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The interfacial compatibility between inorganic particles and polymer is crucial for ensuring high performance of composites. Current efforts to improve interfacial compatibility preferentially rely on organic modification of inorganic particles, leading to their complex process, high costs, and short lifespans due to aging and decomposition of organic modifiers. However, the fabrication of inorganic particles free from organic modification that is highly compatible in polymer still remains a great challenge. Herein, a novel facet‐engineered inorganic particle that exhibit high compatibility with widely used polymer interface without organic modification is reported. Theoretical calculations and experimental results show that (020) and (102) facets of inorganic particles modulate local coordination environment of Ca atoms, which in turn regulate d‐orbital electron density of Ca atoms and electron transfer paths at interfaces between polymer and inorganic particles. This difference alters the molecular diffusion, orientation of molecular chains on surface of inorganic particles, further modulating interfacial compatibility of composites. Surprisingly, the facet‐engineered inorganic particles show exceptional mechanical properties, especially for tensile strain at break, which increases by 395%, far superior to state‐of‐the‐art composites counterparts. Thus, the method can offer a more benign approach to the general production of high‐performance and low‐cost polymer‐inorganic composites for diverse potential applications. [ABSTRACT FROM AUTHOR]

We focused on the efflorescence induced microstructural evolution of ettringite-rich systems prepared with calcium aluminate cement (CAC) and anhydrite. The effects of anhydrite on the visible efflorescence, and the corresponding capillary absorption of CAC-anhydrite mortars were revealed. The composition and microstructure of efflorescence-causing substances were investigated by optical microscope, in-situ Raman spectroscopy, scanning electron microscope, energy dispersive spectrometer, thermogravimetric analysis, and differential scanning calorimetry, at multi-scales. Results indicate that, besides the calcium carbonate, ettringite is another main component of efflorescence-causing substances. Compared with the neat CAC mortars, the addition of anhydrite has a significant effect on the degree of efflorescence by acting on the composition of hydration products and pore structure. In addition, methods are proposed for the prevention of efflorescence of CAC-anhydrite binary system. [ABSTRACT FROM AUTHOR]

Underground oil storage is the development trend for large-scale energy storage. The anhydrite rock cavern oil storage (ARCOS) has the potential to become an oil storage medium, and the tightness and stability are the key parameters to ensure the safety of oil storage. Thus, the novelty of this paper aims to analyze the tightness and stability of ARCOS from experimental and numerical research. In detail, a series of anhydrite rock experiments (permeability experiments, rock surface experiments, breakthrough experiments, water solubility experiments, component experiments and microstructure experiments) are conducted to evaluate the tightness of ARCOS based on Taian's anhydrite mine. A 3D numerical model is built to analyze the stability of ARCOS in two conditions (long-term and injection–production) by the three-dimensional explicit finite difference method. The results show that the permeability of anhydrite rock is low ( 10 - 20 - 10 - 19 m 2 ), the anhydrite rock has high breakthrough pressure (9.61 MPa) which is less than maximum operating pressure (5.52 MPa), the solubility of anhydrite is only 0.011 g/100 g H2O. The maximum displacements of ARCOS under long-term and injection–production are 0.13 m and 0.18 m, respectively. The simulation results show great stability under the two working conditions. The research has a reference for the development of large-scale underground ARCOS. Highlights: A novel underground oil storage method that uses anhydrite rock caverns is proposed. A series of anhydrite rock experiments are conducted to analyze the tightness of oil storage. A 3D numerical model is built to analyze the stability of anhydrite rock cavern. The application and prospects of anhydrite rock cavern oil storage are analyzed. [ABSTRACT FROM AUTHOR]

This case study investigates five fly ashes with high CaO and SO3 levels in their chemical composition and compares the apparent influence of the presence and absence of anhydrite on compressive strength. Another distinguishing feature of the above ashes is that they, more or less, naturally contain anhydrite. Two different series of mixed proportions were adopted. Series 1 is designed to understand the maximum possible replacement level of fly ash. Series 2 is designed to understand the effect of anhydrite on compressive strength development. The mineral composition and glass phase of fly ashes were determined by X-ray diffraction Rietveld analysis. As a result of this study, we have found that concrete containing anhydrite-rich fly ash exhibits a higher strength than concrete containing anhydrite-free fly ash at all ages. The compressive strength increases with an increasing fly ash replacement ratio when anhydrite-rich ash is used, but strength decreases when the replacement level exceeds a certain point. The optimal amount of anhydrite was 2 ± 0.5 kg/m3 of concrete, excluding the anhydrite contained in cement. [ABSTRACT FROM AUTHOR]

Abstract The dissolution of soluble rocks (gypsum/anhydrite) beneath the Mosul Dam by water seepage has been observed upon the initial impoundment; consequently, several sinkholes have been manifested in the vicinity of the dam site. Traditional grouting has been envisaged as a potential remedy; however this measure has not eradicated the problem. The main purpose of this study is to overcome the solubility of the gypsum/anhydrite rocks using chemical grouts. Rock samples were acquired from the Fatha Formation outcrop and problematic layers of brecciated gypsum situated at varying depths beneath the Mosul Dam. Two commercially available liquid polymers, polyurethane (PU) and a mixture of acrylic and cement (ARC) were used to investigate their sealing performance in halting of the solubility of the rocks (gypsum/anhydrite). To simulate the dissolution phenomenon under the influence of artificial hydraulic pressure of the dam and the water flow in its abutments, two distinct laboratory models were devised. The outcomes from the experimental study on both untreated and treated samples revealed that the acrylic-cement composite (ARC) and polyurethane (PU) are influential polymers in halting the solubility of the gypsum rock samples under both factors of water pressure and high-velocity water flow.

This study presents an analytical approach for evaluating the reliability of anhydrite rock tunnels, focusing on their characteristic swelling behavior. Anhydrite rocks, prone to significant expansion upon moisture exposure, pose a challenge in tunnel construction, potentially leading to structural issues such as floor heave and lining damage. To address this, this research develops an elastic swelling analytical solution based on humidity stress field theory, enabling the assessment of time-dependent stress and deformation changes in anhydrite tunnels. The solution's applicability is demonstrated through its application to the Lirang tunnel. The investigation into the effects of support pressure, swelling time, and reserved deformation on tunnel reliability reveals that circumferential stress at the tunnel wall increases by 13.94% and 21.86% for swelling periods of 30 and 365 days, respectively. Similarly, radial displacement escalates by 22.97% and 35.93% over these periods, highlighting the significant impact of swelling behavior. Using a spreadsheet-based First Order Reliability Method (FORM) for analysis, this study finds that the original design of the Lirang tunnel did not meet the desired reliability standards under swelling conditions. However, strategic adjustments in construction variables, such as increasing support pressure to 1.2 MPa or enhancing reserved deformation to 59 mm, elevated the tunnel's reliability to meet safety requirements. This research provides a vital framework for assessing and enhancing the reliability of anhydrite rock tunnels, considering the long-term effects of swelling. It underscores the importance of incorporating swelling behavior in the design and construction of tunnels in anhydrite rock formations, offering valuable insights for optimizing tunnel stability in such challenging geological conditions. [ABSTRACT FROM AUTHOR]

During the Early Cretaceous, massive evaporite accumulations formed in the opening South Atlantic. However, the depositional model of these salts is still poorly constrained at the scale of the West African margin. The present study focuses along the proximal domain of the south Gabon‐Congo‐Cabinda margin and is based on (i) log interpretations of 246 wells crossing undeformed to weakly deformed evaporite intervals and (ii) a structural characterization of the basement. The evaporites show 11 regional evaporite depositional cycles (CI–CXI) bounded by meter‐thick shale beds. The cycles display alternating meter‐scale carnallite‐halite beds that can be correlated over several hundred kilometres, and CVI, CVII, CVIIIa and CX culminate in localized tachyhydrite accumulations. Cross section correlations and isopach maps help to understand the palaeogeographical evolution of each cycle and depositional environments that evolved from relatively deep at the base of cycles, to very shallow at their top. CI formed a mosaic of halite‐prone depocenters deposited in pre‐salt topographic relief. CII and CIII were deposited uniformly over a flattened basin in a highly extended brine pond. From CIV to CVIIIa, the stratigraphic architecture of the salts was shaped by freshwater inflow sourced from the north and possible basement movements. This setting, together with an increased confinement of the proximal domain from the distal one with basin drawdown, favoured the development of depocenters with perennial subaqueous conditions and extreme salinities, in which more than 70 m of tachyhydrite accumulation could locally be preserved. From CVIIIb to CXI, the basin returned to a flat depositional setting without well‐developed depocenters and with increasing subsidence westwards. Marine influx increased starting from CX, allowing the deposition of sulphate beds. The salt section is capped by anhydrite deposits interbedded with clastic and dolomite, before the final marine invasion of the basin. For the first time, this study provides a large‐scale depositional tectonostratigraphic setting of the Aptian salts in the proximal domain of the West African margin. The results are of interest for K‐Mg salts exploration resources in the Aptian and pave the way for further investigation of the salt depositional environment in the distal domain of the margin. [ABSTRACT FROM AUTHOR]

This article presents the results of research on the development of chemically resistant polymer–mineral casting composites based on industrial waste. The aim of this work is to develop a technological basis for obtaining effective inorganic fillers and highly filled composites for use in chlorine-containing environments. On the basis of theoretical data, mineral fillers and a polymer binder for filling composites were selected, optimal quantities of input hardeners and an appropriate thermal curing mode were determined, and the influence of the filling degree on the properties of composites was studied. The influence of various factors on the properties of the obtained composites was also studied, and the possibility of using local raw materials to obtain special-purpose composites was investigated. Ash from a thermal power plant (TPP) was used as an acid-resistant filler in composites. Two components were chosen as binders: phenol formaldehyde resin and mineral filler (TPP ash). As the third component, hydrolytically active fillers—anhydrite, phosphogypsum and phosphate slag—were used. The degree of filling has a significant influence on the properties of composites, including the compressive strength, chemical resistance and degree of curing, the values of which were elucidated across a wide range of composite variations based on the degree of filling. The conducted research allowed us to establish the limit of admissible anhydrite content, which should not exceed 15 mas.%. To optimize the chemical resistance and durability of the composites of the investigated substances, the method of mathematical planning was used. According to the results of this study, the optimal compositions of composites, in terms of anhydrite, phosphogypsum and phosphorus slag contents, were selected. At the maximum possible degree of filling, these composites exhibit high target characteristics. [ABSTRACT FROM AUTHOR]

An experiment was conducted comprising of six corn hybrids that were subjected to drought and irrigated environment in separate columns in soil-plant-atmosphere-research (SPAR) cubes. The treatments and hybrids in SPAR cubes were replicated four times and a two factorial randomized complete block design (RCBD) was used to analyze the effect of drought on hybrids and their effects on traits. Significant drought × hybrid interactions were observed for most of the parameters. All the traits observed under this study were affected by drought conditions. Root volume (RV) and root shoot ratio (RSR) increased, and number of root tips (NRT), number of root forks (NRF), and number of root crossings (NRC) were drastically reduced under drought conditions. The photosynthetic rate (Phot) declined by 57.96% and electron transport rate (ETR) by 54.60% and was negatively correlated with plant height (PH) and root number (RN) during drought stress. Chlorophyll content (SPAD) showed a non-significant correlation with all the traits. As per results, there were significant differences among corn hybrids for different traits studied under the SPAR setup, which indicates that this setup successfully creates differences in treatments. A cumulative drought stress response index (CDSRI) was worked out. DKC-6581 and N61X-3110 were found to be highly drought tolerant as per our findings. [ABSTRACT FROM AUTHOR]

The world-class Jinding deposit in SW China has ~15 Mt of Zn and Pb metals combined, in an evaporite dome containing amounts of gypsum/anhydrite. These gypsum and anhydrite are mainly located in limestone breccias (Member I), gypsum-bearing complexes (Member III), and red mélange, with some occurring as veins in clast-free sandstone (Member IV) and as fractures/vugs of host rock. The gypsum/anhydrite and dome genesis remain equivocal. The gypsum in limestone breccias and in red mélange with flow texture contains numerous Late Triassic Sanhedong limestone fragments. The δ34S (14.1%–17%), δ18O (9.7%–14.6%), and 87Sr/86Sr ratios (0.706913–0.708711) of these gypsum are close to the S-O-Sr isotopes of the Upper Triassic Sanhedong Formation anhydrite in the Lanping Basin (δ34S = 15.2%–15.9%, δ18O = 10.9%–13.1%, 87Sr/86Sr = 0.707541–0.707967), and are inconsistent with the Paleocene Yunlong Formation gypsum in the Lanping Basin (87Sr/86Sr = 0.709406–0.709845), indicating that these gypsum were derived from the Upper Triassic Sanhedong Formation evaporite but not from the Paleocene Yunlong Formation, and formed as a result of evaporite diapirism. The δ34S (14.3%–14.5%), δ18O (10.1%–10.3%), and 87Sr/86Sr ratios (0.709503–0.709725) of gypsum as gypsum–sand mixtures in gypsum-bearing complexes are similar to the 87Sr/86Sr ratios of gypsum in the Yunlong Formation of the Lanping Basin and Cenozoic basins in the northern part of the Himalayan–Tibetan orogen, suggesting that the material source of this gypsum was derived from the Yunlong Formation, and formed as a result of gypsum–sand diapirism. The gypsum veins in clast-free pillow-shaped mineralized sandstone and the gypsum in host rock fractures and vugs formed after the supergene minerals such as smithsonite. The δ34S (−16.3%~−12.7%) and δ18O (−9.8%~−4.7%) of this gypsum indicate that the gypsum is of supergene origin with sulfate derived from the reoxidation of reduced sulfur. We confirmed that the Jinding dome is genetically related to diapir of the Late-Triassic Sanhedong Formation evaporite. Clast-free sandstone and gypsum-bearing complexes in the dome were produced by diapir of the Paleocene Yunlong Formation unconsolidated gypsum–sand mixtures. [ABSTRACT FROM AUTHOR]

In order to optimally design earthen dams, it is inevitable to know the characteristics of its construction, including geological and geotechnical characteristics, as well as awareness of behaviors such as permeability and bedrock permeability changes during water intake and long-term exploitation of the dam reservoir. When the stone bed of the dam construction consists of materials containing gypsum and anhydrite, then these materials will last longer against the continuation of anti-flow. In the study of Hazdar, the influence of the primary permeability values of the Sedang-Basdter of Merash Dam construction, which consists of joints containing gypsum and anhydrite, and hydraulic gradient values on the speed and process of the expansion of the joint, along with the dissolution rate of materials containing gypsum and anhydrite, has been investigated. The amount of expansion of each joint for the duration of a dam is calculated and considering the amount of hydraulic gradient drop in the body of the dam and manat with gypsum, the water loss rate of the dam is evaluated. The results obtained from the circulation test with the hydraulic gradient find that in the length of the water flow path, the rate of increase in the diameter of the joint decreases gradually. Also, along the length of the water flow, in the places where there is purer gypsum, the rate of increase in the diameter of the seams is higher than the rest. [ABSTRACT FROM AUTHOR]

Abstract The interfacial compatibility between inorganic particles and polymer is crucial for ensuring high performance of composites. Current efforts to improve interfacial compatibility preferentially rely on organic modification of inorganic particles, leading to their complex process, high costs, and short lifespans due to aging and decomposition of organic modifiers. However, the fabrication of inorganic particles free from organic modification that is highly compatible in polymer still remains a great challenge. Herein, a novel facet‐engineered inorganic particle that exhibit high compatibility with widely used polymer interface without organic modification is reported. Theoretical calculations and experimental results show that (020) and (102) facets of inorganic particles modulate local coordination environment of Ca atoms, which in turn regulate d‐orbital electron density of Ca atoms and electron transfer paths at interfaces between polymer and inorganic particles. This difference alters the molecular diffusion, orientation of molecular chains on surface of inorganic particles, further modulating interfacial compatibility of composites. Surprisingly, the facet‐engineered inorganic particles show exceptional mechanical properties, especially for tensile strain at break, which increases by 395%, far superior to state‐of‐the‐art composites counterparts. Thus, the method can offer a more benign approach to the general production of high‐performance and low‐cost polymer‐inorganic composites for diverse potential applications.

The promotion of non-autoclaved production technology is vital to realize long-term sustainable development of pipe pile industry. By optimizing the mix proportion and curing condition, non-autoclaved high-strength pile concrete can be produced, thereby facilitating the pipe pile industry. This study was undertaken to prepare high-strength concrete with anhydrite and ground granulated blast-furnace slag (GGBS). The effects of anhydrite, GGBS and steam curing on workability of cement paste as well as compressive strength, hydration process and microstructure of concrete were investigated. Experimental results showed that the addition of anhydrite and GGBS increased the initial flowability and affected the setting time of cement paste. Steam curing promoted the formation of ettringite and significantly improved the early strength of concrete. Anhydrite and GGBS incorporation brought SO42- and amorphous phase into hydration reaction, which was further accelerated by steam curing. For the steam-curing concrete with 5 % anhydrite and 20∼30 % GGBS, compressive strength was more than 108 MPa at 90 days. This study provided a guide for the production of non-autoclaved high-strength pile concrete with anhydrite and GGBS in pipe pile industry.

Water seepage flow can dissolve soluble minerals that exist in rock formations. With the development of the excavated area due to dissolution, the water seepage velocity (discharge) into the dissolved rock will also increase. Therefore, water seepage and dissolution propagation are two interrelated processes. Mosul Dam foundation has experienced these processes since its construction, resulting in karstification in the reservoir and foundation of the dam. The present seepage-dissolution measure to minimize this phenomenon relies on traditional cementitious grouts. However, this measure has not been able to address the issue effectively. Currently, there are a few studies on the chemical remediation of soluble rocks under the influence of high-velocity water flow and water pressure. Therefore, the first part of the current study focuses on the impact of high-velocity water flow and water pressure on the dissolution acceleration of gypsum/anhydrite rocks. In the second part, the waterproof capacity of silica colloidal and its impact on the solubility reduction of the rocks is evaluated. Two distinct laboratory models were designed to simulate rock dissolution in the dam abutments and under the dam. Two sets of experiments were conducted on untreated and silica-treated samples. The experiments were executed on the samples extracted from Fatha Formation outcrop and problematic layers of brecciated gypsum situated at varying depths of the Mosul Dam foundation. The obtained findings reveal that the colloidal silica grout markedly prevents the water seepage impact on the soluble rock and that it can be very useful as an alternative to cement-based grouts. [ABSTRACT FROM AUTHOR]

The new mineral naalasite (IMA2023–027), NaAl(AsO3OH)2⋅H2O, was found at the Torrecillas mine, Iquique Province, Chile, where it is a secondary alteration phase associated with anhydrite, juansilvaite, magnesiokoritnigite and a lavendulan-like phase. Naalasite occurs in tightly intergrown aggregates and druses of equant crystals. Crystals are light to medium pink and transparent, with vitreous lustre and white streak. The Mohs hardness is ~3½. The density is 3.19(2) g⋅cm–3. Optically, naalasite is uniaxial (+), with ω = 1.630(3) and ɛ = 1.660(3) (white light). The empirical formula (based on 9 O apfu) is Na0.92Al0.61Fe3+0.39As2O9H4.07. Naalasite is trigonal, space group R 32, with cell parameters: a = 8.494(4), c = 26.430(13) Å, V = 1651.5(4) Å3 and Z = 9. The structure, refined to R 1 = 3.78% for 641 I > 2σ I reflections, is based on a loose 3D framework of alternating AsO3OH tetrahedra and AlO6 octahedra. The structure is topologically equivalent to that of nafeasite and can be regarded as its Al analogue, even though nafeasite is monoclinic with space group C 2. [ABSTRACT FROM AUTHOR]

Utilization of Portland cement to initiate the dissolution of blast furnace slag (BFS) in super-sulfated cement is limited by low slag substitution level and poor early strength. In this study, a new activator composed of anhydrite and calcium sulfoaluminate cement clinker was proposed to enhance the utilization of BFS in super-sulfated cement. Tests were conducted on the compressive strength, autogenous shrinkage, hydration heat, pH and conductivity of the composites. XRD, 29Si NMR, BSE and MIP were employed. Results reveal that ettringite, gypsum and C-S-H are the primary hydration products. The composites with 20% activator display the highest compressive strength and shrinkage accompanied by the highest hydration heat and degree, as well as the highest quantity of monomer silica tetrahedrons and the largest volume of fine pores. Thermodynamic modeling confirms the critical value for the activator-substitution level. Additionally, the activator-BFS composite exhibited significantly lower carbon emissions compared to Portland cement. [ABSTRACT FROM AUTHOR]

The Dahal Hit cavern in Central Saudi Arabia is the only locality where the Tithonian Hith Anhydrite Formation is exposed in the Middle East. In 2010, a 28.5-m interval in the 90-m-thick Hith Formation was logged and described in the cavern as part of a study to evaluate its sedimentological and sequence-stratigraphic architecture and to identify potential high-permeability layers within the seal of the world's most prolific petroleum system. Seven facies types were interpreted as reflecting sabkha (subaerial) or salina (subaqueous) settings, and their vertical stacking patterns revealed that the logged interval consists of three transgressive–regressive cycles and part of a fourth cycle. The cavern was revisited in 2016 but only to find that the water level had risen by about 50 m rendering further geological studies impossible. The higher level of the water suggests that the cavern was flooded by the flow in the subsurface of treated sewage water released into a former quarry. The quarry is situated about 10 km southeast of the cavern, and the storage of water in it started in 2008. The flow pathways to the Dahal Hit cavern are apparently well-connected karsts, caverns, and high-permeability flow zones present in dolomite layers. [ABSTRACT FROM AUTHOR]

The sky is the limit with regards to the societal impact nanomaterials can have on the lives. However, in this study, it is shown that their potential is out of this world. The planet Mars has an abundant source of calcium sulfate minerals and in this work, it is shown that these deposits can be the basis of transformative nanomaterials to potentially support future space endeavors. Vitally, the methods applied are low cost and require no specialized instruments of great expertise, strengthening the potential involvement of nanotechnology in sustaining Martian inhabitation. Through a scalable eco‐friendly liquid processing technique performed on two common terrestrial gypsum, this simple method presented a cost‐efficient procedure to yield suspensions of large aspect ratio anhydrite nanobelts with long‐term stability that are characterized through scanning electron microscopy and Raman spectroscopy. Transmission electron microscopy shows nanobelts to have a mesocrystal structure, with distinct nanoparticle constituents making up the lattice. Unexpectedly, anhydrite nanobelts have remarkable electronic properties, namely a bandgap that is easily tuned between semiconducting (≈2.2 eV) and insulating (≈4 eV) behaviors through dimensional control measured via atomic force microscopy. To demonstrate the application potential of the nanobelts; optoelectronic, electrochemical, and nanocomposite measurements are made. [ABSTRACT FROM AUTHOR]

Swelling of anhydrite rock causes serious damage to the tunnel and generates high additional costs in the process of tunnel construction and operation and has gradually become one of the main factors that threaten the safety of the tunnel. It is extremely difficult to predict swelling pressures and deformations accurately based on conventional swelling constitutive models. Thus, a new practical swelling constitutive model of anhydrite for tunnel engineering has been developed. First, swelling tests of natural anhydrite samples focusing on the time effect have been designed and conducted, whose test results show that swelling strain-time can be described by the S-curve model and that swelling stress-strain can be described by the quadratic model. Second, a swelling constitutive model with considering the time effect has been developed to reproduce the swelling behavior of anhydrite observed in swelling tests. This model can track the evolution of swelling activity in tunneling, which has practical significance for process simulation and process control of swelling disaster. Then, this model has been implemented within ANSYS for numerical simulation of the Lirang tunnel. Based on simulation results, useful measures have been proposed. Satisfactory results have been achieved according to the feedback from the site. [ABSTRACT FROM AUTHOR]

Secondary ion mass spectrometry was used to test the δ18O and δ34S nanogram‐scale homogeneity of a suite of candidate sulfate minerals, ultimately selecting three barite, two anhydrite, and two gypsum samples from the Royal Ontario Museum that have repeatabilities for their SIMS measurements of better than ±0.39‰ and ±0.37‰ (1s) for oxygen and sulfur isotope ratios, respectively. Metrological splits of each of the seven materials were sent to multiple gas source isotope ratio mass spectrometry laboratories in order to establish their absolute 18O/16O and 34S/32S ratios. The inter‐laboratory results of GS‐IRMS analyses yielded reasonably narrow ranges in δ18OVSMOW, whereas larger variations in δ34SVCDT values were found between the results from the gas source laboratories. All samples have good reproducibility within laboratories of GS‐IRMS 103δ18O values of between ±0.24‰ and ±0.44‰ (1s). The reproducibility within laboratories of GS‐IRMS 103δ34S values range from ±0.07‰ to ±0.99‰ (1s). Here we also discuss some of the current analytical limitations affecting these isotope‐mineral systems. A total of 256 metrological splits have been prepared from each of these seven materials; these aliquots will be made available to the global geochemical community. [ABSTRACT FROM AUTHOR]

This case study investigates five fly ashes with high CaO and SO3 levels in their chemical composition and compares the apparent influence of the presence and absence of anhydrite on compressive strength. Another distinguishing feature of the above ashes is that they, more or less, naturally contain anhydrite. Two different series of mixed proportions were adopted. Series 1 is designed to understand the maximum possible replacement level of fly ash. Series 2 is designed to understand the effect of anhydrite on compressive strength development. The mineral composition and glass phase of fly ashes were determined by X-ray diffraction Rietveld analysis. As a result of this study, we have found that concrete containing anhydrite-rich fly ash exhibits a higher strength than concrete containing anhydrite-free fly ash at all ages. The compressive strength increases with an increasing fly ash replacement ratio when anhydrite-rich ash is used, but strength decreases when the replacement level exceeds a certain point. The optimal amount of anhydrite was 2 ± 0.5 kg/m3 of concrete, excluding the anhydrite contained in cement.

The deterioration of anhydrite rock exposed to a freeze–thaw environment is a complex process. Therefore, this paper systematically investigated the physical and mechanical evolutions of freeze–thawed anhydrite rock through a series of multi-scale laboratory tests. Meanwhile, the correlation between pore structure and macroscopic mechanical parameters was discussed, and the deterioration mechanisms of anhydrite rock under freeze–thaw cycles were revealed. The results show that with the increase in freeze–thaw processes, the mechanical strength, elastic modulus, cohesion, proportions of micropores (r ≤ 0.1 μm), and PT-Ipore throat (0–0.1 μm) decrease exponentially. In comparison, the mass variation, proportions of mesopores (0.1 μm < r < 1 μm), macropores (r ≥ 1 μm), and PT-II pore throat (0.1–4 μm) increase exponentially. After 120 cycles, the mean porosity increases by 66.27%, and there is a significant honeycomb and pitted surface phenomenon. Meanwhile, as the freeze–thaw cycles increase, the frost resistance coefficient decreases, while the damage variable increases. The correlation analysis between pore structure and macroscopic mechanical parameters shows that macropores play the most significant role in the mechanical characteristic deterioration of freeze–thawed anhydrite rock. Finally, it is revealed that the water–rock expansion and water dissolution effects play a crucial role in the multi-scale damage of anhydrite rock under the freeze–thaw environment. [ABSTRACT FROM AUTHOR]

Calcium sulfoaluminate cement (CSA) has excellent chloride (Cl−) binding capacity, which is significantly influenced by the existence of calcium sulfate within mixes. However, impacts of dosage and type of the calcium sulfate on the binding performances and mechanisms are still unclear. In the paper, these impacts in CSA clinker-premixed Cl− system were thoroughly explored with experimental studies, including parameters of fresh properties, hardened properties, and mineralogy aspects. Results showed that calcium sulfate accelerated CSA hydration, reduced the setting time, and sharply decreased Cl− binding due to promoting formation of ettringite (AFt). The stability of Friedel's or Kuzel's salts formed by binding of monosulphoaluminate (AFm) and Cl− was worse than that of AFt. Compressive strength reduced slightly with calcium sulfate increasing. Compared with anhydrite, dihydrate gypsum reduced shrinkage, improving volume stability. [ABSTRACT FROM AUTHOR]

The expansion of irrigated agriculture and the overexploitation of groundwater in the Tabeditt region lead to a serious deterioration of the chemical quality of water. The compilation of hydrogeological and geophysical studies is essential in order to assess the quality of the Plio-Quaternary waters and to determine the origin of the salinization of these waters. In this study, hydrochemical analyses were carried out on groundwater samples in the Tabeditt region. Hydrochemical data have shown that the salinity in this area could exceed 6 g/L. The interpretation of major ion analyses demonstrates that mineralization is controlled by natural processes. The mineralization process consists of the dissolu-tion of evaporite minerals, namely gypsum, anhydrite, and halite. The geoelectrical study is carried out to obtain information about the distribution and quality of water in the Plio-Quaternary. Interpreta-tion of the resistivity models show the presence of two main zones: the first, near Tabeditt Wadi, is characterized by low values, indicating the influence of salt water in the groundwater and the second, located on the right bank of Wadi Jmal, is characterized by variable resistivity values, generally high, indicating the lateral changes in lithological facies, and the presence of fresh water. In such an arid region suffering from scarcity and degradation (or depletion) of water resources, it is important to implement a master plan that keeps under control the number of wells both known and unknown ones taping these aquifers. [ABSTRACT FROM AUTHOR]

Dolomite reservoirs flourished during arid climatic periods in the Middle East, primarily in the Permo-Triassic, Upper Jurassic, and Oligo-Miocene formations. These dolomitized reservoirs are frequently linked to evaporites, exhibit isotopically enriched signatures, and tend to occur predominantly in the more restricted regions of carbonate platforms. These observations strongly support their origin through sabkha and evaporative reflux processes. Consequently, dolomite formation and distribution are primarily influenced by early diagenetic processes and climatic conditions during arid periods. Dolomitization has exerted a significant influence on reservoir properties within the studied carbonate platforms. Porosity distribution and variation are jointly controlled by several factors, including dolomite content, texture, crystal size, anhydrite abundance, dolomite cementation, and the extent of burial compaction. While dolomite textures can vary from fabric-preserving to fabric-destroying, the overall reservoir properties exhibit an ascending pattern from intertidal to shoal facies. This trend is primarily determined by the proximity to the source of dolomitizing brines. The downward percolation of brines, coupled with decreasing dolomitizing potential, leads to an increase in dolomite crystal size within depositional cycles as one moves further away from the anhydrite facies. Proximal areas, characterized by fine-grained intertidal and lagoonal facies, are more susceptible to anhydrite cementation and overdolomitization, resulting in significant porosity reduction. Conversely, in more distal regions, reservoir quality substantially improves, particularly in areas dominated by sucrosic dolomite or grain-rich facies. While this trend may be altered by compaction during burial, it underscores the crucial role of dolomitization in preserving porosity, especially in deeply buried carbonate reservoirs. [ABSTRACT FROM AUTHOR]

Cementitious materials employed in deep‐sea marine engineering must have excellent durability. In this study, the durability of a ternary binder‐based paste composed of Portland cement, calcium aluminate cement, and anhydrite was investigated after deep‐sea exposure at a depth of 3515 m for 438 days. The recovered paste specimen showed significant expansion. However, the hydrate phases in the ternary binder exhibited no changes with the exception of the formation of Friedel's and Kuzel's salts. One reason for this was the transformation from unstable monosulfate to stable ettringite under low‐temperature seawater conditions. However, the additional ettringite formation could lead to significant expansion of the paste specimen. [ABSTRACT FROM AUTHOR]

This study investigates the potential of α‐HH formation from gypsum originating from activated and hydrated natural anhydrite. For this, gypsum was prepared from natural anhydrite and treated in an autoclave process under hydrothermal conditions (150 mbar and 130 °C). For comparison, fgd‐gypsum was treated accordingly. Succinic acid, maleic acid and additional α‐HH seeds were used as crystallization aids. QXRD results show the transformation of gypsum into hemihydrate after a residence time of 8 h and 4 h. SEM images distinguish the α‐HH and β‐HH modifications. For fgd‐gypsum pellets, the β‐HH modification predominates. Gypsum from natural anhydrite shows α‐HH crystals with succinic acid and without crystallization aid. When maleic acid is present, crystals appear as intermediates between α‐HH and β‐HH. To isolate the effect of the crystallization aids, α‐HH and succinic acid were used separately and simultaneously. SEM images indicate the formation of α‐HH from β‐HH. The shapes of the original β‐HH conglomerates are still visible, yet acicular crystals with smooth surfaces (α‐HH) are visible at a high magnification. Longest crystals appear when α‐HH and succinic acid are used simultaneously indicating a synergetic effect of both crystallization aids. [ABSTRACT FROM AUTHOR]

At mid-ocean ridges (MORs), seawater carrying dissolved sulfate (SO4) infiltrates the oceanic crust. Hydrothermal fluid emissions from such systems have much lower δ34S and sulfur is mostly present as reduced sulfide, albeit in lower total sulfur concentrations than in seawater. This has been explained by anhydrite formation and sulfate reduction based on petrographic evidence and mass balance considerations. Here, we utilize the chemical and stable isotope (δ34S, δ18O) systematics in natural anhydrite and pyrite from various locations along the submarine and on-land section of the Mid-Atlantic ridge near Iceland to quantify the key variables that control anhydrite formation and sulfate recycling in the oceanic crust. Hydrothermal anhydrite exhibited δ34S values of +20.6 ± 1.0‰ and δ18O values between +2.4 to +25.3‰. Volcanogenic anhydrite in encrustations showed δ34S values of −1.7 to +21.4‰ and δ18O values between +1.4 and +38.0‰. Hydrothermal pyrite exhibited δ34S values ranging from +3.4 and +19.7‰. Comparison of the natural dataset with results from geochemical isotope modelling revealed that δ34S and δ18O values of anhydrite and pyrite were dependent on the isotope composition of the source fluid, extent of water–rock interaction, temperature, and redox conditions. Departures of δ34S and δ18O values in anhydrite from the source fluid were caused by progressive fluid-basalt interaction where lower δ34S and δ18O values reflected a change in sources of S and O from solely fluid to basaltic origin. The δ18O values of anhydrite were additionally affected by temperature. Quantitative formation of anhydrite mainly occurred at temperatures < 150 °C, whereas at elevated temperatures (>200 °C) reduction of seawater-sulfate to H2S and subsequent pyrite precipitation were found to limit anhydrite formation. Extending our calculations to the oceanic crust revealed that the majority of seawater-sulfate is sequestered into anhydrite (3–38 Tg S yr−1) in vicinity of MORs at < 200 °C at shallow depth (

This article presents the results of research on the development of chemically resistant polymer–mineral casting composites based on industrial waste. The aim of this work is to develop a technological basis for obtaining effective inorganic fillers and highly filled composites for use in chlorine-containing environments. On the basis of theoretical data, mineral fillers and a polymer binder for filling composites were selected, optimal quantities of input hardeners and an appropriate thermal curing mode were determined, and the influence of the filling degree on the properties of composites was studied. The influence of various factors on the properties of the obtained composites was also studied, and the possibility of using local raw materials to obtain special-purpose composites was investigated. Ash from a thermal power plant (TPP) was used as an acid-resistant filler in composites. Two components were chosen as binders: phenol formaldehyde resin and mineral filler (TPP ash). As the third component, hydrolytically active fillers—anhydrite, phosphogypsum and phosphate slag—were used. The degree of filling has a significant influence on the properties of composites, including the compressive strength, chemical resistance and degree of curing, the values of which were elucidated across a wide range of composite variations based on the degree of filling. The conducted research allowed us to establish the limit of admissible anhydrite content, which should not exceed 15 mas.%. To optimize the chemical resistance and durability of the composites of the investigated substances, the method of mathematical planning was used. According to the results of this study, the optimal compositions of composites, in terms of anhydrite, phosphogypsum and phosphorus slag contents, were selected. At the maximum possible degree of filling, these composites exhibit high target characteristics.

Gypsum-based self-leveling has been widely used for its good construction performance and economy. This paper investigated the influence mechanisms of three kinds of water-reducing agents (WRAs) on the properties of anhydrite-based self-leveling floor screeds (ASLF) through macroscopic performance characterization, rheological model fitting, TG-DSC, MIP, SEM, et al. The outcomes conducted that the types, densities, and lengths of the side chain groups of the WRAs had diverse effects on the hardening, rheological parameters, and crystal morphology of ASLF. In descending order, the influence was PCE > SMF > SNF. The anionic groups of PCE affected the crystal growth by adsorbing on the dominant surface of CaSO4·2H2O and reducing the crystal length-diameter ratio. Simultaneously, with the increase of PCE content, the steric resistance effect increased, and the thickness of the surface water film layer increased, resulting in a decrease in the final viscosity and yield strength. ASLF is a power-law fluid that fits the Hershel-Bulkle (H-B) model well. Compared with PCE, the hydration and hardening characteristics of ASLF mixed with SMF and SNF were similar, and the influence was smaller, but a larger amount was required to ensure flowability. The pore size distribution of ASLF-hardened bodies mixed with various superplasticizers was similar. The hardening properties of ASLF were investigated using a variety of methods in this study. Various types of WRAs were investigated for their effects on the hydration and hardening of anhydrite, providing important reference information for ASLF preparation and production.

The accumulation of gypsum waste (GW), such as flue gas desulfurisation gypsum and phosphogypsum, which remains in regulated stacks occupying considerable land resources, is causing significant environment problems worldwide. A promising strategy for treatment and recycling of GW is to convert GW into higher-valued anhydrite, but the traditional energy-intensive calcination method significantly increases the cost of recovery. Here, we report the first solid-like dehydration of gypsum to produce anhydrite at room temperature. Specifically, a 39 nm thick sulfuric acid film (NSF) was fabricated to extract water of crystallization from gypsum and simultaneously enable a phase transformation from gypsum to anhydrite via recrystallization. Using density functional theory calculations, we obtained the activity (0.025) of crystalline water in gypsum, which is higher than the corresponding value in NSF, so that the dehydration can occur spontaneously. Using our developed kinetic model, we attributed the acceleration of this transformation to the lower nucleation potential (56 kJ mol−1) of anhydrite and the more efficient transfer of the mass (several orders of magnitude higher than that for heating gypsum powders) required for growth. This model allows prediction of nucleation and growth contributions from kinetic data for any given recrystallization system. This work not only demonstrates a new type of recrystallization reaction driven by a nano-film reservoir, which differs from bulk solution–solid and gas–solid reactions but also provides a promising strategy for energy-efficient recycling of anhydrite from gypsum waste. [ABSTRACT FROM AUTHOR]

We carry out a chemical treatment (acidization or basification) of typical rock specimens in-situ, and characterize the emerging pattern resulting from the infiltration-precipitation scenario. Galena and limestone samples were treated with sulfuric acid, while pyrite was reacted with sodium hydroxide. Various infiltration techniques were employed, after selection of the most feasible method for each rock separately. The patterns of anglesite (PbSO4), anhydrite (CaSO4) and goethite (FeOOH) deposition presented different alteration modes of the bare rock textures. Among the three deposited minerals, only the anhydrite (CaSO4) displayed a band stratification. The formation of a Liesegang pattern in the rock of highest porosity indicates a plausible correlation between the band formation and a minimum porosity requirement. A banded rock of compact texture could then be formed by a cementation mechanism, governing the long time evolution of the rock. [ABSTRACT FROM AUTHOR]

The Daniudi gas field in China's Ordos Basin is located in the transitional zone between palaeo‐topographic highs and slopes, whereby dissolution‐collapse breccias are widespread within the palaeokarstic reservoir. Abundant cores, well logs and thin sections were used to study palaeo‐topography, palaeokarstic breccia types, diagenesis and reservoir pore characteristics. The results indicated that reservoir quality is controlled by lithology, palaeo‐topography and diagenesis. The extent of palaeokarstic reservoir dissolution was shown to be determined by lithologic differences, whilst only gypsiferous dolostones and finely crystalline dolostones emerged in reservoir formation. Palaeo‐topography was also found to regulate reservoir development. The reservoirs are primarily located 20 m below the Ordovician unconformity in palaeo‐topographic hills and palaeo‐topographic slopes, whilst their depth is palaeo‐topography dependent. Lithology and palaeo‐topography also coordinate the distribution of palaeokarst breccia facies. Clast‐supported and matrix‐supported chaotic breccias were found in argillaceous dolostone strata. However, crackle–mosaic breccias occurred in gypsiferous dolostones and crystalline dolostones, located in palaeogeomorphic residual hills and slopes. Reservoirs generally develop in crackle–mosaic breccias of Ma51 and Ma52 sub‐Members, the quality of such reservoirs is dependent on the development and distribution of palaeokarst breccia facies and diagenesis. Dissolution of dolomite and anhydrite nodules was found to result in moldic pores and dissolution‐enlarged pores. Overall, the most damaging effect on reservoir quality resulted from calcite cement infilling moldic pores, enlarged pores and fractures. [ABSTRACT FROM AUTHOR]

We investigated diagenesis of the sandstones from the DN2 Gas Field of the Kuqa Foreland Basin (KFB), in order to infer the timing of fluid migration and discuss the linkage between fluids and tectonics. The textures and chemical composition of authigenic minerals, fluid evidence from fluid inclusions and formation water measurements were all used to fulfill this aim. Eodiagenesis occurred with the participation of meteoric water and connate water. Mesodiagenesis is related to high salinity fluids, which were attributed as originating from the overlying Neogene Jidike Formation evaporite (principal minerals including halite, anhydrite, glauberite, carnallite and thenardite). The onset of high salinity fluid migration is inferred to occur during the late Miocene (12.4–9.2 Ma) through the use of homogenization temperatures measured in the present study and K‐Ar dating of authigenetic illites from previous work. This period is consistent with the crucial phase (13–10 Ma) that witnessed the rapid uplift of the southern Tianshan Mts and the stage when calcite and anhydrite veins formed in the studied strata. We thus argue that diagenesis related to high salinity fluids occurred as a response to the Tianshan Mts' rapid uplift and related tectonic processes. The flow of high salinity fluids was probably driven by a density gradient and channeled and focused by fractures formed contemporaneously. [ABSTRACT FROM AUTHOR]

This study aimed to reveal the effects of the hydration products AH3 and AFt phases on the hydration and hardening properties of calcium sulfoaluminate (CSA) cement. In addition, the effects of anhydrite ( C S ¯ ) and gypsum ( C S ¯ H 2 ) on the properties of CSA cement were compared. Calcium sulfoaluminate ( C 4 A 3 S ¯) was synthesized with analytical reagents, and the C 4 A 3 S ¯ - C S ¯ -H2O system with different molar ratios of C S ¯ and C 4 A 3 S ¯ was established. The phase compositions and contents of AFt and AH3 were determined by X-ray diffraction (XRD), Rietveld quantitative phase analysis, and thermogravimetric analysis (TG). The effects of pore structure and hydration product morphology on mechanical properties were analyzed by mercury intrusion porosity (MIP) and scanning electron microscopy (SEM). The results showed that the compressive strength exhibited a correlation with the AH3 content. In the case of relatively sufficient anhydrite or gypsum, C 4 A 3 S ¯ has a high degree of hydration, and the AH3 content can be considered to contribute more to the strength of the hardened cement paste. When anhydrite was selected, the combined and interlocked AFt crystals were covered or wrapped by a large amount of AH3. The mechanical properties of the hardened cement paste mixed with anhydrite were better than those of that mixed with gypsum. [ABSTRACT FROM AUTHOR]

Flue gas desulfurization gypsum (FGD gypsum) is obtained from the desulphurization of combustion gases in fossil fuel power plants. FGD gypsum can be used to produce anhydrite binder. This research is devoted to the investigation of the influence of the calcination temperature of FGD gypsum, the activators K2SO4 and Na2SO4, and their amount on the compressive strength of anhydrite binder during hydration. The obtained results showed that as the calcination temperature increased, the compressive strength of anhydrite binder decreased at its early age (up to 3 days) and increased after 28 days. The compressive strength of the anhydrite binder produced at 800 °C and 500 °C differed more than five times after 28 days. The activators K2SO4 and Na2SO4 had a large effect on the hydration of anhydrite binder at its early age (up to 3 days) in comparison with the anhydrite binder without activators. The presence of the activators of either K2SO4 or K2SO4 almost had no influence on the compressive strength after 28 days. To determine which factor, the calcination temperature of FGD gypsum (500–800 °C), the hydration time (3–28 days) or the amount (0–2%) of the activators K2SO4 and Na2SO4, has the greatest influence on the compressive strength, a 23 full factorial design was applied. Multiple linear regression was used to develop a mathematical model and predict the compressive strength of the anhydrite binder. The statistical analysis showed that the hydration time had the strongest impact on the compressive strength of the anhydrite binder using activators K2SO4 and Na2SO4. The activator K2SO4 had a greater influence on the compressive strength than the activator Na2SO4. The obtained mathematical model can be used to forecast the compressive strength of the anhydrite binder produced from FGD gypsum if the considered factors are within the same limiting values as in the suggested model since the coefficient of determination (R2) was close to 1, and the mean absolute percentage error (MAPE) was less than 10%. [ABSTRACT FROM AUTHOR]

Silica diagenetic structures have been recognized in the Ypresian–Priabonian Kef Eddour gypsiferous carbonate formation exposed in the Gafsa Basin, southern Tunisia. These rocks contain a wide range of nodular masses, including anhydrite/gypsum nodules and silica geodes. Three types of silica geodes have been identified based on color, shape, chemical, and mineralogical compositions. A zoned texture characterizes a large number of the geodes, composed of (1) a 3–4 cm thick rim of mixed micro-quartz, (2) length-slow crystals of chalcedony, and (3) euhedral mega-quartz lining the inner cavity of the nodule. XRD analysis reveals that quartz is the only silica polymorph found in most samples. The other silica phases (opaline group = opal-A, opal-C, and opal-CT) are undetectable with X-ray diffractometry (XRD). Fourier-transform infrared spectroscopic imaging (FTIR) and 29Si magic angle spinning nuclear magnetic resonance (MAS NMR) analyses confirm the presence of diagenetic hydroxylated silica forms (silanol sites with two bridging oxygen sites Q2 (–(O)2Si(OH)2), which are interpreted as amorphous opaline quartz precursors. Other non-siliceous groups have been detected, such as SO4 (sulfate evaporites) and CO3 (calcium and magnesium carbonates), and confirmed by petrographic observations. In Mg- and sulfate-rich environments, silica diagenesis tends to proceed discontinuously. During early silicification, pore fluid chemistry (pH < 9) tolerates silica replacements and the development of the microcrystalline and fibrous types of quartz. The silica replacement is slowed down or curtailed later in the innermost layers of anhydrite nodules due to changing pore fluid chemistry (pH values > 9). These processes lead to the development of euhedral silica by force of crystallization, supported by their crystallinity degree, low specific surface area, and ultra-microporosity, which make it more mineralogically competent and chemically resistant in such environments. Dissolved silica could be provided by fluids percolating through the diatom-rich porcelanite beds in the underlying Chouabine Formation. Silica could eventually be supplied post-diagenetically, as a fluid component released by clay mineral transformation and feldspar dissolution of the overlying Neogene sandy and clay-rich formations. [ABSTRACT FROM AUTHOR]

Mineral hydration is an important geological process that influences the rheology and geochemistry of rocks and the fluid budget of the Earth's crust and mantle. Constant-stress differential compaction (CSDC) tests, dry and "wet" tests under confining pressure, and axial-stress tests were conducted for the first time to investigate the influence of triaxial stress on hydration in anhydrite–gypsum aggregates. Characterization of the samples before and after triaxial experiments was performed with optical and scanning electron microscopy, including energy-dispersive spectroscopy and electron backscatter diffraction mapping. Stress–strain data reveal that samples that underwent constant-stress differential compaction in the presence of fluids are ∼ 14 % to ∼ 41 % weaker than samples deformed under wet conditions. The microstructural analysis shows that there is a strong temporal and spatial connection between the geometry, distribution, and evolution of fractures and hydration products. The increasing reaction surface area in combination with pre-existing gypsum in a gypsum-bearing anhydrite rock led to rapid gypsification. The crystallographic orientations of newly formed vein gypsum have a systematic preferred orientation for long distances along veins, beyond the grain boundaries of wall-rock anhydrite. Gypsum crystallographic orientations in {100} and {010} are systematically and preferentially aligned parallel to the direction of maximum shear stress (45 ∘ to σ1). Gypsum is also not always topotactically linked to the wall-rock anhydrite in the immediate vicinity. This study proposes that the selective inheritance of crystal orientations from favourably oriented wall-rock anhydrite grains for the minimization of free energy for nucleation under stress leads to the systematic preferred orientation of large, new gypsum grains. A sequence is suggested for hydration under stress that requires the development of fractures accompanied by localized hydration. Hydration along fractures with a range of apertures up to 120 µ m occurred in under 6 h. Once formed, gypsum-filled veins represent weak surfaces and are the locations of further shear fracturing, brecciation, and eventual brittle failure. These findings imply that non-hydrostatic stress has a significant influence on hydration rates and subsequent mechanical strength of rocks. This phenomenon is applicable across a wide range of geological environments in the Earth's crust and upper mantle. [ABSTRACT FROM AUTHOR]

Mineral replacement reactions mediated by fluids are common in sedimentary basins, where they influence geochemical cycles. Phosphorous (P) pollution of soils, sediments and water bodies is currently a widespread problem. Some apatite accumulations in sediments may have formed through the interaction of P-bearing aqueous solutions with mineral surfaces that result in mineral replacement reactions. Here, we investigate the pseudomorphic replacement of anhydrite single crystals by aggregates of β-tricalcium phosphate and hydroxyapatite upon interaction with a P-bearing solution at temperatures between 120 and 200 °C. SEM imaging is used to study the texture of the aggregates. Rietveld refinement of the X-ray diffraction patterns and Raman spectra analysis of the reacted samples provide information on the kinetics of the replacement. At all temperatures β-tricalcium phosphate forms alongside hydroxyapatite at early stages of the replacement reaction. At T ≥ 180 °C, hydroxyapatite/β-tricalcium phosphate ratio rapidly increases, and hydroxyapatite is the only phase in fully replaced samples. At T < 180 °C hydroxyapatite/β-tricalcium phosphate ratio increases slowly and fully replaced samples still contain significant amounts of β-tricalcium phosphate. The progress of the replacement is facilitated by the formation of porosity. The evolution of the hydroxyapatite/β-tricalcium phosphate ratio and the crystal habit of both phases strongly influence the arrangement of this porosity. The empirical activation energy Ea (kJ/mol) of the replacement reaction is determined by the Avrami and the iso-conversion methods. Both approaches yield an Ea of ~40 kJ/mol. Anhydrite dissolution appears as the rate-limiting process and the overall kinetics of the replacement reaction is controlled by the rate diffusion of dissolved species through the porosity network. The ripening of the metastable β-tricalcium phosphate into hydroxyapatite affects the characteristics of the porosity network and further modulates the kinetics of the replacement. These results may improve the understanding of the mechanisms of P-sequestration by mineral surfaces through coupled dissolution–precipitation reactions and shed light on the origin of apatite accumulations associated to evaporitic sedimentary rocks. [ABSTRACT FROM AUTHOR]

Materials (cement stone samples) in the CaO-K2O-SO3-H2O system with the target phase compositions, including syngenite K2Ca(SO4)2·H2O and calcium sulfate dihydrate CaSO4·2H2O, were prepared from powder mixtures of calcium sulfate anhydrite CaSO4, and/or calciolangbeinite K2Ca2(SO4)3, and potassium sulfate K2SO4 via hydration reactions at a water/powder ratio within an interval of 0.5–0.9. It was revealed that samples with contents of 25, 50, 75 and 100 mol% of syngenite K2Ca(SO4)2·H2O demonstrated a nonlinear dependence of their respective microstructures on their phase compositions. The microstructures of samples with phase compositions of 25 and 75 mol% of syngenite K2Ca(SO4)2·H2O consisted of pillar crystals. The microstructures of samples with phase compositions of 50 and 100 mol% of syngenite K2Ca(SO4)2·H2O consisted of plate crystals. An explanation of microstructure formation was set forth, taking into account equilibria of the dissolution–crystallization processes during cement stone formation. Materials obtained in the CaO-K2O-SO3-H2O system consisting of biocompatible and resorbable (soluble in water) phases can be recommended for testing as potential substances for bone defect treatments. [ABSTRACT FROM AUTHOR]

We present PySulfSat, an open-source Python3 tool for modeling sulfide and anhydrite saturation in magmas. PySulfSat supports a variety of data types (spreadsheets, Petrolog3 outputs, MELTS tbl files). PySulfSat can be used with alphaMELTS for Python infrastructure to track sulfur solubility during fractional crystallization within a single Jupyter Notebook. PySulfSat allows far more customization of calculations than existing tools. For example, the SCSS2− could be calculated with one model using the sulfide composition from a parameterization released with a different SCSS2− model. There are also functions for calculating the proportion of S6+/STot, allowing modeled SCSS and SCAS values to be converted into total S solubility to compare to natural data. We also contain functions for modeling mantle melting in the presence of sulfides using a variety of SCSS and KD models. Extensive documentation and worked examples are available at ReadTheDocs (https://bit.ly/PySulfSatRTD) along with narrated YouTube videos (https://bit.ly/PySulfSatYouTube).

Water seepage flow can dissolve soluble minerals that exist in rock formations. With the development of the excavated area due to dissolution, the water seepage velocity (discharge) into the dissolved rock will also increase. Therefore, water seepage and dissolution propagation are two interrelated processes. Mosul Dam foundation has experienced these processes since its construction, resulting in karstification in the reservoir and foundation of the dam. The present seepage-dissolution measure to minimize this phenomenon relies on traditional cementitious grouts. However, this measure has not been able to address the issue effectively. Currently, there are a few studies on the chemical remediation of soluble rocks under the influence of high-velocity water flow and water pressure. Therefore, the first part of the current study focuses on the impact of high-velocity water flow and water pressure on the dissolution acceleration of gypsum/anhydrite rocks. In the second part, the waterproof capacity of silica colloidal and its impact on the solubility reduction of the rocks is evaluated. Two distinct laboratory models were designed to simulate rock dissolution in the dam abutments and under the dam. Two sets of experiments were conducted on untreated and silica-treated samples. The experiments were executed on the samples extracted from Fatha Formation outcrop and problematic layers of brecciated gypsum situated at varying depths of the Mosul Dam foundation. The obtained findings reveal that the colloidal silica grout markedly prevents the water seepage impact on the soluble rock and that it can be very useful as an alternative to cement-based grouts.

Anhydrite and gypsum are omnipresent in sedimentary rocks of all types. They occur as massive layers or are distributed within other geological formations as in clays. Understanding the conditions of formation and the stability of the hydrated and anhydrous form of calcium sulfate is crucial in an elucidation of the genesis of the geological formations envisaged as potential host rock for radioactive waste disposal. Estimations of the temperature, where gypsum is dehydrated to anhydrite in water vary between 30°C and 60°C. The extremely slow crystallization kinetics of anhydrite at T < 90°C prevents a direct determination of this transition temperature. In the present work the different approaches to fix this temperature are discussed. It is shown that careful assessment of solubility data and calorimetric measurements yields a transition temperature of 42°C ± 1°C. For results essentially deviating from this value methodic deficiencies are revealed and discussed. Thus, a long-standing discussion about the thermodynamic aspect of the gypsum-anhydrite conversion can be closed, not the kinetic part.

To develop novel mineral-filled composites and assess their enhanced properties (stiffness, a good balance between mechanical strength and impact resistance, greater temperature stability), a high-impact polypropylene copolymer (PPc) matrix containing an elastomeric discrete phase was melt mixed with natural CaSO4 β-anhydrite II (AII) produced from gypsum rocks. First, in a prior investigation, the PPc composites filled with AII (without any modification) displayed enhanced stiffness, which is correlated with the relative content of the filler. The tensile and impact strengths dramatically decreased, especially at high filling (40 wt.%). Therefore, two key methods were considered to tune up their properties: (a) the ionomeric modification of PPc composites by reactive extrusion (REx) with zinc diacrylate (ZA), and (b) the melt mixing of PPc with AII surface modified with ethylenebis(stearamide) (EBS), which is a multifunctional processing/dispersant additive. The properties of composites produced with twin-screw extruders (TSEs) were deeply assessed in terms of morphology, mechanical, and thermal performance, including characterizations under dynamic mechanical solicitations at low and high temperatures. Two categories of products with distinct properties are obtained. The ionomeric modification by Rex (evaluated by FTIR) led to composites characterized by remarkable thermal stability, a higher temperature of crystallization, stronger interfacial interactions, and therefore noticeable mechanical properties (high tensile strength (i.e., 28 MPa), increased stiffness, moderate (3.3 kJ/m2) to good (5.0 kJ/m2) impact resistance) as well as advanced heat deflection temperature (HDT). On the other hand, the surface modification of AII with EBS facilitated the dispersion and debonding of microparticles, leading to composites revealing improved ductility (strain at break from 50% to 260%) and enhanced impact properties (4.3–5.3 kJ/m2), even at high filling. Characterized by notable mechanical and thermal performances, high whiteness, and a good processing ability, these new PPc–AII composites may be tailored to meet the requirements of end-use applications, ranging from packaging to automotive components. [ABSTRACT FROM AUTHOR]

The Mid North Sea High (MNSH) region represents one of the least explored areas for the Late Permian Zechstein Hauptdolomit play in the Southern Permian Basin although some of the first offshore wells drilled in the UK were located here. In other parts of the basin such as onshore Poland, the Hauptdolomit Formation ("Hauptdolomit") is an active and attractive exploration target, with oil and gas production from commercial‐sized fields. In the UK, the play has been overshadowed by drilling campaigns in areas to the south of the MNSH which tested plays in the underlying Rotliegend and Carboniferous successions. However, with these areas now in decline, there is increased exploration interest in the Hauptdolomit in the MNSH region, particularly since 2019 when 3D seismic data were acquired and the first hydrocarbon discovery was made at Ossian (well 42/04‐01/1Z). Geochemical data from the latter discovery have pointed to the presence of a prolific petroleum system with the potential for Hauptdolomit reservoirs to be charged both by Zechstein‐generated oils and Carboniferous condensate/gas. With regard to hydrocarbon migration and preservation in the southern MNSH, a detailed evaluation of the effects of the Mid Miocene Unconformity has allowed for a greater understanding of the main factors controlling hydrocarbon preservation and remigration. Reservoir characterization of the Hauptdolomit play has been achieved by integrating petrographic microfacies analyses, core data and petrophysical interpretations. The most important factors controlling reservoir quality are the presence and extent of anhydrite cementation and the presence of high energy shoal facies. Thicker and coarser grained shoal facies are expected to occur along the yet‐to‐be explored Orchard platform margin where numerous prospects have been mapped and refined using recently acquired 3D seismic data. [ABSTRACT FROM AUTHOR]