Many methods have been proposed to analyse SEM‐EDS hypermaps of hydrated cementitious materials but none can fit all purposes. In this presentation, we review existing methods for phase ...identification, stoichiometry quantification, and microstructure quantification in cementitious materials and related materials. We first discuss the unique contribution of SEM‐EDS with respect to the outstanding scientific challenges towards sustainable construction materials. We then compare the SEM‐EDS and image analysis techniques which contribute to answering these challenges. Convergence and divergence in current methods and workflows, and knowledge gaps are highlighted in terms of the specificities of the material (phase assemblage complexity, grain sizes, mixtures, etc.). The discussion is weighted by the required expert knowledge for the sample preparation, microscope operation, and data analysis. We conclude by discussing how microscopy and image analysis integrate into the overall experimental toolkit to investigate and improve cementitious materials.
LAY DESCRIPTION
Concretes, mortars and hardened cement pastes are very complex and heterogeneous. As such, the visualisation of phases in the microstructure is often necessary to understand the processes by which this microstructure forms and evolves. Scanning electron microscopy coupled with energy dispersive spectroscopy (SEM‐EDS) is one of the techniques that allows studying these materials at the micron‐scale level, by forming images combining the elemental composition. But the analysis of the data is challenging due to the heterogeneity of the material. This article is a review of the latest advancements in the analysis of SEM‐EDS data for cementitious materials. It focuses on two aspects, the most successful applications of SEM‐EDS to study the microstructure of hardened cementitious materials; and some of the main methods used to analyse the dataset. The discussion aims to highlight the requirements of each method and each application, so that readers can pick and mix methods to answer their own scientific questions.
In the present study the phase changes in an ordinary concrete standing for 10years in a tidal zone were investigated with a range of techniques. From the exposed surface and inwards different zones ...had formed. SEM–EDS analysis of a polished section of the surface near region, showed a Mg rich layer with a thickness of 10–20μm, as well as the filling of cracks leading from the surface with a Mg rich phase, most likely brucite. In the outermost 2mm, an increase in the calcium carbonate content was identified by XRD and TGA. In the same zone SEM–EDS analyses indicated enrichment in ettringite and thaumasite. In the first 20mm calcium hydroxide leaching was observed using XRD and TGA. Chlorides appeared to have penetrated up to approx. 70mm from the surface. Part of the chlorides were found to be bound in alumina containing phases and in the C–S–H by SEM–EDS. These experimentally observed phase changes generally agreed with the predictions of a thermodynamic model.
The present study is aiming to explore the effect of 4-Hydroxy-6-methyl-3-(3-quinolin-8-yl-acryloyl)-pyran-2-one (HMQP) and 3-3-(4-Dimethylamino-phenyl)-acryloyl-4-hydroxy-6-methyl-pyran-2-one ...(DMPHP) on mild steel (MS) corrosion in acid solution (1 M HCl). The compound was tested at various concentrations (0.001–1 mM) and four temperatures (298, 308, 318, and 328 K) to determine the optimal concentration and temperature range for the best corrosion inhibiting effect. In evaluating the inhibition efficiency, weight loss measurement, potentiodynamic polarization measurement (PDP), electrochemical impedance spectroscopy, SEM/EDS and theoretical methods were used. The inhibition efficiencies increase with increase in concentration and decreases with temperature. The maximum inhibition efficiency was found 90% and 85.4% at 298 K in the presence of 1 mM of DMPHP and HMQP respectively. The experimental adsorption data obeyed the Langmuir isotherm model. The polarization parameters suggest that DMPHP and HMQP are mixed type inhibitors. The results of the EIS study suggest that these compounds inhibit corrosion by adsorption mechanism. A good correlation between theoretical and experimental results was obtained.
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•Inhibition effect of new pyran derivatives for mild steel corrosion has been studied.•Adsorption of both inhibitors follows a Langmuir isotherm.•SEM and EDS were performed for surface study.•The experimental results were well supported by DFT and Monte Carlo simulation.
The effect of CuO addition on the phase composition of clinker and the Cu incorporation into the structure of clinker phases was monitored under laboratory conditions. Separate synthesized CuO‐doped ...clinker phases as well as clinkers with different CuO content up to 4 wt.% were characterized by XRD, optical and electron microscopy with EDS analysis. It has been found that Cu tends to form a separate phase or a double oxide with Ca and incorporates in the clinker phases to a limited extent, except for C4AF. With increasing CuO content in clinker, its phase composition changes, and the size of alite crystals increases.
•Atmospheric corrosion of ZnAlMg coated steel.during world wide exposures.•Localised corrosion with selective corrosion attacks in the eutectic phases.•Sulfate and chloride containing corrosion ...products in corrosion pits.•Zinc hydroxy carbonate and carbonate based LDH in outer parts of corrosion pits.
The atmospheric corrosion of zinc aluminium magnesium (ZnAlMg) coated steel was studied in a worldwide exposure in Europe, East Asia and USA. The mass loss of ZnAlMg coated steel was about 2–3 times lower compared to hot dipped galvanised steel (HDG) after 4 years exposure. The corrosion of ZnAlMg coated steel was highly localised with selective corrosion attacks in the eutectic phases of the coating. Sulfate and chloride containing corrosion products were formed in the corrosion pits while zinc hydroxy carbonate and carbonate containing layered doubly hydroxides (LDH) formed mainly in the outer parts of corrosion attacks.
The archaeological excavations in the site of ‘Piana di San Martino’ (Pianello Val Tidone, Piacenza, Italy) discovered several fragments of pietra ollare (soapstone) artefacts, dating back to the ...Medieval period. A selection of fragments was characterized with micro‐Raman spectroscopy in order to determine their composition, in terms of main and accessory species. The morphology of the crystals and the mineral phases were also investigated with polarized‐light microscopy observations, X‐ray powder diffraction and Scanning Electron Microscopy with Energy‐Dispersive System analyses, which corroborate the Raman results. A detailed characterization was obtained on 12 fragments ascribable to pots and a millstone, made of talc‐schists or chlorite‐schists, including garnet‐bearing chlorite‐schists. Interest findings about the activities related to the use of these artefacts and the alteration processes occurred during their burial period were highlighted by the identification of specific products. Additionally, mobile Raman measurements were performed on the fragments, and a quick and effective evaluation of their composition was successfully achieved. These results highlight the use of mobile Raman instruments in the field of archaeology, specifically referred to pietra ollare findings, for which a preliminary identification may be obtained directly in situ.
Through a multi‐analytical characterization of twelve fragments of artifacts made of pietra ollare (Micro‐Raman, PLOM, XRD and SEM‐EDS), the peculiar aspects of the soapstones and alterations features were investigated. The feasibility of mobile Raman measurements on the fragments were also explored.
Unraveling sorption mechanisms of lead (Pb) to silicon (Si)-rich biochar at molecular scale in aqueous solution are essential for the effective application of the biochars to the remediation of Pb ...and other metal(loid)s pollution in the environment. Thus, this study investigated the contributions of phytoliths and other compounds to the Pb sorption on Si-rich coconut fiber biochar (CFB500) and the corresponding sorption mechanisms using spectroscopic techniques, including the micro-X-ray fluorescence (μ-XRF), X-ray absorption fine structure (XAFS), scanning electron microscopy combined with energy dispersive X-ray spectroscopy, and X-ray diffraction. The μ-XRF and XAFS results showed that K, Ca, Cu, Mn, and Fe were released and significantly related to Pb in Pb-loaded CFB500; four major Pb species were formed with similar structures to lead carboxylate (e.g., Pb(C2H3O2)2), Pb3(PO4)2, PbSiO3, and PbCO3. On phytoliths in CFB500, Pb2+ ions were mainly sorbed on the sites of silicate with a structure similar to PbSiO3. The contribution of binding sites for Pb2+ sorption was ascribed to the outer-wall of carbon skeleton of CFB500, which was stronger than that provided by the mineral oxide aggregate and phytoliths on CFB500. Organic carbon functional groups, inorganic carbonates, silicates and phosphates on CFB500 mostly dominated the sorption sites for Pb2+. Our results suggest that CFB500 was a promising material for the remediation of Pb-contaminated aqueous environments (e.g., wastewater).
Unraveling sorption mechanism of potentially toxic elements (PTEs) by Si-rich biochar can provide guidance for application of biochar-based materials to environmental remediation. Display omitted
•Distribution of Pb in Si-rich coconut biochar was related to K, Ca, Cu, Mn and Fe.•Lead carboxylate, Pb3(PO4)2, and PbSiO3 were major Pb species on Pb-loaded biochar.•Silicates were the dominant sorption sites on biochar's phytoliths for Pb2+.•Pb2+ was mainly sorbed by organic skeleton of biochar with a C−O−Pb or C−O−Pb−O−C.
Chrysotile, one of the six regulated asbestos minerals, is classified as carcinogenic to humans by the International Agency for Research on Cancer. The Balangero mine (Turin, Italy) was the largest ...asbestos mine in Europe, providing extraction of chrysotile fibers until 1990. Chrysotile from Balangero is currently of great interest in fibers toxicity studies focused on the understanding of the mechanisms that induce lung malignancies. One of the crucial factors in the biochemical reactions is the presence of Fe at the fibers surface. Surface reactivity is responsible for the generation of reactive oxygen species, which play an important role in asbestos cyto‐genotoxicity. Moreover, the dissolution of Fe‐bearing phases in the acidic environment of the lysosomes might be considered as possible release of hazardous Fe ions in the lungs. Here, chrysotile from Balangero was characterized by micro‐Raman spectroscopy and scanning electron microscope‐energy dispersive system (SEM‐EDS) analysis to identify the Fe‐bearing impurities associated with asbestos fibers. Micrometric crystals were recognized as Fe oxides, carbonates, and sulfides. Uncommonly reported phases in asbestos minerals were also identified, mainly as mackinawite (Fe(II)S), in different forms. The nature of the Fe compounds containing both Fe(II) and Fe(III) species was verified by micro‐Raman spectroscopy combined with SEM‐EDS analysis.
Fe‐bearing impurities associated with asbestos fibers were identified as Fe oxides, carbonates, and sulfides, including uncommonly reported phases in asbestos minerals.
The novelty of the work is to investigate the application of two new epoxy resins namely as hexaglycidyl N-phenylaminopropoxy-N.N.N-triphenyl propane-1.3-diamine (ERH) and octaglycidyl ...N.N.N.N-tetraphenylamino-N.N.N.N-tetrapropoxy methylene dianiline (ERO) as potential corrosion inhibitors for carbon steel (CS) in 1 M HCl medium. The corrosion resistance was quantified by various techniques namely polarization curve (PC), electrochemical measurement (EIS), scanning electron microscopy coupled with energy dispersive spectroscopy (SEM/EDS), global quantum chemical descriptors (GQCDs) and molecular dynamics (MDs) simulation. EIS data suggest that the corrosion efficiency of ERO (94.1%) is higher than that of the ERH (89.7%) in HCl medium at room temperature. Further, PC results indicate that the corrosion efficiency of ERO (95.6%) is higher than that of the ERH (95.4%) in the presence of 10−3 M of studied inhibitors and also PC data suggest that the two epoxy resins investigated acted as a mixed type inhibitor. Langmuir adsorption isotherm is the most acceptable technique or method to describe the ERH and ERO epoxy resins adsorption on the CS area. SEM/EDS data display the two ERH and ERO epoxy resins can be stopped the acid attack though chemisorption on the CS surface. GQCDs calculations were applied by density functional theory (B3LYP and WB97XD) and Hartree-Fock (HF) methods using 6-31G(d,p) basis sets to study the inhibition efficiencies of the two epoxy resins inhibitors. GQCDs such as EHOMO, ELUMO, energy gaps, electronegativity, hardness, electrophilicity, fractions of electron transferred were calculated and discussed. Other energetic parameters such the free energy of adsorption, the metal-inhibitor energy gaps, the electron transfer back-donation energy and the initial molecule-metal interaction energy were also calculated and discussed. The molecular dynamics simulation approach was performed to investigate the adsorption behaviors of the investigated inhibitors on Fe(110) surface. The results obtained using the computational methods and the molecular dynamics simulations reveal that the ERO inhibitor has more inhibitory effect against corrosion of the Fe-metal than that of the ERH inhibitor. The obtained theoretical results were adapted with experimental inhibition efficiency results.
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•Two epoxy resins (ERH and ERO) were synthesized and investigated as potential anticorrosive protection.•Corrosion efficiency of ERO is higher than that of the ERH in HCl solution.•SEM/EDS analysis displayed the both ERH and ERO inhibitors could effectively block the acids attack by chemisorption.•Theoretically approaches are in good agreement with experimental data.
While large quantities of studies on microplastics in the marine environment have been widely carried out, few were available in the freshwater environment. The occurrence and characteristics, ...including composition, abundance, surface texture and interaction with heavy metals, of microplastics in the surface sediments from Beijiang River littoral zone were investigated. The concentrations of microplastics ranged from 178 ± 69 to 544 ± 107 items/kg sediment. SEM images illustrated that pits, fractures, flakes and adhering particles were the common patterns of degradation. Chemical weathering of microplastics was also observed and confirmed by μ-FTIR. EDS spectra displayed difference in the elemental types of metals on the different surface sites of individual microplastic, indicating that some metals carried by microplastics were not inherent but were derived from the environment. The content of metals (Ni, Cd, Pb, Cu, Zn and Ti) in microplastics after ultrasonic cleaning has been analyzed by ICP-MS. Based on data from the long-term sorption of metals by microplastics and a comparison of metal burden between microplastics, macroplastics and fresh plastic products, we suggested that the majority of heavy metals carried by microplastics were derived from inherent load.
•Occurrence and characteristics of microplastics from Beijiang river sediment were investigated.•A combination of μ-FTIR and SEM illustrated the chemical degradation of microplastics.•The content of metals (Ni, Cd, Pb, Cu, Zn and Ti) in microplastics is investigated by ICP-MS.•We suggested that the majority of heavy metals carried by microplastics were derived from inherent load.
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