Name: determination of aggregate surface morphology at the interfacial transition zone (itz)
Uploaded: 2019-12-16T15:00:00
Description: Watch this Scientific Journal Video about Determination of Aggregate Surface Morphology at the Interfacial Transition Zone ITZ at JoVE.com

The authors gratefully acknowledge the financial support from the National Key R&#38;D Program of China (2017YFB0309904), National Natural Science Foundation of China (Grant Nos. 51508090 and 51808188), 973 Program (2015CB655100), State Key Laboratory of High-Performance Civil Engineering Materials (2016CEM005). Also, greatly appreciate Jiangsu Research Institute of Building Science Co., Ltd and the State Key Laboratory of High-Performance Civil Engineering Materials for funding the research project.

1. Preparation of the model concrete with a single ceramic particle
<ol>
	<li>Mold preparation
	<ol>
		<li>Use a brush to clean the mold (25 mm x 25 mm x 25 mm) and ensure that the inner surfaces of the mold are impurity-free.</li>
		<li>Use another brush to uniformly apply diesel oil on the inner surfaces of the mold for easier mold-release. 
		NOTE: Here, we did not use the common mold for mortar or concrete preparation. As the ceramic particle is around 15 mm in diameter, a cubic plastic mold around 30 mm in le...

<ol>
	<li>Scrivener, K. L., Crumbie, A. K., Laugesen, P. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+Interfacial+Transition+Zone+(ITZ)+Between+Cement+Paste+and+Aggregate+in+Concrete.">The Interfacial Transition Zone (ITZ) Between Cement Paste and Aggregate in Concrete.</a> Interface Science. 12 (4), 411-421 (2004).</li><li>Scrivener, K. L. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Backscattered+electron+imaging+of+cementitious+microstructures:+understanding+and+quantification.">Backscattered electron imaging of cementitious microstructures: understanding and quantification.</a> Cement and Concrete Composites. 26 (8), 935-945 (2004).</li><li>Houst, Y. F., Sadouki, H., Wittmann, F. 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The X-CT technique was applied to roughly determine the geometrical center of the ceramic particle to ensure that the analyzed surface is through the equator of the particle. Thus, the overestimation of the ITZ thickness caused by the 2D artifacts could be avoided38. Herein, the accuracy of obtained results is highly dependent on the flatness of the examined surfaces. Generally, a longer grinding and polishing time contributes to an adequately smooth surface for testing. However, due to the varyin...

At the mesoscopic scale, cement-based materials can be regarded as a three-phase composite comprised of the cement paste, the aggregate, and the interfacial transition zone (ITZ) between them1,2. The ITZ is often treated as a weak link since its increased porosity could act as channels for the ingress of aggressive species3,4 or provide easier pathways for crack growth5,6,7,8,9,10,11. Subsequently, it is of great interest to precisely characterize the properties of the ITZ to evaluate and predict the macro performance of the cement-based materials.
To investigate the ITZ, there has been excessive research on its microstructural features, forming mechanisms, and influencing factors12,13,14 using both experimental and numerical methods. Various techniques have been coupled for ITZ characterization including: mechanical tests, transport tests, mercury intrusion porosimetry (MIP) tests15,16 and nano-indentation17. It is widely accepted that the ITZ is mainly caused by the wall effect, as well as water film, micro-bleeding, one side growth, and gel syneresis18.
With the development of digital image processing method (DIP) in the last two decades19, the morphological characteristics of the ITZ (e.g., volume fraction, thickness, and porosity gradient) can be quantitatively determined. Based on examination of the plane sections using scanning electron microscopy (SEM) with a backscattered electron detector (BSE), the three dimensional (3D) features of ITZ can be derived from the 2D results via stereology theory20. Like the SEM-BSE technique, the nano-indentation technique is also based on the examination of polished surfaces, but it more focuses on the elastic modulus of the existing phases21. However, in both SEM-BSE analysis and the nano-indentation test, the ITZ thickness may be overestimated as the examined cross section rarely goes through the normal direction from an aggregate surface22. However, coupling this with fluorescent 3D confocal microscopy, the overestimation of ITZ could be eliminated and a real ITZ porosity and anhydrous cement content could be obtained23.
Previous studies of influencing factors mainly focused on the cement paste, ignoring the role of the aggregate and its surface texture24,25,26. Since the shape and morphological properties of the aggregate have been extensively described based on quantitative analysis of digital slices obtained from SEM or X-ray computed tomography (X-CT)27,28. However, no research focusing on the effect of the aggregate surface texture on the formation of ITZ region has been performed.
Hereby, we present a protocol to investigate the effect of aggregate surface morphology on the ITZ microstructure formation based on quantitative analysis of SEM-BSE images and a K-means clustering algorithm. A model concrete sample was prepared with spherical ceramic particle acting as the coarse aggregate. X-CT was used to roughly determine the relative location of the particle in the opaque cement matrix before halving the sample. After processing to obtained SEM-BSE images, the uneven distribution of ITZ around single aggregate was observed. Also, an index surface roughness (SR) describing the aggregate surface texture at the pixel level was defined. The K-means clustering algorithm, originally used in the area of signal processing and now widely used for image clustering29,30, was introduced to established a relationship between surface roughness (SR) and porosity gradient (SL).

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			<td>&#934;15 mm</td>
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			<td>Nissin Corporation</td>
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			<td>Buehler</td>
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		</tr>
		<tr>
			<td>High precision cutting machine</td>
			<td>Buehler</td>
			<td>2215</td>
			<td></td>
		</tr>
		<tr>
			<td>Image J</td>
			<td>National Institutes of Health</td>
			<td>1.52o</td>
			<td></td>
		</tr>
		<tr>
			<td>Isopropyl alcohol</td>
			<td>Sinopharm</td>
			<td>M0130-241</td>
			<td></td>
		</tr>
		<tr>
			<td>Matlab</td>
			<td>MathWorks</td>
			<td>R2014a</td>
			<td></td>
		</tr>
		<tr>
			<td>Paper</td>
			<td>Deli</td>
			<td>A4</td>
			<td></td>
		</tr>
		<tr>
			<td>Plastic box</td>
			<td>Beichen</td>
			<td>3630</td>
			<td></td>
		</tr>
		<tr>
			<td>Plastic mold</td>
			<td>Youke</td>
			<td>a=b=c=25mm</td>
			<td></td>
		</tr>
		<tr>
			<td>Polished flannelette</td>
			<td>Buehler</td>
			<td>242150, 00242050, 00242100</td>
			<td></td>
		</tr>
		<tr>
			<td>Release agent</td>
			<td>Buehler</td>
			<td>20-8186-30</td>
			<td></td>
		</tr>
		<tr>
			<td>Scanning Electron Microscopy</td>
			<td>FEI</td>
			<td>Quanta 250</td>
			<td></td>
		</tr>
		<tr>
			<td>Scrape knife</td>
			<td>Jinzheng Building Materials</td>
			<td>CD-3</td>
			<td></td>
		</tr>
		<tr>
			<td>SiC paper</td>
			<td>Buehler</td>
			<td>P180, P320, P1200</td>
			<td></td>
		</tr>
		<tr>
			<td>Ultrasonic cleaner</td>
			<td>Zhixin</td>
			<td>DLJ</td>
			<td></td>
		</tr>
		<tr>
			<td>Vacuum box</td>
			<td>Heheng</td>
			<td>DZF-6020</td>
			<td></td>
		</tr>
		<tr>
			<td>Vacuum drying oven</td>
			<td>ZK</td>
			<td>ZK30</td>
			<td></td>
		</tr>
		<tr>
			<td>Vibrating table</td>
			<td>Jianyi</td>
			<td>GZ-75</td>
			<td></td>
		</tr>
		<tr>
			<td>Wooden stick</td>
			<td>Buehler</td>
			<td>20-8175</td>
			<td></td>
		</tr>
		<tr>
			<td>X-ray Computed Tomography</td>
			<td>YXLON</td>
			<td>Y.CT PRECISION S</td>
			<td></td>
		</tr>
	</tbody>
</table>

determination of aggregate surface morphology at the interfacial transition zone (itz)

Here, we present a comprehensive method to illustrate the uneven distribution of the interfacial transition zone (ITZ) around the aggregate and the effect of aggregate surface morphology on the formation of ITZ. First, a model concrete sample is prepared with a spherical ceramic particle in roughly the central part of the cement matrix, acting as a coarse aggregate used in common concrete/mortar. After curing until the designed age, the sample is scanned by X-ray computed tomography to determine the relative location of the ceramic particle inside the cement matrix. Three locations of the ITZ are chosen: above the aggregate, on the side of the aggregate, and below the aggregate. After a series of treatments, the samples are scanned with a SEM-BSE detector. The resultant images were further processed using a digital image processing method (DIP) to obtain quantitative characteristics of the ITZ. The surface morphology is characterized at the pixel level based on the digital image. Thereafter, K-means clustering method is used to illustrate the effect of surface roughness on ITZ formation.

The porosity distribution of ITZ regions above the aggregate, on the side of the aggregate, and below the aggregate are compared and shown in Figure 432. The porosity of the ITZ above the upper surface appears to be smaller than that on the side or above the aggregate, indicating a denser ITZ microstructure, while the ITZ below the aggregate is always the most porous due to micro-bleeding. Figure 432 shows that eve...

Watch this Scientific Journal Video about Determination of Aggregate Surface Morphology at the Interfacial Transition Zone ITZ at JoVE.com

Determination of Aggregate Surface Morphology at the Interfacial Transition Zone ITZ

Hereby, we proposed a protocol to illustrate the effect of aggregate surface morphology on the ITZ microstructure. The SEM-BSE image were quantitatively analyzed to obtain ITZ's porosity gradient via digital image processing and a K-means clustering algorithm was further employed to establish a relationship between porosity gradient and surface roughness.

Determination of Aggregate Surface Morphology at the Interfacial Transition Zone (ITZ)

Here, we present a comprehensive method to illustrate the uneven distribution of the interfacial transition zone (ITZ) around the aggregate and the effect ...

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JoVE Journal

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