microstructure1. The formation factor is defined as the inverse of the product between the connectivity and the porosity of a concrete2. The formation factor can be calculated from the ratio of the electrical resistivity of concrete and the electrical resistivity of pore solution as presented in equation 13.
<img alt="Equation 1" src="/files/ftp_upload/58432/58432eq01.jpg" />&#160; (1)
Here,
<img alt="Equation 2" src="/files/ftp_upload/58432/58432eq02.jpg" style="font-size: 14px;" />&#160;= electrical resistivity of bulk or concrete (&#937;m);
<img alt="Equation 3" src="/files/ftp_upload/58432/58432eq03.jpg" style="font-size: 14px;" />&#160;= electrical resistivity of pore solution (&#937;m).
The bulk electrical resistivity of concrete may be easily determined on hardened concrete using a resistivity meter, following approaches outlined in AASHTO PP84-17 Appendix X2 and other literature4,5. The purpose of this article is to provide instructions for expressing the pore solution from fresh paste and analysis of the solution ionic composition using X-ray fluorescence (XRF) spectroscopy. The expressed pore solution is tested in the XRF using commercially available materials (cylinders and film). The ionic composition detected by the XRF can be used for multiple concrete durability applications and can also be used to calculate the electrical resistivity of pore solution, to ultimately determine the formation factor6.
Current methods to determine the chemical composition of pore solution, such as inductively coupled plasma (ICP)7, atomic absorption spectroscopy (AAS)8, and ion chromatography (IC)9, can be costly, time-consuming, and quite laborious. Additionally, in some cases, a combination of various methods must be used in order to obtain a complete characterization of the main ionic species in pore solution10. XRF can be used as an alternative to these methods, where the composition of pore solution can be obtained at a relatively lower cost and shorter testing time compared to conventional methods.
XRF is a technique commonly used in the cement industry as it is primarily used to analyze the chemical composition of the manufactured materials for quality control and quality assurance throughout the cement manufacturing process11,12. Therefore, this method will describe how that technique can be used to enable cement manufacturers to use this tool to provide more information about the pore solution composition of different cement batches. Overall, using XRF for pore solutions could potentially extend the use of this technique for multiple applications and could be implemented in the industry relatively quickly.

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	<tbody>
		<tr height="63">
			<td height="63" style="height:63px;width:193px;">Energy Disperssive X-Ray Fluorescence Benchtop Spectrometer</td>
			<td style="width:103px;">Malvern PANalytical</td>
			<td style="width:119px;">Epsilon 3XLE or Epsilon 4</td>
			<td style="width:441px;"></td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:193px;">35 mm Sample Cups for Liquids</td>
			<td style="width:103px;">Malvern PANalytical</td>
			<td style="width:119px;">9425 888 00024</td>
			<td style="width:441px;">Panalytical Consumables Catalogue 2016 for XRF Accessories and Consumables Catalog</td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:193px;">4 micron Polypropylene Film</td>
			<td style="width:103px;">Malvern PANalytical</td>
			<td style="width:119px;">9425 888 00029</td>
			<td style="width:441px;">Panalytical Consumables Catalogue 2016 for XRF Accessories and Consumables Catalog</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:193px;">Syringe, 5 mL</td>
			<td style="width:103px;">VWR</td>
			<td>53548-005</td>
			<td>HSW Norm-Ject Sterile Luer-Slip syringes, Air-Tite</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:193px;">Needle, 16Gx1&#39;&#39;</td>
			<td style="width:103px;">VWR</td>
			<td>89219-334</td>
			<td>Premium Veterinary Hypodermic Needles, Sterile, Air-Tite</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:193px;">Container</td>
			<td style="width:103px;">VWR&#160;</td>
			<td>15704-092</td>
			<td>VWR Specimen containers, Polypropylene with Polyethylene Caps</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:193px;">Pressurized Filter Holder</td>
			<td style="width:103px;">EMD Millipore</td>
			<td>XX4004700</td>
			<td>100 mL capacity, 47 mm filter diameter</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:193px;">MCE Membrane Filter</td>
			<td style="width:103px;">PALL</td>
			<td style="width:119px;">63069</td>
			<td>47 mm diameter, 0.45 &#956;m pore size</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:193px;">Silicone Funnell</td>
			<td style="width:103px;">SpiceLuxe</td>
			<td>SLP-122513-F1</td>
			<td>Top opening 2 1/2&#8243;, Bottom opening 3/4&#8243;, Height 2 3/4&#8243;</td>
		</tr>
	</tbody>
</table>

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.

In this section, representative outcomes of each major step in the methodology are presented. This is done in order to obtain an idea of what is expected at the end of each step and provide useful tips to ensure a correct application of the method.
The first important step consists in the expression of the pore solution from the fresh paste sample. Figure 2 shows a pore solution that is correctly extracted and sealed in a 5-mL syringe. The pore solution in the figure was expressed from a fresh ordinary Portland cement paste with a water-to-cement ratio of 0.36. The sample was mixed 10 min before the image was taken. The pore solution is expected to be clear; however, the color can vary depending on the type of cementitious materials that were used and the age of the sample at the time of the expression.
Before the XRF measurement of the extracted pore solution, it is necessary to calibrate the instrument. In particular, each element whose ionic concentration will be measured needs to be calibrated. A representative calibration plot of the potassium (K+) ions is shown in Figure 3. The figure shows the fitting performed by the software on the intensities measured by the XRF. Note that the root mean square (RMS) error of the fitting should stay below 5%.
After calibration, it is recommended to test a solution of known ionic concentration to determine the accuracy of the machine. The measured composition of the ions using XRF is compared to the theoretical composition of both solutions. According to our experience, assuming a correct preparation of the ionic solutions, this checking step should yield a percentage of errors lower than &#177; 5%. Figure 4 shows the composition results for the spot-checking of the solutions. When the spot-checking yields a percentage of errors higher than &#177; 5%, repeat the calibration of the XRF device.

Table 2 shows a representative set of results for composition and resistivity. While the ionic concentration of the pore solution can vary widely depending on the chemical composition of the cement, the water-to-cement ratio of the system, and the presence of supplementary cementitious materials19, reference values can be obtained from the literature20 for the main ions, as shown in Table 1.

Finally, when calculating the resistivity of a sample, values for early age pore solutions are typically expected to be within 0.05 and 0.25 &#937;m14. Now that the resistivity of the pore solution is known, the bulk resistivity can be obtained using other methods, like uniaxial resistivity, in order to, ultimately, calculate the formation factor, which is typically over 2,000 for good quality concrete4,5,18.
<img alt="Figure 1" class="xfigimg" src="/files/ftp_upload/58432/58432fig1.jpg" /> 
Figure 1: Assembly of the pore solution extraction system. The system consists of a main expression device, a nitrogen tank and tube with a safety pressure gauge and regulator, and a collection container. Always refer to the manufacturer&#39;s instructions and safety precautions for the specific system used. <a href="https://www.jove.com/files/ftp_upload/58432/58432fig1large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>
<img alt="Figure 2" class="xfigimg" src="/files/ftp_upload/58432/58432fig2.jpg" /> 
Figure 2: Correctly extracted and sealed extracted pore solution in a 5-mL syringe. The extracted pore solution should appear clear (i.e., no visible particles) and should be sealed with no air bubbles within the syringe.&#160;
<img alt="Figure 3" class="xfigimg" src="/files/ftp_upload/58432/58432fig3.jpg" /> 
Figure 3: Representative calibration plot of potassium (K+). The x-axis shows the imputed (known) concentrations in ppm, and the y-axis shows the detected (measured) intensities with XRF in cpm. The calibration line calculated from one of the correction models in the software should have the smallest RMS (%), as discussed in section 3 of the protocol. <a href="https://www.jove.com/files/ftp_upload/58432/58432fig3large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>
<img alt="Figure 4" class="xfigimg" src="/files/ftp_upload/58432/58432fig4.jpg" /> 
Figure 4: Sodium ion (Na+) and potassium ion (K+) verification plot. The dashed line represents a 1:1 ratio.The verification plot should show a good correlation (almost a 1:1 relationship with a high R-squared value) between the known concentrations of the sodium and potassium ions and the detected concentrations using XRF. <a href="https://www.jove.com/files/ftp_upload/58432/58432fig4large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>
<table border="1" fo:keep-together.within-page="1" fo:keep-with-next.within-page="always">
	<tbody>
		<tr>
			<td>Ionic Species (i)</td>
			<td>Equivalent conductivity at infinite dilution (&#955;&#730;i)</td>
			<td>Empirical conductivity coefficient&#160;</td>
		</tr>
		<tr>
			<td>(i)</td>
			<td>(z&#955;&#176;i)</td>
			<td>(Gi)&#160;</td>
		</tr>
		<tr>
			<td></td>
			<td>(cm2 S/mol)</td>
			<td>(mol/L)-1/2</td>
		</tr>
		<tr>
			<td>Sodium (Na+)</td>
			<td>50.1</td>
			<td>0.733</td>
		</tr>
		<tr>
			<td>Potassium (K+)</td>
			<td>73.5</td>
			<td>0.548</td>
		</tr>
		<tr>
			<td>Calcium (Ca2+)</td>
			<td>59</td>
			<td>0.771</td>
		</tr>
		<tr>
			<td>Hydroxide (OH-)</td>
			<td>198</td>
			<td>0.353</td>
		</tr>
		<tr>
			<td>Sulfate (SO42-)</td>
			<td>79</td>
			<td>0.877</td>
		</tr>
	</tbody>
</table>
Table 1: Equivalent conductivity at infinite dilution (<img alt="Equation 30" src="/files/ftp_upload/58432/58432eq30.jpg" />) and empirical conductivity coefficients (<img alt="Equation 31" src="/files/ftp_upload/58432/58432eq31.jpg" />&#8203;) for each ionic species&#160;obtained from the literature11. These values are used in order to calculate the electrical resistivity of the pore solution.
<table border="1" fo:keep-together.within-page="1" fo:keep-with-next.within-page="always">
	<tbody>
		<tr>
			<td>Ionic Species&#160;</td>
			<td>Concentration&#160;</td>
		</tr>
		<tr>
			<td>(i)</td>
			<td>(mol/L)</td>
		</tr>
		<tr>
			<td>Sodium (Na+)</td>
			<td>0.16</td>
		</tr>
		<tr>
			<td>Potassium (K+)</td>
			<td>0.39</td>
		</tr>
		<tr>
			<td>Calcium (Ca2+)</td>
			<td>0.02</td>
		</tr>
		<tr>
			<td>Hydroxide (OH-)</td>
			<td>0.18</td>
		</tr>
		<tr>
			<td>Sulfate (SO42-)</td>
			<td>0.2</td>
		</tr>
		<tr>
			<td>Resistivity (&#937;m)</td>
			<td>0.156</td>
		</tr>
	</tbody>
</table>
Table 2: Representative results for the composition and resistivity of a cement paste with a water-to-cement ratio of 0.36 at 10 min. The values in this table are examples of the results obtained using this method.

Watch this Scientific Journal Video about Expression of Cementitious Pore Solution and the Analysis of Its Chemical Composition and Resistivity Using X-ray Fluorescence at JoVE.com

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

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 ...

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Unit 1

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SCIENTISTS IN ACTION

Fabrication and Visualization of Capillary Bridges in Slit Pore Geometry

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A procedure for creating and imaging capillary bridges in slit-pore geometry is presented. The creation of capillary bridges relies on the formation of pillars to provide a directional physical and chemical heterogeneity to pin the fluid. Capillary bridges are formed and manipulated using microstages and visualized using a CCD camera.

A procedure for creating and imaging capillary bridges in slit-pore geometry is presented. High aspect ratio hydrophobic pillars are fabricated and ...

Reservoir Condition Pore-scale Imaging of Multiple Fluid Phases Using X-ray Microtomography

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We present a methodology for the imaging of multiple fluid phases at reservoir conditions by the use of x-ray microtomography. We show some representative results of capillary trapping in a carbonate rock sample.

X-ray microtomography was used to image, at a resolution of 6.6 &#181;m, the pore-scale arrangement of residual carbon dioxide ganglia in the pore-space ...

Energy Dispersive X-ray Tomography for 3D Elemental Mapping of Individual Nanoparticles

Energy dispersive X-ray spectroscopy within the scanning transmission electron microscope (STEM) provides accurate elemental analysis with high spatial resolution, and is even capable of providing atomically resolved elemental maps. In this technique, a highly focused electron beam is incident upon a thin sample and the energy of emitted X-rays is measured in order to determine the atomic species of material within the beam path. This elementally sensitive spectroscopy technique can be extended to three dimensional tomographic imaging by acquiring multiple spectrum images with the sample tilted along an axis perpendicular to the electron beam direction.
Elemental distributions within single nanoparticles are often important for determining their optical, catalytic and magnetic properties. Techniques such as X-ray tomography and slice and view energy dispersive X-ray mapping in the scanning electron microscope provide elementally sensitive three dimensional imaging but are typically limited to spatial resolutions of &gt; 20 nm. Atom probe tomography provides near atomic resolution but preparing nanoparticle samples for atom probe analysis is often challenging. Thus, elementally sensitive techniques applied within the scanning transmission electron microscope are uniquely placed to study elemental distributions within nanoparticles of dimensions 10-100 nm.
Here, energy dispersive X-ray (EDX) spectroscopy within the STEM is applied to investigate the distribution of elements in single AgAu nanoparticles. The surface segregation of both Ag and Au, at different nanoparticle compositions, has been observed.

The use of energy dispersive X-ray tomography in the scanning transmission electron microscope to characterize elemental distributions within single nanoparticles in three dimensions is described.

Energy dispersive X-ray spectroscopy within the scanning transmission electron microscope (STEM) provides accurate elemental analysis with high spatial ...

Failure Analysis of Batteries Using Synchrotron-based Hard X-ray Microtomography

Imaging morphological changes that occur during the lifetime of rechargeable batteries is necessary to understand how these devices fail. Since the advent of lithium-ion batteries, researchers have known that the lithium metal anode has the highest theoretical energy density of any anode material. However, rechargeable batteries containing a lithium metal anode are not widely used in consumer products because the growth of lithium dendrites from the anode upon charging of the battery causes premature cell failure by short circuit. Lithium dendrites can also form in commercial lithium-ion batteries with graphite anodes if they are improperly charged. We demonstrate that lithium dendrite growth can be studied using synchrotron-based hard X-ray microtomography. This non-destructive imaging technique allows researchers to study the growth of lithium dendrites, in addition to other morphological changes inside batteries, and subsequently develop methods to extend battery life.

Synchrotron-based hard X-ray microtomography is used to image the electrochemical growth of dendrites from a lithium metal electrode through a solid polymer electrolyte membrane.

Imaging morphological changes that occur during the lifetime of rechargeable batteries is necessary to understand how these devices fail. Since the advent ...

Measurement of X-ray Beam Coherence along Multiple Directions Using 2-D Checkerboard Phase Grating

A procedure for a technique to measure the transverse coherence of synchrotron radiation X-ray sources using a single phase grating interferometer is reported. The measurements were demonstrated at the 1-BM bending magnet beamline of the Advanced Photon Source (APS) at Argonne National Laboratory (ANL). By using a 2-D checkerboard &#960;/2 phase-shift grating, transverse coherence lengths were obtained along the vertical and horizontal directions as well as along the 45&#176; and 135&#176; directions to the horizontal direction. Following the technical details specified in this paper, interferograms were measured at different positions downstream of the phase grating along the beam propagation direction. Visibility values of each interferogram were extracted from analyzing harmonic peaks in its Fourier Transformed image. Consequently, the coherence length along each direction can be extracted from the evolution of visibility as a function of the grating-to-detector distance. The simultaneous measurement of coherence lengths in four directions helped identify the elliptical shape of the coherence area of the Gaussian-shaped X-ray source. The reported technique for multiple-direction coherence characterization is important for selecting the appropriate sample size and orientation as well as for correcting the partial coherence effects in coherence scattering experiments. This technique can also be applied for assessing coherence preserving capabilities of X-ray optics.

The measurement protocol and data analysis procedure are given for obtaining transverse coherence of a synchrotron radiation X-ray source along four directions simultaneously using a single 2-D checkerboard phase grating. This simple technique can be applied for complete transverse coherence characterization of X-ray sources and X-ray optics.

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Quantification of Hydrogen Concentrations in Surface and Interface Layers and Bulk Materials through Depth Profiling with Nuclear Reaction Analysis

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Protocol of Electrochemical Test and Characterization of Aprotic Li-O2 Battery

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Synchrotron fast tomography was used to dynamically image dissolution of limestone in the presence of CO2-saturated brine at reservoir conditions. 100 scans were taken at a 6.1 &#181;m resolution over a period of 2 h.

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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.

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.

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We describe a beamline setup meant to carry out rapid two-dimensional x-ray fluorescence and x-ray microdiffraction mapping of single crystal or powder samples using either Laue (polychromatic radiation) or powder (monochromatic radiation) diffraction. The resulting maps give information about strain, orientation, phase distribution, and plastic deformation.