Tomography-Based Investigation on the Carbonation Behavior through the Surface-Opening Cracks of Sliced Paste Specimen

Understanding the cracking behavior during carbonation is of high importance, and the cracks can serve as a shortcut for CO2 diffusion, which can further accelerate the carbonation process itself. In this study, a sliced paste sample was taken for an accelerated carbonation test, and the cracking behavior, as well as its impact on carbonation, was investigated through a novel extended attenuation method based on X-ray (XRAM) which is performed primarily on computed tomography (CT). Surface-opening cracks at different carbonation ages were rendered, based on which a full view on the carbonation-cracking behavior was built. The results reveal that the crack paths can rapidly be occupied by CO2, and that leads to the generation of V-shaped carbonation cusps pervading the carbonation fronts. The V-shaped carbonation cusps were mostly generated at the early carbonation age (within 14 days), attesting to a less intact sample surface as compared to the inside area. Moreover, this study confirms that the carbonated area would split into two independent zones with variant carbonation degree due to the increased humidity level near the sample surface. The current work reveals the interconnection between carbonation and cracking, and the results can be used for the designing of cement-based materials with better carbonation and cracking resistance.

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The Basic Physical Principles of Ion, Electron, and X-Ray Detectors and Their Application to Microanalysis

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100117777 ◽

1985 ◽

Vol 43 ◽

pp. 154-157

Author(s):

A.J. Tousimis

Keyword(s):

Ion Beam ◽

Depth Resolution ◽

Sample Surface ◽

High Energy ◽

X Rays ◽

X Ray ◽

Electrons And Ions ◽

Spatial Depth ◽

Minimum Surface Area ◽

Physical Principles

An integral and of prime importance of any microtopography and microanalysis instrument system is its electron, x-ray and ion detector(s). The resolution and sensitivity of the electron microscope (TEM, SEM, STEM) and microanalyzers (SIMS and electron probe x-ray microanalyzers) are closely related to those of the sensing and recording devices incorporated with them.Table I lists characteristic sensitivities, minimum surface area and depth analyzed by various methods. Smaller ion, electron and x-ray beam diameters than those listed, are possible with currently available electromagnetic or electrostatic columns. Therefore, improvements in sensitivity and spatial/depth resolution of microanalysis will follow that of the detectors. In most of these methods, the sample surface is subjected to a stationary, line or raster scanning photon, electron or ion beam. The resultant radiation: photons (low energy) or high energy (x-rays), electrons and ions are detected and analyzed.

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Description of the concrete carbonation process with adjusted depth-resolved thermogravimetric analysis

Journal of Thermal Analysis and Calorimetry ◽

10.1007/s10973-021-10966-1 ◽

2021 ◽

Author(s):

Nico Vogler ◽

Philipp Drabetzki ◽

Mathias Lindemann ◽

Hans-Carsten Kühne

Keyword(s):

Calcium Hydroxide ◽

Bound Water ◽

Reference Method ◽

Microscopic Analysis ◽

Limestone Powder ◽

Gravimetric Analysis ◽

Sample Material ◽

Accelerated Carbonation ◽

Temperature Range ◽

Carbonation Process

AbstractThe thermal gravimetric analysis (TG) is a common method for the examination of the carbonation progress of cement-based materials. Unfortunately, the thermal properties of some components complicate the evaluation of TG results. Various hydrate phases, such as ettringite (AFt), C–S–H and AFm, decompose almost simultaneously in the temperature range up to 200 °C. Additionally, physically bound water is released in the same temperature range. In the temperature range between 450 °C and 600 °C, the decomposition of calcium hydroxide and amorphous or weakly bound carbonates takes place simultaneously. Carbonates, like calcite, from limestone powder or other additives may be already contained in the noncarbonated sample material. For this research, an attempt was made to minimise the influence of these effects. Therefore, differential curves from DTG results of noncarbonated areas and areas with various states of carbonation of the same sample material were calculated and evaluated. Concretes based on three different types of cement were produced and stored under accelerated carbonation conditions (1% CO2 in air). The required sample material was obtained by cutting slices from various depths of previously CO2-treated specimen and subsequent grinding. During the sample preparation, a special attention was paid that no additional carbonation processes took place. As reference method for the determination of the carbonation depth, the sprayed application of phenolphthalein solution was carried out. Microscopic analysis was examined to confirm the assumptions made previously. Furthermore, the observed effect of encapsulation of calcium hydroxide by carbonates caused by the accelerated carbonation conditions was examined more closely.

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Synthesis of magnesium carbonate hydrate from natural talc

Open Chemistry ◽

10.1515/chem-2020-0154 ◽

2020 ◽

Vol 18 (1) ◽

pp. 951-961

Author(s):

Qiuju Chen ◽

Tao Hui ◽

Hongjuan Sun ◽

Tongjiang Peng ◽

Wenjin Ding

Keyword(s):

Crystal Structure ◽

Particle Size ◽

Crystal Growth ◽

Crystal Morphology ◽

Magnesium Carbonate ◽

Organic Additives ◽

X Ray Diffraction ◽

Morphological Transformation ◽

X Ray ◽

Carbonation Process

AbstractVarious morphologies of magnesium carbonate hydrate had been synthesized without using any organic additives by carefully adjusting the reaction temperature and time during the talc carbonation process. At lower temperatures, magnesium carbonate hydrate was prone to display needle-like morphology. With the further increase of the carbonation temperature, the sheet-like crystallites became the preferred morphology, and at higher aging temperatures, these crystallites tended to assemble into layer-like structures with diverse morphologies, such as rose-like particles and nest-like structure. The reaction time had no effect on the crystal morphology, but it affected the particle size and situation of the crystal growth. X-Ray diffraction results showed that these various morphologies were closely related to their crystal structure and compositions. The needle-like magnesium carbonate hydrate had a formula of MgCO3·3H2O, whereas with the morphological transformation from needle-like to sheet-like, rose-like, and nest-like structure, their corresponding compositions also changed from MgCO3·3H2O to 4MgCO3·Mg(OH)2·8H2O, 4MgCO3·Mg(OH)2·5H2O, and 4MgCO3·Mg(OH)2·4H2O.

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Simultaneous x-ray and neutron 4D tomographic study of drying-driven hydro-mechanical behavior of cement-based materials at moderate temperatures

Cement and Concrete Research ◽

10.1016/j.cemconres.2021.106503 ◽

2021 ◽

Vol 147 ◽

pp. 106503

Author(s):

Hani Cheikh Sleiman ◽

Alessandro Tengattini ◽

Matthieu Briffaut ◽

Bruno Huet ◽

Stefano Dal Pont

Keyword(s):

Mechanical Behavior ◽

X Ray ◽

Cement Based Materials

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X-Ray Scattering Studies of Interfacial Microstructures in Inx, Ga1−x As/GaAs Superlattices

MRS Proceedings ◽

10.1557/proc-375-171 ◽

1994 ◽

Vol 375 ◽

Author(s):

Z. H. Ming ◽

Y. L. Soo ◽

S. Huang ◽

Y. H. Kao ◽

K. Stair ◽

...

Keyword(s):

Quantum Wires ◽

Large Angle ◽

Sample Surface ◽

Lateral Direction ◽

Direction Parallel ◽

X Ray ◽

Periodic Arrays ◽

X Ray Scattering ◽

Transmission Electron ◽

Ray Scattering

AbstractInterfacial microstructures in 100-period InxGa1−xAs(15Å)/GaAs(100Å) superlattices grown on GaAs (100) substrates by molecular beam epitaxy were studied by using large angle x-ray scattering techniques. Unusual satellite peaks in the lateral direction parallel to the sample surface were observed in a sample with x = 0.535 grown at 480°C, indicating an in-plane structural ordering. This result is confirmed by high resolution transmission electron microscopy observations that thickness modulation in the InxGa1−xAs layers gives rise to long-range lateral periodic arrays of cluster-like microstructures with spacing on the order of a few hundred Ångstroms. This thickness modulation is found to occur only in [110] direction, thus the material can be viewed as a somewhat disordered array of grown-in parallel quantum wires.

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In Vivo X-ray Computed Tomography Investigations of Crack Damage Evolution of Cemented Waste Rock Backfills (CWRB) under Uniaxial Deformation

Minerals ◽

10.3390/min8110539 ◽

2018 ◽

Vol 8 (11) ◽

pp. 539 ◽

Cited By ~ 5

Author(s):

Yu Wang ◽

Changhong Li ◽

Zhiqiang Hou ◽

Xuefeng Yi ◽

Xiaoming Wei

Keyword(s):

Computed Tomography ◽

Damage Evolution ◽

Waste Rock ◽

Crack Identification ◽

Mining Operations ◽

Cracking Behavior ◽

Value Analysis ◽

X Ray ◽

Waste Rocks ◽

X Ray Computed

Cemented waste rock backfill (CWRB), which is a mixture of tailings, waste rock, cement, and water, is subjected to combination actions in underground mining operations and has been widely used in deep resource mining. While the strength requirement and macroscopic deformation behaviors of CWRB have been well studied, the mesoscopic damage evolution mechanisms are still not well understood. In this work, a CWRB sample with a waste rock proportion of 30% was studied with a uniaxial compression test under tomographic monitoring, using a 450 kV industrial X-ray computed tomography (CT). Clear CT images, CT value analysis, crack identification, and extraction reveal that CWRB damage evolution is extremely inhomogeneous and affected by the waste rock size, shape, and distribution. Furthermore, the crack initiation, propagation, and coalescence behaviors are limited to the existing waste rocks. When deformation grows to a certain extent, the cracks demonstrate an interlocking phenomenon and their propagation paths are affected by the waste rocks, which may improve the ability to resist compressive deformation. Volumetric dilatancy caused by the damage and cracking behavior has closed a link with the meso-structural changes, which are controlled by the interactions between the waste rocks and the cemented tailing paste.

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Influence of pretreatment on the properties of α-Fe2O3 and the effect on photocatalytic degradation of methylene blue under visible light

Water Science & Technology ◽

10.2166/wst.2020.506 ◽

2020 ◽

Vol 82 (11) ◽

pp. 2415-2424

Author(s):

S. Mokhtari ◽

N. Dokhan ◽

S. Omeiri ◽

B. Berkane ◽

M. Trari

Keyword(s):

Methylene Blue ◽

Average Crystallite Size ◽

Sample Surface ◽

X Ray Diffraction ◽

Sem Images ◽

X Ray ◽

Lattice Constants ◽

Electrochemical Pretreatment ◽

Crystal Properties ◽

Rhombohedral Symmetry

Abstract The hematite (α-Fe2O3) nanostructures were synthesized by thermal oxidation of metal at 500 °C under atmospheric pressure. We studied the effect of the electrochemical pretreatment of the substrate before calcinations and its impact on the morphology, crystalline structure, lattice microstructural, and optical properties of α-Fe2O3. Uniform nanosheets were observed on the sample surface after calcination; their dimension and morphology were accentuated by the pretreatment, as confirmed by the SEM images. The characteristics of the nanostructures, analyzed by X-ray diffraction (XRD), revealed a rhombohedral symmetry with the space group R-3c and lattice constants: a = 0.5034 nm and c = 1.375 nm. The average crystallite size and strain, determined from the Williamson-Hall (W-H) plot, showed substantial variations after the substrate pretreatment. The Raman spectroscopy confirmed the changes in the crystal properties of the hematite submitted to pretreatment. The diffuse reflectance allowed to evaluate the optical gap which lies between 1.2 and 1.97 eV, induced by the electrochemical processing. The photocatalytic activity of α-Fe2O3 films was assessed by the degradation of methylene blue (MB) under LED light; 15% enhancement of the degradation for the pretreated specimens was noticed.

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The Effect of Silica Sand Proportion in Laser Scabbling Process on Cement Mortar

Metals ◽

10.3390/met11121914 ◽

2021 ◽

Vol 11 (12) ◽

pp. 1914

Author(s):

Tam-Van Huynh ◽

Youngjin Seo ◽

Dongkyoung Lee

Keyword(s):

Cement Mortar ◽

Silica Sand ◽

Construction Sites ◽

Power Laser ◽

Concrete Repair ◽

X Ray ◽

Micro Cracks ◽

Wide Range ◽

Cement Based Materials ◽

Composition Changes

Cement mortar composite has a wide range of applications on construction sites, including masonry, plastering and concrete repair. In construction sites, scabbling process is a method to remove from a few millimeters to several centimeters of defect concrete surfaces. As a result, it is essential to investigate the scabbling characteristics for cement mortar with different silica sand proportion in laser scabbling process. In this study, 5 types of cement mortar with different silica sand proportions in mixing were fabricated and scabbled by using a high-density power laser beam. The effects of silica sand proportion in color changing and penetration depth of the samples after laser scabbling process were studied. Furthermore, the generation of micro-cracks and pores were observed by using scanning electron microscopy (SEM). In addition, chemical composition changes between processed zone and non-processed zone were also evaluated by Energy Dispersive X-ray (EDX) analysis. The results of this study are expected to provide valuable knowledge in understanding of the laser scabbling process for cement-based materials.

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Experiences on production - usage reasoned malfunctions & development of X-ray tubes used in science and their effects on sediment measurements

10.5194/egusphere-egu21-13341 ◽

2021 ◽

Author(s):

Dursun Acar ◽

Namık Çagatay ◽

Ş. Can Genç ◽

K. Kadir Eriş ◽

Demet Biltekin ◽

...

Keyword(s):

Low Voltage ◽

Measurement Data ◽

Electric Circuit ◽

Sample Surface ◽

Open Circuit ◽

Silicone Grease ◽

X Ray ◽

Negative Results ◽

Contact Points ◽

Measured Sample

<p>Surface fractures at the filament of X-ray tube increase more with metal fatique or wrong cooling&#160; and heating processes. Fractured filament continue to work as repeating open circuit positions in random times with&#160; turning fully conductive state in short time. We are explaining how open circuit flashes at the filament providing wrong measurement results. Their low voltage electric circuit conductive problems&#160; repeat in milliseconds periods. At&#160; the results, it gives the impression of healthy measurement values. Because that the measured sample absorbs photonic energy and direct it to neighbouring elements in continuous element&#160; electron scattering&#160; circulations , by the way that delayed secondary electron energy scatters hide all electron supply extinctions on the semi broken flament wire and indirect counts&#160; continue by the detector from coming reflection energy. ( real counts are not from exact beam&#160; target of sample surface during energy deprivations , and it is impossible to understand that the measurement is inaccurate because it causes similarity as discrete element counts in sedimentation layers ).&#160; Filament voltage arcs do not warn machine with error reporting systems until to whole ruptured filament touch to anode walls or their far displaced edges of 2 broken filament positioning. Erroneous records take their place in the world of science if the lithology was not followed. We collected faulty measurement data from our experiences for indicate when and&#160; how possible to facing such as events.</p><p>For eliminate&#160; explained reasons at above , the tubes must be gently heated and&#160; cooled. Excessive cooling or heating of the tubes or oxid placement and leakeage&#160; at gasget contacts reduces the surface contact areas of the insilators with the corrosion by &#160;condensing water around the rubber insulation gasgets , it causes cooling liquid leakage or increasing humidity at the tube housing block via following serial failures of HV unit such as increasing amounts of the broken tube events. During the replacement of insulating gasgets, enough care should be taken for gasket contact points as oiling&#160; them with&#160; silicone grease as a form of the thin film. High responsibility must be with continuous&#160; result control&#160; and reference correlations on the scientific sample. With this way we can eliminate possible&#160; negative results by malfunctions on measurements.</p>

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Pore Structure Damages in Cement-Based Materials by Mercury Intrusion: A Non-Destructive Assessment by X-Ray Computed Tomography

Materials ◽

10.3390/ma12142220 ◽

2019 ◽

Vol 12 (14) ◽

pp. 2220 ◽

Cited By ~ 8

Author(s):

Xiaohu Wang ◽

Yu Peng ◽

Jiyang Wang ◽

Qiang Zeng

Keyword(s):

Computed Tomography ◽

Pore Structure ◽

High Mass ◽

X Ray ◽

Quantitative Evidence ◽

Mercury Intrusion ◽

Pore Size Distributions ◽

Cement Based Materials ◽

Before And After ◽

X Ray Computed

Mercury intrusion porosimetry (MIP) is questioned for possibly damaging the micro structure of cement-based materials (CBMs), but this theme still has a lack of quantitative evidence. By using X-ray computed tomography (XCT), this study reported an experimental investigation on probing the pore structure damages in paste and mortar samples after a standard MIP test. XCT scans were performed on the samples before and after mercury intrusion. Because of its very high mass attenuation coefficient, mercury can greatly enhance the contrast of XCT images, paving a path to probe the same pores with and without mercury fillings. The paste and mortar showed the different MIP pore size distributions but similar intrusion processes. A grey value inverse for the pores and material skeletons before and after MIP was found. With the features of excellent data reliability and robustness verified by a threshold analysis, the XCT results characterized the surface structure of voids, and diagnosed the pore structure damages in terms of pore volume and size of the paste and mortar samples. The findings of this study deepen the understandings in pore structure damages in CBMs by mercury intrusion, and provide methodological insights in the microstructure characterization of CBMs by XCT.

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