Silicate Liquids Research Articles

Viscosity measurements of selected lunar regolith simulants

Abstract In the context of evaluating lunar construction options, this study focuses on characterizing the viscosities and glass transition properties of lunar regolith simulants to support the development of additive manufacturing processes using molten regolith. Employing the modular TUBS lunar regolith simulant system, we measured the viscosities of different simulants through high-temperature experiments conducted between 1,051 °C and 1,490 °C using Concentric Cylinder viscometry in air. Additionally, Differential Scanning Calorimetry (DSC) was utilized to evaluate the glass transition temperatures, which were in the range between 689 °C and 815 °C. The measured viscosity data were parameterized by the Vogel—Fulcher—Tammann (VFT) equation, adept at describing the viscosities and related properties of silicate liquids. The measured viscosities were compared with the predicted values of six viscosity models. It was shown that the model by Sehlke and Whittington predicts the viscosities of the tested lunar regolith simulants at superliquidus temperatures best, whereby no model adequately predicts viscosities at the glass transition temperature, indicating a need for further research in this area. We infer that 3D printing technologies based on molten lunar regolith, are viscosity-wise best constrained to highland regions. The reduced environment on the Moon influences the 3D printing process in a positive manner.

Impact of oxygen fugacity on the atmospheric structure and emission spectra of ultra-hot rocky exoplanets

Context. Atmospheres above lava-ocean planets (LOPs) hold clues related to the properties of their interiors, based on the expectation that the two reservoirs are in chemical equilibrium. Furthermore, such atmospheres are observable with current-generation space- and ground-based telescopes. While efforts have been made to understand how emission spectra are related to the composition of the lava ocean, the influence of oxygen fugacity has yet to be examined in a self-consistent way. Aims. Here, we investigate the sensitivity of atmospheric emission spectra of LOPs to key geochemical parameters, namely, temperature (T), composition (X), and oxygen fugacity (fO2). We also consider the precision involved in recovering these spectra from observations of hot, rocky exoplanets. Methods. We considered ‘mineral’ atmospheres produced in equilibrium with silicate liquids. We treated fO2 as an independent variable, together with T and X, to compute equilibrium partial pressures (p) of stable gas species at the liquid-gas interface. Above this boundary, the atmospheric speciation and the pressure–temperature structure are computed self-consistently to yield emission spectra. We explored a wide array of plausible compositions, oxygen fugacities (between 6 log10 units below and above the iron-wüstite buffer, IW), and irradiation temperatures (2000, 2500, 3000, and 3500 K) relevant to LOPs. Results. We find that SiO(g), Fe(g) and Mg(g) are the major species below ~IW, ceding to O2(g) and O(g) in more oxidised atmospheres. The transition between the two regimes demarcates a minimum in total pressure (P). Because p scales linearly with X, emission spectra are only modest functions of composition. By contrast, fO2 can vary over orders of magnitude, thereby causing commensurate changes in p. Atmospheres outgassed from reducing melts exhibit intense SiO emission, creating a temperature inversion in the upper atmosphere. Conversely, oxidised atmospheres have lower pSiO and lack thermal inversions, with their resulting emission spectra mimicking that of a black-body. Consequently, the intensity of SiO emission relative to the background, generated by MgO(g), can be used to quantify the fO2 of the atmosphere. Depending on the emission spectroscopy metric of the target, deriving the fO2 of known nearby LOPs is possible with a few secondary occultations observed by JWST.

Iron isotopes of Chang'e-5 soil and mineral components: Implications for post-eruption processes on lunar surface

Due to rapid magma cooling and extensive space weathering, significant disequilibrium crystallization and secondary modification widely occur in lunar mare basalt after its eruption on the lunar surface. In this study, we conducted bulk and in-situ Fe isotope analyses to investigate the post-eruption processes on Chang'e-5 (CE-5) samples. The CE-5 soil shows a minor elevation of δ56Fe value (∼0.05 ‰) relative to the CE-5 basalt clasts. Correlations between Ni and Cu contents with δ56Fe values suggest that the minor increase in the δ56Fe from the CE-5 basalt to soil primarily occurred during evaporation caused by meteorite impacts. Such isotopic variation between CE-5 basalt and soils is notably lower than what is observed for Apollo samples and reflects the low maturity of CE-5 soils. This is consistent with the low Is/FeO value constrained by magnetic approaches. Therefore, measuring the δ56Fe values of lunar soil is suitable to evaluate the degrees of maturity for lunar soils due to space weathering. In-situ analyses of δ56Fe reveal significant variations in different grains of olivine (δ56Fe: −0.57 to −0.17 ‰) and ilmenite (−0.06 to +0.42 ‰) and also in their interior (mainly for olivine). These δ56Fe variations in minerals can be ascribed to the disequilibrium crystallization of lava flow and fast cooling, which is consistent with conclusions based on petrologic observations such as its extensive differentiation and silicate liquid immiscibility. Therefore, the post-eruption processes on the lunar surface could lead to significant variations in isotopic compositions at different scales of basalts, which in turn record the history of late-stage magma evolution and space weathering on the lunar surface.

Structural evolution of liquid silicates under conditions in Super-Earth interiors

Molten silicates at depth are crucial for planetary evolution, yet their local structure and physical properties under extreme conditions remain elusive due to experimental challenges. In this study, we utilize in situ X-ray diffraction (XRD) at the Matter in Extreme Conditions (MEC) end-station of the Linear Coherent Linac Source (LCLS) at SLAC National Accelerator Laboratory to investigate liquid silicates. Using an ultrabright X-ray source and a high-power optical laser, we probed the local atomic arrangement of shock-compressed liquid (Mg,Fe)SiO3 with varying Fe content, at pressures from 81(9) to 385(40) GPa. We compared these findings to ab initio molecular dynamics simulations under similar conditions. Results indicate continuous densification of the O-O and Mg-Si networks beyond Earth’s interior pressure range, potentially altering melt properties at extreme conditions. This could have significant implications for early planetary evolution, leading to notable differences in differentiation processes between smaller rocky planets, such as Earth and Venus, and super-Earths, which are exoplanets with masses nearly three times that of Earth.

Molecular H2 in silicate melts

A series of hydrothermal diamond anvil cell experiments was conducted to constrain the equilibrium distribution of molecular H2 between H2O-saturated sodium aluminosilicate melts and H2O at elevated temperatures (600–800 °C) and pressures (317–1265 MPa). The distribution of H2 between the silicate liquid and the aqueous fluid was achieved through real-time monitoring of the H-H stretching vibration under in situ conditions using Raman vibrational spectroscopy. Results show that the solubility of H2 in silicate melts saturated with H2O decreases as the temperature increases, with control exerted by the mole fraction of H2O in the melt. The dissolution of H2 in the hydrous silicate melts appears to follow Henrian behavior, resembling that of an inert, neutral non-polar species. To express species solubility as a function of temperature (T in K) an empirical equation was developed:ln Km/f = 11.4 (±1.3) *1000 / T (K) − 18.7 (±1.1)where Km/f is the equilibrium constant for the reaction H2(g) = H2(melt). This equation was derived by integrating data from the current and prior experimental studies that include silicate melts with varying H2O saturation levels. It should be deemed applicable within the temperature range of 600–1450 °C and pressures ranging from 0.3 to 3 GPa. The implications are extended into developing an understanding of the H partitioning between H2-rich atmospheres blanketing magma oceans in the early history of planetary bodies. For example, transferring H from primordial atmospheric envelopes to the interior of rocky exoplanets may be less efficient than previously believed, which should be considered in models of volatile retention. Experimental data also suggest that minimal amounts of solar nebula H2 are likely to dissolve in the molten surface of primitive objects in the protoplanetary disk (∼10−5 to 10−9 mol faction H2 in melt), contradicting the highly reducing conditions observed in chondrule mineral compositions.

Two Bond-Exchange modes in sodium silicate liquids

Because of their network structure, the diffusion mechanism of network-forming elements, namely silicon and oxygen, remains unclear. Several diffusion mechanisms have been proposed based on molecular dynamics simulations; however, the bond-exchange motion has not been quantitatively analyzed. This study introduces the concept of bond-breaking/forming particles. By treating the bond-breaking/forming events as instant particles, the bond-exchange event can be interpreted as a pair-correlation function of these particles. Here, examples of sodium silicate liquids at various pressures are presented using the results of force-field molecular dynamics simulations. Analyses of the pair correlation of bond-breaking/forming particles revealed two distinct bond-exchange modes. Only the short mode contributed to the diffusion of the network-forming elements based on comparative analysis of the pressure dependence of the integrated peaks of the pair-correlation functions and the self-diffusion coefficients of silicon.

High proton conduction in zirconium silicate/lignin/ionic liquids based- membranes for high temperature PEM fuel cells

In this work, novel Nafion-free membranes composed of zirconium silicate, lignin, and ionic liquids supported on polytetrafluoroethylene have been synthesized for high-temperature applications. Incorporating lignin into zirconium silicate at room temperature has significantly increased the zirconium silicate’s proton conductivity by two orders of magnitude, from 10−4 to 10−2 S/cm. Furthermore, the addition of ionic liquids caused more enhancement in proton conductivity. Two ionic liquids were studied in this work, 1-Ethyl-3-methylimidazolium bis (trifluoromethyl sulfonyl) imide and 1-Hexyl-3-methylimidazolium tricyanomethanide). The incorporation of 1-Hexyl-3-methylimidazolium tricyanomethanide demonstrated the highest proton conduction at room temperature, reaching 0.106 S/cm with an ion exchange capacity of 1.67 meq/g. This most conductive membrane has also demonstrated a slight decrease in proton conductivity (10−3 S/cm) at 150°C showing a high anhydrous conductivity. The membranes’ conductivity was shown to be stable over time as well. The water uptake and swelling ratio results showed improved water retention and dimensional stability. Additional characterization techniques demonstrated positive effect of lignin and ionic liquids inclusion into zirconium silicate on morphology and mechanical properties. Overall, the reported membranes appear to be suitable for high-temperature proton exchange membrane fuel cell applications.

Learning a reactive potential for silica-water through uncertainty attribution

The reactivity of silicates in aqueous solution is relevant to various chemistries ranging from silicate minerals in geology, to the C-S-H phase in cement, nanoporous zeolite catalysts, or highly porous precipitated silica. While simulations of chemical reactions can provide insight at the molecular level, balancing accuracy and scale in reactive simulations in the condensed phase is a challenge. Here, we demonstrate how a machine-learning reactive interatomic potential trained on PaiNN architecture can accurately capture silicate-water reactivity. The model was trained on a dataset comprising 400,000 energies and forces of molecular clusters at the ωB97X-D3/def2-TZVP level. To ensure the robustness of the model, we introduce a general active learning strategy based on the attribution of the model uncertainty, that automatically isolates uncertain regions of bulk simulations to be calculated as small-sized clusters. The potential reproduces static and dynamic properties of liquid water and solid crystalline silicates, despite having been trained exclusively on cluster data. Furthermore, we utilize enhanced sampling simulations to recover the self-ionization reactivity of water accurately, and the acidity of silicate oligomers, and lastly study the silicate dimerization reaction in a water solution at neutral conditions and find that the reaction occurs through a flanking mechanism.

The kinetic effect induced by variable cooling rate on the crystal-chemistry of spinel in basaltic systems revealed by EPMA mapping

Abstract The crystal-chemical variations of spinels grown as a function of cooling rate (ΔT/Δt) were analyzed via X-ray electron-microprobe (EPMA) maps. Maps were collected serially by using a fixed distance. Spinels solidified from a tholeiitic MOR basaltic liquid (B100) cooled at cooling rates (ΔT/Δt) of 1, 7, 60, and 180 °C/h, between 1300 and 800 °C and at ambient P and fO2. As ΔT/Δt increases, the amount of spinel is invariably <5 area% and its size decreases. Compared to the previous data set collected by common single and selected EPMA analytical points (112 analyses), the kinetic effects induced by ΔT/Δt are here quantitatively captured by a large number of analyses (2052). The TiO2, Al2O3, MgO, and FeOtot show large compositional variations at low cooling rates (from 1 to 60 °C/h), and only the average TiO2 concentration shows a well-defined trend as a function of ΔT/Δt. However, calculated average cation amounts (apfu) unveil quantitative kinetic effects. When ΔT/Δt increases (from 1 to 180 °C/h), only Ti4+ shows a linear decreasing trend, whereas the other major Al3+, Fe3+, Fe2+, and Mg2+ cations alone are scattered. Conversely, the sums of trivalent (Al3++Fe3+) and divalent (Mg2++Fe2+) cations quantitatively capture the effect of the ΔT/Δt. These new outcomes could be the base of novel geospeedometers with significant implications in volcanology, geophysics, and material sciences in regard to silicate melt rheology on Earth. They should be extended to high-pressure, hydrated, and low oxygen fugacity conditions. Furthermore, the analytical approach used here to capture kinetic effects on spinel growth and compositions can be also applied to other crystalline phases grown from silicate liquids.

Decomposition of Sulfide Phases and Subsequent Matte Collection in the Black Top of a Platinum Group Metal Smelter

ABSTRACT This study explored, on a laboratory scale, how matte separates from the gangue in the black top of a PGM smelter. Two PGM concentrates, one with high sulfide content (17.3 mass%, Platreef concentrate) and the other with low sulfide content (1.3 mass%, UG-2 concentrate), were studied in the temperature range of 800°C to 1480°C, which is the temperature gradient across the black top. The results showed that effective matte separation occurs at temperatures when the matte is completely molten, and a substantial amount of liquid silicate phase has formed. The main matte separation mechanism is the coalescence of sulfide prills and their gravitational settling through the continuous path created by the liquid silicate phase. Complete matte separation occurs at lower temperatures in Platreef concentrate (1400°C in Platreef concentrate vs. 1480°C in UG-2 concentrate), due to the higher concentration of liquid silicate phase of lower viscosity, as well as the higher amount of sulfide minerals in this concentrate. PGMs already dissolve and collect in a nickel-iron-based alloy associated with the matte at temperatures as low as 900°C.

Partitioning of Iron Between (Mg,Fe)SiO3 Liquid and Bridgmanite

AbstractThe evolution of the magma ocean that occupied the early Earth is influenced by the buoyancy of crystals in silicate liquid. At lower mantle pressures, silicate crystals are denser than the iso‐chemical liquid, but heavy elements like iron can cause crystals to float if they partition into the liquid phase. Crystal flotation allows for a basal magma ocean, which might explain geochemical anomalies in mantle‐derived magmas, seismic anomalies in the lower mantle, and the source of the Earth's early magnetic field. To examine whether a basal magma ocean is gravitationally stable, we investigate the degree of iron partitioning between (Mg,Fe)SiO3 liquid and bridgmanite. By utilizing ab initio molecular dynamics simulations coupled with thermodynamic integration, we find that iron partitions into the liquid, and increasingly so with increasing pressure. Bridgmanite crystals are found to be buoyant at lower mantle conditions, stabilizing the basal magma ocean.

Formation of layered intrusion: A perspective from vanadium isotopes

Layered intrusions, characterized by their multiple layers, serve as remarkable geological archives of magma evolution in the Earth's crust. However, the magmatic evolution processes that lead to the formation of the chemically diverse layers in the intrusions are still difficult to trace. Here we present V isotope data of whole rocks and mineral separates (clinopyroxene and magnetite) from the Panzhihua layered intrusion in southwest China. The intrusion can be divided into four zones from the base upward: the marginal zone, lower zone, middle zone and upper zone. Both the marginal and upper zones mirror the chemical compositions of the parental magma, with the V isotopic composition being about −0.83‰ ± 0.19‰ (n = 4, 2 s). The lower zone is characterized by Fe-Ti oxide layers, where the whole rocks have a similar V isotopic composition as those of clinopyroxene and magnetite at each depth. The consistency in V isotopic compositions between whole rock and mineral separates reflects the control of silicate liquid immiscibility in forming the Fe-Ti oxide layers. Along the depth profile, whole rocks from the lower zone show limited variations in δ51V values ranging from −0.82‰ to −0.49‰. Such observation reveals the dynamic process of crystallization-mush-immiscibility-layering in charging the generation of repetitive oxide layers. After the formation of the lower zone, the middle zone has a large variation of δ51V values from −0.35‰ to 1.70‰, which can be attributed to fractional crystallization of Fe-Ti oxides. Consequently, the V isotopic signatures indicate that the Panzhihua intrusion was originated from a common basaltic magma and the layering in lower and middle zones resulted from continuous evolution of a single, massive magma unit.

Magnetite geochemistry as a proxy for metallogenic processes: A study on sulfide-mineralized mafic–ultramafic intrusions peripheral to the Kunene Complex in Angola and Namibia

AbstractTrace element concentrations in magnetite are dictated by the petrogenetic environment and by the physico-chemical conditions during magmatic, hydrothermal, or sedimentary processes. This makes magnetite chemistry a useful tool in the exploration of ore-forming processes. We describe magnetite compositions from Ni-Cu-(PGE)-sulfide mineralized rocks from seven mafic–ultramafic intrusions peripheral to the Mesoproterozoic AMCG (anorthosite-mangerite-charnockite-granite) suite of the Kunene Complex of Angola and Namibia to investigate metallogenic processes through the geochemical characterization of Fe-oxides, which were analyzed in-situ via Electron Probe Microanalysis (EPMA), and Laser Ablation-Inductively Coupled Plasma-Mass Spectrometry (LA-ICP-MS). We identified magmatic magnetite, segregated from both a silicate liquid and an immiscible sulfide liquid. Elements like Cr, Co and V suggest that the sulfide-related magnetite segregated from a relatively primitive Fe-rich monosulfide solid solution (MSS). Secondary Cr-rich magnetite appears in intrusions with abundant chromite or Cr-spinel. Two types of hydrothermal magnetite were identified, related to the pervasive replacement of sulfides and a late-stage, low-T fluid circulation event. Magnetite replacing sulfides is associated with serpentinized ultramafic rocks and is preferentially observed in the intrusions with the highest base and precious metal tenors. The high concentration of Ni, Co, Cu, Pd, As and Sb in these grains is corroborated by the identification of micron-size PGE mineral inclusions. We infer that serpentinization during hydrothermal fluid circulation was accompanied by desulphurization of sulfides with metal remobilization and reconcentration to generate magnetite carrying Pd microinclusions. We suggest that the highly serpentinized ultramafic rocks in the Kunene Complex region may become a possible target for economic Ni-Cu-(PGE) mineralization.

SiO2 Content and Chemical Properties of Potassium Silicate Extracted from Sugarcane Bagasse Ash using Sol Technique

Abstract Bagasse is a by-product of the extraction process in sugarcane production. In sugar factories, the bagasse is generally used as fuel in boilers for steam power plants and sugar production. The burning process produces abundant bagasse ash containing high levels of silica (SiO2). The end product of by-product utilization has high economic value and is widely used in various industries, such as absorbent materials, food, rubber products, paints, ceramics, glasses, cement/concrete, toothpaste, cosmetics, pharmaceuticals, and agriculture. The present study investigates the effect of concentration of alkaline solution/KOH (5, 7, and 9 %), extraction time (30, 60, and 90 min) and ratio of sugarcane bagasse ash (SBA) and alkaline solution (1:5, 1:7, and 1:9 w/v) on the characteristic of “intermediate” liquid potassium silicate product. The extraction process was conducted using sol technique. The result showed that silica extraction conducted using KOH 5% at 90 min with ratio of SBA and alkaline solution 1:9 produced liquid potassium silicate with high content of SiO2 (14.85 %) and K2O (19.73%).

Immiscibility in binary silicate liquids: Insight from ab initio molecular dynamics simulations

Immiscibility in binary silicate liquids: Insight from <i>ab initio</i> molecular dynamics simulations

Recycling carbonated hydrous sediments into the mantle source of carbonatite-associated rare-earth-element deposits

Decoding the petrogenesis of carbonatites is of great importance for our understanding of the Earth’s deep carbon cycling and formation of rare-earth-element (REE) deposits. Among global carbonatites, the Cenozoic Mianning-Dechang (MD) carbonatites in the western Yangtze Craton are unique because of their development in a post-collisional zone and host numerous giant-large REE deposits. However, most of previous studies have focused on the late magmatic to hydrothermal stages, while the nature of the mantle source and early-stage magmatic evolution remain largely unexplored. Here we present a combined petrographic, chemical and Sr-Nd-Pb isotopic study on the MD lamprophyres to address these issues. A genetic linkage is revealed between these lamprophyres and the MD carbonatites and syenites by their geochemical similarities and close spatial and temporal associations. Our data suggest a phlogopite-rich carbonated subcontinental lithospheric mantle (SCLM) source metasomatized by subducted carbonated hydrous sediment-derived melts/fluids. Significant fractional crystallization of olivine, clinopyroxene and biotite (±Ti-Fe oxides) from hydrous, K-rich and carbonated primary melts caused the carbonate–silicate liquid immiscibility in the highly evolved melts and thus formation of the MD carbonatites and syenites at shallow depths. Melting of subducted carbonated hydrous sediments not only provides carbonatitic liquids for the SCLM carbonation, but also supplies sufficient water and alkalis that are critical for accumulating and transporting REE in carbonatitic fluids. Post-collisional lithospheric thinning also played a critical role in the formation of carbonatites via triggering the melting of the carbonated SCLM. This study provides new insights into the deep processes during the formation of carbonatites and associated REE deposits in post-collisional zones.

Phase Evolution Behavior during the Reduction Process of Medium‐Silica Fluxed Pellets

To enhance the proportion of domestically manufactured Chinese pellets in the furnace, it is crucial to investigate the impact of calcium flux on the metallurgical characteristics of pellets and analyze the phase evolution behavior during the reduction process of medium‐silica fluxed pellets. This study examines the metallurgical properties of medium‐silica acid pellets and low‐basicity medium‐silica fluxed pellets produced in China. The results indicate that incorporating a small amount of calcium flux significantly enhances reducibility index (RI), reduces reduction swelling index, and lowers reductive degradation index (RDI+3.15 mm) for fluxed pellets. At a basicity level of 0.6, RI for medium‐silica fluxed pellets reaches 66.86%, while RDI−0.5 mm increases to 1.62% with increasing basicity levels. As pellet basicity increases, charge pressure drop (APmax) decreases, CaO content in silicate liquid phase within slag phase increases, and softening–melting zone widens, consequently leading to reduced solid‐phase particle content within pellets and increased fluidity within slag phase.

The role of hydrothermal processes and the formation of the J-M reef and associated rocks of olivine-bearing zone I of the Stillwater Complex, Montana

AbstractSeveral lines of evidence, including hydrous melt inclusions and unusually Cl-rich apatite, have been used to suggest that the reappearance of olivine and PGE-sulfide of the J-M Reef in the Stillwater Complex, Montana, is due to fluid infiltration and hydration melting. This study builds upon the hydration melting model using the programs MELTS and PELE with Stillwater bulk rock compositions for the original protolith. Cl-bearing phases are not modeled by MELTS and thus simple oxide mixtures of either a pure H2O or a H2O + Na2O “faux brine” are added to norite, gabbronorite, and melanorite protoliths at 1050 °C at 2 kbar pressure, conditions for which the nominally “dry” protolith is &gt; 95% solid. Incongruent hydration melting results in up to 37% olivine produced in the melanorite. The olivine Fo content is a function of the partial melt retained on cooling, and ranges between 76 and 86, overlapping the natural range of olivine compositions observed in the rocks. Modeling with the PELE program, which includes a silicate liquid Cl component, sulfur species, and a more complex C-O–H-S fluid, suggests that, for CO2-rich fluids, fluid metal concentrations on the order of 25 ppm Pt, 75 ppm Pd, 0.03 wt.% Cu, and 0.20 wt.% Ni at a fluid/rock mass ratio of ~ 0.25 are needed to account for the observed ore grades. Sulfide and ore metals are readily remobilized for more H2O-rich fluids, consistent with heterogeneous distribution of sulfide and regionally variable ore grades.

The thermal equation of state of the magma Ocean

As the protolunar disk formed by the giant impact with the incoming asteroid Theia started to cool, the Earth condensed in its center as a molten planet. The outer layer, rich in lithophile oxides, formed the magma ocean, whose dynamical behavior heavily influenced the entire evolution of the early Earth. Here, we employ first-principles molecular dynamics simulations to characterize the magma ocean in its initial stage. We compute the compressibility and the viscosity of the molten pyrolite, which best approximates the bulk silicate Earth composition. With an extensive set of calculations, we span the entire relevant pressure-temperature range. We provide a detailed analysis of the athermal and thermal equations of state in various formulations. We obtain a linear temperature dependence for the bulk modulus using the 4th order Birch-Murnaghan equation of state. We show that the liquid silicate accommodates compression by the collapse of the second Si-O coordination sphere, whose corresponding coordination number passes from about 24 at the surface of the magma ocean to about 40 at its deepest point. We found that pyrolite melts have a very low viscosity, about one order of magnitude lower than that of molten basalt. We also propose a revised position of the critical point of the bulk silicate Earth, which lies around 6000 K and 1.1–1.2 kbars.

Thermally-treated asbestos-cement wastes as supplementary precursor for geopolymeric binders: CO2 emission and properties

This article explores the impact of thermally treated asbestos-cement waste (ACWT) on metakaolin-based geopolymers, using liquid sodium silicate (LSS) and liquid potassium silicate (LKS) as alkali activators. Through statistical mixture design, various formulations were tested for rheological parameters, mineralogical composition, efflorescence mass, electrical conductivity, compressive strength, and CO2 emissions. Formulations with sodium silicate exhibited higher yield stress compared to those with potassium silicate, while flash setting occurred in LKS-activated mixtures with high ACWT content. Alkali activator content significantly affected mechanical strength and leachate electrical conductivity. CO2 emissions were higher for LKS-activated formulations but lower for those with more ACWT. Finally, by incorporating ACWT, it was possible to optimize the formulations, resulting in high compressive strength, reduced free ions, and reduced negative environmental impact.