Ambient drying of partially water-penetrated concrete: chemical phase and pore structure changes and drying behaviour under hyperspectral imaging observation

Ambient Drying of Partially Water-Penetrated Concrete: Chemical Phase and Pore Structure Changes and Drying Behaviour Under Hyperspectral Imaging Observation

Synchrotron-based in-operando multi-scale X-ray scattering analyses are used to connect microstructural changes to phase changes in kaolinite on heating from 30 °C to 1150 °C. Combined ultra-small-angle and small-angle X-ray scattering (USAXS and SAXS) data are modeled to determine the hierarchical morphology of kaolinite comprising nano-scale interlayer pores, meso-scale pores, and larger interparticle voids, while wide-angle X-ray scattering (WAXS) data reveal the simultaneous evolution of molecular phases in kaolinite. We found that the transformation of kaolinite to metakaolin corresponds to the disappearance of nano-scale porosity, and the onset of sintered phases such as mullite consistent with the overall reduction in porosity. The emergence of nanoscale particulate features on heating above 900 °C corresponds to the onset of sintered phases such as spinel and mullite. This study illustrates the application of multi-scale X-ray scattering measurements to connect the thermally induced phase changes with changes in pore structure and fine morphology evolution.

ABSTRACT: The tight sandstone reservoirs present a viable option for geological CO2 storage. The stability and safety of the reservoir rock are fundamental for long-term CO2 storage. However, the injection may lead to interactions between H2O, CO2, and rock, potentially impacting the mineral composition and physical properties of the reservoir. This ultimately leads to a decrease in the mechanical properties of the rock and disrupts the stability of the reservoir in high-pressure environments. In this study, rock mechanics experiments, nuclear magnetic resonance (NMR) experiments, and scanning electron microscopy (SEM) experiments were carried out to investigate the changes in mechanical properties, pore size, and microstructure of cores with different mineral compositions treated with aqueous carbonate solution under different confining pressures, in order to analyze the effects of the dynamic CO2 storage process on reservoir stability. The results show that the presence of CO2 under confining pressure leads to a decrease in rock strength. Carbonic acid solution can effectively dissolve feldspars and clay minerals in the rock composition, causing changes in pore structure and leading to a decrease in rock strength. The study aims to provide insights and recommendations for developing oil and gas extraction and carbon sequestration. 1. INTRODUCTION Carbon dioxide geological storage technology is one of the effective ways to mitigate the global warming trend, and its basic principle is to inject captured carbon dioxide into deep underground rock pores for long-term isolation and fixation (Chen et al., 2023; Farquhar et al., 2015). Among the many potential storage media, tight sandstone reservoirs have received great attention from scientists and industry for their complex pore structure and high storage capacity (Bachu et al., 1994; Michael et al., 2009). However, CO2 injection affects the porosity, permeability, and mechanical properties of reservoirs, which may cause reservoir damage and reduced storage efficiency (Yu et al., 2012). For example, CO2 reacts chemically with minerals in the rock, which may lead to dissolution or precipitation of minerals, and thus change the physical structure of the rock (Fischer et al., 2010). The physical structure of the rock may be altered. Therefore, the mechanical response of rocks during CO2 injection must be thoroughly studied to ensure the safety and efficiency of the storage process. In recent years, in the field of CO2 geological storage research, scholars have carried out a large number of experimental and simulation studies, aiming to explore the mechanism of CO2 interaction with reservoir rocks and trying to predict and optimize the reservoir performance (Vafaie et al., 2023). The CO2 has different dissolution capacities for different minerals, leading to changes in the microstructure and mechanical properties of mineral surfaces, which indirectly leads to the decline of rock mechanical properties, thus affecting the production of unconventional oil and gas and reservoir stability (Vogt et al., 2014; Zhang et al., 2020; Zhang et al., 2022). Among various minerals, carbonate minerals (e.g., calcite and dolomite) have the highest solubility and the fastest reaction rate, while silicate minerals such as feldspar and quartz have lower solubility and slower reaction rate (Memon et al., 2022; Ranjith et al., 2019; Xing et al., 2019). Under the combined effect of CO2, the compressive strength and modulus of elasticity of the rock are significantly reduced (Huang et al., 2020; Rathnaweera et al., 2015; Zhou et al., 2024). The geological sequestration of carbon dioxide is a dynamic process, with the continuous injection of fluids, the formation pressure gradually increases. In fractured and low-permeability formations, the physical properties of rocks are affected by the increase in pore pressure, and their physical properties change significantly, which affects reservoir capacity (Dávila et al., 2017; Pavan & Govindarajan, 2023; Vialle & Vanorio, 2011). Zhao et al. carried out CO2 in brine solution saturated dense sandstone reservoir core samples for oil repulsion and explained the increase in porosity and permeability due to the increase in pore pressure (Zhao et al., 2021). Liteanu et al. investigated the effect of supercritical CO2 on rock mechanics, where carbonic acid solution led to stress corrosion fracturing and strength reduction of rocks (Liteanu et al., 2013).

The hyperspectral and multispectral image fusion process, commonly known as the multisharpening process (also known as the hypersharpening process), results in the creation of unobservable high spectral and spatial resolution hyperspectral remote sensing data, by combining (or fusing) a hyperspectral image, characterized by a high spectral resolution, with, especially, a high spatial resolution multispectral one. There are several approaches in the literature performing such a process, in particular, those based on the spectral unmixing concept. The latter fusion methods aim to extract pure-material spectra from the high spectral resolution hyperspectral image and combine them with their corresponding proportions extracted from the high spatial resolution multispectral image. However, most of these methods, which mainly consider the standard linear mixing model, do not address the spectral variability phenomenon, precisely due to the considered data mixing model, which does not handle variations in illumination and atmospheric conditions or material composition inducing spectral variability. Neglecting such a phenomenon may lead to errors in the fusion process, thus decreasing the spatial and spectral qualities of sharpened products. In this paper, a new hyperspectral and multispectral data fusion method, based on the linear spectral unmixing concept that deals with spectral variability, is proposed. This approach, based on a multiplicative Nonnegative Matrix Factorization (NMF) technique, substantially extends the multiplicative Coupled NMF (CNMF) algorithm by considering a linear data mixing model that addresses the considered phenomenon. Indeed, the introduced approach minimizes new cost functions involving matrices with specific structures in order to deal with the spectral variability phenomenon. The proposed method is applied to synthetic and real data, and its effectiveness is evaluated with established performance criteria. Experimental results show that the designed algorithm globally yields sharpened hyperspectral data with fine spectral and spatial fidelities. Also, these results demonstrate that the proposed technique globally outperforms the tested literature approaches.

In present work, friction stir processing (FSP) is utilized for fabrication of aluminium based metal matrix surface composites by incorporating nano-SiC particles. The effects of multi-pass FSP and cooling environment on microstructural evolution and mechanical properties are investigated in detail. Higher FSP passes produce more uniformly distributed surface composites. Cooling environment during FSP affects the peak temperature, grain refinement, post processing cooling time and mechanical properties. Results reflected that five pass underwater friction stir processed surface composites with water temperature below the ambient condition (at 10 degree Celsius) exhibit highest microhardness of 181 HV and ultimate tensile strength (UTS) of 401 MPa as compared to base metal of microhardness of 85 HV, UTS of 321 MPa and surface composite of same pass processed with ambient conditions having microhardness of 150 HV and UTS of 370 MPa. Thus, it can be deducted that cooling environment has significant effect on microstructural changes and mechanical properties of fabricated surface composites. The results of mechanical properties of this study strongly corroborates with the microstructural evolution. The analysis of microstructural changes and SiC particles dispersion was studied using optical microscopy and FESEM respectively.

The detection of the beginning demineralization process of dental hard tissue remains a challenging task in dentistry. As an alternative to bitewing radiographs, optical and spectroscopic technologies showed promising results for caries diagnosis. The aim of the present work is to give an overview of optical and spectroscopic properties of healthy and carious human teeth in vitro by means of Raman spectroscopy (RS), optical coherence tomography (OCT) and hyperspectral imaging (HSI). OCT was able to represent microstructural changes below the enamel surface and revealed increased scattering for white spot lesions and a white scattering trail for deeper lesions. HSI showed similar absorbance characteristics for healthy and demineralized enamel over the entire spectrum and a characteristic absorbance peak at 550 nm for discolored lesions. Already at early carious stages (white spot), we found a distinct loss of hydroxylapatite-related intensity at 959 cm-1 in demineralized regions with RS. Healthy and demineralized tooth surfaces can be distinguished at different signal levels by means of RS, OCT and HSI. The presented modalities provide additional information to the current clinical diagnosis of caries such as microstructural changes, quantification of the demineralization and imaging of caries-related chemical changes.

Pore structure description of mortars containing ground granulated blast-furnace slag by mercury intrusion porosimetry and dynamic vapour sorption

Vis–NIR hyperspectral imaging in visualizing moisture distribution of mango slices during microwave-vacuum drying

Microstructural changes and mass transport in cement-based materials: A modeling approach

Orange-fleshed sweet potatoes {OFSP} (Ipomoea batatas (L.) Lam) contain high levels of beta carotene, an important provitamin A carotenoid. Stored sweet potato roots undergo many physiological changes that affect their beta carotene content and bioaccessibility as well as the tissue microstructure. This study investigated the changes in microstructure, beta carotene content and in vitro bioaccessibility of stored OFSP roots. Roots of two varieties of OFSP, Ejumula and SPK004/6/6 were each stored under the following conditions: in a pit (17-21 oC, RH 90-100%), saw dust (19-23oC, RH 86- 100%), dark room (24.5-28 oC, RH 68-100%) and ambient (24-27 oC, RH 68-100%). Samples were drawn monthly from each of the storage treatments and analyzed for changes in beta carotene content, in vitro bioaccessibility and tissue microstructure. Stored roots of Ejumula variety contained significantly more (P 0.05) beta carotene than those of the SPK004/6/6 variety. There was no significant difference (P 0.05) between varieties in regards to beta carotene bioaccessibility. Roots stored in pits retained higher beta carotene content compared to roots stored under other conditions. In vitro bioaccessibility was significantly higher (P 0.05) in roots stored in pits compared to roots stored under saw dust, dark room and ambient conditions. Samples of OFSP roots stored under ambient and dark room conditions retained the least amount of beta carotene and had the least amount of bioaccessible beta carotene. There was an increase in the level of cell wall lignification during storage of OFSP. The extent of lignification varied with storage method used. The roots stored under ambient and dark room conditions showed higher levels of lignification compared to those stored under sawdust and in pits. There were no differences in lignification between the different varieties studied. The study shows that storage of OFSP roots using methods that maintain low temperatures leads to higher retention of beta carotene and maintains higher in vitro bioaccessibility.Key words: Storage, beta carotene, bioaccessibility, microstructure

Mechanical loading causes material deformation, resulting in changes in mechanical properties due to microstructural alterations such as the multiplication of dislocations and evolution of grain morphology. Blast loading, a condition where materials deform at high strain rates, results in significant plastic deformation. This rapid deformation induces intense mechanical stresses, causing complex microstructural changes that influence the mechanical behavior and performance of the materials. Consequently, designing structures to withstand blast loading requires understanding the relationship between microstructure and property evolution. As the primary objective of this study, post-localized blast experiments have been conducted to elucidate the variability in microstructural response of Austenitic stainless steel (ASS) 316 L, characterized by its face-centered cubic crystal structure. Localized blast loads were applied to square test plates, 2 mm thick, with a circular exposed area of 106 mm in diameter. Quantitative mechanical property data from key zones within the deformed dome were determined through using a novel micro-tensile testing approach and nanoindentation tests. Electron backscatter diffraction (EBSD) in scanning electron microscopy (SEM) technique was employed to characterize the microstructural changes in the selected samples. The results revealed that blast loading induced complex mechanical and microstructural changes in ASS 316 L, including enhanced material strength, reduced ductility, and significant alterations in grain orientation and misorientation distributions. The materials underwent significant strain hardening due to the increased stress and deformation, resulting in a more resistant to plastic deformation and the greatest internal strain accumulations. Texture analysis underscored the influence of deformation geometry, with Goss and Copper emerging as predominant texture components.

Wet–dry (W–D) cycles significantly impact concrete durability by influencing moisture distribution and microstructural evolution. This study employs hyperspectral imaging (HSI) as a rapid, non-destructive technique to visualise surface moisture profiles in concrete subjected to controlled W–D cycles designed to approximate field exposure conditions via short-term partial water penetration and ambient drying. Concrete specimens with varying water-to-cement ratios and curing regimes were examined. HSI effectively revealed moisture gradients, including capillary rise equilibration after initial cycles and drying retardation caused by aggregates. Gravimetric measurements validated the HSI results. Complementary X-ray diffraction and mercury intrusion porosimetry analyses indicated depth-dependent microstructural changes, such as enhanced hydration and porosity reduction in inner layers, contrasted by surface leaching. The findings suggest a moisture redistribution between pore size scales, which may influence pore connectivity during cyclic moisture exposure. This study offers new insights into moisture transport dynamics and microstructural responses under W–D cycling, approximating typical environmental exposure, and proposes preliminary guidance for establishing standardised W–D testing protocols to support improved durability assessments of concrete infrastructure. • Hyperspectral imaging visualises moisture profiles in concrete during wet–dry cycles. • Wet–dry cycles with partial water penetration simulate field exposure. • Aggregate content influences drying rates and moisture transport in concrete. • Moisture redistribution observed and linked to depth-dependent pore structure changes. • Integrated HSI, XRD, and MIP analyses clarify surface and bulk durability mechanisms.

Solid oxide cells (SOC) are exciting both for their capability of fuel-flexible electricity generation and their promise in the production of green H2; however, their degradation and long-term performance remain important questions. Operating individual button cells to characterize these changes is prone to cell-to-cell variations, whereas large-area cell/stack life testing requires considerable resources. In both cases, full cell characterization usually must wait until the completion of the life test, which may delay getting results for months or years. While progress has been made in observing microstructural changes over time (termed here time-resolved characterization) using techniques like non-destructive transmission x-ray microscope tomography, such experiments are difficult to implement, especially the effect of current is unexplored due to geometrical and gas environmental limitations of the system.Presented here is a method to rapidly obtain time-resolved microstructural information of the same cell in tandem with electrochemical measurements. While SOC degradation arises due to a range of processes, this work focuses on the microstructural evolution of Ni-YSZ fuel electrodes that occurs during electrolysis operation, which is known to be a key issue. Two key experimental features allowed time-resolved characterization of multiple cells simultaneously: (1) the use of Ni-YSZ symmetric cells allows multiple cells of different size in a single test by avoiding the need for gas seals, and (2) the use of laser milling to allow controlled removal of a portion of each cell during the test.Here we illustrate the method for the case of low steam content and high current density, designed to exacerbate and accelerate electrolysis degradation due to the highly reducing conditions achieved. Tape-cast planar electrode-supported Ni-YSZ symmetric cells were laser cut into precise geometries with well-defined projected areas and easily removable sections. Four cells with projected areas of 1, 1, 0.75, and 0.5 cm2 were connected in series within the same furnace at 800 C and a gas environment of 97% H2 and 3% H2O. A current of 0.75 A was run through three of the cells, resulting in current densities of 0.75, 1.0, and 1.5 A/cm2, while one was maintained with no current. The life test lasted for 500 h, and the microstructure was observed at 0, 200, and 500 hours.Figure 1 shows the microstructures observed at the highest current density by polished cross-sectional SEM and FIB-polished sections under conditions that provided Ni/YSZ contrast. Microstructural degradation had occurred by 200 h and became immense at 500 h, due to high current density in these reducing conditions. By 200 hours, grain boundaries become enriched with Ni, likely due to the formation of Ni-Zr intermetallics in the ultra-low pO2 induced by local overpotential as reported by Chen[1] and Szasz[2]. Additionally, the electrode-electrolyte interface becomes nanoporous and a Ni enriched fracture is present ~2 μm into the electrolyte. By 500 hours, the Ni rich nanoporosity has progressed more than 10 μm into the electrolyte and created islands of large grains surrounded by Ni-rich deposits.Electrochemical impedance spectroscopy measurements show a clear initial decrease in polarization resistance followed by an overall impedance increase by 200 hours. These correspond to the initial electrochemical boost from the production of a nanoporous structure, followed by the deactivation of areas of the cell due to the large fractures through the electrolyte.[1] M. Chen et al., “Microstructural Degradation of Ni/YSZ Electrodes in Solid Oxide Electrolysis Cells under High Current,” J. Electrochem. Soc., vol. 160, no. 8, pp. F883–F891, 2013, doi: 10.1149/2.098308jes.[2] J. Szász et al., “High-Resolution Studies on Nanoscaled Ni/YSZ Anodes,” Chem. Mater., vol. 29, no. 12, pp. 5113–5123, 2017, doi: 10.1021/acs.chemmater.7b00360.Figure 1: Microstructural and electrochemical changes of a symmetric Ni-YSZ SOC undergoing 1.5 A/cm2 in reducing conditions at 0, 200, and 500 hours. Cathode is on the left in all images; anode is on the right. a, b, c) Backscatter electron imaging reveals destruction of the dense YSZ electrolyte over the lifetime of the experiment. Lines of brighter phases on the anode side of fractures are Ni deposits. d, e, f) Focused Ion Beam cross sections reveal nanoporosity forming in the first 10 μm from the cathode-electrolyte interface at 200 and 500 hours. Charging is evident as a result of curtaining from the nanoporous features in the electrolyte. g) Electrochemical impedance spectroscopy shows the initial decrease in resistance from 0 to 48 hours followed by increasing resistance due to microstructure evolution. Figure 1

Investigation of moisture migration of MWCNTs concrete after different heating-cooling process by LF-NMR

Nowadays, hyperspectral imaging technique has been abroad and successfully used for quality inspection of food products. In this study, the microstructural changes of mulberry were investigated by scanning electron microscope (SEM). Furthermore, NIR hyperspectral imaging system was used to predict the distribution of Pesticide residues in mulberry leaves with the aid of Gas Chromatography. It is primary to extract the characteristic wavelengths in the prediction and visualization of Pesticide residues in mulberry leaves. Successive projections algorithm (SPA), Stepwise regression(SR) and Regression coefficients (RC) were utilized. MLR was applied to build prediction models based on spectral feature in characteristic wavelengths. The best model SPA‐MLR ( and RMSEP = 38.789) was implemented into the pesticide residues visualization procedure. This study demonstrated that pesticide residues distribution map clearly showed the distribution of Pesticide residues in mulberry leaves.Practical applicationsWell understanding the effect of Pesticide residues to biological structure is very important for revelation of novel biological function and mechanism of action of the protein. To facilitate more quickly and effectively detect the types of pesticide residues on the surface of mulberry leaves, the microstructural changes of mulberry were investigated by scanning electron microscope (SEM). Furthermore, NIR hyperspectral imaging system was used to predict the distribution of Pesticide residues in mulberry leaves with the aid of Gas Chromatography.