Quantitative X-ray Diffraction Analysis Research Articles

Phase evolution and heavy metal solidification of cement desulphurized electrolytic manganese residue composite cementitious system under steam curing conditions based on thermodynamic simulation

The mechanical properties and microstructure of desulphurized electrolytic manganese (D-EMR) cement mortar under steam curing at 80 °C for 7 h and 7 days and standard curing for 3 days and 28 days were studied. The hydration products, microstructure and pore distribution were studied by Quantitative X-ray diffraction analysis (QXRD), scanning electron microscopy-energy dispersive X-ray spectroscopy (SEM-EDS), thermogravimetric-differential thermal analysis (TG-DTA) and backscattered electron (BSE). At the same time, the evolution of hydration products with age and the existence form of heavy metals under different curing conditions were simulated by GEMS thermodynamics. The results show that steam curing can promote the hydration reaction of cement and the secondary hydration of D-EMR. With the extension of steam curing time, the mechanical properties of the early stage are significantly improved. At a D-EMR content of 15 %, the compressive strength of D-EMR cement mortar after steam curing for 7 days is 1.15 times that of the control group under the same conditions, and the content of calcium hydroxide (CH) is 65.91 % of the control group. Steam curing can significantly improve the degree of C3S hydration of cement clinker and the secondary hydration of D-EMR, and increase the degree of polymerization of hydrated calcium silicate (C-S-H) gel. In addition, thermodynamic simulation showed that when the pH value was greater than 7.5, Mn2+ was mainly stable in the form of Mn(OH)2, MnOOH and Mn3O4, and there was no leaching risk. This will provide theoretical support for the use of D-EMR as a new type of supplementary cementitious material (SCM).

Effect of iron bearing minerals on iron ore processing

In the current study, elemental analysis and microscopic investigations were conducted to characterize the minerals present in an iron ore sample. The iron content was below 24%, with the dominant iron-bearing minerals being hematite and magnetite. Consequently, gravity and magnetic separation methods were employed to enhance the iron content. However, the processing results less than what was expecting due to incomplete sample characterization. The sample was further analyzed using quantitative X-ray diffraction analysis. This more comprehensive examination revealed additional iron-bearing minerals as goethite, ankerite, and limonite. The behavior of these minerals likely contributed to the unsuccessful separation process which was thoroughly explored in this article. Understanding the mineralogical composition of iron ores is paramount for optimizing processing operations and achieving successful outcomes.

Impact of desulphurized electrolytic manganese residue-assisted cementitious materials on silicate cement hydration and environmental safety assessment

The use of electrolytic manganese residue (EMR) as a mineral admixture is an efficient way of utilization, but its high content of gypsum phase limits its utilization. In this paper, EMR was desulphurized by means of high temperature reduction roasting to remove the hindrance when utilized as a mineral admixture. The effect of desulphurized EMR (D-EMR) on the formation of major hydration products such as C–S–H and calcium hydroxide (CH), as well as on the degree of hydration of cement clinker, was explored based on mechanical properties, hydration kinetics, thermogravimetry-differential scanning calorimetry (TG-DTG) and Quantitative X-ray diffraction analysis (QXRD). In particular, the mineral phase evolution, the change rule of pore solution and the leaching behavior of heavy metals were simulated in conjunction with thermodynamics. The results show that the D-EMR content of 15 %, comparable mechanical properties and microscopic morphology to the control group can be obtained, while C3S and C2S hydration can be promoted by a factor of 1.08 and 1.28, respectively, without the risk of heavy metal leaching. Based on the thermodynamic simulation of heavy metal solidification by cement clinker minerals, it can be seen that heavy metals in D-EMR composite slurry are solidified mainly by Mn(OH)2 precipitation and weak adsorption effect, and it is safe even at the level of 30 % replacement, provided that the pH value of the leaching solution is greater than 7.5. In addition, the desulphurization technology is feasible from the perspective of environmental protection, and saves 200,000 CNY in emission costs.

Hydration of a 2-component CSA-OPC-mix – timing of component blending & setting on demand

With the ongoing development of new technologies like 3D printing, the requirements for the performance of cementitious materials become more complex. Setting on demand, while the workability of the material is retained until placement, is an important aspect of this usage. A ternary CSA-OPC-C$ system was developed to achieve setting on demand in a 2-component setup, where two retarded cementitious components were mixed after specific times of storage. The kinetics of the individual systems and the blend were examined by heat flow calorimetry, quantitative X-ray diffraction and pore water analysis. The rheological development was monitored by a penetration test method. The results show that the performance of the blend is independent of the storage time of the individual components and can be tailored by changes in the retarder dosage in the individual components. The initial reaction in the blend is characterized by the simultaneous dissolution of ye'elimite and C3S, resulting in the formation of ettringite as the sole detectable hydrate phase. The fate of silicon remains unclear as with the methodology at hand no silicon incorporating hydrate phase can be identified.

Surface conductivity of clays

SUMMARY Clay minerals are extensively used in a wide range of applications. In particular, clay-bearing formations are considered as suitable radioactive waste repository. Electrical resistivity tomography is an appropriate tool to monitor the properties of clay-bearing locations. However, an inherent drawback of a conventional resistivity survey is its ambiguity in distinguishing between the effects of groundwater salinity, clay content and porosity. A discrimination can be achieved on the basis of the induced polarization method that provides a complex conductivity. The main purpose of this study is the investigation of the complex conductivity of clay samples with a special focus on the contribution of surface conductivity produced by an excess of ions in the electrical double-layer coating the solid particles. Six clay mixtures were selected that include an almost pure kaolinite sample, a sample consisting of a mixture of kaolinite, illite and smectite, a crushed saponite breccia, a Ca-bentonite sample and two illite clay samples. Besides the enriched kaolinite, the other samples are natural geomaterials that contain more than 40 weight per cent clay minerals. The mineralogical compositions of the samples were determined by quantitative X-ray diffraction analysis. The clay powder was mixed with a varying volume of sodium chloride solution to get plastic state clay samples with varying water content. The samples were investigated by the spectral induced polarization method in a frequency range between 1 mHz and 1 kHz. The resulting complex conductivity spectra indicate a decrease of the real part of the electrical conductivity with rising water content for the illite, bentonite and saponite breccia samples. The overall conductivity of these clay samples is dominated by their surface conductivity. In contrast, the electrical conductivity of kaolinite and kaolinite–illite mixture does not show any significant changes with the water content. For all samples, the imaginary part of electrical conductivity increases at low water content. The real part of the surface conductivity indicates a linear dependence on the volumetric clay content. The slope of this linear relationship can be used to distinguish the types of clay. The ratio between imaginary conductivity and surface conductivity, which decreases with increasing clay content, proves to be a suitable parameter that characterizes the connectivity of clay aggregates in the sample. The surface conductivity of the pure kaolinite sample has been determined in an additional multisalinity experiment. The resulting surface conductivity is in good agreement with the experiment of varying water content. The multisalinity experiment has shown that the resulting petrophysical parameters depend on the procedure of sample packing, which may lead to anisotropy. The effect of anisotropy is attributed to the alignment of the plate-like kaolinite particles in the course of the packing and consolidation procedure.

Combined use of mullite and basalt fiber to inhibit the strength decline of oil well cement stone under alternating conditions of temperature rise and fall

During the development process of heavy oil with steam huff and puff, the wellbore undergoes alternating conditions of temperature rise and fall, leading to a significant decline in the strength of the cement sheath. This work studied the inhibition effect and mechanism of the composite material composed of mullite and basalt fiber on the strength decline of cement stone (the hardened body of cement slurry) under simulated wellbore temperature alternating conditions from 80 °C to 260 °C. The pore structure distribution of cement stone was investigated by mercury intrusion porosimetry (MIP), the microstructure and phase composition of cement stone was characterized by scanning electron microscope (SEM) and energy dispersive spectrometer (EDS), together with quantitative X-ray diffraction (XRD) analysis. After 4 rounds of curing under alternating temperature conditions, the compressive strength of cement stone containing mullite and basalt fiber composite material was 28.6 MPa at 260 °C, which was only 9.2 % lower than that at 80 °C. However, the compressive strength of the blank cement stone without composite materials decreased to 22.5 MPa at 260 °C, which was 20 % lower than that at 80 °C. After 4 rounds of alternating temperature cured, the harmful pores of the cement stone without composite materials increase, and the xonotlite flakes and stacks together. The cement stone added with mullite has a finer pore structure after 4 rounds of alternating temperature cured because mullite reacts with portlandite to form C-A-S-H gel. The xonotlite remains fibrous, and a small amount of new phase hibschite is formed. Furthermore, basalt fiber can react with C-A-S-H gel at high temperatures, and the two phases are closely combined to further improve the high-temperature resistance of cement stone.

Quantitative Determination of the Compositional Inhomogeneity in NMC Cathode Materials by Williamson-Hall Analysis

Over the past decades, the co-precipitation synthesis technique has been used, particularly for making LiNixMnyCozO2 (NMC) cathode materials for lithium-ion batteries (LIBs), due to better control of particle morphology and higher compositional homogeneity in the final NMC product compared to other methods. However, the co-precipitation method introduces complexity and consumes large amounts of energy and water, which can increase cost. This has led researchers to investigate solid-state NMC synthesis techniques in order to improve sustainability and reduce LIB cost [1-3]. Obtaining homogeneous mixing of transition metals at the atomic scale by solid-state methods remains a challenge. Since compositional homogeneity has a vital effect on the electrochemical performance of the NMCs, it is essential to quantitatively estimate the degree of inhomogeneity in cathode materials for the development of new synthesis methods.In the present study, a quantitative X-ray diffraction (XRD) analysis technique using the Williamson-Hall (WH) method is used to determine the degree of inhomogeneity in NMC precursors and NMC cathode materials. In this regard, single-phase rock salt (RS) precursors with varying degrees of transition metal homogeneity were prepared by combining NiO, MnO and CoO by grinding for different times, followed by heating under an Ar flow. Then, NMC cathode materials were made by heating the RS-precursors with lithium carbonate in air. EDS elemental maps showed that transition metal inhomogeneity existed in the RS-precursors and final NMCs and that this inhomogeneity is primarily associated with the Mn distribution (Figure 1(a)). Furthermore, the compositional inhomogeneity became reduced with increasing precursor grinding time.Using a WH analysis method, composition variation in the NMC precursor and in the final NMC product could be quantitatively determined from conventional XRD powder patterns. Utilizing this analysis, it was found that inhomogeneity in the precursor is translated into the final NMC, so that a similar trend in the degree of inhomogeneity was observed for both synthesized precursors and their NMC products (Figure 1(b) and (c)). Additionally, NMCs with high compositional homogeneity showed much better electrochemical performance compared to the samples with higher degree of inhomogeneity. We believe the proposed method is highly useful in the development of new cathode precursors and in predicting the performance of the NMC cathode materials by quantitatively determining their degree of compositional inhomogeneity.

From Coupling Second-Order Stresses to Understanding and Predicting the Structural Response of a Dioctahedral Smectite

AbstractThe employment of clay minerals in the transport of water, nutrients, and contaminants depends on a few factors, including permeability, hydration behavior, ion-exchange efficiency, and more. With the application of external stress, it is still difficult to understand how clay particles swell and collapse, how water is retained, how hydration heterogeneities are formed within crystallites, and how interlamellar space is organized. The present work studied the link between geochemical, thermal, kinetic constraints (established at the laboratory scale), and intrinsic clay features by exchanging Na-rich montmorillonite (SWy2) with Ni2+, Mg2+, or Zn2+ cations. By comparing the experimental 00l reflections with the calculated reflections obtained from the structural models, quantitative X-ray diffraction (XRD) analysis has enabled the building of a theoretical profile describing the layer stacking mode (LSM) and allowed the description of interlayer space (IS) configuration along the c* axis. Regardless of the type of the exchangeable cations (EC), XRD modeling revealed that all samples exhibited interstratified hydration behavior within the crystallite size, which probably indicates partial or incomplete saturation of the IS. This theoretical result was defined by the appearance of two hydration states (1W and 2W), which were unrelated to the strain strength creating a higher degree of structural heterogeneity. Using the theoretical decomposition of the observed XRD patterns, the identification of all distinct layer populations and their stacking mode was achieved. The segregated LSM are, therefore, obviously superior as a function of stress strength.

Combined use of fly ash and silica to prevent the long-term strength retrogression of oil well cement set and cured at HPHT conditions

The long-term strength retrogression of silica-enriched oil well cement poses a significant threat to wellbore integrity in deep and ultra-deep wells, which is a major obstacle for deep petroleum and geothermal energy development. Previous attempts to address this problem has been unsatisfactory because they can only reduce the strength decline rate. This study presents a new solution to this problem by incorporating fly ash to the traditional silica-cement systems. The influences of fly ash and silica on the strength retrogression behavior of oil well cement systems directly set and cured under the condition of 200 °C and 50 MPa are investigated. Test results indicate that the slurries containing only silica or fly ash experience severe strength retrogression from 2 to 30 d curing, while the slurries containing both fly ash and silica experience strength enhancement from 2 to 90 d. The strength test results are corroborated by further evidences from permeability tests as well as microstructure analysis of set cement. Composition of set cement evaluated by quantitative X-ray diffraction analyses with partial or no known crystal structure (PONKCS) method and thermogravimetry analyses revealed that the conversion of amorphous C-(A)-S-H to crystalline phases is the primary cause of long-term strength retrogression. The addition of fly ash can reduce the initial amount of C-(A)-S-H in the set cement, and its combined use with silica can prevent the crystallization of C-(A)-S-H, which is believed to be the working mechanism of this new admixture in improving long-term strength stability of oil well cement systems.

Wet carbonation of C3A and pre-hydrated C3A

The carbonation of C3A and pre-hydrated C3A was studied at different initial pH values, temperatures, pre-hydration and carbonation times. Based on these investigations, the reaction kinetics of C3A under humid conditions were considered in more detail. The reaction products were characterized by quantitative X-ray diffraction (QXRD) and thermogravimetric analysis (TGA). C3A shows no significant reaction when carbonated directly in suspension, however, it has been observed that pre-hydrated C3A can be carbonated. A higher reaction degree was obtained with increasing hydration time. Consistent with reaching a stable pH, no further reaction of the hydrate phases was detected after ~20 min, indicating fast kinetics of the carbonation reaction. At temperatures ≤21 °C, the CaCO3 polymorph vaterite was found to be the main phase. At a pre-hydration temperature of 40 °C, C3AH6 appeared as a stable hydrate phase, but showed no reaction with CO2 under our experimental conditions.

Direct evidence of the shockley tetragonal L1’ phase in a bulk Fe-Pd alloy

Direct evidence is provided for the existence of the tetragonal L1’ phase, first predicted by Shockley in 1938, in bulk Fe - 62 at% Pd alloys aged at 525 ∘C. L1’ existence as the dominant phase is supported by quantitative x-ray diffraction analysis. This is combined with transmission electron microscopy of the polytwinned microstructure, examining the diffracted intensities in specific superlattice reflections where the complete extinction in L10 is relaxed in L1’. Ordering to L1’ appears to occur directly from the A1 parent phase at 525 ºC, while aging at 650 ºC only produces L10. The possibility of L1’ ordering may have consequences for the ferromagnetic properties of classic and important binary alloy systems where L10 is the assumed equilibrium phase.

Experimental investigation on the spalling failure of a railway turnout made from Hadfield steel

In a rail track structure, a turnout is used as a transition between straight and branching rails and therefore withstands complex dynamic rolling and impact loading. This paper reports a comprehensive failure investigation of a railway off-track turnout made from Hadfield austenitic cast steel. The worn turnout was examined using optical microscopy, scanning electron microscopy, micro-hardness, and quantitative X-ray diffraction analyses. A ball-on-disc sliding wear test was also applied to evaluate the impact of work-hardening on the wear property. The turnout exhibited surface embrittlement, severe cracking, delamination, and spalling characteristics. Severe plastic deformation of the worn turnout was observed with the formation of densely packed mechanical twins, which facilitated crack propagation. The rail top developed a gradient hardness (HV0.1) profile from the rail top of 8.9 GPa, the cracked subsurface of 5.9 GPa to the bulk steel of 2 GPa. The rail top was also found to have accumulated an extremely high residual compressive stress of 500–650 MPa. Strain induced martensite transformation was repeatedly evidenced by X-ray diffraction peak of the ferritic (110) plane although the highly strained and nanocrystallised ferrite was only detected on the severely deformed rail top. Comparative sliding wear tests showed highly deteriorated wear resistance of the strain-hardened rail top as compared to the bulk steel.

Micro-chemomechanical properties of red mud binder and its effect on concrete

Red mud is a hazardous waste generated from alumina production, and its safe disposal is a worldwide issue. Although some previous studies have reused red mud in cement-based composites, there is still a lack of research on the nano-scale chemomechanical properties of red mud binders. In this paper, atomic force microscopy with innovative QI™ mode, quantitative backscattered electron image, and quantitative x-ray diffraction analysis are conducted to uncover that Young's modulus of the C-(A)-S-H phase was decreased due to high content of red mud. The high porosity of corresponding binders allowed C-(A)-S-H gel to grow relatively unimpededly, resulting in lower packing density and lower modulus. The incorporation of red mud promoted the formation of aluminium-bearing phases and increased both Al/Ca, Si/Ca, and Fe/Ca ratio of formed C-(A)-S-H gel, especially for calcined red mud. At a moderate replacement ratio, the unreacted red mud enhanced the skeleton of the binder matrix with a filler effect. However, in concrete block samples, the size of red mud was insufficient to transfer the stress over limestone particles to mitigate the weak zones of blocks, and the reactivity of red mud always played a critical factor. Besides, recycling red mud in concrete blocks with a dry mix method overcomes the issue of workability reduction.

Geochemical modeling of CO2 sequestration in ultramafic mine wastes from Australia, Canada, and South Africa: Implications for carbon accounting and monitoring

Passive carbonation in ultramafic mine wastes results from the spontaneous reaction of gangue minerals with carbon dioxide (CO2) to form stable carbonate minerals that store CO2. Mines can benefit from unintentional CO2 sequestration to offset greenhouse gas (GHG) emissions. Quantitative X-ray diffraction (QXRD) analysis of numerous samples of mine wastes has typically been used to quantify passive carbonation rates. This analysis yields valuable information about carbon sinks; however, extensive mineralogical assessments are technically demanding and cost-prohibitive for routine carbon accounting. Alternatively, we explored using inverse geochemical modeling to estimate passive carbonation rates and monitor CO2 sequestration in active mines. Water chemistry data, tailings mineralogy, and operational information routinely collected by mines were used as inputs for models. The predictive capabilities of the models were tested for Mount Keith nickel mine (Australia), Diavik diamond mine (Canada) – for which rates were previously determined using QXRD. A new site — Venetia diamond mine (South Africa) — was used to illustrate the potential of geochemical modeling for carbon accounting and as a long-term monitoring tool for CO2 sequestration. Mount Keith models predicted passive carbonation rates (3900 g CO2/m2/yr) consistent with previous QXRD assessments (2400 g CO2/m2/yr; 172 samples) using only two water samples. CO2 removal rates for Diavik were found to be impacted by seasonality and to range between ∼375 and 510 g CO2/m2/yr, showing similarities with previous QXRD rates estimates (313–350 g CO2/m2/yr). With the long-term water chemistry records (2009–2018) available for Venetia mine, we predicted calcite as the main CO2 sink and that ∼14,875 t CO2 were stored in the kimberlite residues impoundments (3.5 km2) over 9 years at a rate of ∼470 g CO2/m2/yr. Moreover, long-term monitoring shows a decline in CO2 removal rates at Venetia, possibly due to changes in kimberlite reactivity and current mine waste disposal practices. Overall, inverse modeling proved that it can be a viable alternative or complement to QXRD techniques for carbon accounting in active mines, substantially reducing the need for mine waste sampling and permitting long-term monitoring. Moreover, the model shows how passive carbonation rates change dynamically with the mine production and waste management practices. Simultaneously, the model provides insights into potential mineral reactions operating in tailings and that regulate carbon sequestration mechanisms. For that reason, this accounting technique has an enormous potential to assist in decision-making for implementing enhanced CO2 sequestration strategies (e.g., enhanced rock weathering) and to support carbon sequestration monitoring, validation, and reporting in active mines.

Importance of amorphous content, surface energy, and preferred orientation on the accurate quantification of cement minerals in clinkers

In this study, a quantitative phase analysis of nine different clinkers was performed using X-ray diffraction (XRD). Density function theory simulation was also used to support the observed phenomenon of the micro-grinding-induced variation of the preferred orientation effect on certain mineral phases. Regardless of the micro-grinding, the amount of ferrite solid solution (C4AF) phase was overestimated in the quantitative XRD (QXRD) result when amorphous content was excluded during the QXRD analysis. Meanwhile, when the amorphous content was considered, a reasonable amount of C4AF phase was obtained in the clinker with the micro-grinding. Although the phase transition of the alite (C3S) (M3) phase to the nano-crystalline phase was observed during micro-grinding, the well-refined preferred orientation was confirmed at the C3S (M3) peaks. Thus, it was revealed that these crystallographic effects induced by micro-grinding can contribute to the accurate quantification of clinker materials.

Witness to strain: Subdomain boundary length and the apparent subdomain boundary density in large strained olivine grains

Abstract Electron backscatter diffraction (EBSD) investigation of strain mainly uses polycrystalline samples to study fabric development. We extend the use of EBSD for the analysis of large single mineral grains by measuring the apparent surficial subdomain boundary density per unit area, reported here as unit segment length (USL). We apply this USL technique to examine and quantify the plastic deformation recorded by naturally shocked olivine in the low to moderately shocked ureilite meteorite Northwest Africa 2221 and the highly shocked martian dunitic cumulate meteorite Northwest Africa 2737, by assessing the types of subdomain boundaries and the increase of subdomain misorientation with increasing shock metamorphism. We further compare USL results for the shocked olivine in the meteorites with those for the terrestrial deformation of Hawaiian olivine. USL of olivine increases with shock level, and USL from shocked olivine is significantly greater than that of terrestrially deformed olivine. USL is a promising tool for the quantification of plastic deformation in large single crystals from shock as well as terrestrial deformation. The results derived from USL measurements along with local EBSD maps are complementary with quantitative 2D X-ray diffraction analysis of crystal deformation and disruption, leading to a more comprehensive understanding of characteristic shock deformation recorded by large single crystals.

Ash characterisation formed under different oxy-fuel circulating fluidized bed conditions

The CO2-intensive oil shale power industry accounts for more than 70% of the Estonian energy sector, producing large amounts of ash that are mainly landfilled. Adopting oxy-fuel technology in the Estonian energy sector, in conjunction with CO2 storage, can be a critical tool for reducing carbon footprint. Nevertheless, several differences in ash formation under oxy-fuel conditions can be expected, which can lead to additional ash handling/utilization and related environmental concerns. In this context, the composition of oil shale ash was obtained from a series of combustion experiments in a 60 kWth circulating fluidized bed (CFB) test unit under both air and oxy-fuel combustion regimes studied by means of physical, chemical analysis as quantitative X-ray diffraction and element analysis for ashes from different separation ports. During the experimental work, special attention was given to understanding the impacts of the boiler temperature, recycled flue gas (RFG), and elevated oxygen concentration. As a result, the primary goal of this research is to characterise the ash produced by oxy-fuel combustion of oil shale in order to gain a better understanding of its chemical and mineral compositions, including Ca-Mg silicates and clay minerals, as well as to investigate the behaviour of the formation of free lime and anhydrite, which are the major compounds influencing potential ash utilisation routes. The results show that although the decomposition of calcium carbonates was limited during oxy-fuel combustion because of the high CO2 partial pressure, the contents of secondary silicates and anhydrite were slightly higher. The increased particle temperature and the higher SO2 partial pressure (with RFG) can explain this. The particle size distributions (PSDs) were wider under oxy combustion, and the specific surface area (SSA) in Filter ashes were much higher under elevated inlet O2% atmosphere. Oxy-fuel combustion had no significant impact on the concentration of elements in the ash. Overall, the mineralogy of the ashes formed in air and oxy-fuel combustion environments is similar, yet slight differences exist in the formation of clay minerals in the case of increased oxygen concentrations and with the application of RFG as a result of the increased residence time of the particles.

Structure and Mechanical Properties of Porous TiNi Alloys with Ag Nanoparticles

The work studies the influence of the silver dopant (<0.5 at.%) on the structure and mechanical properties of porous TiNi alloys obtained by self-propagating high-temperature synthesis. These alloys are of high scientific and practical interest in medicine. The presence of silver in the TiNi alloy will ensure improved cytocompatibility and antibacterial properties. The TiNi porous alloys with 0.2 and 0.5 at.% Ag nanoparticles have multiphase composition. Quantitative X-ray diffraction analysis of the obtained alloys showed that an increase in the silver content is accompanied by a quantitative decrease in the austenite phase TiNi(B2) and an increase in the martensite phase TiNi(B19’), as well as in secondary phases Ti2Ni, Ti4Ni2O. Evenly distributed silver nanoparticles up to 10 nm were found in the surface layer by transmission electron microscopy. The results of the scanning electron microscopy showed that inclusions containing silver are located mainly in the zones of Ti2Ni peritectic crystallization. The mechanical characteristics were studied by means of compression tests and it was found that with an increase in the silver dopant, the elastic modulus and elastic limit decrease, but the maximum deformation to fracture increases significantly. It was found that with an increase in the volume fraction of silver, the plastic properties of the alloy increase. No dependency of the tensile strength on the amount of silver was found.

Corrigendum: Mechanism of long-term strength retrogression of silica-enriched Portland cement assessed by quantitative X-ray diffraction analysis

Corrigendum on: Qin J, Pang X, Li H and Zhang Z (2022), Mechanism of long-term strength retrogression of silica-enriched Portland cement assessed by quantitative X-ray diffraction analysis. Front. Mater. 9:982192. doi: 10.3389/fmats.2022.982192 In the published article, there was an error in Figures 4, 8, 9, 10 and 11 as published. The mass absorption coefficient (MAC) is not corrected when calculating the phase compositions of the sample 180d-FS-1. The corrected Figure 4, 8, 9, 10 and 11 and its caption appear below.PAGE \ 2 \ 6 MERGEFORMAT 3

Production of concrete pipes by carbonation curing in an inflatable enclosure

Production of concrete pipes using ambient pressure (AP) carbonation curing in an inflatable enclosure was studied. The process was developed to replace traditional steam curing in order to reduce energy consumption, improve concrete performance and sequester carbon dioxide in pipes. The ambient pressure carbonation was compared with high pressure (HP) carbonation at 5 bar and normal hydration references. A composite structure of calcium carbonate with CSH was found in concrete after AP carbonation. Multiple techniques including quantitative X-ray diffraction analysis (QXRD), thermogravimetry analysis (TGA), Raman spectroscopic analysis, and scanning electron microscopy (SEM) were applied to characterize the strength development and microstructural enhancement of such cementitious matrix. The results demonstrated that AP carbonated pipes had comparable CO2 uptake, three-edge-bearing test (TEBT) strength, absorption, and resistance to internal-hydraulic pressure with HP carbonated ones. In addition, AP carbonation provided nucleating sites for CSH gel growth, thus contributing to the improved performance of concrete pipes while sequestrating CO2 and reducing the overall carbon footprint. Lastly, the carbon sequestration cost is lower in AP than in HP carbonation, which confirms the economic benefits of using AP in early-age carbonation curing of cement-based products.