Porosity Of Samples Research Articles

Enhanced coalbed methane recovery by microwave-induced thermal fracture

Abstract The investigation on microwave-induced permeabilization and response of coal under microwave heating is of great significance for the industrial application of microwave heating technology instead of traditional heating in coalbed methane mining. Santanghu coal is used as a sample to measure the permeability and porosity of coal samples before and after microwave heating. The fracture changes of coal samples before and after heating are compared to observe the penetration effect of microwaves on coal samples. Based on the technology of directional drilling and continuous tubing technology in petroleum engineering, a technology of increasing the production of coalbed methane by microwave heating in a wide range of coal seams is proposed. The feasibility of this enhanced production method is validated through COMSOL Multiphysics simulations, which model the temperature field distribution within coal seams under various microwave parameters. This approach highlights the potential of microwave technology in coalbed methane recovery. The results show that: (1) the thermal field of coal samples under microwave heating is inhomogeneous. The average length and area of the cracks of the coal samples increased under microwave radiation, and the cracking of the coal samples confirmed the cracking effect of microwaves on the coal samples. (2) With prolonged microwave heating, coal samples exhibit an initial decrease followed by an increase in porosity and permeability, a trend attributed to the expansion of solid particles that occupy and reduce pore spaces. (3) The in-situ microwave heating technique for coalbed methane extraction overcomes the challenges of long-distance microwave transmission loss and methane backflow in transmission pipelines, utilizing continuous pipelines for extensive microwave heating of coal seams. (4) The microwave power and intermittent heating duration have a significant effect on the temperature field distribution of the coal seam, and when the heating duration is 60 days, 1600 W is used to have an effective temperature field distribution while avoiding the waste of heat. When the power is constant at 1600 W, the effective temperature range is wider when the intermittent heating duration is 60 days.

Study of Damage Mechanism and Evolution Model of Concrete under Freeze–Thaw Cycles

Researching the mechanical characteristics of concrete subjected to the freeze–thaw cycle is crucial for building engineering in cold climates. As a result, uniaxial compression tests were performed on concrete samples exposed to various freeze–thaw (F–T) cycles, and the measurements of the pore size distribution, porosity, and P-wave velocity of the saturated concrete samples were obtained, both before and after being exposed to the F–T cycles. Concrete’s F–T damage mechanism and damage evolution model were thoroughly examined. Using rock structure and moisture analysis test equipment to observe the T2 spectrum, the results showed that the F–T cycles can cause the internal structure of the samples to deteriorate. Porosity and F–T cycles have a positive correlation, although P-wave velocity has a negative correlation with the F–T cycles. As the F–T cycles increased, the specimens’ peak strength and elastic modulus steadily declined, while the peak strain clearly exhibited an increasing trend. A microscopic F–T damage model that takes into account the pore size distribution was developed, based on the relative changes in the pore structure distribution (PSD), before and after the F–T cycles. The concrete sample damage evolution law under various F–T cycles was examined using the following metrics: total energy, pore size distribution, static and dynamic elastic moduli, porosity, and P-wave velocity. Uniaxial compressive strength (UCS) and peak strain tests were used to evaluate the accuracy of the pore size distribution damage model, as well as that of five other widely used damage models.

Investigating the effect of polymer additives on the rheology of SiC/clay paste for use in Direct Ink Writing method

AbstractIn this study, we investigated the impact of polyethylene glycol, sodium carboxymethyl cellulose, and polyvinyl alcohol on the rheological behavior, printability, and mechanical/physical properties of 3D‐printed scaffolds for high‐temperature applications using SiC/clay ceramic paste. Employing the Direct Ink Writing method, varying concentrations of each polymer (PEG: 2.5%–10% weight, CMC: .6%–1.8% weight, PVA: .25%–1% weight) were incorporated into the composition. The resulting SiC/clay paste, with adjusted additive content, was used to 3D‐print scaffold structures through Direct Ink Writing. Sintering of clay‐bonded SiC samples were carried out at 1300°C for 1 h in an ambient atmosphere. The research revealed that altering the additive amounts significantly influenced the rheological behavior, mechanical properties, and physical characteristics of the printed specimens. Notably, the ideal properties with additive concentrations (10% wt PEG, 1% wt PVA, and .6% CMC) were identified, providing the best outcomes in terms of printability and firing results. High density samples with 2.09, 1.93, and 1.79 g/cm3, high compression strength of 20.82, 14.5 and 12.53 MPa with 32.26%, 42.5%, and 52.63% open porosity for samples containing PVA, CMC, and PEG modifiers were obtained, respectively. Additionally, the study led to the development of a high solid loading printable paste with an 80% weight.

Enhancing microstructural integrity and mechanical performance of thick wire-arc directed energy deposited eutectic aluminum-silicon solid structure through continuous multi-pass friction stir processing

In wire-arc directed energy deposition (waDED), fabricating larger 3D components with single-layer tracks is challenging due to limitations in track thickness, requiring the development of bead overlapping strategies. However, fusion-based 3D-printed aluminum structures often show porosity and coarse-grained microstructures, limiting their industrial applications. To address these limitations, this study employs continuous multi-pass friction stir processing (FSP) on a waDED-produced aluminum block (140 mm × 150 mm × 28 mm). The severe plastic deformation induced by FSP triggers dynamic recrystallization (DRX), promoting the formation of equiaxed grains with an average grain size 8.75 times smaller than the as-fabricated waDED sample (67.03 μm vs 7.66 μm). Transmission Electron Microscopy (TEM) revealed decreased dislocation loops post-FSP, indicating DRX and dislocation annihilation. X-ray micro-computed tomography (X-CT) examination showed complete elimination of porosity in the waDED sample, owing to the intense mechanical stirring induced during FSP. Scanning electron microscopy (SEM) images of the waDED samples showed fibrous eutectic networks disrupted by FSP, leading to a uniform distribution of broken Si particles within the α-Al matrix. Hardness decreased by approximately 38 % (86 HV0.1 vs 53 HV0.1), while the average ultimate tensile strength decreased by about 4 % in the FSP-treated samples (159.19 MPa vs 153.02 MPa). Additionally, the formation of alpha fiber and weak cube texture components during FSP enhances ductility, as evidenced by a sixfold improvement in elongation (1.93 % vs 11.59 %). This textural transformation contributes to the characteristic deeper and more uniform dimples in the FSP-treated samples, indicative of ductile fracture, compared to the premature failure patterns in as-deposited samples.

A preliminary exploration of waste red-bed as a supplementary cementitious material

A red-bed is a type of continental clastic sedimentary stratum, with red serving as the main color. This type of stratum accounts for 20% of the land area in China. In the process of infrastructure construction, a large amount of waste red-bed is generated. Waste red-bed exacerbates the shortage of land resources and is a misuse of resources. In this study, a preliminary exploration of the recycling of waste red-bed in central Yunnan Province was conducted. The studied red-bed contains approximately 30% clay minerals and was used as supplementary cementitious material (SCM) instead of clay after calcination. Through laboratory characterization, environmental impact assessment, and cost analyses, the feasibility of using the red-bed as a type of SCM was demonstrated. The results show that the dehydroxylation reaction of clay minerals in the red-bed was almost complete after calcination at 800 °C. A pozzolanic reaction occurred, and additional heat was released after the addition of the calcined red-bed (CRB) to the cement mortar. When the cement replacement ratio increased from 10% to 30%, the strength activity index decreased from 98.2% to 82.2%, which met the relevant requirements. However, compared with the control samples, the samples with replacement ratios of 40% and 50% had lower mortar fluidities by 57.3% and 75.5% and higher porosities by 33.3% and 20.0%, respectively. Owing to the dilution effect of the cement and the decrease in the mortar fluidity, the internal structure of the sample porosity increased, and the strength decreased dramatically. In addition, the environmental impacts, energy consumption, and cost of using waste red-bed as a SCM were quantitatively analyzed via a carbon emission index and a cost index.

Quantification of the effect of fracturing on heterogeneity and reservoir quality of deep-water carbonate reservoirs

The Shiranish Formation represents one of the most important fractured reservoirs in northern Iraq. In this work, the petrophysical properties of the formation have been fully characterised using microscopy, core analysis, and well log analysis using conventional methods as well as new quantitative diagenetic approaches. During this work we have developed methods to quantify a petrophysical heterogeneity index (χ), reservoir quality indicator (RQI), and fracture effect index (FEI) for each of the stratigraphic units of the formation. The FEI was calculated by dividing the difference between the mean permeability of the wireline log data and the mean permeability of the unfractured core plug samples by the difference between the mean porosity of the wireline log data and the mean porosity of the unfractured core plug samples. This study shows that the Shiranish Formation has a fracturing pore system in all the characterised units, but it is particularly well developed in U.4, which shows the best reservoir quality (A and B). The new methods developed in this study can be applied to any carbonate formation to provide a trustworthy way to obtain a reservoir quality indicator linked to the petrophysical heterogeneity of the studied formation.

Stability and performance of BTC-based MOFs for environmental applications

Two series of open metal site MOFs, HKUST-1 and MIL-100(Fe), have been successfully prepared using different methods of synthesis. Their features depend on the synthetic route as well as their role play in different environmental applications. The stability and performance of these BTC-based MOFs have been tested bearing in mind Congo Red (CR) removal, humidity adsorption and iodine capture and release. HKUST-1 and MIL-100(Fe) samples could offer a remarkable role in the adsorption of CR from aqueous solutions. However, the lability of HKUST-1 in water is revealed as a drawback for its reutilization in both static and agitation conditions. The former contrasts to the stability under ambient moisture. MIL-100(Fe) shows promising properties in both CR adsorption in aqueous solutions and humidity adsorption. Nonetheless, the performance largely depends on the synthesis conditions. Although CR removal is based on surface interaction, there is a relation between the adsorpted quantity and the specific surface area. The size and nature of iodine allows the diffusion in the pores of both HKUST-1 and MIL-100(Fe) MOFs. This way, the uptake of iodine is driving by the porosity and surface area of samples rather than their inherent nature. As a rule, the results of this work indicate that not only is it important the specific nature of the MOF chosen for a given application but also the way in which it has been synthesized and the conditions in which they are used. MIL-100(Fe)-R is revealed as the best suitable candidate to be used as a sorbent for CR in aqueous solutions, moisture and I2 gas.

Microstructure and mechanical properties of 316L stainless steel manufactured by multi-laser selective laser melting (SLM)

The microstructure and mechanical properties of 316L stainless steel samples manufactured by dual-laser selective laser melting technology, were investigated in compare with that of the single-laser scanning samples. It was found that the porosity of the dual-laser overlap samples was lower than that of single laser forming samples due to the different laser energy density absorbed by the powders. Furthermore, it was found that the crystal structure and crystal orientation of both zones were similar. From the TEM observation, it was noted that the number density of nano-oxides in the overlap zone was higher than that in the single laser forming zone. This reason was suggested as the difference of the oxygen content inside the melt pool during the forming process. The strength and microhardness of the single-laser samples was lower than that of the dual-laser overlap samples, but the elongation was higher. By analyzing the strengthening mechanism, it was revealed that Orowan strengthening was the main reason for the difference. These results could guide the large-size component manufactured using the muti-laser selective laser melting technology.

Post-failure deformation mode switching in volcanic rock.

Beyond a threshold applied compressive stress, porous rocks typically undergo either dilatant or compactant inelastic deformation and the response of their physical properties to deformation mode is key to mass transport, heat transport and pressure evolution in crustal systems. Transitions in failure modes-involving switches between dilatancy and compaction-have also been observed, but to date have received little attention. Here, we perform a series of targeted mechanical deformation experiments on porous andesites, designed to elucidate complex post-failure deformation behaviour. By investigating a sample suite and effective pressure range that straddles the transition between positive and negative volumetric responses to compression, we show two post-failure critical stress states: a transition from compaction to dilation ( ), and a transition from dilation to compaction, which we term . We demonstrate that multiple switches in deformation mode can be driven by stress application under conditions relevant to the shallow crust. While the effect on fluid flow properties of compaction-to-dilation switching may be masked by a net reduction in sample porosity, samples that underwent dilatant-to-compactant failure mode switching exhibited an increase in permeability of approximately two orders of magnitude, despite only slight net volumetric change. Such a substantial permeability enhancement underscores the importance of post-failure deformation in influencing solute and heat transfer in the crust, and the generation of supra-hydrostatic fluid pressures in volcanic environments.

Diagenesis including cataclastic band development in the Permian Penrith Sandstone, Vale of Eden Basin, England

Diagenesis in the Penrith Sandstone is characterized by early hematite and mixed illite/smectite cementation, followed by burial compaction, feldspar and two episodes of quartz cementation. The primary quartz overgrowths are characterized by heterogenous luminescence; however, the secondary quartz overgrowths are characterized by thinner and darker luminescence. Cataclasis post-dates primary quartz cementation, and significantly reduces grain and pore aperture size. The apex of mercury volume for a deformed sample was reduced up to three times in comparison with the undeformed rock. Dissolution occurred during cataclasis as authigenic hematite was removed in deformation zones, improving pore aperture size and consequently enhancing sandstone porosity and permeability. Recent fracturing created fractured-pores and improved porosity and permeability in tight cataclastic samples. Evidence for syn-cataclastic dissolution is observed in the samples studied. This is indicated by the dissolution of authigenic feldspars and the enhancement of poroperm parameters adjacent to cataclastic zones and the absence of hematite cement within them. Based on those the sequence of diagenetic evolution in the Penrith Sandstone can be reconstructed. Host samples were characterized by good to very good poroperm values, varying between 20 and 24% porosity and from 809÷1445 mD permeability. Cataclastic core plugs have 13÷21% porosity and 0.12÷39 mD permeability. The porosity reduction by cataclasis was estimated to be as much as 4.5% on average. Fracturing and dissolution improved poroperm parameters in studied samples. Recently fractured core plugs have about 292 mD permeability on average. Dissolution-cataclastic samples have 32% porosity and 18 mD permeability, whereas dissolution-host samples have 31% porosity and maximum permeability as much as 2469 mD on average. Cataclasis occurred in combination with in situ significant reservoir dissolution and fracturing may improve a sandstone reservoir in excellent quality.

Study on microscopic pores and permeability changes of coal frozen by liquid nitrogen based on CT scanning

ABSTRACT Liquid nitrogen freezing has a certain promoting effect on improving the permeability of coal samples. In order to study the quantitative changes in the pore structure and permeability of coal samples after liquid nitrogen freezing, this paper carried out a three-dimensional reconstruction of the pore space structure of coal samples based on CT scanning experiments, and based on this, the porosity, connected pore volume, the equivalent pore radius, pore coordination number and permeability were studied based on the reconstruction model. The results show that the porosity of the coal samples in group B is 42.02% higher than that in group A after freezing with liquid nitrogen, the average value of the total connected pore volume, pore equivalent radius and coordination number of coal samples in group B are greater than those in group A, and they have increased by 16.5%, 2.95% and 14.8% respectively; the permeability in group B is 26.86% higher than that of group A, indicating that the pore connectivity and permeability of the coal samples in the liquid nitrogen freezing group have been significantly improved.

Prediction of material toughness using ensemble learning and data augmentation

ABSTRACT The present work investigates the impact resistance of metallic parts produced using Laser Powder Bed Fusion and the possibility of its prediction using machine learning algorithms. The challenge lies in finding optimal process parameters before printing based on the existing data. Economic constraints often result in the availability of only a limited amount of data for predictive purposes. In this work, around one hundred data points from Charpy impact tests on AlSi10Mg0.5 were used to analyse the correlation between the impact resistance and process parameters, including information about sample porosity. The present research implements a data augmentation technique that artificially increases the volume of training data by applying domain-specific transformations to the original limited dataset. Using this technique, the dataset had been extended to over one thousand data points. To identify the most suitable approach for the specific issue at hand, several algorithms were explored: Regression Neural Network, K-Nearest Neighbours, Decision Tree, Random Forest, AdaBoost, Gradient Boosting, XGBoost, as well as ensemble combinations of Random Forest with AdaBoost, Gradient Boosting, and XGBoost algorithms. The results suggest that the Random Forest and the boosting algorithms generalise best given the sparse testing data. The best-performing models yield a prediction fitness reaching 86 percent. Therefore, an effective model for predicting the impact resistance had been developed and can be used to optimise the quality of additively manufactured parts.

Improving the technology of gluten-free bread from composite flour mixtures

The article presents the research on the development of bread technology from gluten-free composite mixtures: No. 1 from a mixture of rice and flax flour (70: 30), No. 2 from flax and corn flour (50: 50) and No. 3 from pumpkin and corn flour (50: 50). A sociological survey conducted has shown that potential consumers are interested in expanding the line of gluten-free food products in the Saratov region. The following technological parameters for the production of gluten-free bread were determined: proofing time – 100 minutes, chamber temperature 35°С and relative air humidity 40%. The bread was baked for 9 minutes at 200°С and 35 minutes at 180°С with a relative humidity in the working chamber of 40%. Physicochemical studies showed that the moisture content in three samples of gluten-free bread was 1.17 times higher than the norm (46.0) compared to the control. In turn, the acidity of the sample crumb was in the range of 5.5–7.2 degrees, respectively, which exceeded the norm. The crumb porosity of the developed samples was 65.22–68.03%, respectively, while less than 68% was explained by the use of gluten-free mixtures, which were unable to form an elastic elastic frame in the products. The developed gluten-free bread contained QMAFAnM, coliform bacteria, Staphylococcus aureus, bacteria of the genus Proteus, mold fungi and pathogenic microorganisms, including Salmonella, and complies with TR CU 021/2011.As a result of the research, sample No. 3 was selected from pumpkin and corn flour (50: 50), which had high performance in terms of overall physicochemical and organoleptic characteristics. The selected sample had dimensional stability, pleasant taste, aroma and baked crumb.

3D imaging and flow analysis of sandstone pore structure

Abstract Micro CT technology can provide three-dimensional high-precision digital images with micrometer (or smaller) resolution, offering robust technical support for the study of the internal structure of rocks. Based on the data obtained from the CT scanning of Leopard sandstone, a series of image processes were carried out using the Avizo software to extract pore distribution. The watershed algorithm was employed to independently segment each pore, and the largest sphere algorithm was used to establish a sphere-tube model. Based on the constructed pore network model, quantitative analyses of the porosity, fractal dimensions, permeability, and other parameters of the sandstone sample were conducted. Moreover, the connectivity of the pores was analyzed using an automatic skeleton model. Results show: ① CT scanning digital core technology can not only visualize the three-dimensional connectivity and isolated pores of sandstone but also quantitatively characterize the pore structure parameters; ② The analyzed Leopard sandstone has a connected porosity of 13.76%, an isolated porosity of 0.53%, and the pore radius is mainly concentrated in the 0-70μm small pore range, occupying 76.1% of the total pore volume; ③ The lower the sample porosity, the higher the fractal dimension, indicating a more complex pore structure.

Analysis on Fractal-Permeability Characteristics of Construction Waste Filling Body in Gob

The mine application of construction waste permeability filling body is an effective way to avoid the collapse of overlying rock strata caused by coal mining, to solve the questions of surface resource occupation and pollute the ecological environment, and to promote regional hydrogeological balance. Based on the infiltration test on twelve groups of non-cemented and cemented samples with different particle size ratio, the variation characteristics of permeability coefficient of non-cemented and cemented construction waste samples with different fine content and cement were analyzed. The porosity of non-cemented samples and cemented ones was obtained, the relationships of fine content and porosity, permeability coefficient were analyzed, the relationships of fractal dimension and porosity, permeability coefficient on non-cemented samples and cemented ones were discussed. The results showed that fine content was negatively correlated to the permeability coefficient of non-cemented samples and non-cemented ones. The porosity decreased with fine content increasing, the porosity of non-cemented samples ranged from 5.007~7.029%, and the one of cemented samples was 3.230~6.508%. Fractal dimension of non-cemented samples and cemented ones were fine aggregate> medium coarse aggregate> coarse aggregate, and the fractal dimension of non-cemented samples was less than the cemented ones, the porosity and the mass fractal dimension could well represent the relationship between the permeability and fine content.

Thermodynamic Coupling Forming Performance of Short Fiber-Reinforced PEEK by Additive Manufacturing.

In this work, the PEEK/short carbon fiber (CF) composites were prepared, a new thermodynamic coupling (preheating and impact compaction) process of the FDM method is proposed, and the warp deformation mechanism was obtained by finite element simulation analysis. Results show that a new method could improve the forming quality of an FDM sample. The porosity of FDM samples of the PEEK/CF composite gradually decreased from 10.15% to 6.83% with the increase in impact temperature and frequency. However, the interlayer bonding performance was reduced from 16.9 MPa to 8.50 MPa, which was attributed to the influence of the printing layer height change from the printhead to the forming layer. To explain the above phenomenon, a thermodynamic coupling model was established and a relevant mechanism was analyzed to better understand the interlayer mechanical and porosity properties of PEEK/CF composites. The study reported here provides a reference for improving the forming quality of fabricated PEEK/CF composites by FDM.

Investigating correlations between microstructural characteristics and mechanical properties of coral sand mortar with different silica fume contents

The use of coral sand in concrete and mortar for ocean engineering has led to significant reductions in construction costs and improved construction efficiency. However, this approach poses challenges such as low strength, high brittleness, and high porosity. To address these challenges, this study incorporated silica fume to enhance the mechanical properties of the mortar and investigated the effects of different silica fume contents on the hydration process, pore structure, and strength of coral sand mortar. Additionally, this study introduced a novel iterative approach combining low-field nuclear magnetic resonance and scanning electron microscopy image analysis to determine transverse relaxivity (ρ2). During the early hydration process, the intensity spectrum of coral mortar exhibited three peaks at 298, 1841, and 299 au, corresponding to transverse relaxation times (T2) of 0.64, 6.83, and 83.10 ms, respectively. Over a 6 h hydration period, the spectrum of the specimen prepared with white cement exhibited an additional peak that gradually merged with the main peak. As the curing period extended from 7 to 28 days, the porosity of coral sand mortar decreased by 3.77–4.55 %, while the strength increased by 7.43–14.35 MPa across silica fume contents ranging from 6 % to 24 %. With increasing silica fume content, the calcium–silicon ratio of the samples gradually decreased, promoting the formation of more floccus C–S–H gels. Consequently, the sample porosity first decreased slightly. After 28 days of curing, the coral sand mortar containing 12 % silica fume exhibited the highest strength owing to the increased amount of floccus C–S–H gels. These gels gradually filled the pores between the fibrous C–S–H gels, forming a compact spatial reticular structure. This structure mitigated the adverse impact of high porosity on mortar strength.

Structural effects on thermal conductivity of micro-thick Li4Ti5O12-based anode

This study investigates the structural effects on the cross-plane thermal conductivity of Li4Ti5O12-based anode active material. Three structures are investigated: a basic structure consisting of LiBr/LiCl/Li4Ti5O12, polyvinylidene difluoride, and Super P (sample #1); a structure without Li4Ti5O12 (sample #2); and a structure without LiBr/LiCl (sample #3). Despite its high porosity level (77%), sample #1 exhibits higher thermal conductivity than sample #3 (64% porosity) in both air and vacuum conditions, potentially due to the extra structural bonding provided by LiBr/LiCl. The observed difference in cross-plane thermal conductivity between air and vacuum conditions provides insights into the configuration of the anode's active material in the heat transfer direction. The lower limit corresponds to the parallel thermal circuit configuration of active material and air, which is the product of the sample's porosity and thermal conductivity of air. Our analysis suggests that in sample #2, the anode's active material and air inside the pores demonstrate a more serial configuration, while in sample #3, they exhibit a more parallel configuration in the heat transfer direction. However, the thermal conductivity difference observed for sample #1 falls below the theoretical lower bound indicating significant thermal radiation within the pores. Furthermore, the in-plane thermal conductivity is predominantly controlled by the copper foil. Sample #2 exhibits the lowest in-plane thermal conductivity. This is attributed to the severe oxidization of the copper foil by LiBr/LiCl, which is confirmed by structure characterization.

Characterization of Porosity Changes during Reaction of Coke and Coke Analogues with CO2 Using Micro‐Computer Tomography

Understanding the porosity of coke and how it changes during reaction is key for understanding coke reactivity and minimizing coke consumption in the blast furnace. The change in porosity of coke and coke analogue samples after reaction with CO2 is assessed using high‐resolution micro‐computer tomography (micro‐CT) scans. High‐resolution micro‐CT scans (2.35 μm voxel−1) are carried out before and after reaction with CO2 at 1100 °C. 3D micro‐CT measurements are validated against standard 2D measurements, and used to quantitatively assess the porosity evolution in the samples. The porosity and pore connectivity of the coke and analogue samples increase in reaction with CO2. Most of the increase in porosity occurs in the pores <60 μm. Inert maceral‐derived component (IMDC) regions in coke A are more reactive than reactive maceral‐derived component (RMDC) regions. This is possibly related to the higher proportion of fine pores in unreacted IMDC compared to RMDC. Characterization of larger coke and coke analogue samples using micro‐CT at lower resolution (9.65–16.72 μm voxel−1) allows the rate‐controlling mechanism to be determined as likely to be mixed control, with both chemical reaction and pore diffusion‐controlling reaction rate. This finding demonstrates that high‐ and lower‐resolution micro‐CT datasets should be considered complementary.

Deformation and mechanical properties of foamed concrete under various components and pore structure

Based on macroscopic experimentation and microcosmic testing techniques, the effects of water-binder ratio, water reducer, fly ash and rubber particle content on the settlement, compressive and folding strength, dried shrinkage rate and microstructure of foamed concrete were investigated. The sample's porosity and average pore diameter were measured and combined with the sample's settlement, mechanical properties and dry shrinkage to analyze the difference of the microstructure and its influence on the macro properties in order to provide a basis for the control of the settlement and dry shrinkage of foamed concrete. The results demonstrated that the optimal water-to-binder ratio enhanced the ability of the froth and cementitious material to disperse, as well as the cementitious material's capacity to uniformly envelop the bubbles. It is evident that the water-reducing agent can enhance the pore structure of foamed concrete because the pore wall structure is more complete. By re-hydration of fly ash with the calcium hydroxide produced by cement hydration, internal cavities can be filled to a greater extent. Rubber powder can reduce the strength and increase the settlement deformation of foamed concrete, but it can effectively limit the concrete's dry shrinkage deformation. The settlement of the earlier slurry will alter the pore structure of the later material, and the pressure will fracture and fuse the internal pores, resulting in smaller porosity and larger mean aperture.