Search

In Gale crater on Mars, abundant secondary calcium (Ca) and magnesium (Mg) sulfate minerals are common as veins and cement in the sedimentary strata of Mount Sharp. However, the climate and source of aqueous sulfate (SO42-) during their formation are not well understood. Our δ34S analysis of surficial deposits in the Rio Puerco necks region show that oxidation of bedrock sulfides with negative δ34S (-37 to -6‰) leads to abundant formation and co-occurrence of Ca-sulfate veins and Mg-sulfate-rich salt with similar negative d34S values (-33 to -13‰). Additionally, the negative δ18O values of SO42- (-7 to +3‰) and gypsum hydration water (-9 to +1‰) are consistent with local meteoric precipitation, implying their origin from shallow water-rock interactions. Our geochemical comparisons between the Rio Puerco necks region and Gale crater strongly suggest the importance of sulfide weathering and short-lived water activity under a dry climate in the past on Mars. [ABSTRACT FROM AUTHOR]

It is crucial to study the application of nano materials in order to improve the properties of cement-based composites. The durability of concrete pitches into a key factor for sustainable infrastructure development. The performance of Ultra High Performance Concrete (UHPC) on exposure to aggressive chemical attack is also one of the durability concern. In the present research work, the durability of UHPC specimens in aggressive chemical media was investigated on six series of specimens by replacing 0% to 5% of nano ZrO2 particles by cement weight. The effects of nano ZrO2 particle content on resistance against aggressive chemical attacks were assessed by weight loss, strength loss and physical deterioration. Eight different aggressive chemical media such as hydrochloric acid, nitric acid, sulfuric acid, ammonium chloride, magnesium chloride, sodium chloride, magnesium sulphate and sodium sulphate were used for different exposure periods up to 120 days. The specimens with 3% nano ZrO2 particles content exhibited better durability performance in all the aggressive chemical media, which proved excellent performance in terms of lesser weight loss, minimal physical deterioration and high retention of compressive strength of specimens at all ages of exposure period. The higher retention in strength loss and weight loss was observed against aggressive chemical attack on 3 wt% of nano ZrO2 particles replaced UHPC mix, which reduced the weight loss by 11.80% to 14.70% and strength loss by about 14.85% to 18.34% in comparison to control mix without nano ZrO2 particles. [ABSTRACT FROM AUTHOR]

Serratia plymuthica UBCF_13 is known as an auxin-producing bacteria that produced Indole-3-Acetic Acid (IAA) best on YM media. Optimization of IAA production by UBCF_13 has been studied based on incubation time, pH, tryptophan concentration, culture media types, and the addition of wall-affecting agents and metals. A previous study demonstrated that the maximum IAA production of UBCF_13 was found in YM media with 300 µg/ml tryptophan. The data from the former study have not shown the maximum level of tryptophan for IAA production. Meanwhile, the effect of each component of YM media on IAA production is still unknown. This study is aimed to screen the effect of the YM media component and the best concentration of tryptophan on IAA production by UBCF_13. IAA production was screened based on each YM media component (mannitol, yeast extract, K2HPO4, MgSO4, NaCl, and CaCO3) and tryptophan levels (100-1000 µg/ml). Results show 600 µg/ml of tryptophan was the best concentration on YM media and produced the highest level of IAA of 197 µg/ml. Mannitol and magnesium sulfate content in the YM medium contributed most to IAA production by UBCF_13. [ABSTRACT FROM AUTHOR]

The focus of this research was to advance concrete protective coatings that are extremely resistant to chemical attacks. Fly ash was also used as a supplementary cementitious material to increase the concrete's impermeability. We were able to investigate the specimens' durability by performing tests at various stages of the curing process. Two types of epoxy coatings were applied to the concrete samples. They are subjected to a variety of environmental conditions by immersing them in 1% standard solutions of magnesium sulphate, sodium chloride, and sulfuric acid. The loss of strength caused by chemical exposure was interpreted as a sign of a chemical attack. According to the findings, samples containing Epoxy-2 are more resistant to acid attack, while Epoxy-1 is more resistant to corrosion. The main significance of this research in an aggressive chemical environment was to use low-grade concrete with protective coatings rather than higher-grade concrete. [ABSTRACT FROM AUTHOR]

This study demonstrates how sulphate attack on exposed marine concrete structures causes ettringite formation in the water environment. Creating ettringite is linked to concrete's ability to repel and expand. The early formation of ettringite, which happens immediately, is the process that controls stiffening without damaging expansion and is linked to the management of time in the Portland cement paste environment (within hours). Though it does not show any reaction in a marine environment, this mechanism will cause a harmful expansion later after several seasons of exposure (DEF). Delayed ettringite formation (DEF) formed at late stages due to cracking and spalling in forms. For both external and internal attacks on sulphate-containing cells, DEF can be tested. Magnesium sulphate (MgSO4) must first be converted before being used another way (ettringite) to make hydrated calcium aluminate sulphate. DEF may occur at marine concrete structures, but it is not linked to sulphate attack but instead to seawater chloride intrusion, which causes corrosion of the concrete structures. As a result, the reaction of DEF is linked to sulphate and another mechanism that can contribute to concrete cracking and spalling. [ABSTRACT FROM AUTHOR]

In the concrete industry, cement-less concrete made from alkali activated industrial waste such as fly ash and slag has emerged out to be the best low-carbon emission alternative to OPC. The investigation of sustainability of such an unique self cured self-compacting concrete from the strength and durability point of view is quite essential for its implications in the field. In this paper, the fly ash based self-compacting geopolymer concrete (SCGC) has been designed after verifying the fresh and mechanical properties by replacing fly ash with different percentages of ground granulated blast furnace slag (GGBFS) and varying the molarity of sodium hydroxide solution with self curing under ambient condition. As per the fresh property investigation, the SCGC with more than 30% GGBFS did not exhibit the results within the EFNARC limitations. The specimens containing 30% GGBFS with 12 molarity attained the highest strength in 28 and 56 days of maturation. The sulfuric acid attack was the most hazardous among all chemical attacks, and the SCGC specimens were less affected than SCC in all cases of exposure to adverse environment, as established from the durability studies with normal water, sea water, 5% concentration of sulfuric acid and 5% concentration of magnesium sulphate. The SCGC specimens containing 30% of GGBFS offered the highest resistance to all the chemical attacks. [ABSTRACT FROM AUTHOR]

The article presents a new technology for the manufacture of building products, including the formation of a structural concrete layer on high alumina cement, its curing, laying a gypsum-concrete layer with subsequent drying of the product, characterized by increase of the product strength. The electrical resistance of the concrete layer is measured during curing. At the minimum value, a 10–50% magnesium sulfate solution is applied onto the surface of the concrete layer, and at the maximum value - a gypsum-concrete layer is placed followed by drying of the products at 105–110 °C. This technology allows one to perform heat treatment at elevated temperatures. The studies were carried out for a concrete mix with a water-cement ratio of 0.45 and 0.55. The proposed method allows one to reach the grade strength at insignificant elongation deformations. The presented technology belongs to the building materials industry and can be used in the manufacture of double-layer concrete products at building factories. [ABSTRACT FROM AUTHOR]

The limonite has low nickel grade of laterite family and contains goethite [FeO (OH)] and hematite (Fe2O3). The new way for reducing the other elements is selective reduction. Selective reduction is the better way to get the product of Fe-Ni. The nickel ore obtains some variations temperature of 950 °C, 1050 °C and 1150 °C with the holding time 60, 90 and 120 minutes and also the different of anthracite coal reductant percentage those are 5, 10 and 15%. The reduction of laterite was using magnesium sulfate additive is around 10wt% and continued with the process of magnetic separation. X-ray Diffraction (XRD) results show the dominant phases are magnesioferrite (Fe2MgO4), magnetite (Fe3O4), fayalite (Fe2SiO4), iron-nickel (FeNi), iron sulfide (FeS) and wustite (FeO). XRF (X-Ray Fluorescence) characterization shows the optimum process for the weight per cent and recovery of nickel at the temperatures 1150 °C for 90 minutes with 5% reductant those are 2.086 wt.% and 80.68%, respectively. The microstructure consists of ferronickel with the largest grain size is 13.2 µm and impurities elements. It is indicated the selective reduction could increase the Ni per cent and separated Ni from its initial form. [ABSTRACT FROM AUTHOR]

In this depiction, the single crystals of tristhiourea zinc magnesium sulphate were synthesized and obtained from an acidic solution by slow evaporation solution growth method. Single crystal X ray diffraction was carried out to make out the lattice parameters and structure of the crystals. SEM analysis shows the surface morphology of the grown crystals. FTIR and FT Raman studies confirm the presence of the expected functional groups. The absorption and transmission spectrum of the crystal shows the lower cutoff wavelength of the crystal at 230.4nm. The thermal stability of TZME crystal was confirmed by TG-DSC analysis. The mechanical behavior and strength of the crystals were reviewed by Vicker’s micro hardness method. [ABSTRACT FROM AUTHOR]

In cement production waste of various industries (metallurgical, chemical, etc.) is widely used. This contributes to the improvement of environmental protection and intensification of the clinker firing process, as well as improving the quality of clinker by modifying clinker minerals. Due to the large variety of wastes, the decision to use them effectively in the production of Portland cement clinker should be based on the results of scientific research both in the laboratory and in the industrial environment.The presence of trace impurities (titanium, zinc, sulfur, chromium, manganese, etc.) in many wastes of nonferrous metallurgy and chemistry plants predetermined the need to study their role in the burning processes of the raw mix and the formation of clinker phases. The research of many scientists is devoted to this problem. In the study of V. V. Timashev and his students, as well as I. Maki, F. Taylor and others, special attention was paid to the modification of clinker minerals as a way to increase the hydration activity of clinker. The most common modifying materials are wastes containing sulphates and magnesium oxide. It was found that magnesium oxide stabilizes the M3- form C3S, and sulfate ions stabilize the M1-form. This contributes to the strength of the modified clinker cement. However, the problem of using these wastes remains very important. At a number of plants, the use of sulfate waste leads to a deterioration of the clinker firing process, the appearance of rings in the furnace, an increase in clinker dusting, and a decrease in the hydration activity of cement. The aim of our work was to study the anomalous effect of sulfate waste on the phase composition of Portland cement clinker. This is especially important for cement plants using limestone with a high content of magnesium oxide. The effect of SO3 and MgO separately and at their joint presence in the raw mixture was studied. It is established that sulphates and magnesium oxide influence on the process of clinker formation, the phase composition of clinker and, accordingly, the properties of cements. The degree of their influence is manifested due to the formation of metastable compounds and alloys at the stage of solid-phase sintering, changes in the composition and properties of the main clinker melt, the formation of liquation zones of the melt, changes in the crystallization rate of the clinker phases, the formation of solid solutions. It was established the optimum content of magnesium oxide and the ratio of MgO/SO3 in the raw mixture, which ensures the normal firing of clinker. The strength of cement based on modified clinker is significantly increased. [ABSTRACT FROM AUTHOR]

Contributions to the behavior of rock materials under various conditions provide a practical knowledge about issues relating the performance and long-term serviceability of rocks. In this study, various limestones with varying textural features were investigated in terms of their resistance against magnesium sulfate weathering tests. For this purpose, initial physico-mechanical properties of limestones were determined. Then, rock materials were subjected to magnesium sulfate weathering tests (up to 20 cycles) and the variation in physico-mechanical properties were determined for each rock type. As a result of laboratory tests, compared to initial rock properties, effective porosity (ne, %) increased in the range of 3% ‒ 14% and 12% ‒ 35% after 10th and 20th magnesium sulfate weathering cycles, respectively. Uniaxial compressive strength of rocks (UCS, MPa) decreased by 9% ‒ 24% after 10th cycles and by 32% – 58% after 20th cycles. Brazilian tensile strength of rocks (BTS, MPa) decreased in the range of 7% ‒ 19% and 20% ‒ 49% after 10th and 20th cycles, respectively. Similar to the variations in UCS and BTS, Tangential Young Modulus (Eti, GPa) also decreased at a rate of 13% ‒ 28% and 23% ‒ 64% after 10th and 20th cycles, respectively. However, the values of Tangential Poisson’s Ratio (vti) fluctuated with progressive accelerated weathering cycles, which could be linked to varying axial and lateral strain rates at 50% of UCS values for the limestones investigated. Furthermore, the variation in crack initiation stress σCI(MPa) due to progressive magnesium sulfate tests were also evaluated considering two strain-based methods and the findings showed that σCI of limestones slowly decreased with increasing weathering test cycles. It could be claimed that cyclic magnesium sulfate tests performed on rock materials would be beneficial for assessing the long-term serviceability of rocks. In this context, mud-supported limestones seem to have a greater resistance against magnesium sulfate weathering tests compared to the grain-supported ones. However, the number of samples should be increased in order to achieve a comprehensive understanding about the degradation processes of limestones. [ABSTRACT FROM AUTHOR]

Magnesium oxide and magnesium sulfate were known to react with water to form magnesium hydroxide and magnesium hydroxide heptahydrate. Thermal energy was released during the reaction, and the formed product can be decomposed reversibly when heat is applied. They can be used as thermochemical heat storage materials because of high reaction enthalpy and reversibility. In this study, magnesium oxide was formed into honeycomb shape so that the high temperature air for heat storage or low temperature humid air could be passed through flutes of the honeycomb with minimum pressure drop. Mechanical and thermal properties of the prepared honeycombs were measured and discussed. [ABSTRACT FROM AUTHOR]

In this work, the Lorentz curves of the crystal MgSO3.6H2O:Co and aqueous solutions of CoCl2.6H2O, CoSO4.7H2O are presented. The absorption spectra α(π) of the complex [Co(H2O)6]2+ in three aqueous solutions of CoSO4.7H2O (1%, 1.5%, 2%) are measured in spectral region 2.07 - 3.1 eV. The first and second derivatives of α(π) are calculated. The Fermi energies of cobalt levels are also calculated. [ABSTRACT FROM AUTHOR]

This article describes the possible causes of low strength magnesia binder, mixing an aqueous solution of magnesium sulfate. The results of X-ray diffraction are shown. [ABSTRACT FROM AUTHOR]

ZnS-MgS nanocomposites was successfully prepared by the microwave assisted solvothermal method using a domestic microwave oven. The prepared sample was annealed at 100 °C for 1 hr to improve the ordering. Grain sizes and lattice parameters were determined by carrying out X-ray powder diffraction measurements. Scanning electron microscopy (SEM) shows the morphology. AC electrical measurements were carried out on pelletised samples at various temperatures ranging from 40-150 °C. Results of the present study reveal that the space charge contribution plays a significant role in the charge transport process and polarizability. [ABSTRACT FROM AUTHOR]

Magnesium sulphate (Mg) in vitro directly relaxes smooth muscle including myometrium. It is thought to compete with Ca thus, inhibit L-type Ca channel entry and contractility. Currently, the clinical evidence for using Mg as a tocolytic agent, such as for threatened preterm labour, is questionable: A Cochrane systematic review concluded that Mg for tocolysis in vivo is ineffective(1). We investigated whether the presence of the hormone oxytocin, which also effects calcium signalling dynamics, alters the tocolytic capability of Mg on human myometrium in vitro and if the effect (if any) could be reversed with the oxytocin antagonist, atosiban. Methods: Isometric tension recordings were performed on strips of myometrium (1x5x2mm) obtained from 10 pregnant women undergoing pre-labour Caesarean section (with consent and ethical approval). Paired strips from the same woman were superfused with physiological saline and the effect of increasing [Mg] from 1.2mM (control) to 12mM in the presence and absence of oxytocin (0.5nM) was compared by calculating the mean effective concentration causing 50% reduction in force amplitude of contraction (EC50). In a subset of experiments (n=4), the effect of increasing [Mg] in the presence of Atosiban (10-7M) on oxytocin-induced contractions was compared to Mg alone. Results: Elevated [Mg] produced a significant, dose-dependent inhibition of phasic, spontaneous myometrial contractions: EC50 2mM, complete inhibition achieved at 3.4mM. In contrast, application of oxytocin significantly increased the [Mg] required to affect contractions, such that at 2mM Mg there was little reduction in force amplitude (98.5% of control). The EC50 was 10mM and full abolition of activity in all but 2 cases was achieved at 12mM (i.e.10 times greater than [Mg] in control solution). The addition of Atosiban reduced the [Mg] at which oxytocin-induced contractions were inhibited, from 12mM to 6mM. Conclusion: In vitro, Mg at therapeutic doses (<2.5mM) significantly reduces spontaneous contractility of the myometrium however, the effect of Mg is significantly reduced in the presence of oxytocin; it is only effective at suprapharmacological concentrations. We suggest that the changed hormonal milieu in pregnancy, specifically towards oxytocin, underlies the poor tocolytic ability of Mg in vivo. Preliminary data suggest atosiban may reduce the EC50 for Mg and raises the question of whether, clinically, oxytocin antagonists should be used in combination with Mg for uterine tocolysis. [ABSTRACT FROM AUTHOR]