Total Porosity Research Articles

Effect of limestone powder on mechanical properties of concrete based on Griffith’s microcracking theory

In order to reveal the influence mechanism of limestone powder on the mechanical properties of concrete, the manufactured sand concrete with a water-cement ratio of 0.45 was taken as the research object. The effects of different limestone powder contents (0 %, 5 %, 10 %, 15 %, and 20 %) on the compressive strength of concrete were explored based on Griffith’s microcracking theory. The nano-indentation, ultra-depth-of-field microscopy, LF NMR, and other methods were used for testing. The test results show that with the increase of limestone powder content, the elastic modulus of the Interfacial Transition Zone (ITZ) and the paste increases first and then decreases, the thickness of the ITZ decreases first and then increases, and the total porosity of the paste decreases first and then increases. The microstructure of the ITZ and the paste is the densest, corresponding to the maximum compressive strength of the concrete as the limestone content is 10 %. It is found that the thickness of ITZ can be regarded as the initial crack of concrete. The compressive strength of concrete calculated by Griffith’s microcracking theory formula is the same as the measured value. The research results provide a theoretical reference for the influence mechanism of limestone powder on the mechanical properties of concrete.

New capabilities of application of gamma-ray logging in borehole geophysical investigations through steel string

Borehole geophysical investigations through steel string (both drill and casing) are becoming increasingly important. Gamma-ray logging (GR) is a mandatory and one of the main methods for investigating oil-and-gas reservoirs and near-surface rocks. It is characterized by high efficiency under the aforementioned measurement conditions. GR is used to identify bed boundaries, evaluate lithology, estimate shaliness, identify reservoirs, etc. Traditionally, the determination of granu- lometric shaliness is the main goal of quantitative interpretation for GR. Gamma-ray logging has been successfully used for many decades. However, increasing the accuracy of determining granulometric shaliness, expanding the informativeness of the method to determine mineral clayness, and developing procedures for using GR data in estimating other petrophysical parameters are topical issues. Based on logging materials, the paper examines the features of using the main interpretation parameter of GR (the relative difference parameter – index ΔІγ) in boreholes in the presence of a steel column and proposes new methodological approaches to the use of GR data when interpreting measurements in oil-and-gas and engineering-geological boreholes. Through numerous ex- amples, the invariance (constancy) of the interpretation parameter of gamma-ray logging has been proven under different borehole conditions, types of logging tools, etc. An approach has been proposed for obtaining optimal reference values when determining this parameter, which increases the accuracy of estimating shaliness parameters. A method has been developed for determining mineral clayness, which is an important quantity in itself and is necessary for determining other petrophysical parameters from loggingdata. A multiplicative method has been created for determining the total porosity of shaly rocks using a combination of neutron logging and gamma-ray logging, which makes it possible to avoid using the hydrogen index of clay minerals. The novelty of the developments is supported by patents, and their effectiveness is confirmed by the results of borehole tests and comparisons with independent determinations of parameters (laboratory core studies, traditional methods of interpretation). The proposed approaches are an important component of the investigation technologies for oil-and-gas reservoirs and near-surface rocks, developed at the Institute of Geophysics of the National Academy of Sciences of Ukraine.

Study on the radon exhalation rate of phyllite under thermal effects

As a result of human underground mining activities, phyllite has been extensively reused to make raw ceramic materials and concrete aggregates. Building materials are a significant source of indoor radon, and radon gas emitted from phyllite poses radiation risks to humans. High temperatures can alter the structural properties of rocks, impacting radon exhalation. Thus, this study examined phyllite's radon exhalation rate after heat treatment ranging from 25 °C to 1000 °C. The effects of changes in pore structure and mineral composition on phyllite's radon exhalation were analyzed in detail using nuclear magnetic resonance (NMR), polarizing optical microscopy (POM), three-dimensional microscopy (3DM), and scanning electron microscopy (SEM). Results indicate that the radon exhalation rate initially increases and then decreases with rising temperature. This rate correlates positively with both total porosity and micropore porosity. Processes such as free water evaporation, pyrite oxidation, quartz phase transformation, and chlorite dehydroxylation within phyllite contribute to pore development and the movement of free radon within pore spaces. The highest total porosity and radon exhalation rate occur at 700 °C, measuring 8.6 % and 6.14 Bq/m2·h, respectively—4.30 times and 1.18 times higher than at 25 °C. Additionally, mineral decomposition and melting reduce pore connectivity and effective porosity, hindering radon migration. These findings offer guidance for assessing radon radiation risks and indoor radon potential in phyllite-based building materials.

Reservoir characterization of GABO field in the niger delta basin using facies and petrophysical analyses

This study investigates the GABO field in the onshore Niger Delta Basin using well logs and core samples, with a focus on rock type distribution, reservoir continuity, and petrophysical properties to enhance hydrocarbon exploration accuracy. The research involved detailed analysis of core descriptions and images from GABO-20, along with petrophysical data from wells GABO-4, GABO-12, GABO-13, GABO-20, and GABO-51, aiming to identify rock types, evaluate reservoir quality, and determine the spatial distribution of petrophysical properties. The methodology included rigorous well log quality checks, data correlation between wells, petrophysical property evaluation, and lithofacies description. The analysis revealed thirty-five hydrocarbon-bearing zones, with GABO-20 showing average shale fraction values between 0.111 and 0.335, total porosity ranging from 0.242 to 0.329, and hydrocarbon saturation from 0.667 to 0.923, indicating substantial porosity and hydrocarbon saturation conducive to extraction. Well correlations demonstrated excellent sand-shale continuity within the reservoir intervals. Lithofacies analysis of the GABO-20 core identified eight distinct facies, including shale poles, liquid-rich shales, and sandstone poles, revealing a complex distribution of reservoir qualities with significant variations in potential. Cores 1 and 2 exhibited favourable conditions for hydrocarbon production, while Core 3 showed lower reservoir quality due to increased clay content. The depositional settings of the GABO field, particularly in the lower delta plain and delta front zones, showed well-developed reservoir bodies with moderate potential in the tidal zone and little potential in the shaly prodelta environment. This distribution highlights the complexity of the deltaic system and its implications for reservoir modeling and utilization. Reservoir zones associated with High-Quality Reservoir Facies exhibited strong petrophysical properties, suggesting excellent hydrocarbon production potential. The study underscores the importance of detailed reservoir characterization to optimize recovery strategies, offering valuable insights into the distribution and quality of reservoir sands, reducing subsurface uncertainty, and emphasizing the integration of facies and petrophysical approaches for a better understanding of reservoir characteristics in the GABO field.

Studying the effect of irrigation water quality (fresh water, treated water and wastewater) on some soil physical and chemical proper-ties and the protein content in the paulownia leaves.

Samples of soil irrigated with three types of water: Fresh water (F), wastewater (W), fresh water and wastewater (F1W1, alternative irrigation) were collected at two depths (0-15 cm and 15-30 cm) for two consecutive years. The bulk density, true density, soil total porosity, electrical conductivity, pH, percentage of organic matter, and concentration of phosphorus and potassium were measured. In addition, the length and circumference of paulownia tree trunk were measured, and the protein content of dry and green leaves was estimated. The results showed the differences in the apparent density values, as wastewater irrigation decreases the apparent density and increased the soil total porosity. The results also indicated that there were significant differences in the soil PH between the three treatments, as treated water irrigation decreased the pH and insignificantly increased the soil electrical conductivity. However, there were significant differences when irrigating with wastewater, as the electrical conductivity and organic matter content increased in the soil irrigated with wastewater compared to soil irrigated with fresh water at two depths (0-15cm and 15-30cm). Moreover, the concentrations of phosphorus and potassium increased in the soil irrigated with wastewater and treated water compared to fresh water. Furthermore, there were significant differences in the height of paulownia tree and its trunk circumference when irrigating with treated water compared to wastewater and fresh water. As for the protein content in paulownia leaves, it was observed that there were significant differences when irrigating with wastewater compared to treated water and fresh water. There was high protein content in the dry and green leaves when irrigating with the three types of water, but the highest protein content was for wastewater irrigation.

Simulation of the effects of nanopores at different scales on the wettability of coal

The structural difference of nanopores at different scales in coal is one of the important factors that affect the wettability of coal. Therefore, it is necessary to determine influences of nanopores at different scales in coal on the wettability thereof from the perspective of molecular structure. Taking coal samples collected from Pingdingshan (PDS), Hebi (HB), Xiegou (XG), and Changping (CP) as research objects, the nanopore combination types of the interface were divided by using Materials Studio (MS) molecular simulation software and Image Pro Plus (IPP) image processing software, fractal theory and wettability dynamic simulation method, and the fractal characteristics of different nanopore combination types and the wetting angle change characteristics of active water were analyzed. The effects of total porosity and fractal dimension of pore structure on wettability of nanopores were discussed. The results show that the nanopore combinations in coal can be divided into three types according to the diameter of water molecules: those separately dominated by diffusion pores, adsorption-diffusion pores, and adsorption pores. As the diameter of dominant pores decreases, the fractal dimension decreases and the structure becomes increasingly simple. The wetting angle of active water in diffusion pores changes as follows: it rapidly decreases at first, then tends to stabilizes, before increasing slightly; that in adsorption-diffusion pores changes in this way: it rapidly decreases after transient fluctuations, then basically stabilizes, and finally slightly increases; that in adsorption pores changes as follows: it fluctuates for a long period, then decreases with fluctuations, and finally basically stabilizes. As the total porosity of nanopores increases, the wetting angle decreases linearly. If the porosity is similar, the negative influence of fractal dimension on the wettability of coal interfaces by active water increases as the scale of dominant pores in pore combinations decreases.

Sustainable construction materials from alkali-activated waste fiberglass and waste refractory

In this work, waste fiberglass was up-cycled, alone, or mixed with used alumina-zirconia-silica (AZS) refractory from dismantled glass melting furnaces. Alkali activation was performed by suspending fiberglass and fiberglass/AZS powders in NaOH aqueous solution of various concentrations (8M, 6M, and 3M). The activation of waste fiberglass with 8M NaOH yields a gel with calcium and sodium-containing aluminosilicate hydrates. The addition of AZS refractory enabled the release of aluminates into the solution, which had beneficial effects on the mechanical properties. Low molarity activation yielded weaker materials which could be used as precursors for firing at moderate temperatures (800 °C and 1000 °C) to create cellular glass-ceramics, with a total porosity of up to 92 %. The firing of 8M activated samples resulted in glass ceramics with a 66–75 % porosity range and compressive strength of 10–23Mpa. The compressive strength-to-density ratio before and after firing was comparable to that of established commercial construction materials.

Manufacturing of heavy tungsten alloys from nano-sized metal oxides via simultaneous reduction-sintering powder treatments

Heavy tungsten alloys are of great importance in the engineering and mining industries as well as the military and medical applications because of their stability at high temperatures, high strength and dense structures. The present study develops a novel technology for the production of heavy tungsten alloys via thermal treatment of nano-sized metal oxides based on simultaneous reduction and sintering processes. Heavy tungsten alloy (95W-3Ni-2Fe) was produced from the reduction of mixed nano-sized metal oxides precursor in H2 at 1000 o C followed by sintering at 1350–1450 o C for 30–90 min. The reduced and sintered samples were characterized by XRD to follow up the crystallinity, total porosity measurement was used to find out the densification properties, the grain structure and morphology were examined by RLM and SEM attached with EDAX. Micro-hardness tester was also used to investigate the influence of sintering conditions on the grain densification. A fundamental study on the kinetics of reduction of mixed nano-sized metal oxides precursor was performed by isothermal and non-isothermal techniques. Both results from isothermal and non-isothermal tests were used to calculate the activation energy which was correlated with macro- and micro-structures to predict the corresponding reduction mechanism. However, the influence of sintering temperature and time on the crystallinity of the produced phases, grain structure, morphology, total porosity, pore-size distribution, bulk and apparent densities, and the hardness of sintered compacts was extensively investigated. The results revealed that the presence of NiO and/or Fe2O3 in the mixed metal oxides precursor was very important to ease the reducibility of WO3 as the metallic phases of Ni and/or Fe act as a catalyst for the reduction of WO3. The rate of reduction proceeds faster in the following order: NiO > Fe2O3 > mixed oxide > WO3. In non-isothermal experiments, it was found that the heating rate has a considerable effect on the reduction of precursor, i.e., the lower the heating rate, the higher the degree of reduction. It might be reported that the use of nano-sized metal oxides particles in the fabrication of heavy tungsten alloys greatly affects the main properties of the produced alloy. With the increase in sintering time, larger sizes of dense grains were developed, and the matrix became denser as a result of sintering and re-crystallization effects. The higher the sintering time, the higher the grain densification and the less pores formed in the matrix. On the other hand, with the increase in the sintering temperature, the grain boundaries were well defined in which the grains were composed of tungsten metal and surrounded by inter-metallics. The higher the temperature, the higher the XRD peak intensities of metallic tungsten and intermetallics as a result of sintering and re-crystallization.

Pore structure evolution of mortars with manufactured sand aggregate under the influence of aggregate size and water saturation environment

To investigate the effect of aggregate size on pore structure and pore evolution in water saturation of manufactured sand aggregate (MSA) mortars, five MSA mortars with small range of aggregate sizes were prepared and their pore characterization were monitored over 365 days. The findings showed that an increased surface volume ratio (SVR) leads to an increase in total and macroporous porosity, and three pores with different connectivity were quantified using double T2 cutoff method. Moreover, continued hydration by unhydrated cement caused an increase in micropores during the initial stage of service in a water-saturated environment for 365 days, and an increase in macropores at the later stage as a result of enhanced hydraulic solvation, furthermore, solvation was more significant in the mortar with larger SVR to the point where it eventually produced pores larger than 100 μm. This research would provide guidance for the durability evaluation of cement mortars.

Freeze-thaw resistance and service life prediction of fly ash incorporated ultra-high ductility magnesium phosphate cement-based composites

To develop ultra-high ductility magnesium phosphate cement-based composites (UHDMC) suitable for cold areas and fully utilize solid waste, the effects of fly ash (FA) substitution and freeze-thaw cycles on the mechanical properties and freeze-thaw resistance of UHDMC specimens were explored. The mechanism of freeze-thaw damage was revealed by mercury intrusion porosimetry (MIP) and scanning electron microscope (SEM). Freeze-thaw damage model for UHDMC was established to predict its service life. The results showed that, after 300 freeze-thaw cycles, the compressive strength retention rate of the UHDMC specimens with FA substitution from 10 % to 30 % was above 88.7 %, and the tensile strain maintained above 3.48 %, still presenting the characteristics of multi-cracking and strain hardening. Meanwhile, after 600 freeze-thaw cycles, the mass loss rate and the dynamic elastic modulus of UHMPC specimens with FA substitution from 10 % to 30 % were below 1.38 % and above 81.1 %, respectively. The mechanical properties were mainly related to the total porosity and macropores. The effect of the water solubility of prismatic struvite-K crystals and the secondary hydration production of filamentous struvite potassium crystals on the matrix presented well explanation for the excellent freeze-thaw resistance of UHDMC specimens with FA substitution from 10 % to 30 %. At last, a freeze-thaw damage model for UHDMC specimens with FA substitution below 30 % based on the Weibull probability distribution function was established, predicting that their service life was up to 232 years in the northeastern of China.

Long-term durability of iron-rich geopolymer concrete in sulphate, acidic and peat environments

This study assesses the behaviour of iron-rich type F fly ash geopolymer concretes (GC) exposed to simulated sulphate, acidic, and peat environments, typical of those encountered in tropical peatlands. GC and Portland cement (PC) concrete of comparable strengths were exposed to a range of simulated solutions for 18 months, including 5 % magnesium sulphate (MgSO4), 5 % sodium sulphate (Na2SO4), 1 % and 3 % sulfuric acid (H2SO4) and peat. The GC generally outperformed PC in all conditions. The GC showed a significant increase in strength in the first year, along with enhanced durability properties. Microstructural analysis indicated a decrease in total porosity and pore size. This was attributed to continuing geopolymerization leading to the foration of additional N-A-S-H gel, which filled the pores and solidified the concrete matrix. However, compressive strength decreased at 18 months due to crack propagation caused by drying shrinkage. In Na2SO4, GC attained an 8.9 % and 6.3 % increase in compressive strength at 12 and 18 months, respectively, again attributed to ongoing geopolymerization. GC exposed to MgSO4 exhibited a significant decrease in compressive strength of approximately 11 % at 12 months and 19.8 % at 18 months, attributed to the formation of lower-strength M-A-S-H from reaction between MgSO4 and N-A-S-H gel. After 12 months GC exposed to 1 % and 3 % H2SO4 demonstrated a decrease in compressive strength of approximately 1.2 % and 4.5 %, respectively, together with 2 % and 3 % mass loss. Chemical and microstructural data confirmed this strength reduction due to the vulnerability of N-A-S-H to when exposed to H2SO4. GC exposed to peat solution exhibited a 1.25 % increase in compressive strength at 12-month, but a decrease of 11.3 % at 18-month. Microstructural analysis observed a reduction in Na+ within GC matrix, and the presence of gypsum. The reduction in pore sizes and total porosity suggested generation of zeolite crystalline material was contributing to the pore filling.

Spatial Variability in Soil Water-Physical Properties in Southern Subtropical Forests of China

Quantification of soil water-physical properties and their spatial variation is important to better predict soil structure and functioning, as well as associated spatial patterns in the vegetation. The provision of site-specific soil data further facilitates the implementation of enhanced land use and management practices. Using geostatistical methods, this study quantified the spatial distribution of soil bulk density (SBD), soil moisture (SM), capillary water-holding capacity (CWHC), capillary porosity (CP), non-capillary porosity (NCP), and total porosity (TP) in southern subtropical forests located at the Tropical Forest Research Center in Pingxiang City, China. A topographic map (scale = 1:10,000) was used to create a grid of l km squares across the study area. At the intersections of the grid squares, the described soil water-physical properties were measured. By calculating the coefficient of variation for each soil water-physical property, all measured soil water-physical properties were found to show moderate spatial heterogeneity. Exponential, gaussian, spherical, and linear models were used to fit the semivariograms of the measured soil water-physical properties. Across all soil water-physical properties, the range A0 variable (i.e., the separation distance between the semivariance and the sill value) measured between 3419 m and 14,156 m. The nugget-to-sill ratio ranged from 9 to 41%, indicating variations in the level of spatial autocorrelation among the soil water-physical properties. Many of the soil water-physical properties were strongly correlated (as assessed using Pearson correlation coefficients). Spatial distribution maps of the soil water-physical properties created via ordinary kriging (OK) showed that most water-physical properties had clumped (aggregated) distributions. SBD showed the opposite spatial pattern to SM and CWHC. Meanwhile, CP and TP showed similar distributions.

Phase evolution and microstructure changes induced by accelerated carbonation in natural hydraulic lime paste with GGBFS addition

Carbonation is a primary factor driving the continuous improvement of the long-term performance of natural hydraulic lime (NHL). This research systematically examines the impact of accelerated carbonation (3 % CO2) on the carbonation depth, phase composition, microstructure, and compressive strength of hardened natural hydraulic lime (NHL) pastes mixed with different amounts of ground granulated blast furnace slag (GGBFS), termed as S-NHL. The findings show that the hydration reaction products of GGBFS and Ca(OH)2 (CH), such as C3AH10, C4AĈH11, and C-S-H, densify the microstructure of S-NHL, resulting in a decrease in carbonation depth with increasing GGBFS content. Accelerated carbonation (AC) promotes the rapid transformation of a significant quantity of CH into calcite in S-NHL, with the carbonation of CH occurring more readily than the carbonation of hydration reaction products. Throughout the AC process, NHL contains only calcite-type calcium carbonate. In contrast, after 28 days of AC, the carbonation of hydration reaction products such as C3AH10 and C-S-H in S-NHL produces a minor amount of aragonite and vaterite. AC continuously reduces the total pore volume and porosity of S-NHL, but the average pore diameter and most probable pore diameter initially decrease and then slightly increase. AC significantly reduces the large pores in S-NHL, ultimately resulting in pores predominantly composed of capillary pores (50–1000 nm). AC facilitates the development of compressive strength in S-NHL paste, with the increase in compressive strength being positively correlated with its CH content.

Effects of occasional tillage on soil physical and chemical properties and weed infestation in a 10-year no-till system

Few studies have investigated how one-time targeted tillage of long-term no-till fields impacts topsoil properties and weed dynamics. An on-farm trial was implemented in 2020 to test the effects of occasional tillage (OT) in Morocco with a long-term no-tillage (NT) system and rainfed field crops: durum wheat (Triticum durum), faba bean (Vicia faba minor), and chickpea (Cicer arietinum). Four treatments were established, namely, continuous NT with crop residues maintained (“NT + residue”); continuous NT with crop residues not maintained (“NT-residue”); shallow inversion tillage (“shallow OT”); and deep non-inversion tillage (“deep OT”). We assessed the effect of these treatments on soil physical and chemical properties in 0–10 and 10–20 cm soil depths after crop harvest of the 2020–2021 (year 1) and 2021–2022 (year 2) growing seasons corresponding to 1 and 2 years after OT, respectively. In addition, we evaluated the effect of the treatments on weed populations and the effect of the legume crop rotated with wheat on soil nitrogen (N) and weed density. In year 1, deep OT reduced the water content at field capacity and available water capacity at 0–10 cm compared to continuous NT; the cation-exchange capacity (CEC) under deep OT was lower than in NT-residue and NT + residue at 0–10 cm and 10–20 cm, respectively. Furthermore, deep OT increased ammonium-N (NH4-N) at 0–10 and 10–20 cm compared to NT + residue but reduced exchangeable potassium (K) at 10–20 cm depth compared to NT-residue. In year 2, shallow OT had lower total porosity at 10–20 cm than NT + residue, while shallow and deep OT recorded higher water-stable aggregates at 0–10 cm than NT + residue; at 10–20 cm, deep OT recorded lower CEC than NT + residue. However, deep OT had higher nitrate-N (NO3-N) and available sulfur (S) than NT-residue at 10–20 cm. Occasional tillage did not significantly affect 10 out of 19 of the soil properties evaluated, including soil organic matter (SOM), in all the years and did not help reduce the stratification of soil nutrients in NT. In year 1, 50 days after OT, deep OT reduced the weed density by 46% compared to NT + residue, while in year 2, 406 days after OT, shallow OT reduced weed density by 53% compared to NT-residue. Regarding the effect of the legume rotated with wheat, faba bean appeared to be the better preceding or following wheat crop as it resulted in higher residual soil mineral N and lower weed infestation than chickpea.

Livestock and poultry waste compost as an amendment in medium for pumpkin seedlings

This research evaluated cow dung compost (CDC), goose dung compost (GDC), and duck dung compost (DDC) as peat addition in growing media used for the production of pumpkin seedlings. Commercial substrate (peat: vermiculite: perlite=3:1:1, v/v) was used as the control (CK). The partial addition in peat of each waste compost in the mixtures were 10%, 20%, and 30% (v/v). The results showed that all compost in mixtures increased bulk density, total porosity, electrical conductivity, and mineral content, but negatively affected the pH and organic matter of the growing media compared to CK. CDC in mixture increased ventilation porosity and gas-water ratio and decreased water-holding porosity compared to CK, which was the opposite of the effect of GDC and DDC. The mixtures elaborated with GDC showed better growth, biomass, gas exchange parameters, and physiological indicators of seedling plants than other treatments in varying degrees, which depended on the additional amount of GDC. DDC inhibited plant growth and gas exchange parameters, especially in high addition rate; however, it had a slight promotion effect on chlorophyll content and quality because DDC was rich in minerals. GDC was better than CDC and DDC as a partial addition for peat in the cultivation of pumpkin seedlings.

Effects of Varied Tillage Practices on Soil Quality in the Experimental Field of Red-Soil Sloping Farmland in Southern China

Red-soil sloping farmland in southern China plays a crucial role in the local economy and food production. However, improper tillage practices have resulted in topsoil degradation and deteriorating soil quality. This study investigated changes in soil physico-chemical properties under four tillage methods—cross-slope ridge tillage (RT), down-slope ridge tillage (DT), plastic mulching (PM), and conventional tillage (CT)—on red-soil sloping farmland. The study applied the Soil Management Assessment Framework (SMAF) to assess the influence of these tillage practices on soil quality. Results indicated that PM can increase the total porosity of the soil, reduce soil bulk density, and simultaneously decrease soil surface-water evaporation, significantly improving the soil’s water-retention capacity. RT improved soil aggregate formation and stability, leading to increased macro-aggregate content, mean weight diameter, and soil water-stable aggregate stability rates. PM and RT effectively preserved soil nutrients like total nitrogen and organic matter, although PM lowered soil pH, potentially causing acidification. RT demonstrated the highest soil quality, with PM following. Crop growth positively impacted soil macro-aggregate content and stability, showing continuous improvement in soil structure and quality (p < 0.05). Priority should be given to RT in red-soil sloping farmland, followed by PM and CT, while avoiding DT if possible. This research furnishes valuable scientific substantiation for the selection of optimal tillage practices in the preservation of soil quality on red-soil slopes.

Use of a Glaciogene Marine Clay (Ilulissat, Greenland) in a Pilot Production of Red Bricks.

Uplifted occurrences of fine-grained glaciogene marine sediments are found throughout the northern hemisphere. These sediments could be used to produce local construction materials, to rely less on imported construction materials from southern regions. In this study, a representative occurrence from Ilulissat, West Greenland, was investigated as a potential resource for local brick production. The study comprised three parts: (1) raw material characterization based on grain size distribution, major element chemistry, including total carbon, sulfur, and chloride concentrations, mineralogy, morphology, and Atterberg limits; (2) the production of test bricks at a Danish brickwork; and (3) testing of the bricks based on total shrinkage, water absorption, hygroscopic adsorption, open porosity, bulk density, compression strength, and mineralogy. The bricks produced proved to have excellent compression strength, low open porosity, and low water absorption. The shrinkage could be reduced by adding 10% chamotte to the marine sediment. Based on the investigated properties, this indicates that this type of clay is highly suitable as a resource for bricks.

Optimization of soil hydrological properties in degraded grasslands by soil amendments

Soil amendments facilitate the restoration of degraded soil fertility and vegetation productivity. Soil hydrological functions are crucial for assessing soil degradation and restoration in grassland ecosystems. However, the manner in which soil amendments drive changes in the hydrological properties of grassland ecosystems at different soil depths remains unclear. In this study, we conducted a five-year soil amendment experiment in a semi-arid grassland of the Loess Plateau to evaluate the impact of aluminum sulfate (AS) and biochar (BC), both individually and in combination, on the hydrological properties of soil profiles. The results showed that AS significantly increased saturated water-holding capacity (SWHC) by 19.04 %, field capacity (FC) by 27.39 %, soil water storage (SWS) by 1.57 %, and saturated hydraulic conductivity (Ks) by 19.03 % in the upper soil layer (0–40 cm). BC application increased SWHC by 20.09 %, FC by 17.56 %, SWS by 12.94 %, and Ks by 16.66 % in the 0–40 cm soil layers. The combined effects of AS and BC optimized the soil hydrological properties by increasing SWHC, FC, SWS, and Ks by 25.74 %, 35.45 %, 18.47 %, and 25.80 %, respectively. These improvements were driven by significant changes in the soil organic matter, fine root biomass, total porosity, clay content, and soil bulk density. Notably, the soil amendments did not significantly affect the hydrological properties of the deep soil layer (40–80 cm). Our study demonstrated that the strategic use of AS and BC, particularly in combination, effectively enhanced soil fertility and hydrological functions, thereby increasing grassland ecosystem productivity. These findings offer critical insights for sustainable grassland management and highlight the potential of tailored soil amendments to restore and improve soil fertility and plant productivity in degraded grassland ecosystems.

Pore structure and adsorption capability of marcolithotypes in the Weizhou mining area, western margin of Ordos Basin

Differences in the pore and fracture systems of four marcolithotypes (bright，semi‐bright, semi‐dull and dull) in coal reservoirs affect the quality of coalbed methane (CBM) and constrain exploration and development of CBM. In this paper, vitrinite reflectance (RO), maceral composition, proximate analysis, scanning electron microscopy (SEM), mercury intrusion porosimetry (MIP), low‐field nuclear magnetic resonance (NMR) and high‐pressure isothermal adsorption experiments and the mathematical method of fractal dimension were carried out on high‐rank coal samples of different marcolithotypes from the Weizhou mining area in the western margin of Ordos Basin. The results show that from bright coal to dull coal, the RO and vitrinite content gradually decrease, while the mineral content and Aad gradually increase. SEM images show that the bright and semi‐bright coals develop open fractures, whereas semi‐dull and dull coals develop closed fractures. According to pore size distribution established by MIP and NMR, the proportion of seepage pores gradually increased from bright coal to dull coal, and MIP fractal dimension of seepage pores (DM2; 2.3352, 2.3532, 2.3755 and 2.4727, respectively) and NMR fractal dimension of seepage pores (DN2; 2.8767, 2.9142, 2.9297 and 2.9981, respectively) show that the structure of the seepage pore is progressively more complex from bright coal to dull coal. In addition, percentage of NMR adsorption pores progressively increases from bright coal to dull coal (64.96%, 76.64%, 82.04% and 89.67%, respectively), but total porosity of bright coal (6.74%) is much greater than that of dull coal (1.34%), which results in that bright coal also has the strongest CH4 adsorption capability (Langmuir volume is 22.898 cm3/g).

Impact of closed pores on gas transport and its implication for optimizing drainage borehole design

Mining disturbances can rupture the closed pores, releasing the gas and potentially triggering gas accidents. The pre-drainage of gas via boreholes is the primary measure for preventing coal and gas outbursts. Nevertheless, the influence of closed pores on gas migration remains unclear, leading to suboptimal borehole spacing and radius. Therefore, a gas–solid coupled model incorporating closed pores was developed to investigate the influence of closed pores on gas migration during gas drainage (GD). Subsequently, response surface methodology was employed to investigate the input parameters and their interactions on residual gas content (RGC) and pre-drainage time (PDT). Finally, an optimization methodology for borehole spacing/radius was presented. The results show that both RGC and PDT exhibit a positive correlation with the ratio of closed porosity to total porosity (λ) and the ratio of closed pore diffusion coefficient to that of the open pore (Do/Dc). Initially, the total gas production is primarily extracted from fractures and open pores, followed by closed pores in the later stages. Single-factor analysis demonstrates that λ, permeability, and Do/Dc have a more significant impact on RGC and PDT compared to borehole spacing and borehole radius. Borehole spacing interacts more strongly with λ, permeability and Do/Dc than borehole radius. An optimization method for borehole spacing and borehole radius, constrained by PDT, RGC, and the number of boreholes, is proposed using response surface optimization maps. This method provides guidance for borehole construction to optimize GD efficiency and minimize RGC.