Search Results (321)

Ultra-high-performance concrete (UHPC) matrix faces critical challenges of high carbon footprint and significant autogenous shrinkage. Supersulfated cement (SSC), a potentially lower-carbon binder comprising ground granulated blast-furnace slag and gypsum, offers a promising alternative. This study systematically investigated the effect of gypsum type—phosphogypsum (PG), dihydrate gypsum (DH), and anhydrite (AH)—on the early hydration and shrinkage behavior of UHPC matrix incorporating 30% SSC as Portland cement replacement. A multi-technique approach, including mechanical testing, isothermal calorimetry, XRD, TG-DSC, SEM, LF-NMR, and autogenous shrinkage measurements, was employed. Results demonstrate that gypsum type critically governs sulfate dissolution kinetics, thereby dictating phase assemblage and microstructural evolution. DH provides relatively rapid sulfate dissolution, promoting earlier AFt and gel formation, which is associated with the highest early strengths and a marked reduction in autogenous shrinkage. AH shows a slower but sustained sulfate supply, resulting in comparable 28-day strength with moderate shrinkage reduction. PG yielded the lowest autogenous shrinkage (374 μm/m at 7 d), but it also suffered from severe early-age retardation due to soluble phosphate impurities, as evidenced by the delayed hydration peak and lowest 3 d strength. This behavior is mainly related to strong early-age retardation, delayed hydration, delayed setting, and a prolonged low-stiffness state. These findings suggest that appropriate gypsum selection in SSC enables tailored early-age performance and improved volume stability in the UHPC matrix, offering guidance for utilizing industrial by-products such as phosphogypsum in sustainable high-performance concrete design. Full article

Located in eastern China, the Nanshu area is abundant in groundwater resources with favorable water quality, acting as a critical water supply source for the region. In recent years, the regional groundwater environment has been significantly disturbed by continuous anthropogenic activities, which has aroused widespread concern. In this study, correlation analysis, principal component analysis, hydrochemical methods, the Entropy Weight Water Quality Index, and the Human Health Risk Assessment model were comprehensively applied to systematically investigate groundwater in the Nanshu area. The research objectives are to determine the health risk levels of regional groundwater and provide a scientific basis for the protection and rational utilization of groundwater resources. The results indicate that groundwater in the study area is weakly alkaline freshwater, dominated by the HCO₃-Ca hydrochemical type. With favorable groundwater circulation conditions and weak evaporative concentration effects, it generally exhibits the typical natural hydrogeochemical characteristics of shallow groundwater in the piedmont regions of northern China. The chemical composition of groundwater is mainly controlled by water–rock interactions. The dissolution of silicate minerals, gypsum, halite and sepiolite, together with significant reverse cation exchange, collectively shape the hydrochemical composition, and natural hydrogeological conditions form the basic pattern of regional water quality. The overall potability of groundwater in the study area is moderate. Approximately 30% of the groundwater is unsuitable for direct drinking due to anthropogenic pollution, and agricultural activities and domestic sewage discharge have become key factors causing local water quality degradation. Non-carcinogenic health risks posed by groundwater nitrate vary significantly among different populations. The risk level for infants and young children is much higher than that for adults, posing a substantial health threat to sensitive populations. According to the findings, it is recommended to focus on controlling the groundwater risk sources in the central area, strengthen the dynamic monitoring of water quality in water source zones, and strictly regulate regional development activities, so as to achieve the sustainable utilization of groundwater resources. Full article

The common root characteristic of CO₂ and air pollutants in the power industry, both derived from fossil fuel combustion, provides a natural basis for their synergistic emission reduction. However, existing studies suffer from the lack of a multi-pollutant synergistic evaluation system and an imperfect emission reduction technology database, which hinder their ability to support low-cost and high-efficiency emission reduction practices in the industry. Targeting the minimization of synergistic emission reduction costs and the maximization of emission reduction effects, this study integrated the process and economic parameters of 11 power generation technologies and 55 pollutant control technologies to establish a full-chain energy conservation and emission reduction technology database for the power industry, through literature research, industry surveys, and data mining. Based on the definition of pollution equivalent in the Environmental Protection Tax Law, we innovatively developed an air pollutant equivalent normalization evaluation method and constructed a two-dimensional coordinate system comprehensive evaluation system for CO₂ and air pollutants, enabling quantitative analysis and visual evaluation of the synergistic emission reduction effects of various technologies. The results show that new energy power generation technologies such as nuclear power and wind power, as well as O₂/CO₂ cycle combustion, ammonia-based desulfurization, and SNCR-SCR combined reduction technologies, exhibit excellent synergistic emission reduction performance for CO₂ and multiple pollutants. In contrast, some conventional pollutant control technologies, such as the limestone-gypsum method and traditional electrostatic precipitation, have significant CO₂ emission increase antagonistic effects. This study also completed the two-dimensional classification of 66 emission reduction technologies based on “emission reduction efficiency-economic cost”, identified application scenarios for different types of technologies, and proposed optimized paths for synergistic emission reduction adapted to the development of the power industry. The research findings fill the gap in quantitative standards for multi-pollutant synergistic emission reduction, provide theoretical support and detailed technical references for emission reduction technology selection and environmental policy formulation in the power industry, and help the industry achieve the dual development requirements of the “double carbon” goal and air quality improvement. Full article

To enhance the engineering performance of fine-grained composite soils with unbalanced particle gradation, high plasticity, and poor water stability, a synergistic stabilization strategy combining particle structure regulation and microbially induced calcium carbonate precipitation (MICP) was proposed. The particle size distribution and fundamental engineering properties of a titanium gypsum–clay (TSC) composite soil were first optimized through systematic single-factor blending tests. The results indicate that a TS:C ratio of 60:40 significantly improved gradation characteristics, reduced plasticity, and enhanced both compaction behavior and load-bearing capacity. Based on the optimized gradation framework, MICP treatment was subsequently introduced to further enhance water stability. The effects of key parameters, particularly the type of calcium source, on the evolution of water stability were systematically investigated. X-ray diffraction (XRD) and scanning electron microscopy (SEM) were employed to elucidate the underlying reinforcement mechanisms. The results demonstrate that the water stability coefficient increased markedly from 0.35 to 0.83 following MICP treatment, while strength degradation under water immersion was effectively mitigated. Microscopic observations reveal that microbially precipitated calcite fills pore spaces and forms a continuous cementation network via particle bridging and interfacial bonding, leading to an approximately 32% reduction in porosity. Overall, the proposed synergistic strategy offers an effective and sustainable approach for improving the water stability and structural integrity of complex fine-grained composite soils. Full article

For the purpose of investigating the hydrochemical signatures and formation processes of mine water at the Feicheng Coal Mine, a total of 61 samples, including fifth limestone water (FLW), old goaf water (OGW), and ordovician limestone water (OLW), were collected and examined via statistical and hydrochemical approaches. The assessment of mine water suitability for irrigation employed sodium percentage (Na%), sodium adsorption ratio (SAR), permeability index (PI), and magnesium hazard ratio (MHR). The mine water proves slightly alkaline, featuring Na⁺ as the leading cation and SO₄²⁻/HCO₃⁻ as the leading anions. By average concentration, cations decrease in the order Na⁺ > Ca²⁺ > Mg²⁺, and anions decrease as SO₄²⁻ > HCO₃⁻ > Cl⁻. The hydrochemical types of OLW and FLW samples were primarily Ca-HCO₃ and Ca-Mg-Cl, whereas the OGW samples were predominantly of the Na-Cl-SO₄ and Na-HCO₃ types. Rock weathering serves as the main control on water chemistry, with hydrochemical components sourced largely from evaporite and carbonate dissolution. The sodium present in the water is likely attributable to silicate mineral dissolution or cation exchange processes. Cation exchange, with forward exchange dominant, is also a key hydrogeochemical process in the study area. SI results reveal that calcite and dolomite have reached saturation, while gypsum and halite remain undersaturated and tend to dissolve further. Irrigation suitability assessments indicate that most of the water quality in the Feicheng Coal Mine is excellent or good. A limited number of samples exhibited relatively high salinity, and most of them can be directly irrigated. To this end, this study proposes targeted treatment solutions, thus facilitating mine water development and utilization. Full article

This study presents the results of research on the modification of gypsum with bio-waste to improve its thermal insulation properties and to evaluate the influence of the type and amount of the additive on the physical, mechanical, and microstructural properties of the composite. Various fractions of plant-based bio-waste were used in amounts ranging from 0.75 to 10% by weight. The thermal conductivity coefficient and thermal diffusivity were determined. Additionally, analyses of dimensional stability over time, visual appearance, and phase distribution uniformity were conducted. Mechanical tests included surface hardness measurements. In order to determine the material’s durability, water absorption and frost resistance tests were performed, and structural changes and properties after these cycles were analyzed. It was found that selecting the appropriate type and proportion of additive makes it possible to obtain composites with a favorable balance between thermal insulation, dimensional stability, and mechanical performance. The conducted research confirms the potential for effective use of bio-waste as a gypsum-modifying raw material, contributing to the development of sustainable building materials with a reduced environmental footprint and improved functional parameters. Full article

The reflectivity of the bare soil surface (BSS) is influenced by soil type, moisture, salinity, tillage, erosion, and other factors. To investigate the direct impact of erosion on the spectral characteristics of the BSS (SCBSS), a study site in the forest-steppe zone (Mtsensk district, Oryol Oblast, Russia), unaffected by salinity, carbonates, gypsum, and other factors, was selected. To suppress the influence of moisture and tillage, a multitemporal soil line (MSL) construction method was selected, which averages the influence of these factors, using the effect of big data. It was possible to reduce the influence of various factors on the SCBSS to two: zonal soil types and the extent of soil degradation from erosion (erosion degree). Soil types and erosion degree were determined by a ground survey with excavation of 488 pits/soil profiles. It was found that the relationship of soil types on the SCBSS has the form of a second-degree polynomial with a determination coefficient of R² = 0.95. Spectral reflectance decreases across the zonal series of soils: sod-podzolic, light gray forest, gray forest, dark gray forest, podzolized chernozem, leached chernozem, typical chernozem, and meadow-chernozem soils. The influence of erosion leads to a linear increase in reflectance for each soil type in the following erosion degree series: non-eroded, slightly eroded, moderately eroded, and strongly eroded. Superimposing two functional relationships yields a distribution in the form of a polynomial ladder. This distribution maintains the general trend of a polynomial decrease in soil reflectance across the zonal series with stepwise deviations at the erosion degree. The polynomial ladder allows us to demonstrate how the erosion degree can change the spectral characteristics of one soil type to those of another. Full article

The Saoura Valley (southwestern Algeria) hosts14 oases that primarily depend on groundwater in an endorheic basin. The hydrogeological system is bisected by the Saoura Wadi into two distinct compartments: an active, interconnected eastern compartment (Mio–Plio–Quaternary alluvial aquifer and terraces of the Great Western Erg) and a passive, fossil western compartment (Guir Hamada and Cambro–Ordovician aquifers). In September 2024, 51 groundwater samples were collected from nine oases. Temperature ranged from 16.2 to 31.4 °C and pH ranged from 7.1 to 7.85. Total dissolved solids (TDS) varied widely (179–4480 mg/L; median of 454 mg/L), with electrical conductivity between 280 and 7000 µS/cm. Three main hydrochemical facies were identified: Ca–Mg–SO₄–Cl (30%), Na–Cl–SO₄ (55%), and hypersaline types in the terminal inferoflux zone. Nitrate concentrations exceeded the WHO guideline (50 mg/L) in 22% of samples, attributed to localized agricultural and domestic inputs. Geochemical evolution is controlled by evaporite dissolution (gypsum, halite), cation exchange, and evaporative concentration, with a downstream salinity gradient from freshwaters near the Great Western Erg toward hypersaline inferoflux. Comparison with historical data (1941, 1963, and earlier studies) indicates a trend of increasing salinization since the 1990s, associated with intensive borehole pumping and irrigation return flow. These findings suggest risks to the long-term sustainability of the Saoura oases. Full article

During fires, the temperature difference between indoor and outdoor environments induces out-of-plane deformation in steel studs. Due to the differential coefficients of thermal expansion between panels and steel, the panels exert a restraining effect on the studs. However, there remains a lack of systematic experimental and theoretical models addressing the failure modes, restraining mechanisms, and synergistic effects of various panels on steel studs. This study conducted high-temperature bending tests to compare the failure modes, load–displacement curves, and key mechanical parameters (peak load, elastic stiffness) of connections combining steel studs with three types of panels: autoclaved lightweight concrete (ALC) panels, fire-resistant gypsum boards, and medium-density calcium silicate board. The research clarifies the constraining effect and temperature sensitivity of different panels. Based on experimental data, a bending constitutive model was developed to quantify the attenuation of the out-of-plane constraining effect at elevated temperatures. The results indicate that the load–displacement curves exhibit three distinct stages: Elastic Ascending Stage, Elastoplastic Ascending Stage, and Post-Peak Stage. A two-stage bending constitutive model was proposed and formulated. Comparison between numerical simulations and experimental specimens in terms of failure modes and characteristic parameters demonstrated that simplifying the panels as spring elements, with stiffness defined by the proposed bending constitutive model, yields errors within 15%, confirming the accuracy of the model. This study systematically investigates the influence of sheathing panels on the high-temperature out-of-plane mechanical behavior of cold-formed steel studs, innovatively proposes a two-stage bending constitutive model, provides theoretical and data support for cold-formed steel structural fire-resistant design, and offers new perspectives and methodologies for future research. Full article

This study investigates the activation potential of various activators for ferronickel slag (FNS) and the associated phase evolution. First, the existing forms of MgO in FNS were identified by analyzing its phase composition across different particle sizes. Subsequently, FNS was activated using six types of activators—Ca(OH)₂, CaO, NaOH, KOH, Na₂CO₃, and a Ca(OH)₂–gypsum composite—under steam curing at 80 °C for 7 days. The setting time, fluidity, hydration products, and mechanical properties of the activated systems were systematically examined. The results show that finer water-cooled FNS particles contain abundant amorphous phases, including amorphous MgO, which can react with Ca-based activators to form hydrotalcite—a reaction not observed with Na- or K-based activators. Compared with Na- or K-based activators, Ca-containing activators, particularly the Ca(OH)₂–gypsum combination, exhibited superior activation performance. In addition, distinct microstructures were observed: NaOH activation promoted the formation of a yarn ball-like N–A–S–H gel, while KOH activation led to a knotted-fiber-bundle-like K–A–S–H phase, the latter showing potential for enhancing the crack resistance of cement-based materials. These findings provide new insights into the activator-dependent hydration mechanisms of FNS and support its value-added utilization in sustainable construction materials. Full article

The rational utilization of industrial solid waste is an effective way to reduce environmental pollution. This study investigated the potential application of fluorogypsum (FG), flue gas desulfurization gypsum (FGD), phosphogypsum (PG), and titanium gypsum (TG) in the production of excess-sulfated slag cement (ESSC). It further investigated the effects of different types of gypsum on the performance and hydration process of ESSC through a wet grinding process. The results showed that as the pH value of the gypsum increased, the setting time of ESSC decreased, and hydration heat release occurred earlier. Phase analysis and microstructural characterization indicated that the type of gypsum affected the hydration rate, microstructure, and quantity of hydration products of ESSC, thereby influencing its compressive strength. To further improve the performance of ESSC, a wet grinding process was employed to enhance particle activity and promote hydration reactions. PG, due to its high solubility, demonstrated a better activation effect; after wet grinding, the 28 d compressive strength reached 40.03 MPa. Meanwhile, ESSC pastes prepared with high-pH FG exhibited not only good early strength (3-day strength of 21.93 MPa) after wet grinding but also excellent water resistance, with a softening coefficient of 0.96. This study clarifies the impact of gypsum type on ESSC performance and provides valuable insights for enhancing its properties. Full article

Concrete poses many environmental and economic problems due to its heavy reliance on natural resources. The objective of this study was to explore the potential of utilizing recycled materials, specifically waste glass powder and demolition sand, to assess their effectiveness in reducing the formation of delayed ettringite and consequently enhancing the strength of sustainable concrete. This study assesses the combined effects of waste glass powder and demolition sand on stable, sustainable concrete under sulfate exposure. A comprehensive experimental program included 23 mixes using different types of fine aggregate in concrete: standard sand, demolition sand, and mixes with 10–30% ground glass fines replacing Portland cement (PC). Also, the effects of added sodium sulfate and gypsum (1%, 3%, and 5%) on compressive, tensile, and flexural strengths were analyzed by conducting mechanical tests at 7, 28, and 56 days. Finally, SEM, EDS, and XRD were conducted to analyze the microstructures of the concrete mixes. Using gypsum and sodium sulfate provides sulfate ions to study their effects on Delayed Ettringite Formation and mechanical performance. The results of the present work showed that the optimal mix (20% glass powder with 1–3% gypsum) achieved a 21% increase in 28-day compressive strength and a denser microstructure with reduced microcracking. Gypsum showed more stable behavior under the tested conditions compared with sodium sulfate. The microstructure studies supported this conclusion and further demonstrate that optimal amounts of glass result in a denser concrete matrix with less cracking, which is used much more effectively. Full article

Frequent drilling fluid lost circulation in the Kuqa foreland area of the Tarim Oilfield severely constrains drilling efficiency and safety. The complex formation structures and diverse lost circulation types in this region are compounded by a lack of systematic classification in existing studies and weak correlation between mechanism analysis and field plugging measures, leading to a deficiency in quantitative decision-making for lost circulation prevention and control. Based on lithology analysis, loss zone pressure differential calculation, well log interpretation, and core observations, this study establishes an integrated “formation–lithology–pressure” diagnostic and classification method for lost circulation. A systematic classification framework comprising five types of lost circulation channels and mechanisms was developed. Based on this, the dominant lost circulation types and characteristics of three typical vertical formations in the Kuqa foreland were clarified: ① The supra-salt sandy conglomerate formations (e.g., Q1x, N2k) are dominated by permeability loss, where the loss rate (V) and bottomhole pressure differential (ΔP) exhibit a strong positive correlation (V ∝ ΔP). On-site application of graded bridging plugging formulations achieved a first-attempt success rate of ≥90%. ② The salt–gypsum formations (E1-2km) are primarily characterized by induced fracture loss, with a weak correlation between V and ΔP and dynamic fracture opening/closing behavior. Conventional rigid plugging materials showed limited effectiveness, resulting in a first-attempt success rate of <50%. ③ The K1bs formation is dominated by vertically developed natural fracture loss, where V and ΔP also demonstrate a strong positive correlation. In a specific Keshen block, a power-law relationship between the fracture aperture (W) and loss rate was established (W = 0.26·V^0.62, R² = 0.98), providing a basis for predicting fracture aperture and optimizing plugging formulations, with a plugging success rate of ≥80%. The classification system and quantitative criteria developed in this study effectively link lost circulation mechanisms, dynamic characteristics, and engineering countermeasures, offering theoretical support and a decision-making framework for optimizing lost circulation prevention and control measures and improving success rates in the Kuqa foreland area. Full article

Synthetic gypsum (SG) is produced in massive quantities, yet hazardous impurities limit its reuse. This review summarized the impurity types in various SGs and the corresponding removal methods. Physical methods, such as washing, screening, magnetic separation, and others, exploit solubility and size/density differences to remove soluble salts and particulates. Chemical methods, including acid leaching, precipitation/solidification, and so on, can dissolve or immobilize phosphates, fluorides, and heavy metals. Flotation utilizes the differences in the physicochemical properties of solid surfaces to remove insoluble impurities. The thermal treatment is mainly used to decompose organics and improve whiteness. Microbial methods achieve environmentally friendly cleanup through metabolic leaching or microbially induced carbonate precipitation. The phase-transformation method is a recently developed method that can achieve synergistic effects of deep impurity removal and high-value utilization by reconstructing gypsum crystals to release co-crystallized impurities. Most impurity-removal methods target only a single type of impurity. At present, purifying SG requires a combination of multiple methods, which is not recommended from a cost perspective. Subsequent research on removing impurities from SG should focus on simultaneously removing multiple major impurities in a single process, as well as the synergistic effects between impurity removal and the high-value utilization of gypsum. Full article

Modular construction refers to the use of factory prefabricated integrated module units. The modular steel construction unit SHS (Square Hollow Section) group column is a structure composed of four independent steel column units. Due to its compositional characteristics with voids, the fire resistance performance differs from ordinary steel columns, necessitating specific study. This paper employed a sequentially coupled thermal–mechanical analysis to investigate this. The effectiveness of the simulation model was first validated by comparing the simulated time–temperature curves and fire resistance limits with experimental results. A parametric analysis was then conducted to evaluate the influence of various factors, including the load ratio, cavity spacing, insulation type, gypsum board thickness, slenderness ratio, steel yield strength, and inner panel type, on the fire resistance limit. The results show that when the gypsum board thickness increased from 10 mm to 30 mm, the fire resistance limit correspondingly increased by 126%, 120%, 130%, and 130% for load ratios of 0.4, 0.5, 0.6, and 0.7, respectively. When the steel yield strength increased from 235 MPa to 690 MPa, the fire resistance limit increased by 20%, 21%, 24%, and 43% for load ratios ranging from 0.4 to 0.7. For inner panels of Glass Fiber, Rock Wool, Mineral Wool, and Plasterboard, the corresponding fire resistance limit ratios for load ratios of 0.4 to 0.7 were 1:1.13:1.24:1.45, 1:1.14:1.23:1.46, 1:1.11:1.2:1.42, and 1:1.08:1.18:1.41, respectively. It can be found that the best way to increase the fire resistance of the modular column is to increase the thickness of the gypsum board. A simplified calculation formula for the fire resistance limit of SHS group columns was derived through regression analysis, and recommendations for fire protection design were proposed, providing valuable insights for the future design and application of SHS group columns in steel modular construction. Full article