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A growing rock engineering activity in cold regions is facing the threat of freeze-thaw (FT) weathering, especially in high mountains where the sunny-shady slope effects strongly control the difference in weathering behavior of rocks. In this paper, an investigation of the degradation of petrophysical characteristics of sandstone specimens subjected to FT cycle tests to simulate the sunny-shady slope effects is presented. To this aim, non-destructive and repeatable testing techniques including weight, ultrasonic waves, and nuclear magnetic resonance methods on standard specimens were performed. For the sunny slope specimens, accompanied by the enlargement of small pores, 100 FT cycles caused a significant decrease in P-wave velocity with an average of 23%, but a consistent rise of 0.18% in mass loss, 34% in porosity, 67% in pore geometrical mean radius, and a remarkable 14.5-fold increase in permeability. However, slight changes with some abnormal trends in physical parameters of the shady slope specimens were observed during FT cycling, which can be attributed to superficial granular disaggregation and pore throat obstruction. Thermal shocks enhance rock weathering on sunny slopes during FT cycles, while FT weathering on shady slopes is restricted to the small pores and the superficial cover. These two factors are primarily responsible for the differences in FT weathering intensity between sunny and shady slopes. The conclusions derived from the interpretation of the experimental results may provide theoretical guidance for the design of slope-failure prevention measures and the selection of transportation routes in cold mountainous regions.

Hydrochar is an urban soil amender that supports plant growth on slopes. It is a biomass-derived carbon-rich material produced by the hydrothermal carbonation process; thus, it has a different pore structure from biochar produced by pyrolysis. The effects of hydrochar on the hydraulic properties of unsaturated compacted soils and the underlying pore-level soil-hydrochar interaction mechanisms are unclear. In this study, silty-clay sand was amended by grass-derived hydrochars produced at two hydrothermal carbonisation temperatures (180 and 240 degrees C, denoted as H-180 and H-240, respectively) with different mass proportions (fH\textbackslash{}documentclass[12pt]{minimal} \textbackslash{}usepackage{amsmath} \textbackslash{}usepackage{wasysym} \textbackslash{}usepackage{amsfonts} \textbackslash{}usepackage{amssymb} \textbackslash{}usepackage{amsbsy} \textbackslash{}usepackage{mathrsfs} \textbackslash{}usepackage{upgreek} \textbackslash{}setlength{\textbackslash{}oddsidemargin}{-69pt} \textbackslash{}begin{document}$${f}_{{\textbackslash{}text{H\ }}}$$\textbackslash{}end{document}). The pore and throat size distributions, water retention curves (WRCs) and hydraulic conductivity functions (HCFs) of the soils with and without amendment were measured. The results showed that hydrochar improved the soil water retention capability as the smaller hydrochar particles filled the soil pores with diameters larger than 290 mu m. Compared with the increase in air-entry value made by H-180, the one made by H-240 was more substantial as this type of hydrochar altered the soil pores to be smaller in size. Hydrochar also increased the hydraulic conductivity of the soil by half to one order of magnitude due to the increase in the throat frequency and the presence of hydrochar intra-pores. One exception was the amendment by H-180 at fH\textbackslash{}documentclass[12pt]{minimal} \textbackslash{}usepackage{amsmath} \textbackslash{}usepackage{wasysym} \textbackslash{}usepackage{amsfonts

Renewable energy sources are indispensable to meet the rising demand of energy usage while reducing the negative environmental impact of utilising fossil fuels. Gasification is an efficient technology to convert biogenic waste into valuable gaseous products. The rate of conversion of char, produced in an intermediate step in the conversion, plays an essential role in the conversion of biogenic materials. The conversion of char is significantly affected by properties such as the structure of the char and its alkali content. This thesis presents findings related to the influence of char pore structure development and alkalis content on char gasification, as well as the alkali release during gasification and co-gasification. Experimental results show that the generation of micropores are directly proportional to the observed reactivity up to 70% of char conversion, after which the catalytic effects of potassium become the dominating factor. Furthermore, investigations of the effect of different intrinsic potassium contents on woody char reactivity demonstrate that no alkali surface saturation point is reached, as is the case for high-ash chars. Application of a modified random pore model enabled a successful capture of the later stages of char conversion in comparison to other kinetic models applied. Alkali release and sample mass changes were monitored simultaneously, using a thermogravimetric analyser together with a surface ionization detector (TGA-SID). The studies revealed a significant release of alkali as woody char conversion approaches completion during CO2 gasification. For straw char the release of alkali decreased continuously throughout the conversion process. Similar results were obtained for biochar gasification under steam conditions in a fixed bed reactor. However, in this case the process is more complex, including transfer of alkali between pa, Förnybara energikällor behövs för att möta den ökande efterfrågan på energianvändning, samtidigt med behoven av att minska den negativa miljöpåverkan som användningen av fossila bränslen medför. Förgasning är en effektiv teknologi för att omvandla biogent avfall till värdefulla gasformiga produkter. I omvandlingsprocessen förkolas biomassan till biokol i ett intermediärt steg. Hastigheten för omvandlingen av biokolet spelar en avgörande roll vid förgasningen av biogena material. Denna omvandling påverkas väsentligt av biokolets egenskaper såsom kolstruktur och dess alkaliinnehåll. I denna avhandling presenteras resultat som relaterar till inverkan av kolstrukturens utveckling och innehåll av alkalier vid förgasningen av biokol samt frigörandet av alkali under förgasning och samförgasning. Experimentella resultat visar på att genereringen av mikroporer är direkt proportionellt mot observerad reaktivitet upp till 70 procents kolomvandling. Därefter är de katalytiska effekterna huvudsakligen relaterade till kaliumhalten. Vidare så observerades ingen effekt av alkalimättnad av kolytan på biokolets reaktivitet vid studier med biokol från trämaterial med olika halter av kalium, något som observerats tidigare för biokol med högre innehåll av aska. Tillämpning av en modifierad randomiserad modell för utvecklingen av porer resulterade i en lämplig beskrivning av de slutliga stadierna i omvandlingen av biokol jämfört med andra kinetiska modeller. Frigörandet av alkalier och förändringar i provernas massa undersöktes med hjälp av termogravimetrisk analys tillsammans med en ytjonisationsdetektor (TGA-SID). Studierna visar att en betydande mängd alkalier frigörs mot slutet av biokolets omvandling under koldioxidförgasning. För biokol från halm observerades däremot ett fortsatt minskat frigörande av alkalier under hela omvandlingsprocessen. Liknande re, QC 2023-04-26

The current ability to predict the carbonation resistance of alkali-activated materials (AAMs) is incomplete, partly because of widely varying AAM chemistries and variable testing conditions. To identify general correlations between mix design parameters and the carbonation rate of AAMs, RILEM TC 281-CCC Working Group 6 compiled and analysed carbonation data for alkali-activated concretes and mortars from the literature. For comparison purposes, data for blended Portland cement-based concretes with a high percentage of SCMs (≥66% of the binder) were also included in the database. The results show that the water/CaO ratio is not a reliable indicator of the carbonation rate of AAMs. A better indicator of the carbonation rate of AAMs under conditions approximating natural carbonation is their water/(CaO + MgOeq + Na2Oeq + K2Oeq) ratio, where the index ‘eq’ indicates an equivalent amount based on molar masses. This finding can be explained by the CO2 binding capacity of alkaline-earth and alkali metal ions; the obtained correlation also indicates an influence of the space-filling capability of the binding phases of AAMs, as for conventional cements. However, this ratio can serve only as an approximate indicator of carbonation resistance, as other parameters also affect the carbonation resistance of alkali-activated concretes. In addition, the analysis of the dataset revealed peculiarities of accelerated tests using elevated CO2 concentrations for low-Ca AAMs, indicating that even at the relatively modest concentration of 1% CO2, accelerated testing may lead to inaccurate predictions of their carbonation resistance under natural exposure conditions., Green Open Access added to TU Delft Institutional Repository ‘You share, we take care!’ – Taverne project https://www.openaccess.nl/en/you-share-we-take-care Otherwise as indicated in the copyright section: the publisher is the copyright holder of this work and the author uses the Dutch legislation to make this work public., Materials and Environment

The demand for new sensors with specific and highly enhanced features has been on the rise today. Factors like sensitivity, response time, recovery rate, cost, size, ease of operation, and reliability play a crucial role in determining the quality of a sensor system. Although, currently, a large variety of sensors are available to monitor fluid flow, temperature, humidity, and pressure, among others. Most of these sensors are expensive, not easy to operate, and have a lower response rate, making them unsuitable for prolonged and extensive use. To improve upon the criteria above, porous carbon-based materials have supported the most promising advancement in material properties, enabling significant advancements to overcome limits previously associated with conventional sensor materials. Carbon-based structures have several advantages over commonly used sensor materials, owing to their superior physio-chemical properties. These carbonaceous structures can be easily synthesized and scaled up to yield fewer densification defects. Furthermore, carbon-based materials have proven to be a more cost-effective and environmentally friendly alternative to currently used electronic materials and are more efficient in their performance. Porous carbon-based materials are being investigated as a viable candidate for sensing applications as their mesoporous and microporous structures aid in the adsorption of the sensing element. Controlled pore size, higher surface area, more accessible synthesis techniques, potential to functionalize with various materials, and physical and chemical loadable active sites are some of the characteristics that make porous carbon-based materials a suitable sensing material with applications in multiple domains. Porous bio-enzymatic sensors based on carbon, electrochemical sensors, multifunctional health monitoring sensors, detection of pesticide residues, detection of DNA-RNA, drug delivery system, bio-electrode have been widely reported in recent year

Renewable energy sources are indispensable to meet the rising demand of energy usage while reducing the negative environmental impact of utilising fossil fuels. Gasification is an efficient technology to convert biogenic waste into valuable gaseous products. The rate of conversion of char, produced in an intermediate step in the conversion, plays an essential role in the conversion of biogenic materials. The conversion of char is significantly affected by properties such as the structure of the char and its alkali content. This thesis presents findings related to the influence of char pore structure development and alkalis content on char gasification, as well as the alkali release during gasification and co-gasification. Experimental results show that the generation of micropores are directly proportional to the observed reactivity up to 70% of char conversion, after which the catalytic effects of potassium become the dominating factor. Furthermore, investigations of the effect of different intrinsic potassium contents on woody char reactivity demonstrate that no alkali surface saturation point is reached, as is the case for high-ash chars. Application of a modified random pore model enabled a successful capture of the later stages of char conversion in comparison to other kinetic models applied. Alkali release and sample mass changes were monitored simultaneously, using a thermogravimetric analyser together with a surface ionization detector (TGA-SID). The studies revealed a significant release of alkali as woody char conversion approaches completion during CO2 gasification. For straw char the release of alkali decreased continuously throughout the conversion process. Similar results were obtained for biochar gasification under steam conditions in a fixed bed reactor. However, in this case the process is more complex, including transfer of alkali between pa, Förnybara energikällor behövs för att möta den ökande efterfrågan på energianvändning, samtidigt med behoven av att minska den negativa miljöpåverkan som användningen av fossila bränslen medför. Förgasning är en effektiv teknologi för att omvandla biogent avfall till värdefulla gasformiga produkter. I omvandlingsprocessen förkolas biomassan till biokol i ett intermediärt steg. Hastigheten för omvandlingen av biokolet spelar en avgörande roll vid förgasningen av biogena material. Denna omvandling påverkas väsentligt av biokolets egenskaper såsom kolstruktur och dess alkaliinnehåll. I denna avhandling presenteras resultat som relaterar till inverkan av kolstrukturens utveckling och innehåll av alkalier vid förgasningen av biokol samt frigörandet av alkali under förgasning och samförgasning. Experimentella resultat visar på att genereringen av mikroporer är direkt proportionellt mot observerad reaktivitet upp till 70 procents kolomvandling. Därefter är de katalytiska effekterna huvudsakligen relaterade till kaliumhalten. Vidare så observerades ingen effekt av alkalimättnad av kolytan på biokolets reaktivitet vid studier med biokol från trämaterial med olika halter av kalium, något som observerats tidigare för biokol med högre innehåll av aska. Tillämpning av en modifierad randomiserad modell för utvecklingen av porer resulterade i en lämplig beskrivning av de slutliga stadierna i omvandlingen av biokol jämfört med andra kinetiska modeller. Frigörandet av alkalier och förändringar i provernas massa undersöktes med hjälp av termogravimetrisk analys tillsammans med en ytjonisationsdetektor (TGA-SID). Studierna visar att en betydande mängd alkalier frigörs mot slutet av biokolets omvandling under koldioxidförgasning. För biokol från halm observerades däremot ett fortsatt minskat frigörande av alkalier under hela omvandlingsprocessen. Liknande re, QC 2023-04-26

Renewable energy sources are indispensable to meet the rising demand of energy usage while reducing the negative environmental impact of utilising fossil fuels. Gasification is an efficient technology to convert biogenic waste into valuable gaseous products. The rate of conversion of char, produced in an intermediate step in the conversion, plays an essential role in the conversion of biogenic materials. The conversion of char is significantly affected by properties such as the structure of the char and its alkali content. This thesis presents findings related to the influence of char pore structure development and alkalis content on char gasification, as well as the alkali release during gasification and co-gasification. Experimental results show that the generation of micropores are directly proportional to the observed reactivity up to 70% of char conversion, after which the catalytic effects of potassium become the dominating factor. Furthermore, investigations of the effect of different intrinsic potassium contents on woody char reactivity demonstrate that no alkali surface saturation point is reached, as is the case for high-ash chars. Application of a modified random pore model enabled a successful capture of the later stages of char conversion in comparison to other kinetic models applied. Alkali release and sample mass changes were monitored simultaneously, using a thermogravimetric analyser together with a surface ionization detector (TGA-SID). The studies revealed a significant release of alkali as woody char conversion approaches completion during CO2 gasification. For straw char the release of alkali decreased continuously throughout the conversion process. Similar results were obtained for biochar gasification under steam conditions in a fixed bed reactor. However, in this case the process is more complex, including transfer of alkali between pa, Förnybara energikällor behövs för att möta den ökande efterfrågan på energianvändning, samtidigt med behoven av att minska den negativa miljöpåverkan som användningen av fossila bränslen medför. Förgasning är en effektiv teknologi för att omvandla biogent avfall till värdefulla gasformiga produkter. I omvandlingsprocessen förkolas biomassan till biokol i ett intermediärt steg. Hastigheten för omvandlingen av biokolet spelar en avgörande roll vid förgasningen av biogena material. Denna omvandling påverkas väsentligt av biokolets egenskaper såsom kolstruktur och dess alkaliinnehåll. I denna avhandling presenteras resultat som relaterar till inverkan av kolstrukturens utveckling och innehåll av alkalier vid förgasningen av biokol samt frigörandet av alkali under förgasning och samförgasning. Experimentella resultat visar på att genereringen av mikroporer är direkt proportionellt mot observerad reaktivitet upp till 70 procents kolomvandling. Därefter är de katalytiska effekterna huvudsakligen relaterade till kaliumhalten. Vidare så observerades ingen effekt av alkalimättnad av kolytan på biokolets reaktivitet vid studier med biokol från trämaterial med olika halter av kalium, något som observerats tidigare för biokol med högre innehåll av aska. Tillämpning av en modifierad randomiserad modell för utvecklingen av porer resulterade i en lämplig beskrivning av de slutliga stadierna i omvandlingen av biokol jämfört med andra kinetiska modeller. Frigörandet av alkalier och förändringar i provernas massa undersöktes med hjälp av termogravimetrisk analys tillsammans med en ytjonisationsdetektor (TGA-SID). Studierna visar att en betydande mängd alkalier frigörs mot slutet av biokolets omvandling under koldioxidförgasning. För biokol från halm observerades däremot ett fortsatt minskat frigörande av alkalier under hela omvandlingsprocessen. Liknande re, QC 2023-04-26

In circumstances with wastewater and seawater, the behavior of multi-ions including calcium, chloride and others in concrete attracts attention. The present study investigated the multiple mechanisms that could happen under the special field situation above, including calcium leaching, chloride transport and multi-ion coupling. To realize the interactive ingress of multi ions, the simulation method for the processing of the individual mechanisms and the mutual influences is adopted. The distributions of the diversified ions are analyzed with the influence of the interfacial transition zone. The time-spatial distribution of porosity and its evolution mechanisms are investigated by considering the interaction with calcium ions in both pore solution and solid phase. The results indicate that calcium leaching would dominantly speed up chloride transport due to the coarsened pore structure, while the multi ions electrochemical coupling effect would facilitate calcium leaching in the early stage but subtly delay calcium leaching in the later stage.

In circumstances with wastewater and seawater, the behavior of multi-ions including calcium, chloride and others in concrete attracts attention. The present study investigated the multiple mechanisms that could happen under the special field situation above, including calcium leaching, chloride transport and multi-ion coupling. To realize the interactive ingress of multi ions, the simulation method for the processing of the individual mechanisms and the mutual influences is adopted. The distributions of the diversified ions are analyzed with the influence of the interfacial transition zone. The time-spatial distribution of porosity and its evolution mechanisms are investigated by considering the interaction with calcium ions in both pore solution and solid phase. The results indicate that calcium leaching would dominantly speed up chloride transport due to the coarsened pore structure, while the multi ions electrochemical coupling effect would facilitate calcium leaching in the early stage but subtly delay calcium leaching in the later stage., Green Open Access added to TU Delft Institutional Repository 'You share, we take care!' - Taverne project https://www.openaccess.nl/en/you-share-we-take-care Otherwise as indicated in the copyright section: the publisher is the copyright holder of this work and the author uses the Dutch legislation to make this work public., Materials and Environment

Due to the heterogeneous nature of soil pore structure, processes such as nitrification and denitrification can occur simultaneously at microscopic levels, making prediction of small-scale nitrous oxide (N2O) emissions in the field notoriously difficult. We assessed N2O+N2 emissions from soils under maize (Zea mays L.), switchgrass (Panicum virgatum L.), and energy sorghum (Sorghum bicolor L.), three potential bioenergy crops in order to identify the importance of different N2O sources to microsite production, and relate N2O source differences to crop-associated differences in pore structure formation. The combination of isotopic surveys of N2O in the field during one growing season and X-ray computed tomography (CT) enabled us to link results from isotopic mappings to soil structural properties. Further, our methodology allowed us to evaluate the potential for in situ N2O suppression by biological nitrification inhibition (BNI) in energy sorghum. Our results demonstrated that the fraction of N2O originating from bacterial denitrification and reduction of N2O to N2 is largely determined by the volume of particulate organic matter occluded within the soil matrix and the anaerobic soil volume. Bacterial denitrification was greater in switchgrass than in the annual crops, related to changes in pore structure caused by the coarse root system. This led to high N-loses through N2 emissions in the switchgrass system throughout the season a novel finding given the lack of data in the literature for total denitrification. Isotopic mapping indicated no differences in N2O-fluxes or their source processes between maize and energy sorghum that could be associated with the release of BNI by the investigated sorghum variety. The results of this research show how differences in soil pore structures among cropping systems can determine both N2O production via denitrification and total denitrification N losses in situ.

Most of the previous studies on the effects of pore structure on soil water retention behaviour are limited to a single drying and wetting cycle. This study evaluated the effects of pore structure on water retention behaviour for specimens prepared at different pore structures of similar density, subjected to drying-wetting cycles. Specimens were compacted at two density states equivalent to loosely compacted fill slopes (80% relative compaction, e = 0.78), and densely compacted slopes or subgrade compaction specifications (95% relative compaction, e = 0.50) at different water contents on the wet side (20%) and dry side (10%) of the optimum water content. The results show that loosely compacted specimens prepared on the wet side have a lower water retention ability due to the larger formed macropores. They also show a significantly higher degree of hysteresis which decreases with drying and wetting cycles. For loosely compacted specimens, there is a higher increase in water retention ability with cycles for specimens prepared on the dry side, due to more drying and wettinginduced pore evolution and volumetric changes. Increasing compaction density results in a higher water retention ability but reduces the number of cycles needed to achieve water retention equilibrium with dryingwetting cycles, subsequently behaving as scanning curves. This is attributed to the less pore evolution and smaller volumetric strain at lower void ratios. Pore structure effects on water retention behaviour subjected to drying-wetting cycles should be considered in civil engineering designs for earth structures, such as loosely compacted fill materials.

Renewable energy sources are indispensable to meet the rising demand of energy usage while reducing the negative environmental impact of utilising fossil fuels. Gasification is an efficient technology to convert biogenic waste into valuable gaseous products. The rate of conversion of char, produced in an intermediate step in the conversion, plays an essential role in the conversion of biogenic materials. The conversion of char is significantly affected by properties such as the structure of the char and its alkali content. This thesis presents findings related to the influence of char pore structure development and alkalis content on char gasification, as well as the alkali release during gasification and co-gasification. Experimental results show that the generation of micropores are directly proportional to the observed reactivity up to 70% of char conversion, after which the catalytic effects of potassium become the dominating factor. Furthermore, investigations of the effect of different intrinsic potassium contents on woody char reactivity demonstrate that no alkali surface saturation point is reached, as is the case for high-ash chars. Application of a modified random pore model enabled a successful capture of the later stages of char conversion in comparison to other kinetic models applied. Alkali release and sample mass changes were monitored simultaneously, using a thermogravimetric analyser together with a surface ionization detector (TGA-SID). The studies revealed a significant release of alkali as woody char conversion approaches completion during CO2 gasification. For straw char the release of alkali decreased continuously throughout the conversion process. Similar results were obtained for biochar gasification under steam conditions in a fixed bed reactor. However, in this case the process is more complex, including transfer of alkali between pa, Förnybara energikällor behövs för att möta den ökande efterfrågan på energianvändning, samtidigt med behoven av att minska den negativa miljöpåverkan som användningen av fossila bränslen medför. Förgasning är en effektiv teknologi för att omvandla biogent avfall till värdefulla gasformiga produkter. I omvandlingsprocessen förkolas biomassan till biokol i ett intermediärt steg. Hastigheten för omvandlingen av biokolet spelar en avgörande roll vid förgasningen av biogena material. Denna omvandling påverkas väsentligt av biokolets egenskaper såsom kolstruktur och dess alkaliinnehåll. I denna avhandling presenteras resultat som relaterar till inverkan av kolstrukturens utveckling och innehåll av alkalier vid förgasningen av biokol samt frigörandet av alkali under förgasning och samförgasning. Experimentella resultat visar på att genereringen av mikroporer är direkt proportionellt mot observerad reaktivitet upp till 70 procents kolomvandling. Därefter är de katalytiska effekterna huvudsakligen relaterade till kaliumhalten. Vidare så observerades ingen effekt av alkalimättnad av kolytan på biokolets reaktivitet vid studier med biokol från trämaterial med olika halter av kalium, något som observerats tidigare för biokol med högre innehåll av aska. Tillämpning av en modifierad randomiserad modell för utvecklingen av porer resulterade i en lämplig beskrivning av de slutliga stadierna i omvandlingen av biokol jämfört med andra kinetiska modeller. Frigörandet av alkalier och förändringar i provernas massa undersöktes med hjälp av termogravimetrisk analys tillsammans med en ytjonisationsdetektor (TGA-SID). Studierna visar att en betydande mängd alkalier frigörs mot slutet av biokolets omvandling under koldioxidförgasning. För biokol från halm observerades däremot ett fortsatt minskat frigörande av alkalier under hela omvandlingsprocessen. Liknande re, QC 2023-04-26

Unconventional reservoir resources are important to supplement energy consumption and maintain the balance of supply and demand in the oil and gas market. However, due to the complex geological conditions, it is a significant challenge to develop unconventional reservoirs efficiently and economically. At present, unconventional reservoirs are extensively studied, covering a wide range of areas, with special attention to the multiscale characterization of pore structures and fracture networks, description of complex fluid transport mechanisms, mathematical modeling of flow properties, and coupled analysis with multiphysics fields. This work briefly describes the multiscale and multiphysics influences on fluids in unconventional reservoirs, and the modeling and simulation work conducted to analyze them, with the aim to provide some theoretical basis for enhanced recovery from these geo-energy resources. The present article also aims to enhance the community’s knowledge of other potential utilizations associated with some unconventional reservoirs, specially related to environmentally-driven projects, including permanent greenhouse gas storage and cyclic underground energy storage., Petroleum Engineering

Unconventional reservoir resources are important to supplement energy consumption and maintain the balance of supply and demand in the oil and gas market. However, due to the complex geological conditions, it is a significant challenge to develop unconventional reservoirs efficiently and economically. At present, unconventional reservoirs are extensively studied, covering a wide range of areas, with special attention to the multiscale characterization of pore structures and fracture networks, description of complex fluid transport mechanisms, mathematical modeling of flow properties, and coupled analysis with multiphysics fields. This work briefly describes the multiscale and multiphysics influences on fluids in unconventional reservoirs, and the modeling and simulation work conducted to analyze them, with the aim to provide some theoretical basis for enhanced recovery from these geo-energy resources. The present article also aims to enhance the community’s knowledge of other potential utilizations associated with some unconventional reservoirs, specially related to environmentally-driven projects, including permanent greenhouse gas storage and cyclic underground energy storage.

The influences of liquid-binder ratio and mixing sequence on the performance of superabsorbent polymer (SAP)-containing alkali-activated slag (AAS) mortar are investigated in this study. It is found that the SAP absorbs much less liquid in upper supernatant of AAS than in water. Mixing SAP with liquid first induces a larger absorption capacity of the SAP than mixing it with solid first. Increasing the liquid-binder ratio improves the flowability but reduces the strength of AAS mortar with SAP. Nonetheless, the strength of internally cured mixtures is higher than that of the reference even with an extra liquid-binder ratio of 0.09. The reason behind lies in the refinement of capillary and gel porosity by internal curing, despite the presence of large voids originated from SAP. The autogenous shrinkage of AAS paste is reduced significantly by the incorporation of SAP but the further mitigating effect of increased liquid-binder ratio is limited., Materials and Environment

AbstractPore structures determine reservoir storage capacity, control rock transportation characteristics and represent microscopic properties of the rock. Therefore, the characterization and quantification of the pore structures of tight oil and gas reservoir are of primary importance for quality evaluation and the successful production of these unconventional resources. In this study, we obtained X-CT images with two resolutions of the same tight sandstone and studied the pore structures and heterogeneity of tight sandstone using digital rock technology combined with fractal theory. In traditional Euclidean space, digital image analysis shows that the pore structure of tight sandstone is mainly flat, isolated pores that occupy a large number ratio in high-resolution images and a large volume ratio in low-resolution images. Most seepage channels are mainly composed of large pores. The porosity analysis of 2D and 3D suggests that the representative elementary volume of low-resolution digital rock is 300 voxels, and the axial heterogeneity of tight sandstone is stronger than the bulk heterogeneity. In non-Euclidean space, fractal characterization parameters indicate that the fractal dimension (FD) of low-resolution digital rock is 2.6548, that of high-resolution digital rock is 2.6194, and the FD of tight sandstone is insensitive to imaging resolution. The lacunarity of high-resolution digital rock is obviously larger than that of low-resolution digital rock, which suggests that lacunarity can be used to analyze the heterogeneous structures with similar FD of tight sandstone precisely.

This work investigates the role that pore structure plays in colloid retention across scales with a novel methodology based on image analysis. Experiments were designed to quantify–with robust statistics–the contribution from commonly proposed retention sites toward colloid immobilization. Specific retention sites include solid-water interface, air-water interface, air-water-solid triple point, grain-to-grain contacts, and thin films. Variable conditions for pore-water content, velocity, and chemistry were tested in a model glass bead porous medium with silver microspheres. Concentration signals from effluent breakthrough and spatial profiles of retained particles from micro X-ray Computed Tomography were used to compute mass balances and enumerate pore-scale regions of interest in three dimensions. At the Darcy-scale, retained colloids follow non-monotonic deposition profiles, which implicates effects from flow-stagnation zones. The spatial distribution of immobilized colloids along the porous medium depth was analyzed by retention site, revealing depth-independent partitioning of colloids. At the pore-scale, dominance and overall saturation of all retention sites considered indicated that the solid-water interface and wedge-shaped regions associated with flow-stagnation (grain-to-grain contacts in saturated and air-water-solid triple points in unsaturated conditions) are the greatest contributors toward retention under the tested conditions. At the interface-scale, xDLVO energy profiles were in agreement with pore-scale observations. Our calculations suggest favorable interactions for colloids and solid-water interfaces and for weak flocculation (e.g., at flow-stagnation zones), but unfavorable interactions between colloids and air-water interfaces. Overall, we demonstrate that pore-structure plays a critical role in colloid immobilization and that Darcy-, pore- and interface-scales are consistent when the pore structure is taken into account.

Microstructural and compositional analysis of historical mortars is an active research field, not only to guarantee the use of compatible repair measures, but also to guide the design of novel efficient materials. Despite the crucial role of Roman mortars in building history, there is a significant lack of knowledge of their pore system in relation to building techniques and durability. From these premises, this research focuses on the structural mortars of the Realillo aqueduct (Archaeological Site of Baelo Claudia, Spain). This construction is especially interesting from a durability point of view, as in addition to being in a windy coastal area, the water-proof potential of the material is a major issue. Complementary experimental techniques (petrography, computed tomography, X-ray fluorescence, X-ray diffraction (micro and conventional), thermal analysis, pycnometry, physisorption, Hg porosimetry, and SEM-EDS) are applied within a multidisciplinary approach, including the Vitruvian guidelines and comparative analysis with coetaneous buildings. The size and shape of the pores and the porous volume distribution have been linked to hydraulicity, and to cohesion and weathering resistance. Total and open porosity can be related to waterproof worsening, and the entrapped air pores detected could indicate inadequate placement. The shrinkage cracks can be related to the sea sand aggregate. Thermal analysis and C-A- S-H gel indicate hydraulic phases, but with different hydraulicity levels. This variation could be related to the non-high-purity limestone and/or to the recipe. The differences in binder/aggregate ratios and petrographic classification confirm the distinct compositions. Non-standardized manufacturing or building stages could be related to compositional variations. This research has provided significant insights into durability and manufacturing issues by integrating a micro–macro pore structure study within multianalytical and interdisci- plinary research. T

Superabsorbent polymers (SAPs) are used as internal curing agents in cementitious materials, which reduce autogenous shrinkage in concrete as they have a low water-to-cement ratios and improve the freeze-thaw resistance. However, the compressive strength of concrete may also be reduced due to additional voids in the hydrated cement matrix. In this study, we fabricated a delayed absorption type of SAP (I-SAP) composed of cross-linked modified acrylate and studied its absorption characteristics and effect on compressive strength after 28 days. Furthermore, the effect of curing conditions on the strength of concrete and hydrated cement paste with SAP were investigated. The absorption capacity of I-SAP in the synthetic pore solution and deionised water was examined and compared with that of a conventional SAP, and the former was absorbed more by I-SAP. The results revealed that the compressive strength of concrete increased with the addition of I-SAP, particularly with the curing condition of 60% RH. Although the compressive strength of hydrated cement paste with I-SAP reduced in water or sealed curing conditions, no loss of strength in the paste cured at 60% RH was seen. The cement matrix densification due to hydration of belite around the SAP surface is the main mechanism for strength development in concrete cured at sealed and 60% RH. However, the voids formed by SAP control the compressive strength of hydrated paste.

Geopolymers are three-dimensional aluminosilicate frameworks, synthesized from the aluminosilicate sources activated by alkali solutions under mild conditions. They are widely regarded as sustainable construction materials. The understanding of geopolymer pore structures is important for their development. The mechanical properties of geopolymers depend on their pore structures. Currently, the pore structures are often studied using destructive methods, which cannot be used in longitudinal studies. Thus, new methods are required to characterize the time-dependent properties of geopolymers. In this thesis, the following advanced 1H and 129Xe nuclear magnetic resonance (NMR) methods were applied to study the polymerization, curing, and pore structure of geopolymers: 1H relaxometry, 1H cryoporometry, 129Xe spectroscopy, and 129Xe relaxometry. As a result, several interconnected mesopores with different pore sizes were found. Additionally, three factors were found to affect the geopolymerization and pore structures: water-to-solid ratio (w/s), silicon-to-aluminum ratio (Si/Al), and NH4OH posttreatment. High w/s favors large pore sizes and enhanced pore connectivity. Low Si/Al = 1 contributes to the formation of the zeolite phase, resulting from the formation of a gel phase with low Si/Al during geopolymerization. The NH4OH posttreatment did not change pore sizes, but it did increase the level of pore connectivity., Tiivistelmä Geopolymeerit ovat kolmiulotteisia alumiinisilikaattirakenteita, jotka syntetisoidaan alumiinisilikaattilähteistä, jotka aktivoidaan alkaliliuoksella miedoissa olosuhteissa. Niitä pidetään laajalti ympäristöystävällisinä rakennusmateriaaleina. Geopolymeerihuokosrakenteiden ymmärtäminen on tärkeää niiden sovellusten kannalta. Geopolymeerien mekaaniset ja absorptio ominaisuudet riippuvat niiden huokosrakenteista. Tällä hetkellä huokosrakenteita tutkitaan yleensä destruktiivisilla menetelmällä, jolloin pitkittäistutkimus ei ole mahdollista. Tämän vuoksi geopolymeerien ajasta riippuvien ominaisuuksien karakterisointiin tarvitaan uusia menetelmiä. Tässä väitöskirjassa geopolymeerien polymeroitumisen, kovettumisen ja huokosrakenteen tutkimiseen sovellettiin edistyneitä 1H- ja 129Xe NMR-menetelmiä: 1H-relaksometriaa, 1H-kryoporometriaa, 129Xe-spektroskopiaa ja 129Xe-relaksometriaa. Tutkimuksessa löydettiin useita toisiinsa liittyneitä mesohuokosia, joiden huokoskoko oli erilainen. Tutkimuksessa huomattiin, että geopolymeerien polymeroitumiseen ja huokosrakenteeseen vaikuttaa kolme tekijää: vesi/kiintoainesuhde (w/s), pii/alumiini suhde (Si/Al) ja jälkikäsittely NH4OH:lla. Suuri w/s suosii suuria huokoskokoja ja parantaa huokosten kytkeytyneisyyttä. Matala Si/Al = 1 edistää zeoliittifaasin muodostumista, mikä johtuu sellaisen geelifaasin muodostumisesta, jossa on alhainen Si/Al geopolymeroinnin aikana. NH4OH-jälkikäsittely ei muuttanut huokoskokoa, mutta lisäsi huokosten kytkeytyneisyyttä.

Microstructural and compositional analysis of historical mortars is an active research field, not only to guarantee the use of compatible repair measures, but also to guide the design of novel efficient materials. Despite the crucial role of Roman mortars in building history, there is a significant lack of knowledge of their pore system in relation to building techniques and durability. From these premises, this research focuses on the structural mortars of the Realillo aqueduct (Archaeological Site of Baelo Claudia, Spain). This construction is especially interesting from a durability point of view, as in addition to being in a windy coastal area, the water-proof potential of the material is a major issue. Complementary experimental techniques (petrography, computed tomography, X-ray fluorescence, X-ray diffraction (micro and conventional), thermal analysis, pycnometry, physisorption, Hg porosimetry, and SEM-EDS) are applied within a multidisciplinary approach, including the Vitruvian guidelines and comparative analysis with coetaneous buildings. The size and shape of the pores and the porous volume distribution have been linked to hydraulicity, and to cohesion and weathering resistance. Total and open porosity can be related to waterproof worsening, and the entrapped air pores detected could indicate inadequate placement. The shrinkage cracks can be related to the sea sand aggregate. Thermal analysis and C-A- S-H gel indicate hydraulic phases, but with different hydraulicity levels. This variation could be related to the non-high-purity limestone and/or to the recipe. The differences in binder/aggregate ratios and petrographic classification confirm the distinct compositions. Non-standardized manufacturing or building stages could be related to compositional variations. This research has provided significant insights into durability and manufacturing issues by integrating a micro–macro pore structure study within multianalytical and interdisci- plinary research. T

Microstructural and compositional analysis of historical mortars is an active research field, not only to guarantee the use of compatible repair measures, but also to guide the design of novel efficient materials. Despite the crucial role of Roman mortars in building history, there is a significant lack of knowledge of their pore system in relation to building techniques and durability. From these premises, this research focuses on the structural mortars of the Realillo aqueduct (Archaeological Site of Baelo Claudia, Spain). This construction is especially interesting from a durability point of view, as in addition to being in a windy coastal area, the water-proof potential of the material is a major issue. Complementary experimental techniques (petrography, computed tomography, X-ray fluorescence, X-ray diffraction (micro and conventional), thermal analysis, pycnometry, physisorption, Hg porosimetry, and SEM-EDS) are applied within a multidisciplinary approach, including the Vitruvian guidelines and comparative analysis with coetaneous buildings. The size and shape of the pores and the porous volume distribution have been linked to hydraulicity, and to cohesion and weathering resistance. Total and open porosity can be related to waterproof worsening, and the entrapped air pores detected could indicate inadequate placement. The shrinkage cracks can be related to the sea sand aggregate. Thermal analysis and C-A- S-H gel indicate hydraulic phases, but with different hydraulicity levels. This variation could be related to the non-high-purity limestone and/or to the recipe. The differences in binder/aggregate ratios and petrographic classification confirm the distinct compositions. Non-standardized manufacturing or building stages could be related to compositional variations. This research has provided significant insights into durability and manufacturing issues by integrating a micro–macro pore structure study within multianalytical and interdisci- plinary research. T

Superabsorbent polymers (SAPs) are used as internal curing agents in cementitious materials, which reduce autogenous shrinkage in concrete as they have a low water-to-cement ratios and improve the freeze-thaw resistance. However, the compressive strength of concrete may also be reduced due to additional voids in the hydrated cement matrix. In this study, we fabricated a delayed absorption type of SAP (I-SAP) composed of cross-linked modified acrylate and studied its absorption characteristics and effect on compressive strength after 28 days. Furthermore, the effect of curing conditions on the strength of concrete and hydrated cement paste with SAP were investigated. The absorption capacity of I-SAP in the synthetic pore solution and deionised water was examined and compared with that of a conventional SAP, and the former was absorbed more by I-SAP. The results revealed that the compressive strength of concrete increased with the addition of I-SAP, particularly with the curing condition of 60% RH. Although the compressive strength of hydrated cement paste with I-SAP reduced in water or sealed curing conditions, no loss of strength in the paste cured at 60% RH was seen. The cement matrix densification due to hydration of belite around the SAP surface is the main mechanism for strength development in concrete cured at sealed and 60% RH. However, the voids formed by SAP control the compressive strength of hydrated paste.

Pore structure and methane adsorption of coal reservoir are closely correlated to the coalbed gas occurrence and outburst. Full-scale pore structure and its fractal heterogeneity of coal samples were quantitatively characterized using low-pressure N2 gas adsorption (LP-N2GA) and high-pressure mercury intrusion porosimetry (HP-MIP). Fractal pore structure and adsorption capacities between outburst and nonoutburst coals were compared, and their geological significance to gas occurrence and outburst was discussed. The results show that pore volume (PV) is mainly contributed by macropores ( > 1000 nm) and mesopores (100-1000 nm), while specific surface area (SSA) is dominated by micropores ( < 10 nm) and transition pores (10 - 100 nm). On average, the PV and SSA of outburst coal samples are 4.56 times and 5.77 times those of nonoutburst coal samples, respectively, which provide sufficient place for gas adsorption and storage. The pore shape is dominated by semiclosed pores in the nonoutburst coal, whereas open pores and inkbottle pores are prevailing in the outburst coal. The pore size is widely distributed in the outburst coal, in which not only micropores are dominant, but also, transition pores and mesopores are developed to a certain extent. Based on the data from HP-MIP and LP-N2GA, pore spatial structure and surface are of fractal characteristics with fractal dimensions Dm1 (2.81 - 2.97) and Dn (2.50 - 2.73) calculated by Menger model and Frenkel-Halsey-Hill (FHH) model, respectively. The pore structure in the outburst coal is more heterogeneous as its Dn and Dm1 are generally larger than those of the nonoutburst coal. The maximum methane adsorption capacities (VL: 15.34 - 20.86 cm 3 / g) of the outburst coal are larger than those of the nonoutburst coal (VL : 9.97-13.51cm 3 / g). The adsorptivity of coal samples is governed by the micropores, transition pores, and Dn because they are positively correlated with the SSA. The outburst coal belongs to tectonically de

Unconventional reservoir resources are important to supplement energy consumption and maintain the balance of supply and demand in the oil and gas market. However, due to the complex geological conditions, it is a significant challenge to develop unconventional reservoirs efficiently and economically. At present, unconventional reservoirs are extensively studied, covering a wide range of areas, with special attention to the multiscale characterization of pore structures and fracture networks, description of complex fluid transport mechanisms, mathematical modeling of flow properties, and coupled analysis with multiphysics fields. This work briefly describes the multiscale and multiphysics influences on fluids in unconventional reservoirs, and the modeling and simulation work conducted to analyze them, with the aim to provide some theoretical basis for enhanced recovery from these geo-energy resources. The present article also aims to enhance the community’s knowledge of other potential utilizations associated with some unconventional reservoirs, specially related to environmentally-driven projects, including permanent greenhouse gas storage and cyclic underground energy storage.

To characterize the coal measure shale pore structure of the Xiashihezi Formation in the Sunan Syncline block, a series of experiments were conducted. Results show that the main components of the shales are clay minerals and quartz, and organic matter, fluid escaping, interlayer, intercrystalline and interparticle pores are well-developed. The shale pore specific surface area (SSA) is concentrated in the pores with the size of < 50 nm and is significantly higher in the pores with the size of < 5 nm, indicating that these pores have an important effect on gas adsorption. The shale pore volume is mainly concentrated near the pore size of 10 nm, followed by 10,000-100,000 nm, indicating that in addition to the fractures, the matrix pores with a size of about 10 nm contribute the most to pore volume and free gas accumulation. The volume and SSA of the micropore, small pore, and mesopore increase with the TOC content when it is lower than 6%, leading to higher porosity and total pore SSA of the shales. However, this positive correlation disappears under the compaction effect when the TOC content is higher than 6%. The clay mineral content has negative correlations with the volume and SSA of the mesopore and macropore under the compaction and pore blockage effects, but it correlates poorly with those of the micropore and small pore, causing a decrease in the shale porosity as it increases, while the brittle mineral can promote mesopore and macropore development and is conducive to micropore and small pore maintenance when its content is higher than 45%. As a result, the shale porosity tends to increase with the brittle mineral content. This study is helpful in clarifying the coal measure shale gas enrichment law in the block and in providing fundamental support for coal measure gas efficient development.

Multi-stage hydraulic fracturing combined with horizontal drilling has been widely implemented to enhance oil/gas production from shale reservoirs. One method of reservoir stimulation is to use low-salinity fracturing fluid that mixes with existing high-salinity formation brine. This process either activates existing natural fractures or generates new fractures thus enhances reservoir communication. However, it is still unclear how the in-situ geochemistry change would affect shale surface energy and fracture/micro-fracture propagation, and far less research has investigated the effect of salinity on shale micromechanics. This impedes the proper evaluation of hydraulic fracturing influence on the stability of shale reservoirs with different mineralogy. In this study, the strength of shale samples with different composition at different saturation conditions were measured using nano-indentation techniques together with atomic force microscopy (AFM) and scanning electron microscopy (SEM). In addition, geochemical modelling with the combination of surface complexation and disjoining pressure isotherm were performed to examine the role of physicochemical reactions on shale micromechanical properties. Nano-indentation tests confirm that brine saturation can decrease samples’ indentation moduli regardless of mineralogy. We also found that decreasing salinity would further decrease indentation modulus of calcite-, quartz- and illite-rich shale samples by 43.8%, 19.2%, and 33.3%, suggesting that rock micromechanics are indeed affected by the geochemistry. Compared to dry condition, calcite- and quartz-rich shales have greater indentation moduli reduction after low salinity brine saturation (64.3% and 45.4%) than the illite-rich sample (32.2%), indicating that fluid-rock interactions associated with shale micromechanics are also influenced by mineralogy. Thermodynamics calculation shows that the shift of the disjoining pressure isotherm from strongly negative to positive lik

Alkali activated materials (AAMs) have gained great attention as a new low-carbon binder. However, their durability performance, e.g. chloride ingress resistance, still needs further improvement. This study attempts to enhance the chloride binding of AAMs by activating slag with sodium aluminate with the aim to promote the in-situ formation of layered double hydroxides (LDHs). The evolution of pH and ions in the pore solution, reaction products and microstructure were determined to investigate the dynamic activation process. Results show that the sodium aluminate stabilizes the pH environment at around 12.7 during the curing ages. The Mg-Al-LDH with higher Al-O tetrahedra (denoted as Al(OH)4−) contents is promoted, enhancing the chloride absorption capacity. A new reaction mechanism is proposed to describe the activation process. This study reveals that the extra Al(OH)4−in a relatively low pH environment prevents the competition between Mg2+ and Si-O tetrahedra to react with Al(OH)4−, promoting the formation of LDH and C(N)-A-S-H simultaneously.

Unconventional reservoir resources are important to supplement energy consumption and maintain the balance of supply and demand in the oil and gas market. However, due to the complex geological conditions, it is a significant challenge to develop unconventional reservoirs efficiently and economically. At present, unconventional reservoirs are extensively studied, covering a wide range of areas, with special attention to the multiscale characterization of pore structures and fracture networks, description of complex fluid transport mechanisms, mathematical modeling of flow properties, and coupled analysis with multiphysics fields. This work briefly describes the multiscale and multiphysics influences on fluids in unconventional reservoirs, and the modeling and simulation work conducted to analyze them, with the aim to provide some theoretical basis for enhanced recovery from these geo-energy resources. The present article also aims to enhance the community’s knowledge of other potential utilizations associated with some unconventional reservoirs, specially related to environmentally-driven projects, including permanent greenhouse gas storage and cyclic underground energy storage., Reservoir Engineering

The influences of liquid-binder ratio and mixing sequence on the performance of superabsorbent polymer (SAP)-containing alkali-activated slag (AAS) mortar are investigated in this study. It is found that the SAP absorbs much less liquid in upper supernatant of AAS than in water. Mixing SAP with liquid first induces a larger absorption capacity of the SAP than mixing it with solid first. Increasing the liquid-binder ratio improves the flowability but reduces the strength of AAS mortar with SAP. Nonetheless, the strength of internally cured mixtures is higher than that of the reference even with an extra liquid-binder ratio of 0.09. The reason behind lies in the refinement of capillary and gel porosity by internal curing, despite the presence of large voids originated from SAP. The autogenous shrinkage of AAS paste is reduced significantly by the incorporation of SAP but the further mitigating effect of increased liquid-binder ratio is limited., Materials and Environment

Carbonation has been proven to be a promising way to improve the mechanism properties and durability of steel slag products. CA bacteria can promote the hydration of CO2. In this study, one kind of alkali-resistant CA bacteria was chosen to investigate its effects on the carbonation process of γ-C2S. Results showed that bacteria could increase the compressive strength of carbonized γ-C2S by 19.0%. Main products of carbonized γ-C2S were vaterite, calcite and SiO2 gel. The addition of bacteria could only accelerate the deposition of calcium carbonate, while hardly changing the types and properties of the carbonation products. Additionally, accelerated carbonation makes it harder for the carbon dioxide to diffuse inward, leading to the decline of accelerating carbonation effect. However, CA bacteria could change the morphology of calcium carbonated during the carbonation process of β-C2S and further accelerate the hydration process of β-C2S. The pore structure can also be refined with the incorporation of bacteria.

Nanoscale manganese oxide with different morphologies were developed at room temperature using different precursor salts (potassium permanganate and manganese sulfate). The obtained nanoscale morphologies, i.e., rod and sphere-shaped were characterized using BET surface area analyzer, SEM, TEM, and XRD. The manganese oxide possessed the rod and sphere-like morphologies with different pore structures. The adsorption of methylene blue on mesoporous manganese oxide followed the pseudo-second-order kinetics and best fitted with the Freundlich adsorption isotherm model with a removal capacity of 2914 mg g−1. The effect of irradiation time on degradation efficiency was also examined, which followed the first-order kinetics with a degradation efficiency of 93.12%. Furthermore, the recycling studies revealed that the spherical manganese oxide retained over 90% of the photodegradation efficiency after three cycles of methylene blue degradation, which proves its stability for practical applications. Therefore, mesoporous manganese oxide with significant adsorption and remarkable photodegradation capability can provide a way forward to fine-tune the material's properties for effective environmental remediation.

Geomaterials and filling fluids properties that are pertinent to a geologic porous media can be characterized using a range of methods, such as nuclear magnetic resonance, X-rays, infrared spectroscopy, and neutron scattering (NS). In this context, NS features as an important tool elucidate key properties of a porous medium, which has recently gained significant attention. Key rock properties that can be measured by NS include: rock texture (i.e. crystallographic preferred orientation), mechanical properties (i.e. stress and strain) as well as porous medium properties (pore porosity, pore size and connectivity). In addition, NS imaging can help elucidate the phase behaviour of confined reservoir fluids in rock matrix under prevailing pressures and temperatures. Thus, a precise characterization of these properties (amongst other multiphase flow attributes) is critical for several applications in varied fields such as hydrocarbon reservoirs, geothermal systems, crystallography, geomechanics and geochemistry. Low neutron attenuation by most substances (deep sample penetration) and strong neutron attenuation by hydrogen are essential features of neutrons that allow NS to collect high-quality data across a wide variety of subsurface conditions. These features enable NS to be ideally suited to some applications as compared to other techniques such as X-rays and magnetic resonance imaging (MRI). For example, X-rays may not have sufficient resolutions for examining nanopore structures and confined fluids. Contrastingly, MRI is limited by the visualization of a range of pore sizes. However, NS can capture angstrom-to-micron-scale information of atomic to meso-to-macro-scale structures of rocks and fluids (i.e. hydrogen-rich fluids) inside a porous medium. These insights are vital for predictive reservoir models, where meaningful reservoir-scale (hectometre-scale) predictions can be performed. However, when compared to X-rays, neutrons have weak sources and/or low signals; th

Nanoscale manganese oxide with different morphologies were developed at room temperature using different precursor salts (potassium permanganate and manganese sulfate). The obtained nanoscale morphologies, i.e., rod and sphere-shaped were characterized using BET surface area analyzer, SEM, TEM, and XRD. The manganese oxide possessed the rod and sphere-like morphologies with different pore structures. The adsorption of methylene blue on mesoporous manganese oxide followed the pseudo-second-order kinetics and best fitted with the Freundlich adsorption isotherm model with a removal capacity of 2914 mg g−1. The effect of irradiation time on degradation efficiency was also examined, which followed the first-order kinetics with a degradation efficiency of 93.12%. Furthermore, the recycling studies revealed that the spherical manganese oxide retained over 90% of the photodegradation efficiency after three cycles of methylene blue degradation, which proves its stability for practical applications. Therefore, mesoporous manganese oxide with significant adsorption and remarkable photodegradation capability can provide a way forward to fine-tune the material's properties for effective environmental remediation.

Geomaterials and filling fluids properties that are pertinent to a geologic porous media can be characterized using a range of methods, such as nuclear magnetic resonance, X-rays, infrared spectroscopy, and neutron scattering (NS). In this context, NS features as an important tool elucidate key properties of a porous medium, which has recently gained significant attention. Key rock properties that can be measured by NS include: rock texture (i.e. crystallographic preferred orientation), mechanical properties (i.e. stress and strain) as well as porous medium properties (pore porosity, pore size and connectivity). In addition, NS imaging can help elucidate the phase behaviour of confined reservoir fluids in rock matrix under prevailing pressures and temperatures. Thus, a precise characterization of these properties (amongst other multiphase flow attributes) is critical for several applications in varied fields such as hydrocarbon reservoirs, geothermal systems, crystallography, geomechanics and geochemistry. Low neutron attenuation by most substances (deep sample penetration) and strong neutron attenuation by hydrogen are essential features of neutrons that allow NS to collect high-quality data across a wide variety of subsurface conditions. These features enable NS to be ideally suited to some applications as compared to other techniques such as X-rays and magnetic resonance imaging (MRI). For example, X-rays may not have sufficient resolutions for examining nanopore structures and confined fluids. Contrastingly, MRI is limited by the visualization of a range of pore sizes. However, NS can capture angstrom-to-micron-scale information of atomic to meso-to-macro-scale structures of rocks and fluids (i.e. hydrogen-rich fluids) inside a porous medium. These insights are vital for predictive reservoir models, where meaningful reservoir-scale (hectometre-scale) predictions can be performed. However, when compared to X-rays, neutrons have weak sources and/or low signals; th

Geomaterials and filling fluids properties that are pertinent to a geologic porous media can be characterized using a range of methods, such as nuclear magnetic resonance, X-rays, infrared spectroscopy, and neutron scattering (NS). In this context, NS features as an important tool elucidate key properties of a porous medium, which has recently gained significant attention. Key rock properties that can be measured by NS include: rock texture (i.e. crystallographic preferred orientation), mechanical properties (i.e. stress and strain) as well as porous medium properties (pore porosity, pore size and connectivity). In addition, NS imaging can help elucidate the phase behaviour of confined reservoir fluids in rock matrix under prevailing pressures and temperatures. Thus, a precise characterization of these properties (amongst other multiphase flow attributes) is critical for several applications in varied fields such as hydrocarbon reservoirs, geothermal systems, crystallography, geomechanics and geochemistry. Low neutron attenuation by most substances (deep sample penetration) and strong neutron attenuation by hydrogen are essential features of neutrons that allow NS to collect high-quality data across a wide variety of subsurface conditions. These features enable NS to be ideally suited to some applications as compared to other techniques such as X-rays and magnetic resonance imaging (MRI). For example, X-rays may not have sufficient resolutions for examining nanopore structures and confined fluids. Contrastingly, MRI is limited by the visualization of a range of pore sizes. However, NS can capture angstrom-to-micron-scale information of atomic to meso-to-macro-scale structures of rocks and fluids (i.e. hydrogen-rich fluids) inside a porous medium. These insights are vital for predictive reservoir models, where meaningful reservoir-scale (hectometre-scale) predictions can be performed. However, when compared to X-rays, neutrons have weak sources and/or low signals; th

Geomaterials and filling fluids properties that are pertinent to a geologic porous media can be characterized using a range of methods, such as nuclear magnetic resonance, X-rays, infrared spectroscopy, and neutron scattering (NS). In this context, NS features as an important tool elucidate key properties of a porous medium, which has recently gained significant attention. Key rock properties that can be measured by NS include: rock texture (i.e. crystallographic preferred orientation), mechanical properties (i.e. stress and strain) as well as porous medium properties (pore porosity, pore size and connectivity). In addition, NS imaging can help elucidate the phase behaviour of confined reservoir fluids in rock matrix under prevailing pressures and temperatures. Thus, a precise characterization of these properties (amongst other multiphase flow attributes) is critical for several applications in varied fields such as hydrocarbon reservoirs, geothermal systems, crystallography, geomechanics and geochemistry. Low neutron attenuation by most substances (deep sample penetration) and strong neutron attenuation by hydrogen are essential features of neutrons that allow NS to collect high-quality data across a wide variety of subsurface conditions. These features enable NS to be ideally suited to some applications as compared to other techniques such as X-rays and magnetic resonance imaging (MRI). For example, X-rays may not have sufficient resolutions for examining nanopore structures and confined fluids. Contrastingly, MRI is limited by the visualization of a range of pore sizes. However, NS can capture angstrom-to-micron-scale information of atomic to meso-to-macro-scale structures of rocks and fluids (i.e. hydrogen-rich fluids) inside a porous medium. These insights are vital for predictive reservoir models, where meaningful reservoir-scale (hectometre-scale) predictions can be performed. However, when compared to X-rays, neutrons have weak sources and/or low signals; th

Alkali activated materials (AAMs) have received worldwide attention due to its lower embodied energy and environmental impact than that of traditional cementitious materials. However, the activators with high alkalinity may raise the risk of alkali silica reaction (ASR) induced deterioration when reactive aggregates are used, which thereby limits the commercial use of AAMs. Not speaking the ASR induced long-term expansion, the early-age reaction of AAMs prepared with reactive aggregates is largely unknown. In this paper, isothermal calorimetry, thermogravimetry (TG) and mercury intrusion porosimetry (MIP) were adopted to study the heat evolution, mineralogical changes and pore structures of early-age ordinary Portland cement (OPC) mortar and water-glass activated slag/fly ash mortars. In each system, emphasis were made to understand the differences between mixtures prepared with standard inert quartz sands and reactive fine aggregates. The results show that the mortars prepared with reactive aggregates generated more heat in the wetting and dissolution stage. Particularly, the water-glass activated slag mortar presented the highest heat flow peak. Meanwhile, the results of TG illustrate that higher amount of reaction products were formed in water-glass activated mortars prepared with reactive aggregates than that with inert quartz sands. These findings suggest that the reactive aggregates are evidently involved in the early-age alkaline reaction of AAMs system., Materials and Environment

Clamp-firing system is a cost-effective technology used to produce burnt clay bricks in many West African countries including Ghana. However, this firing system generates between 7%- 15% of waste in a form of burnt broken bricks and with time creates disposal problems. In this work, burnt clay broken bricks were sampled and pulverised to 75 microns and used as a partial replacement of cement between 10-40 wt. %. Two different sets of mortars were prepared, one from Portland cement as the binder whereas the other set using Portland cement-pulverised bricks as their binders. Compressive strength test was performed on the mortars after moisture exposure at 3, 7 and 28 days. Water absorption test was used to study the pore structure of the optimum mortar mix. The results of the Portland cement-pulverised bricks mortars were compared with the Portland cement mortars. The results of the study indicated that 30 wt.% of the pulverised brick used to replace Portland cement gave the optimum mortar mix. The pore structure of the cement-pulverised brick mortar mixture showed a significant reduction compared to the Portland cement mortars. Si and Al MAS NMR studies revealed that pore structure reduction was due to polymerisation of aluminosilicate hydrates. The study recommends the use of waste powdered burnt clay brick as a supplementary cementitious material and possible means to provide alternative solutions to the disposal of waste burnt broken bricks.

Alkali activated materials (AAMs) have received worldwide attention due to its lower embodied energy and environmental impact than that of traditional cementitious materials. However, the activators with high alkalinity may raise the risk of alkali silica reaction (ASR) induced deterioration when reactive aggregates are used, which thereby limits the commercial use of AAMs. Not speaking the ASR induced long-term expansion, the early-age reaction of AAMs prepared with reactive aggregates is largely unknown. In this paper, isothermal calorimetry, thermogravimetry (TG) and mercury intrusion porosimetry (MIP) were adopted to study the heat evolution, mineralogical changes and pore structures of early-age ordinary Portland cement (OPC) mortar and water-glass activated slag/fly ash mortars. In each system, emphasis were made to understand the differences between mixtures prepared with standard inert quartz sands and reactive fine aggregates. The results show that the mortars prepared with reactive aggregates generated more heat in the wetting and dissolution stage. Particularly, the water-glass activated slag mortar presented the highest heat flow peak. Meanwhile, the results of TG illustrate that higher amount of reaction products were formed in water-glass activated mortars prepared with reactive aggregates than that with inert quartz sands. These findings suggest that the reactive aggregates are evidently involved in the early-age alkaline reaction of AAMs system.

In this paper, composite material C-S-H/PEG1000 was prepared by multi-scale porous material C-S-H as support and phase change material (PCM) PEG1000 by melt blending, so that it can reduce hydration heat of cementitious system utilizing the characteristics of releasing and storing energy of PCM. TEM, IR, DSC-Tg, BET, MIP and various other characterization methods were used to discuss the feasibility of C-S-H as carrier and investigate the morphology, pore structure and stability of the C-S-H/PEG1000 composite. The change of hydration heat and feathers of pore structure as while as its effect on compressive strength were also tested when the composite was added into the cementitious system. Study shows that the PEG1000 can be well embedded into the hollow inside space of C-S-H to form dense blocks in the form of physical adsorption, with good bonding state and thermal stability, which can decrease heat releasing rate and total heat of the hydration process in cementitious system. The early strength was pretty influenced with different addition of C-S-H/PEG1000, however, the later strength was improved.

The widespread application of alkali-activated fly ash/slag (AAFS) concrete requires satisfaction of a series of performance criteria both from its early age properties (e.g. workability, strength) and long-term stability. In this study, long-term (till 180 days) natural chloride diffusion tests were conducted to evaluate the chloride diffusion in AAFS concretes prepared with different slag content, water-binder (w/b) ratio, alkali content, and sandaggregate ratio. The results revealed that the free chloride diffusion coefficient (Df) of AAFS concretes was between 0.4-1.8×10-12 m2/s. The slag content and w/b were found as dominant parameters affecting the long-term chloride transport in AAFS concretes, while the sandaggregate ratio presented a limited effect. MIP results indicated that capillary pores in AAFS reached percolation and became disconnected after 180 days. The long-term chloride diffusivity of AAFS concretes was closely related to the threshold pore diameter and volume of pores > 5 nm. The more larger pores, the higher chloride diffusion coefficient was.

The structural tailoring of pores is essential to high-performance Fe/N/C electrocatalysts for the oxygen reduction reaction (ORR) in proton exchange membrane fuel cells. Current strategies for pore structure engineering are usually accompanied with a drastic change of the intrinsic activity-related surface, which may mask the real effects of the porous structure on ORR activity. Herein, a mild carbon dioxide (CO2) etching method was used to flexibly tailor the pore structure of Fe/N/C electrocatalysts without drastic changes in their surface structure and property. In this way, via employing the Fe/N/C electrocatalysts as a model, the intrinsic impact of the pore structure on ORR activity was revealed. In addition, the CO2 etching method developed a high-quality electrocatalyst (sample Fe/N/C–5% CO2) with polarization performance exceeding that of the commercial Pt/C catalyst in the fuel cell working voltage region (>0.65 V). This work will promote the ongoing intensive studies on the rational design of the pore structures in the Fe/N/C electrocatalysts.

Recently, there has been increased use of calcium-nitrite and calcium-nitrate as the main components of chloride- and alkali-free anti-freezing agents to promote concrete hydration in cold weather concreting. As the amount of nitrite/nitrate-based accelerators increases, the hydration of tricalcium aluminate (C(3)A phase) and tricalcium silicate (C3S phase) in cement is accelerated, thereby improving the early strength of cement and effectively preventing initial frost damage. Nitrite/nitrate-based accelerators are used in larger amounts than usual in low temperature areas below -10 degrees C. However, the correlation between the hydration process and strength development in concrete containing considerable nitrite/nitrate-based accelerators remains to be clearly identified. In this study, the hydrate composition (via X-ray diffraction and nuclear magnetic resonance), pore structures (via mercury intrusion porosimetry), and crystal form (via scanning electron microscopy) were determined, and investigations were performed to elucidate the effect of nitrite/nitrate-based accelerators on the initial strength development and hydrate formation of cement. Nitrite/nitrate-AFm (aluminate-ferret-monosulfate; AFm) was produced in addition to ettringite at the initial stage of hydration of cement by adding a nitrite/nitrate-based accelerator. The amount of the hydrates was attributed to an increase in the absolute amounts of NO2- and NO3- ions reacting with Al2O3 in the tricalcium aluminate (C(3)A phase). Further, by effectively filling the pores, it greatly contributed to the enhancement of the strength of the hardened cement product, and the degree of the contribution tended to increase with the amount of addition. On the other hand, in addition to the occurrence of cracks due to the release of a large amount of heat of hydration, the amount of expansion and contraction may increase, and it is considered necessary to adjust the amount used for each concrete work.

Recently, there has been increased use of calcium-nitrite and calcium-nitrate as the main components of chloride- and alkali-free anti-freezing agents to promote concrete hydration in cold weather concreting. As the amount of nitrite/nitrate-based accelerators increases, the hydration of tricalcium aluminate (C(3)A phase) and tricalcium silicate (C3S phase) in cement is accelerated, thereby improving the early strength of cement and effectively preventing initial frost damage. Nitrite/nitrate-based accelerators are used in larger amounts than usual in low temperature areas below -10 degrees C. However, the correlation between the hydration process and strength development in concrete containing considerable nitrite/nitrate-based accelerators remains to be clearly identified. In this study, the hydrate composition (via X-ray diffraction and nuclear magnetic resonance), pore structures (via mercury intrusion porosimetry), and crystal form (via scanning electron microscopy) were determined, and investigations were performed to elucidate the effect of nitrite/nitrate-based accelerators on the initial strength development and hydrate formation of cement. Nitrite/nitrate-AFm (aluminate-ferret-monosulfate; AFm) was produced in addition to ettringite at the initial stage of hydration of cement by adding a nitrite/nitrate-based accelerator. The amount of the hydrates was attributed to an increase in the absolute amounts of NO2- and NO3- ions reacting with Al2O3 in the tricalcium aluminate (C(3)A phase). Further, by effectively filling the pores, it greatly contributed to the enhancement of the strength of the hardened cement product, and the degree of the contribution tended to increase with the amount of addition. On the other hand, in addition to the occurrence of cracks due to the release of a large amount of heat of hydration, the amount of expansion and contraction may increase, and it is considered necessary to adjust the amount used for each concrete work.

A basic investigation into whether a geopolymer can be utilized as a part of an artificial barrier during radioactive waste disposal was conducted in this study. Geopolymers are comprised primarily alumina and silica, and they exhibit negligible leaching owing to the absence of calcium. Studies on geopolymers are limited compared to those on other cementitious materials because the physical characteristics of geopolymers vary with the production conditions. In this work, metakaolin based geopolymers were prepared, and their diffusion performance was analyzed. The results indicate that the diffusivity of cesium in a geopolymer is affected by the type of alkali activator. Sodium-activated geopolymers had higher cesium adsorption capacity than potassium-activated geopolymers. The cesium adsorption capacity also had a significant effect on the diffusivity of cesium in the geopolymers. It was shown that, in addition to the pore structure and surface area, the mobility of water affects the diffusion performance of the geopolymer.

Porous biodegradable scaffolds provide a physical substrate for cells allowing them to attach, proliferate and guide the formation of new tissues. A variety of techniques have been developed to fabricate tissue engineering (TE) scaffolds, among them the most relevant is the thermally-induced phase separation (TIPS). This technique has been widely used in recent years to fabricate three-dimensional (3D) TE scaffolds. Low production cost, simple experimental procedure and easy processability together with the capability to produce highly porous scaffolds with controllable architecture justify the popularity of TIPS. This paper provides a general overview of the TIPS methodology applied for the preparation of 3D porous TE scaffolds. The recent advances in the fabrication of porous scaffolds through this technique, in terms of technology and material selection, have been reviewed. In addition, how properties can be effectively modified to serve as ideal substrates for specific target cells has been specifically addressed. Additionally, examples are offered with respect to changes of TIPS procedure parameters, the combination of TIPS with other techniques and innovations in polymer or filler selection., Peer Reviewed, Postprint (published version)

Geopolymers are emerging construction materials with lower carbon dioxide emissions compared to the conventional cementitious materials. The knowledge of the curing process and the related pore structures are important for optimizing the properties of these materials for different applications. The curing process and final pore structure are sensitive to the amount of used water, however the specifics are unclear. The curing process and pore structures of metakaolin-based geopolymers with a narrow water-to-solid (w/s) ratio (0.59–0.66) were monitored by nuclear magnetic resonance (NMR) relaxometry and cryoporometry. The 14-day curing process was investigated by monitoring the change of T₂ and T₁ relaxation times and water signal intensity. After the curing, the pore structures were characterized by 2D T₁-T₂ correlation and T₂-T₂ exchange measurements of absorbed water. The pore size distributions (PSDs) were measured with NMR cryoporometry and compared to nitrogen physisorption and mercury intrusion porosimetry (MIP) results. We found that the relaxation times decreased as the pore structure of the geopolymers matured during the curing while the dissolution and the condensation periods of the curing were distinguished by the changes in signal amplitude reflecting the proton density. After the curing, three distinct pore sizes and connectivity between pores were identified from T₁-T₂ and T₂-T₂ spectra. Their PSDs were measured, and they were found to correspond to two different pore sizes originating from the arrangement of clusters and defective pores. In the narrow w/s ratio (0.59–0.66), the curing times were the same for all samples when cured at 24 °C while the pore sizes were observed to increase as a function of the w/s ratio.

A basic investigation into whether a geopolymer can be utilized as a part of an artificial barrier during radioactive waste disposal was conducted in this study. Geopolymers are comprised primarily alumina and silica, and they exhibit negligible leaching owing to the absence of calcium. Studies on geopolymers are limited compared to those on other cementitious materials because the physical characteristics of geopolymers vary with the production conditions. In this work, metakaolin based geopolymers were prepared, and their diffusion performance was analyzed. The results indicate that the diffusivity of cesium in a geopolymer is affected by the type of alkali activator. Sodium-activated geopolymers had higher cesium adsorption capacity than potassium-activated geopolymers. The cesium adsorption capacity also had a significant effect on the diffusivity of cesium in the geopolymers. It was shown that, in addition to the pore structure and surface area, the mobility of water affects the diffusion performance of the geopolymer.

A basic investigation into whether a geopolymer can be utilized as a part of an artificial barrier during radioactive waste disposal was conducted in this study. Geopolymers are comprised primarily alumina and silica, and they exhibit negligible leaching owing to the absence of calcium. Studies on geopolymers are limited compared to those on other cementitious materials because the physical characteristics of geopolymers vary with the production conditions. In this work, metakaolin based geopolymers were prepared, and their diffusion performance was analyzed. The results indicate that the diffusivity of cesium in a geopolymer is affected by the type of alkali activator. Sodium-activated geopolymers had higher cesium adsorption capacity than potassium-activated geopolymers. The cesium adsorption capacity also had a significant effect on the diffusivity of cesium in the geopolymers. It was shown that, in addition to the pore structure and surface area, the mobility of water affects the diffusion performance of the geopolymer.