Sulfate Solution Research Articles

Presence of Pseudomonas aeruginosa in feces exacerbate leaky gut in mice with low dose dextran sulfate solution, impacts of specific bacteria.

The impact of Pseudomonas aeruginosa (PA) was explored in a mouse model with non-diarrheal gut permeability defect using 1.5% dextran sulfate solution (DSS) plus antibiotics (ATB) with or without orally administered PA. As such, ATB+DSS+PA mice induced more severe intestinal injury as indicated by stool consistency and leaky gut (FITC-dextran assay, bacteremia, and endotoxemia) with an increase in serum cytokines, liver enzyme, and hepatocyte apoptosis when compared with ATB+DSS mice. There was no abnormality by these parameters in the non-DSS group, including water alone (control), antibiotics alone (ATB+water), and antibiotics with PA (ATB+water+PA). Despite a similarly fecal microbiome patterns between ATB+DSS and ATB+DSS+PA groups, a higher abundance of Pseudomonas, Enterococci, and Escherichia-Shigella was detected in ATB+DSS+PA mice. Additionally, the additive pro-inflammation between pathogen molecules, using heat-killed P. aeruginosa preparations, and LPS against enterocytes (Caco2) and hepatocytes (HegG2), as indicated by supernatant IL-8 and expression of several genes (IL-8, NF-kB, and NOS2) are demonstrated. In conclusion, presence of P. aeruginosa in the gut exacerbated DSS-induced intestinal injury with spontaneous translocation of LPS and bacteria from the gut into the blood circulation (leaky gut) that induced more severe systemic inflammation. The presence of pathogenic bacteria, especially PA in stool of the healthy individuals might have some adverse effect. More studies are in needed.

Copper–Chitosan-Modified Magnetic Textile as a Peroxidase-Mimetic Catalyst for Dye Removal

Copper chitosan attached to a magnetic synthetic nonwoven textile was manufactured using a simple, rapid, and green procedure employing chitosan dissolved in diluted acetic acid and treatment with copper sulfate solution. The prepared copper–chitosan-modified textile exhibited peroxidase-mimetic activity which was subsequently used for the degradation (decolorization) of important organic dyes, namely methylene blue, Congo red, and Bismarck brown Y, in the presence of hydrogen peroxide. After 5 h of treatment at 22 °C, 87.5%, 79.5%, and 87.7% dye removal were observed for methylene blue, Congo red, and Bismarck brown Y, respectively. The textile bound catalyst can be easily recovered from the reaction mixture after the process is completed.

The Use of Phosphonates to Inhibit Salt Crystallization: A Laboratory Study for the Sustainable Conservation of Mural Paintings in the Hypogea Context

This research is focused on the laboratory study of salt crystallization inhibitor products as new materials for conservation treatments which can be applied to mortars and painted plasters; as is well known, salt crystallization is one of the most frequent causes of decay processes on decorated architectural surfaces in a wide range of environments. Specifically, the study targets the field of the preventive conservation of mural paintings within rupestrian heritage sites. For the first time, systematic investigations were performed on mock-ups made of plaster painted with two different pigments: yellow ochre and carbon black. Two types of phosphonate inhibitors, PBTC (2-phosphonobutane-1,2,4-tricarboxylic acid) and ATMP (aminotris (methylene phosphonic acid)), were chosen and applied at two different concentrations. Given the limited literature available, and the presence of pigments potentially sensitive to treatment with salt inhibitors, preliminary tests were required. Their effects on the chromatic features of the pigments were evaluated visually and using colorimetry. The changes in the behaviour of water circulation in the mortar resulting from the treatments were evaluated through water vapour permeability and absorption tests. Accelerated crystallization experiments were carried out to assess how inhibitors could influence the growth of salts and the resulting material damage. The latter was carried out by employing sodium sulphate and calcium sulphate solutions, quantifying the damage to the specimens through material loss in weight and the percentage of painted surface loss. Based on the overall results, the product with the best performance was identified was ATMP 0.1% (by volume) in deionized water. The obtained results show that salt inhibitor treatments are promising for in situ application and could represent an innovative approach to promote the sustainable conservation of mural painting, particularly those located in hypogeal contexts, where the salt supply cannot be removed and slowing the growth of salts and/or changing their crystalline habitus may be effective in limiting their damage.

Experimental Study on the Mechanical Properties of C30 Molybdenum Tailings Concrete after High-Temperature and Sulfate Corrosion

In order to study the durability of molybdenum tailings concrete after a specific period of wet-dry cycle tests and exposure to high temperatures, this paper investigates the rule of change of the mechanical properties of molybdenum tailings concrete under the coupled influence of sulfate corrosion and high-temperature environmental conditions. A total of five C30 concrete prisms with molybdenum tailings content (0%, 25%, 50%, 75%, and 100%) were considered in the tests, with sulfate solution concentrations of 0 g/L, 20 g/L, and 50 g/L, and exposure temperatures of 25° at room temperature and 400° at high temperature, respectively. The test results showed that the mass loss rate of concrete prisms with different molybdenum tailings substitution rates under sulfate corrosion and high temperature environment showed an increasing and then decreasing trend. The specimens with 25% molybdenum tailings content still maintain high mechanical properties after wet-dry cycle tests of sulfate solution and high temperature, and the reduction of peak stress in this group is only 11%, and the reduction of elastic modulus is 1%; the rest of the molybdenum tailings content has a reduction of peak stress of about 25%, and the reduction of modulus of elasticity is more than 10%. The plastic deformation capacity of molybdenum tailings concrete decreases under the single-factor effects of wet-dry cycle tests of sulfate solution and high temperature effects, but the plastic deformability capacity of the specimens is enhanced under the combined effects of multiple factors. The stress-strain curve formulas for molybdenum tailings concrete under high temperature, wet-dry cycle tests of sulfate solution, and coupled wet-dry cycle tests of sulfate solution and high temperature were fitted. The results of this study can provide experimental data and valuable references for the engineering application of molybdenum tailings concrete under wet-dry cycle tests of sulfate solution and high temperature conditions, laying a foundation for further research.

Coordination, hydration, and diffusion of vanadyl cations in negatively charged polymer membranes

Charged polymer membranes that selectively transport ions are crucial for advancing electrochemical technologies for water purification, resource recovery, and energy generation/storage. Recent studies suggest that the ion selectivity trends of such membranes are due to ion dehydration at the membrane/solution interface, where ions that require less energy to shed their hydration can partition more favorably into the membrane. However, direct evidence of ion dehydration in polymer membranes at relevant conditions is scarce, with claims based primarily on correlations between ion hydration energies and membrane transport properties. The objective of this study was to investigate the electronic environment, local coordination, and hydration of vanadyl counter-ion in negatively charged membranes with broadly varying water content via x-ray absorption spectroscopy. The results highlight that vanadyl counter-ions maintain similar oxidation state, electronic state, and coordination number in the membranes as in aqueous solutions of vanadyl sulfate and that vanadyl dehydration is unlikely in these membranes. However, as the membrane water content decreases, the vanadyl diffusion coefficient decreases and the activation energy of diffusion increases. We attribute these significant changes in membrane transport properties to increased Coulombic interactions between vanadyl and the fixed charge groups, resulting from a decreased dielectric constant of the membrane, rather than to ion dehydration at the membrane/solution interface. This study represents significant progress in understanding the mechanisms that govern ion transport in charged polymer membranes over a broad range of water content, highlighting the critical role of Coulombic interactions between the fixed charges and mobile ions.

Efficient photocatalytic degradation of Rhodamine B dye by undoped and zinc doped zirconium dioxide NPs

Undoped and Zinc-doped Zirconium Dioxide (ZrO2) nanoparticles (NPs) were synthesized via the co-precipitation method, employing Zirconium (IV) Oxynitrate hydrate (ZrO2N2·xH2O), Zinc Sulfate (ZnSO4·7H2O), and ammonia solution as precursor materials at room temperature. A comprehensive characterization of the structural, morphological, optical, and catalytic properties of the prepared samples was conducted using various techniques. Powder X-ray diffraction (PXRD) analysis revealed that the synthesized NPs exhibited a tetragonal phase structure, with crystallite sizes decreasing as doping concentration increased. Scanning electron microscopy (SEM) images confirmed the spherical shape of the NPs. Energy-dispersive X-ray spectroscopy (EDX) verified the presence of Zr, O, and Zn elements with high purity. Raman spectroscopy corroborated the tetragonal structure of the synthesized ZrO2 NPs. Ultraviolet–visible (UV–Vis) spectroscopy studies determined the cutoff wavelengths, while Tauc plot enabled the calculation of band gap energies. Fourier transform infrared spectroscopy (FTIR) confirmed the functional groups present in the synthesized samples. Photoluminescence spectroscopy provided evidence of defects and charge carrier recombination processes. The catalytic efficacy of the synthesized ZrO2 NPs was demonstrated through the degradation of Rhodamine B dye under visible and UV light.

Degree of sulfation of freeze-dried calcium alginate sulfate scaffolds dramatically influence healing rate of full-thickness diabetic wounds.

Diabetic foot ulcer (DFU) is a chronic and non-healing wound in all age categories with a high prevalence and mortality in the world. An ideal wound dressing for DFU should possess the ability of adsorbing high contents of exudate and actively promote wound healing. Here, we introduced the calcium alginate sulfate as a new biomaterial appropriate for use in wound dressing to promote the healing of full-thickness ulcers in a diabetic mouse model. In this regard, alginate sulfate (Alg-S) solutions with different degree of substitution (DS) of 0.2, 0.5, and 0.9 were synthesized, freeze-dried, crosslinked by calcium cations, purified by washing and refreeze-dried. Primary analyses including swelling ratio, porosity content and mechanical properties revealed that all Alg-S scaffolds possess necessities for use as a wound dressing. After confirming the cytocompatibility of both alginate and alginate sulfate-based scaffolds by MTT assay, they were used as wound dressing for healing of full-thickness ulcers in diabetic mice. The results of wound healing process confirmed that calcium alginate sulfate scaffolds can heal the wounds faster than both alginate-treated and non-treated wounds. Furthermore, the histological analyses of healed tissues reveled normal regeneration of the skin tissue layers and collagen deposition similar to the healthy tissue.

Systematic long-term investigation on Cu2ZnCdS4 wide band gap semiconducting materials for optics and luminescence applications

Copper Zinc Cadmium Sulfide (Cu2ZnCdS4) semiconducting material compound synthesized using a new economic beneficial route. Copper sulfate, zinc sulfate, cadmium sulfate and thiourea salt solutions were utilized for Cu2ZnCdS4 compound formation. Basic characteristics like pH value, electrical conductivity, concentration measurements were investigated for several hundred samples. Optics transmittance was investigated by UV – Vis spectrophotometer within the 350 to 950 nm range. Photo luminescence measurement was examined by using photo–fluorometer. Optic properties of Cu2ZnCdS4 compound were investigated through photo-calorimeter measurements including mixed wavelength bands. The real time investigated noteworthy results from several hundred samples are presented and discussed.

Efficient separation and recovery of cobalt from grinding waste of cemented carbide using a sulfuric acid-sodium persulfate mixed solution

The mechanical processing of cemented carbide often generates a considerable amount of grinding waste from cemented carbide (GWCC), which serves as an important secondary resource for recovering Co and W. However, efficient separation of tungsten carbide (WC) and Co from GWCC remains challenging. This study tested an efficient process for separating Co from GWCC using a mixed solution of H2SO4-Na2S2O8. Under optimum conditions of 20 g/L H2SO4, 30 g/L Na2S2O8, 60 °C, and 1 h, the leaching efficiency of Co reached 97.0 %, compared to only 58.6 % when using H2SO4 alone. The kinetics of Co leaching in H2SO4 and H2SO4-Na2S2O8 solutions were determined to be a combination of chemical reaction control and diffusion control, suggesting that Co leaching rate in H2SO4 solution is significantly enhanced by introducing Na2S2O8. Finally, complete recovery of Co was achieved, and pure Co powder with a flower-cluster morphology was prepared from the leaching solution through oxalic acid precipitation followed by vacuum pyrolysis. The regenerative WC and Co powder can be recycled for cemented carbide production.

Innovative strategies for ammonia nitrogen removal in rare earth tailings: An advanced element recycling process using leaching, chemical precipitation and adsorption

Residual ammonium salt in closed rare earth mining sites leads to elevated levels of ammonia nitrogen in the surrounding environment. To mitigate ammonia nitrogen pollution at its source, a cost-effective and environmentally friendly recycling process was proposed. This process involves leaching residual ammonia nitrogen using a magnesium sulfate solution, followed by chemical precipitation for ammonia nitrogen removal. Additionally, nitrogen can be recovered as ammonia gas through the thermal decomposition of precipitates, allowing for further ammonia nitrogen adsorption from the leachate. The residual ammonium salts leaching rate reached 96.38 % with a 0.1 mol/L magnesium sulfate solution at a flow rate of 0.6 mL/min. The chemical precipitation method achieved a maximum nitrogen removal rate of 86.87 %, with an activation energy of 2.6 kJ/mol, indicating a relatively rapid process. At 190 °C, the ammonia nitrogen release rate of precipitates was 82.5 % after 2 h of thermal decomposition. The adsorption process was consistent with pseudo-second-order kinetics models using thermal decomposition products. Overall, the comprehensive removal rate of residual ammonium salts from the closed rare earth mining site was approximately 83.3 % in recycling process, optimizing the utilization of phosphorus, magnesium, and nitrogen and achieving efficient and environmentally friendly nitrogen removal.

Exploring the impacts of liquid accelerators on sulfate resistance and calcium leaching behavior of wet-mixed shotcrete

The performance of shotcrete used in underground tunnel construction is often compromised by the challenging service environment, causing severe deterioration and structural integrity concerns. Developing high-quality accelerating agents can be a viable approach to mitigate this effect. This study formulates alkali-free fluorine-free (AF-I); alkali-free fluorine-containing (AF-II); and low-alkaline (AC) liquid accelerators and explores their impacts on sulfate resistance and calcium leaching behavior of shotcrete, utilizing semi-immersion and short-term tank water testing protocols on a time-resolved basis. Microstructural analysis of eroded shotcrete was conducted employing XRD, TGA and SEM to reveal underlying mechanisms. Additionally, ionic analyses of simulated leaching systems, including groundwater and 5% sodium sulfate solution were performed using ICP-OES to monitor calcium activity and assess leaching behaviors. Results indicate that shotcrete accelerated with AF-II exhibits the strongest resistance, whereas shotcrete with AC suffers the severest deterioration. The primary deterioration mechanism of shotcrete with AC was majorly due to high ettringite and gypsum corrosion, whereas AF-I and AF-II induces little ettringite corrosion. In terms of leaching behavior, AF-II demonstrates superior calcium leaching mitigation, with leachability indices in groundwater and sodium sulfate solution measuring 0.06 and 0.19, and 0.02 and 0.16 higher values, respectively, compared to AF-I and AC. Findings of this study provide valuable insights into the application and performance of shotcrete in sulfate-prone environments, aiming to mitigate potential deterioration through optimal accelerator selection.

The Relationship Between the Knowledge, Attitudes and Practices of Herders on Hygienic Milking and The Contamination Risk of Milk with Cryptosporidium Oocyst in Kaduna State, Nigeria

Dairy products are consumed by millions on daily basis worldwide and as such the potential for foodborne illness is a major concern. This study investigated the occurrence of Cryptosporidium oocyst in cow bulk milk and the knowledge, attitudes, and practices of herders towards hygienic milking in selected Local Government Areas (LGAs) of Kaduna State, Nigeria. A total of 120 milk samples were collected for this study. Detection of Cryptosporidium oocyst in milk samples was carried out by concentration technique using Magnesium Sulphate (MgSO4) solution and stained with Modified Ziehl Neelsen method. Sixty (60) structured questionnaires were administered to herders in the study area to identify possible risk factors and assess their knowledge, attitudes and practices toward hygienic milking. The overall prevalence of Cryptosporidium oocysts in cow bulk milk was 11.7% (14/120). Questionnaires administered showed that the majority of the respondents had poor knowledge (88.3%), negative attitudes (85.0%) and adopted unsatisfactory practices (95.0%) to hygienic milking. The occurrence of Cryptosporidium oocysts in cow bulk milk from this study suggests that the dairy cattle in these LGAs have a high potential for transmitting Cryptosporidium to humans. Hence the findings of this study are of great public health significance as these group of animals sampled produce milk for consumption in both urban and rural communities. Therefore, inhabitants of these LGAs should be informed and educated on the need to improve sanitary measures while milking these animals and the need for adequate pasteurization of milk before consumption.

Establishing fire protection patterns in wood using impregnation compositions from inorganic salts

An issue related to using inorganic salts for fire protection of wood is to ensure their flame-inhibiting ability and compatibility with wood and application technology. That is why the object of research was to establish the effectiveness of inhibitory properties of mixtures of inorganic salts during interaction with the flame and enabling interplay with wood. A synergistic increase in the inhibitory capacity of mixtures of aqueous solutions of salts of diammonium phosphate and ammonium sulfate at a ratio of 2:1, and for a mixture based on orthophosphoric acid, urea, and oxyethylidenediphosphonic acid in the concentration range of 20–25 % by mass, has been proven. During the interaction of the specified mixtures with the wood surface, it was found that after application to the wood surface, the dispersed component of the free energy of the wood surface decreased to zero; instead, the polar component increased 13 times, which indicates a change in the wood surface. During the tests of wood samples on the effect of the burner flame, it was found that the untreated sample ignited on second 53, and the flame spread throughout the sample for 102 s. On the other hand, the samples treated with a mixture of an aqueous solution of phosphate and ammonium sulfate, as well as a mixture of aqueous solutions based on orthophosphoric acid and urea and oxyethylidenediphosphonic acid, did not catch fire, the flame did not spread over the surface, and the flammability index was 0. The practical significance is that the results were taken into account when designing flame retardant compositions for wood. Thus, there are reasons to assert the possibility of targeted regulation of wood protection processes through the use of mixtures of inorganic salts capable of forming a protective layer on the surface of the material that inhibits the burning of wood

Facile Synthesis of CuxS Electrocatalysts for CO2 Conversion into Formate and Study of Relations Between Cu and S with the Selectivity

AbstractThe conversion of CO2 into formate (HCOO−), a techno‐economically feasible product, can be achieved using earth‐abundant CuxS electrocatalysts, but questions remain regarding how catalyst structure, composition, and reaction environment influence product selectivity. A novel synthesis method based on electrodeposition of Cu foam and its subsequent sulfidation via immersion in sulfur saturated toluene solution resulted in CuxS foams. Catalytic activity studies found that HCOO− selectivity is dependent on electrochemical activation at higher overpotentials. To understand the effects of activation, determine the active forms of the catalysts, and identify the role of sulfur, the electrodes are carefully characterized as well as gaseous and sulfur dissolved in electrolyte. This included study of the effects of intentional addition of solution sulfur species, identification of the sulfur loss, determination of the electrode composition and relating sulfur speciation to observed product selectivity. It is found that residual sulfur stabilizes Cu+ during electrolysis at potentials favoring HCOO− production, in contrast to pristine Cu that undergoes complete reduction and shows poor HCOO− selectivity. Sulfur in both the catalyst and dissolved in electrolyte are of dynamic nature, and surface residues of SO42− species are identified in all activated catalysts which correspond with enhanced HCOO− production.

Quartz crystal microbalance analysis of effects of surfactants on dissolution kinetics of poly(4-hydroxystyrene) partially protected with t-butoxycarbonyl group

Abstract Surfactants comprise water-repellent and water-attracting moieties and have been used to improve the lithographic performance of resist materials. However, the effects of surfactants on the dissolution kinetics of these materials are still unclear. In this study, the effects of surfactants on the dissolution kinetics of partially-protected poly(4-hydroxystyrene) (PHS) in 0.26 N tetramethylammonium hydroxide aqueous solution was investigated using a quartz crystal microbalance method. Anionic (sodium n-octanonate, sodium 1-hexanesulfonate, n-dodecylbenzenesulfonic acid, and sodium n-dodecyl sulfate), cationic (methylamine hydrochloride, dodecyltrimethylammonium chloride, and 30% ammonium lauryl sulfate solution), nonionic (sorbitan monooleate, polyoxyethylene(23)lauryl ether, and polyoxyethylene(10)hydrogenated castor oil), and amphoteric (35% lauryl dimethylaminoacetic acid solution) surfactants were examined. The surfactant significantly affected the dissolution kinetics of the PHS films. The surfactant effects were significantly reduced by protecting the hydroxyl groups of PHS. The effect of the surfactant on the dissolution kinetics depended on the surfactant rather than on the surfactant type.

Mechanical and durability performance of eco-friendly geopolymer-stabilized soil

This work compared the mechanical performance and the durability of clayey soil stabilized using mechanochemically activated geopolymer (MAG) with conventionally activated geopolymer (CAG). The effect of ground-granulated blast-furnace slag (GGBS) content on the long-term durability of geopolymer-stabilized soil has also been studied. The samples of geopolymer stabilized soils were immersed in 1% magnesium sulphate (MgSO4) solution for 60 and 120 days. The appearance, ultrasonic pulse velocity, unconfined compressive strength (UCS), and FTIR spectroscopy of those samples were considered to evaluate their sulphate erosion resistance. Before the exposure to the MgSO4 solution, the UCS of MAG samples was higher (12%–45%) than that of CAG-stabilized soil. Furthermore, the strength of the geopolymer-stabilized soil improved by 114%, 247%, and 361%, at 50%, 75%, and 100% GGBS content, respectively. After exposure to the MgSO4 solution, the results showed that the mechanochemically activated geopolymer-stabilized soil has better resistance to sulphate erosion than the conventionally activated geopolymer-stabilized soil. The residual UCS for MAG and CAG samples were 93% and 89% when exposed to 1% magnesium sulphate solution for 60 days, whereas they declined to 70% and 58%, respectively, after 120 days of immersion.

Chromium oxide nanoparticles in‐situ immobilized onto nitrogen‐doped carbon plates with boosted catalytic activity toward nitrogen reduction reaction

AbstractA chromium oxide‐based nanocomposite (Cr2O3@NC) is designed and prepared via a simple pyrolysis route with Cr‐based metal organic framework (MOF) as a template. The research results indicate that Cr2O3 nanoparticles have an average size of ~70 nm and are in situ formed and imbedded onto the Cr‐based MOF‐derived 2D N‐doped carbon microplates. When employed as an inexpensive electrocatalyst for nitrogen reduction reaction (NRR) to synthesize ammonia, Cr2O3@NC demonstrates an improved and stable catalytic activity in comparison with bare Cr2O3. A large ammonia production rate of 29.42 μg mg−1cat h−1 under a lower potential of −0.4 V versus reversible hydrogen electrode (RHE) can be acquired with a Faradic efficiency of 9.89% in sodium sulphate solution. Additionally, a satisfactory selectivity can also be achieved without hydrazine byproduct. The greatly promoted catalytic activity of Cr2O3@NC is regarded to be concerned with its desirable structures such as 2D planar topological structure with expanded active surface area, abundant catalytic sites, and effective combination with conductive carbon.

Effect of Anions on Deformation of Gallium-Based Liquid Metal in Solution.

In this study, deformation behaviors of gallium-based liquid metals in acidified cupric sulfate or cupric chloride solutions with varying concentrations of chloride anion or sulfate anion were investigated to explore their potential applications in soft machines and electronics. Gallium-based liquid metals are known for their unique deformability, making them promising materials for various fields. Previous research has shown that deformation of the liquid metal can be achieved in the presence of acidified cupric or ferric salts. However, the specific influence of different anions on the deformation process remains unclear. Our findings indicate that the deformation rate of the liquid metal increases with higher concentrations of chloride ions and decreases with higher concentrations of sulfate ions in the solution. UV-vis absorbance spectra of the solutions were analyzed to identify the formation of hydrated cupric cations. It was observed that increasing the concentration of Cl- ions promotes the formation of cupric-chloro complexes, thereby reducing the concentration of hydrated cupric ions in the solution. Furthermore, the addition of sulfate ions to the solution enhances the ionic strength of the medium, leading to the dissociation of cupric-chloro complexes. Additionally, sulfate ions can form insoluble layers with gallium ions, which impede the deformation of the liquid metal. The deformation rate of the liquid metal was found to be inversely correlated with the concentration of cupric ions in the solution. These results provide valuable insights into the deformable behavior of gallium-based liquid metals and their potential applications in liquid metal-based soft robots. This study highlights the importance of understanding the role of different anions in the deformation process of liquid metals, shedding light on the design and optimization of soft machines and electronics utilizing these materials.

Sulfate attack on portland-dolomite cement exposed to sodium sulfate solution at 5 ℃ and 20 ℃

The purpose of the study is to investigate the sulfate resistance of portland-dolomite cement (PDC) with varying dolomite contents, when exposed to sodium sulfate solution at 5 ℃ and 20 ℃. Visual appearance, expansion, mass change, and compressive strength of PDC mortars were tested, and XRD, FTIR, and SEM analyses were conducted to examine deterioration products and microstructure. Results indicate that at 20 ℃, the incorporation of 10 % dolomite in PDC had a negligible impact on sulfate resistance, whereas higher dolomite replacements of 20 % and 30 % notably diminished it. In contrast, exposure at 5 °C led to more severe deterioration in all PDC samples, regardless of dolomite content, and the higher dolomite content, the poorer resistance to sulfate attack. The increased formation of ettringite and gypsum resulted in reduced sulfate resistance of PDC at 20 ℃. However, at 5 ℃, the presence of dolomite significantly promoted the formation of thaumasite at later stages, which caused initial ettringite and subsequent late-stage thaumasite sulfate attack, ultimately leading to the failure of PDC. The findings suggest that PDC should be carefully considered when used in sulfate-rich environments, particularly at low temperatures.

Modeling nonlinear stress-strain model for sulfate dry-wet cycle erosion of concrete: considerations for the initial compaction stage

Sulfate dry-wet cycle erosion significantly affects the mechanical properties of concrete. Investigating the uniaxial compressive stress-strain relationship under these conditions is essential for developing accurate constitutive models. This study analyzes the uniaxial stress-strain curves of concrete subjected to dry-wet cycles in 5% and 15% sulfate solutions. The results show that the initial compaction phase in the stress-strain relationship is particularly pronounced under increasing sulfate concentrations and cycle counts. The concrete experiences an extended compaction phase, which accounts for up to 35.71% of the total strain process. This finding challenge traditional constitutive models, which struggle to accurately describe this phase. To address this issue, the study develops a nonlinear stress-strain model for concrete, incorporating the initial damage caused by sulfate dry-wet cycle erosion, based on Weibull statistical damage mechanics principles. The research indicates that the effects of sulfate concentration and cycle count are predominantly reflected in the pronounced nonlinearity of the skeleton strain function’s opening size (a) and shape characteristics (b), modeled using a fourth-degree polynomial. The model demonstrates an excellent fit to experimental data with an R2 value of 0.99989, showing that the proposed nonlinear stress-strain relationship effectively captures the uniaxial mechanical behavior of concrete under sulfate dry-wet cycle erosion and provides a robust framework for developing constitutive models in such environments.