An attempt has been made to bring out the influence on strength and volume change behavior of fabric changes and new cementitious compound formation in a soil upon addition of various lime contents ...and with curing periods. The effects of changes in fabric of treatment with various lime contents (0, 2, 4 and 6%) and with curing periods (0, 7, 14 and 28days) have been evaluated by one-dimensional consolidation tests, in terms of void ratio changes and compressibility. The strength of soil treated with different lime contents with curing periods up to 28days, and with the optimum lime content of 6% up to one year has been determined by unconfined compression tests. Comparison of effects of lime on the strength and volume change behavior of the soil brings out that the formation of flocculated fabric and cation exchange significantly reduces the compressibility of soil but marginally increases the strength. Cementation of soil particles and filling with cementitious compounds of the voids of flocculated fabric in the soil marginally reduces the compressibility but significantly increases the strength. Thus, the mechanism of volume change behavior of soil treated with lower lime content at short curing periods is distinctly different from that of the soil treated with optimum lime content at longer curing periods. This is consistent with the increase in the permeability caused by the addition from 2 to 4% lime and the decrease following the addition of 6% lime. Changes consistent with mechanical behavior have been determined by scanning electron microscope, X-ray diffraction and thermal analyses, energy dispersive X-ray spectrometer and pH value in microstructure, mineralogy, chemical composition and alkalinity, respectively.
•Effect of lime treatment on plasticity and compaction characteristics of soil•Effect of soil–lime reactions on short-term and long-term strength and alkalinity•Compressibility and volume change behavior of lime treated soil with curing period•Role of change in fabric on strength and permeability with curing period•Detailed analytical analysis and its effect on geotechnical properties
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•EDS/SEM analysis proved the purity of the RbMgPO4 compound with a uniform grain distribution with a microrod-like structure..•DSC analysis reviled the existence of two reversible ...phase transitions located at T1 and T2 .•T1 discloses the coexistence of order-disorder and displacive components, while T2 appears as a displacive one.•The Raman analysis showed that external modes are the most influenced by temperature.•The number of correlated unit cells decreases and the structure becomes more disordered at high temperatures.
Rubidium magnesium monophosphate RbMgPO4 compound was synthesized using the solid− state method. XRPD analysis, at room temperature, confirmed that the sample exhibits an unusual three-fold Pna21 superstructure in the orthorhombic system. EDS analysis proved the absence of external elements. SEM micrograph showed a microrod-like structure of grains with a uniform distribution. This compound undergoes two phase transitions of a ferroelectric nature at T1 = 448/433 K and T2 = 466/458 K (Heating/Cooling) revealing a rich polymorphism in the solid-state. These phase transitions were investigated using Raman spectroscopy analysis. The first shows a moderate reconstructive character revealing the coexistence of order-disorder and displacive components, while the second appears as a displacive one. These transitions are originated from the rotation of both MgO4 and PO4 in an inverse direction and a change of Mg coordination, to reach a high symmetry. Based on the order-disorder model, the analysis of the wavenumber, intensity, and width allowed us to attain information and to determine the thermal coefficients and the activation energies in each region. The temperature dependence of Raman spectra showed that the most important changes were observed in the external modes. The estimated critical values of the exponents (δ1,δ2) and (ξ01, ξ02), deduced from the reduced intensity of the thermosensitive band, were determined.
Apatite is a common accessory mineral in igneous, sedimentary and metamorphic rocks. It has potential as a provenance indicator in sedimentary systems, as it can host a wide variety of trace elements ...in its crystal structure and can yield thermochronological age information. However, the processes controlling the trace element and U-Pb systematics of metamorphic apatite remain poorly understood, and metamorphic apatite remains significantly under-represented in compositional provenance databases linking apatite trace-element chemistry to its corresponding parent rock type. We investigate the trace-element and U-Pb systematics of metamorphic apatite from a suite of 22 bedrock samples of diverse metamorphic grade and protolith type, sampled from a variety of metamorphic terranes. Metamorphic apatite from low- to medium-grade metapelites and metabasites can be easily distinguished from granitic apatite as it is significantly depleted in Th, REE, and Y. Depletion in Th and REE+Y is attributed to growth of co-genetic epidote, which is the dominant carrier phase of the REE+Y, Th, and U in all the low- to medium-grade samples mapped by laser ablation quadrupole inductively coupled plasma mass spectrometry (LA-Q-ICP-MS) and energy dispersive X-ray spectroscopy (EDS). Apatite U contents in low- to medium-grade metapelites and metabasites are more variable than the Th and REE+Y contents, but are typically low. Consequently, grains from these rock types are often undateable by the U-Pb LA-ICP-MS method and thus are underrepresented in apatite U-Pb detrital datasets, but can still be identified as low- to medium-grade metamorphic apatite by their trace-element characteristics. Low-grade metapelite apatite is difficult to distinguish from low-grade metabasite apatite, which is likely due to the growth of U-, Th-, and REE-rich epidote in both lithologies. Detrital (granitic) apatite is stable in very low-grade (e.g. pumpellyite-actinolite facies) metasedimentary samples, while neo- or re-crystallized metamorphic apatite is widespread by the upper-greenschist facies. LA-Q-ICP-MS imaging demonstrates that low REE+Y, Th, and U metamorphic apatite rims can nucleate on detrital igneous apatite precursors with high REE+Y, Th, and U. With increasing metamorphic grade, 1) relict detrital apatite is consumed, 2) the coherence of the U-Pb concordia systematics dating metamorphism improves, and 3) the degree of dispersion on metamorphic apatite multi-element plots decreases. The highest-grade metamorphic apatite samples investigated are paragneisses, some of which have locally undergone anatexis. Apatites from these samples yield well constrained TW concordia intercept ages and minor dispersion on multi-element plots (which is attributed to the absence of epidote) and closely resemble apatite from S-type granites in their trace element characteristics.
Microorganisms, especially those habiting mining environments, are of great importance for the retention of toxic metals in the environment. This work aimed to isolate a copper removing-microorganism ...from sediments of an Acid Mine Drainage-affected environment and to study the cellular responses trigger by metal presence. Apiotrichum loubieri M12 was able to tolerate and remove Cu(II) from liquid culture media, reaching a 30–35% removal capacity when it was exposed to 40 μg mL−1 Cu(II) after 48 h. Analysis of the biomass exposed to the metal through SEM-EDS showed copper presence on the cell surface and variations in the proportion of other biomass constituent elements. Proteomics revealed that the presence of Cu(II) induces differential expression of intracellular proteins involved in a wide variety of metabolic processes. Interestingly, a specific response to the metal was detected in cell-free supernatants, in which copper binding proteins were identified. A large number of proteins with metal ion binding sites were detected both at intra and extracellular levels. The microorganism responds not only by adjusting intracellular protein expression, but also by adjusting expression of proteins in the extracellular space.
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•Steel substance was protected by a mixed type inhibitor.•EIS results proved the 96% inhibition efficiency.•Elemental analysis proved successful Quercetin:Ce complexes adsorption.
The ...low-inhibition potency and the toxic nature of most of the conventional organic molecules in corrosion inhibition of metals against the chloride-containing solution, has forced the researchers to develop eco-friendly compounds. In the present study, (2-(3,4-dihydroxyphenyl)-3,5,7-trihydroxy-4H-chromen-4-one), called Quercetin, was selected as green corrosion inhibiting molecules for the steel protection against NaCl solution. The Quercetin molecules' ability for reaction with Ce (III) ions, forming hybrid organic-inorganic compounds was studied. The type of interactions between the Quercetin molecules and trivalent-cerium ions was investigated via FT-IR and UV–Vis (in water solution) analyses. The corrosion inhibition potency of the mixture of Quercetin:Ce was examined using polarization and EIS methods. Electrochemical achievements reflected that the Quercetin:Ce complexes could retard mild steel corrosion by a high inhibition efficiency degree of 96% via mixed cathodic and anodic inhibition mechanisms. The inhibited and uninhibited metal samples' surface morphology and microstructure were explored by FE-SEM, GIXRD, and EDS/Mapping techniques. The high presence of Ce atom in the deposited film evidences sufficient Quercetin:Ce adsorption.
To date, there is not sufficient knowledge to fully understand the occurrence, transport and fate of residual uranium (U) from uranium mill tailings (UMT). Herein this study investigated different U ...release behaviors from natural UMT (without grinding) under four simulated acid rain (pH = 2.0–5.0) compared with controlled scenario (pH = 6.0) for 25 weeks. The results showed that the most notable U release was observed from UMTpH2.0, followed by UMTpH3.0 whereas a nonlinear relationship between pH and U release was observed from UMTpH4.0–6.0. The divergence of U release behaviors was attributed to the presence of minerals such as calcite and clinochlore. Autunite, a secondary mineral formed after leaching, might regulate U release in UMTpH3.0–6.0. Fick theory model revealed the shift of U release mechanism from surface dissolution to diffusion transport for UMTpH2.0, UMTpH3.0 and UMTpH5.0 at varied stage, whereas UMTpH4.0 and UMTpH6.0 displayed univocal dissolution and diffusion mechanism, respectively. This study highlights the necessity of performing long-term leaching tests to detect the “shift event” of leaching kinetics and to better understand the mechanism of U release influenced by mineralogy of the natural UMT under simulated acid rain conditions, which is conducive to developing UMT management strategies to minimize the risk of U release and exposure.
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•25-weeks leaching behaviors of U from UMT demonstrated over a wide pH range.•Extremely high U release observed in the UMTpH2.0 scenario, whereas nonlinear effects occurred under moderate pHs.•Intricacy of mineral-solution geochemistry accountable for the nonlinear effects.•Clearly visible “shift event” of release mechanism in specific leaching scenarios discovered.•Formation of autunite (Ca(UO2)2(PO4)2·11H2O) act as U release barrier.
The formation of autunite could regulate uranium release in the uranium mill tailings, and the “shift event” of leaching mechanism was found after long-term leaching.
The flexibility in the production of concrete permits the incorporation of numerous industrial by-products as a feasible replacement for conventional natural ingredients. Generally, the ...physicochemical characteristics of the industrial by-products result in variations in the microstructure of concrete. Several petrographic techniques have been used in concrete to understand the alternation in the microstructure of the material instigated by the addition of different industrial by-products. Various petrographic techniques, such as scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDS), have been successfully implemented in the field of research in the last decades for microstructural characterization. Currently, the usage of iron-steel slag in concrete has opened an extensive range of potentials for understanding the microstructural behaviour of iron-steel slag as Portland cement (PC), natural coarse and natural fine aggregates (NCA & NFA) replacement in concrete. This paper briefly reviews some of the microstructural features indicating the physical (pore structure, interfacial transition zone (ITZ), shape, etc.) and chemical characteristics of iron-steel slag-based concrete. The effects of different variables, such as slag content, curing conditions, and mixing techniques, on the microstructure are also examined. The microstructure evaluation reveals the complex behaviour of iron-steel slag in concrete, as in some cases its utilization has proved to be beneficial. On the other hand, its presence beyond a certain limit degrades the microstructural behaviour of concretes. This review highlights the general trends in understanding the variation in compressive strength as well as microstructural characteristics over the range of replacement of slag in concrete as a potential replacement of cement, fine and coarse aggregate.
Glass fiber reinforced concrete (GFRC) comprises of hydration products of cement or cement plus sand, and glass fibers which take part in the concrete as reinforcement characteristics. GFRC has been ...used for over 50 years in several construction elements, such as facade panels, decorative no recoverable formwork, and other products. However, various anchor elements and pad hooks are needed to attach large or small parts made of GFRC panels to the main structure of the buildings. The corrosion rate of embedded metal fasteners over time is related to the water impermeability properties of the GFRC elements. In this study, corrosion of an electro galvanized pad hook embedded in 10–20 mm of the GFRC panel was investigated as a result of the salt spray test performed in accordance with ASTM B 117 standards. At the end of the experiment, the embedded pad hook was taken from the GFRC and analyzed by scanning electron microscopy, energy‐dispersive spectroscopy methods. The results showed that the embedded pad hook in the GFRC, which was examined in the test procedures comply with the TS EN 12467 standards, was not corroded by 120‐h test carried out in accordance with ASTM B 117 standards.
Model predictive control (MPC) is a popular control technique to regulate multiphase electric drives (EDs). Despite the well-known advantages of MPC, it is sensitive to parameter detuning and lacks ...the capability to eliminate steady-state errors. The appearance of an offset between the reference and measured currents can significantly jeopardize the performance of the ED. This article suggests the use of a memory-based model predictive control (MB-MPC) that activates a compensation term when the parameter mismatch is detected. The suggested MB-MPC is universal for any multiphase machine if spatial harmonics are neglected since the proposed method does not consider any of the secondary x-y planes. Experimental results in two different rigs with six- and nine-phase induction motors prove this universality as well as its capability to eliminate current and speed offsets.
