Search Results (304)

To achieve the large-scale, high-value utilization of vanadium–titanium slag (VTS) in the metallurgical industry, this study replaces blast furnace slag (BFS) with VTS to construct a quaternary all-solid-waste cementitious system composed of VTS, BFS, steel slag (SS), and desulfurization gypsum (DG). It systematically investigates the effects of VTS content (0–60%) on the mechanical properties, leaching toxicity, and hydration heat behavior of the system. XRD, TG–DSC, and SEM–EDS techniques are employed to explore the influence of VTS on hydration behavior and microstructural evolution. The results show that when VTS replaces 30% of the BFS (A3, VTS:BFS:SS:DG = 3:3:3:1), the 28-day compressive strength reaches 31.33 MPa. The leaching concentrations of heavy metals in all specimens are far below the standards for drinking water quality. Hydration heat analysis reveals that the incorporation of VTS advances the acceleration period of hydration. The A3 specimen maintains a relatively high heat release rate in the middle and later stages (after 72 h), and its cumulative heat release is significantly higher than that of the system without VTS, revealing the “slow hydration” mechanism of VTS at later stages. The [SiO₄]–[AlO₄] bonds in VTS undergo a depolymerization–repolymerization process. In addition, an appropriate amount of VTS promotes the deposition of hydration products such as ettringite (AFt), C–S–H, and C–A–S–H gels through micro-filling effects and heterogeneous nucleation, thereby improving the microstructure of the system. However, excessive VTS (≥45%) significantly inhibits the hydration reaction and reduces gel formation due to the decrease in highly reactive BFS components and the increased TiO₂ content. This study provides new insights into the resource utilization of VTS in multi-solid-waste cementitious materials. In addition, VTS-based cementitious materials are suitable for practical scenarios with low early strength requirements, such as goaf backfilling. Therefore, future studies should further investigate the long-term sulfate resistance and carbonation resistance of these materials under real application conditions. 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 fresh mine water (FLW), old goaf water (OGW), and old lode water (OLW)—were collected and examined via statistical and hydrochemical approaches for the assessment of mine water suitability for irrigation employed sodium content (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

A low-titanium-slag-based multi-solid-waste cementitious system was developed for cemented paste backfill. The cementitious binder was prepared from low-titanium slag (LTS), steel slag (SS), municipal solid waste incineration (MSWI) fly ash, and flue gas desulfurization gypsum (FGDG), while lead–zinc tailings were used as the aggregate for backfill materials preparation. The activation of low-titanium slag, proportion optimization, and strength development mechanisms were systematically investigated. Mechanical grinding effectively activated low-titanium slag, and its activity index reached 108% after 90 min of grinding at 28 d. Steel slag alone could not fully activate low-titanium slag in the ternary system, whereas the incorporation of MSWI fly ash significantly enhanced the synergistic activation effect. The quaternary system with 40% MSWI fly ash replacement showed higher cumulative heat release and better later-age strength. The optimum backfill proportion was a solid mass concentration of 81% with a binder-to-tailings ratio of 1:4, yielding a 28 d compressive strength of 11.07 MPa with satisfactory flowability and setting behavior. Microstructural results indicated that the continuous formation of ettringite and gel phases promoted pore refinement and matrix densification. Moreover, the leaching concentrations of Pb, Zn, Cr, and soluble Cl were all below the relevant groundwater quality limits. These results demonstrate a feasible route for the high-value co-utilization of low-titanium slag and MSWI fly ash in cemented backfill materials. Full article

This research reveals the coupling mechanism between structural deformation and hydrocarbon accumulation. The Dibei area in the Kuqa Depression represents a key hydrocarbon exploration domain within the northern Tarim foreland basin. Although extensive studies on stratigraphy, sedimentology, and accumulation mechanisms have been conducted, the control of segmented deformation on traps remains poorly understood. Furthermore, the synergistic regulation mechanism involving paleo-uplifts, salt thickness, synsedimentation, and erosion is still ambiguous. Based on high-quality 2D and 3D seismic data, this study integrates tectonic evolution balanced restoration with physical modeling. We conducted two sets of 3D sandbox experiments: “differential paleo-uplift and salt thickness” and “synsedimentation-erosion.” This approach systematically investigates the control of tectonic evolution on trap formation. Results show a strong correspondence between the “subsalt–salt–supra-salt” structural deformation and trap types. The supra-salt layer is dominated by detachment fold traps, whereas the subsalt layer features thrust-fold anticline traps. The basement paleo-uplift governs structural segmentation and trap distribution. Salt thickness modulates strain partitioning and trap stability. Synsedimentation optimizes trap conditions via tectono-sedimentary coupling. Erosional unconformities serve dual functions as both migration pathways and seal beds. These four factors work synergistically throughout the entire petroleum system, from “trap formation–migration–accumulation–preservation.” It enriches the genetic theory of salt-related structures in foreland basins. The findings provide a reference for predicting favorable exploration zones, evaluating trap characteristics, and assessing resource potential in the Kuqa Depression. Full article

Gypsum (CaSO₄·2H₂O) crystallization is highly sensitive to the supersaturation pathway, which governs the balance between nucleation and crystal growth and ultimately controls growth morphology. In this study, gypsum was synthesized via two contrasting routes—diffusion-controlled crystallization and rapid precipitation—using identical reactant systems to enable a direct comparison of distinct kinetic regimes. A polycarboxylate-based superplasticizer was incorporated to investigate pathway-dependent additive effects. Time-resolved observations reveal that rapid precipitation is characterized by high nucleation density under steep supersaturation, whereas diffusion-controlled crystallization proceeds under gradually increasing supersaturation with restricted nucleation and sustained anisotropic growth. Powder X-ray diffraction confirms the formation of phase-pure gypsum under all conditions. Scanning electron microscopy shows that the presence of the superplasticizer reduces crystal number density and modifies crystal habit in both pathways, although the extent and manifestation of these effects depend strongly on the governing kinetic regime. Under diffusion-controlled conditions, the increasing superplasticizer dosage promotes the transition from elongated to more tabular morphologies, while rapid precipitation results in dense, intergrown aggregates under high supersaturation. Overall, the results demonstrate that the effectiveness of the superplasticizer is not intrinsic but depends on the crystallization pathway. These findings provide new insight into how supersaturation profiles mediate the interplay between additive interactions and growth processes, enabling improved control over gypsum crystal morphology. 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

High-salinity water environments, e.g., saline lacustrine basins and lagoons, represent significant sedimentary settings on Earth. They serve not only as crucial archives of paleoclimate and paleoenvironmental evolution but also as favorable realms for the development of high-quality hydrocarbon source rocks. Although traditional views suggested that high salinity inhibits biological activity and is thus detrimental to source rock formation; recent hydrocarbon discoveries in formations such as the Leikoupo Formation (Sichuan Basin) and Majiagou Formation (Ordos Basin) in China have confirmed the exceptional hydrocarbon generation potential of source rocks in such settings. Focusing on major sedimentary basins in China, this review synthesizes how high-salinity settings critically control the integrated “generation-storage” sequence of hydrocarbon source rocks. Research indicates that moderate salinity can promote blooms of halophilic microorganisms, e.g., algae, cyanobacteria, resulting in high primary productivity. Concurrently, salinity-driven stable water stratification creates a strongly reducing bottom water environment, which greatly facilitates the preservation of organic matter, establishing a synergistic enrichment model of “high productivity—excellent preservation.” Products of high-salinity environments, such as evaporites, e.g., gypsum, halite, can act as catalysts, lowering the activation energy for hydrocarbon generation and enhancing hydrocarbon yield. Additionally, associated organic salts provide supplementary material for hydrocarbon generation. Regarding reservoir quality, the laminated structures formed in high-salinity settings, combined with organic–inorganic synergistic diagenesis, e.g., dolomitization, organic acid dissolution, and hydrocarbon-generation overpressure, collectively shape high-quality reservoirs with significant heterogeneity. Despite important progress, challenges remain, including the quantitative analysis of primary factors controlling organic matter enrichment, the threshold of salinity inhibiting biological communities, and the prediction of strongly heterogeneous reservoirs. Saline settings serve as critical carbon sinks in the geological carbon cycle through high primary productivity, enhanced preservation conditions, and distinctive mineral assemblages, playing a particularly important role in the formation of hydrocarbon source rocks and long-term carbon sequestration. Future research should integrate modern saline lake observations with high-resolution characterization techniques to deepen the understanding of the formation mechanisms of high-salinity source rocks, aiming to provide theoretical guidance and exploration targets for petroleum systems in similar geological settings worldwide. Full article

Chloride-induced deterioration is a major threat to the durability of marine concrete structures, especially in tidal and submerged zones. This study simulated these environments by immersing C45 concrete specimens in NaCl solutions (5%, 10%, 15%) under both constant immersion and wet–dry cycles. Compressive strength tests, low-field NMR for pore structure, chloride ion profiling, and SEM-EDS analyses were conducted. A modified chloride diffusion model was developed based on Fick’s second law, incorporating time- and concentration-dependent parameters. The results showed that higher NaCl concentrations and tidal zone exposure significantly accelerated concrete degradation. In the tidal zone, wet–dry cycles led to larger macropore formation, higher chloride penetration, and more severe microstructural damage compared to the submerged zone. Compressive strength initially increased and then declined in high-salinity environments, with strength losses reaching up to 25% under 15% NaCl after 120 days. NMR data confirmed the transformation of micropores and mesopores into macropores, especially in the tidal zone. SEM-EDS analysis revealed decalcification, gypsum formation, and Friedel’s salt accumulation on eroded surfaces. It was determined that chloride ion diffusion behavior in concrete is significantly influenced by the chloride content and diffusion concentration, as well as the exposure zone. The developed model indicates that depth increased over time and with concentration. The proposed diffusion model achieved high fitting accuracy (R² > 0.97), effectively capturing the effects of erosion age and salt; this makes it a reliable tool for predicting chloride ion ingress in marine concrete, and for supporting service life evaluation and durability design. Full article

Red mud, a major solid waste from the alumina industry, suffers from an extremely low utilization rate due to its high alkalinity, complex chemistry, and particularly low cementitious activity, which drives the need for novel activation strategies. This study presents a new method for red mud activation through electrochemical treatment, which simultaneously enables iron recovery as a valuable by-product. The electrochemical activation was systematically investigated by performing experiments in alkaline, neutral, and acidic electrolytes. The alkaline system showed a pronounced enhancing effect on the electrochemical process. Under alkaline conditions, the average Faradaic efficiency exceeded 80%. The electrochemical treatment modified the microstructure of red mud particles and transformed iron oxides into magnetic species, which could be effectively separated via magnetic separation. More importantly, this activation process significantly enhanced the cementitious activity of the treated red mud by removing iron oxide that encapsulates reactive aluminosilicate phases and increasing surface reactivity. When used as a supplementary cementitious material with ordinary Portland cement and gypsum, the electrochemically activated red mud demonstrated remarkably improved mechanical properties, with 28-day compressive strength reaching up to 69 MPa. Characterization analysis revealed that the electrochemical activation promoted the formation of key hydration products, including C-S-H gel (formed through both OPC hydration and pozzolanic reactions between activated red mud and portlandite), ettringite, and portlandite. This work provides a green and low-carbon pathway for the stepwise utilization of red mud through activation and resource recovery. Full article

Raman spectroscopy is essential for the in situ identification of lunar minerals, yet weak signals and stringent payload constraints demand instruments with high throughput and mechanical robustness. Here a microscope-coupled spatial heterodyne Raman spectrometer (SHRS) is developed for stable, adjustment-free operation, with performance set by an explicit sampling analysis that links magnification, pixel pitch, and detector format to achievable spectral resolution and range. The interferometer geometry is fixed in service and is established using removable alignment blocks referenced to the Littrow condition during integration and then removed from the optical path, which mitigates backlash, creep, and dust sensitivity while preserving reinstallability for verification. Guided by the sampling analysis, the laboratory prototype meets a 100–3600 cm⁻¹ spectral range with an effective resolution better than 10 cm⁻¹, further corroborated by the narrow FWHM of the diamond Raman line. Representative minerals are recovered at the expected wavenumber, and a broad-scan of gypsum retrieves the sulfate fundamentals and the O–H stretching envelope near 3400 cm⁻¹, indicating maintained coverage and sensitivity into the high-wavenumber region relevant to bound water. A comparative study of sampling magnification confirms the sampling-limited predictions and shows that higher magnification improves effective SNR and peak visibility with only minor changes in width, providing practical guidance for compact SHRS design under low-signal conditions. The results support a compact, slit-free SHRS as a credible basis for future lunar and other planetary deployments. Full article

In recent decades, the need to embrace the concepts of the circular economy and ecological transition has become increasingly apparent, especially in the civil engineering sector. This research aims to study a Cement-Bound Granular Material (CBGM) pavement layer using the industrial by-product Anhydrous Calcium Sulphate (ACS) as a partial replacement for Portland Cement (PC) by weight. The dual objective is to reduce environmental impact and ensure long-term high mechanical performance. Mechanical tests conducted at different curing periods (7, 28, 96, and 120 days) showed compressive strength gains of up to 180%. The evolution of the mechanical behavior was correlated with the formation of the gypsum dihydrate and ettringite hydrated phases, found by quantitative XRD analysis, to reinforce the cement matrix. Finite element simulations and fatigue life predictions using Miner’s rule over pavement lifespans of 15, 20, and 30 years indicated an increase in durability by a factor of 4.68 for the ACS-enhanced mixture compared to traditional PC-only formulations. Leaching tests show the material performs within acceptable environmental thresholds, even if its classification and acceptance may differ across regulatory systems, suggesting a solid basis for its application in sustainable practices. Full article

Understanding the carbonation behavior of lime-based mortars is essential for ensuring material compatibility and long-term durability in architectural restoration. This study presents a comparative spectroscopic and mineralogical analysis of eleven mortar samples collected from both the original (11th–12th century) and modern extension walls of a historic structure. X-ray diffraction (XRD) and attenuated total reflectance–Fourier transform infrared spectroscopy (ATR-FTIR) were employed to assess the mineralogical composition and carbonation maturity. The results indicate that the historic mortars have undergone complete carbonation, as evidenced by sharp and well-defined calcite bands, whereas the modern repair mortars display broader carbonate peaks, suggesting ongoing carbonation processes. XRD analysis confirmed the dominance of calcite and gypsum, along with the presence of illite, albite, and microcline, indicating mineralogical signatures of both binder transformations (such as carbonation and sulfate formation) and aggregate contributions. The weak water absorption bands and limited sulfate signals observed in the spectra further suggest advanced aging and mineral stabilization in the historic mortars. These findings highlight the differing carbonation kinetics between historic and modern lime mortars and emphasize the importance of selecting repair materials with compatible chemical and physical aging characteristics. The combined use of XRD and ATR-FTIR proves to be an effective diagnostic approach to guide restoration material selection and support the long-term integrity of masonry structures. Full article

This study assessed natural radioactivity values and corresponding radiological hazards in gypsum samples collected from the investigated area. The geologic context mainly includes tertiary and quaternary sedimentary formations with gypsum horizons of Early Messinian age, interbedded with layers of limestone and marl. A total of thirty-five gypsum samples were collected and analyzed for the ²³⁸U, ²³²Th, and ⁴⁰K activity concentration using High-Purity Germanium (HPGe) gamma-ray spectrometry. The mean activity concentrations for the gypsums are reported at 73 ± 87 Bq kg⁻¹, 14 ± 17 Bq kg⁻¹, and 35 ± 201 Bq kg⁻¹ for ²³⁸U, ²³²Th, and ⁴⁰K, respectively. Several related radiological hazard indices were estimated from the various activity concentrations, including radium equivalent activity (Ra_eq) and absorbed dose rate (D_air). All gypsum analyzed fell below international safety limits for radiological risk, as evidenced by the observed radium equivalent activity (Raeq), with a maximum value of 456 Bq kg⁻¹, and the total annual effective dose (AED) values from 0.09 to 1.26 mSv y⁻¹ remaining between these two values. The results indicate the levels of radioactive hazards of the gypsum samples were generally below global safety standards, but individual samples (i.e., S17, S20, S24, S26, S30, S35) exceeded one or more of the hazard indices. Statistical assessment of the samples, with respect to their radiological hazard and natural radioactivity, was also undertaken as a way of seeking further insights into their relationships, productivity, and characteristics. This included Pearson correlation, hierarchical cluster analysis (HCA) and principal component analysis (PCA). The evidence suggests that for the gypsums, ²³⁸U was the greatest contributor to radiological hazards, influencing all hazard indices. Full article

Black crusts are multilayered alteration products that develop on historic masonry exposed to urban pollution. This study investigates the west enclosure wall of the XVII^th-century Golia Monastery in Iași, Romania—located along a busy traffic corridor—and presents multi-analytical results on two lime-based mortar fragments exhibiting well-developed blackened surface layers. Both the exposed (blackened) finishes and protected verso areas were analyzed using portable X-ray fluorescence (pXRF), scanning electron microscopy with energy-dispersive X-ray analysis (SEM–EDX), micro-FTIR spectroscopy, X-ray diffraction (XRD), CIE Lab colorimetry and optical microscopy (OM). The data reveal gypsum-rich surface layers enriched in traffic-derived particles, including metal oxides and soot, with marked contrasts relative to the minimally altered verso. Handheld XRF and SEM–EDX indicate elevated sulfur and associated traffic-related elements within porous gypsum matrices, while FTIR and XRD consistently identify calcium sulfate as the dominant secondary phase. Colorimetric measurements additionally document pronounced lightness loss and visible darkening on exposed surfaces. These results demonstrate the onset of directional sulfation and black crust formation on mortars under urban pollution pressure and establish an integrated analytical protocol for diagnosing black crusts on historic lime mortars in urban heritage settings. 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