Silicate Materials Research Articles

Performance of precursor characteristics in the realisation of geopolymer concrete: a review

Geopolymers are inorganic polymers whose formation is based on the reaction between precursors and reagents, which may be alkaline or acidic. The geopolymerisation process involves the reaction between alumina and silicate materials, known as precursors and reagents, which produces a three-dimensional polymeric network. This review provides a detailed classification of precursors used globally for geopolymer concrete (GPC) production, along with their various oxide contents. As the precursors used in the process of geopolymerisation involve a wide range of variations in their physio-chemical features, it is difficult to control the properties of GPC without going into a micro-level understanding of the precursor characteristics that affect the geopolymerisation mechanism. A comprehensive study was conducted on the influence of these physio-chemical precursor characteristics on the geopolymerisation process and the development of GPC properties. Finally, critical observations are drawn for the design of suitable precursors, along with possible methods to achieve the desired GPC property development.

Utilization of copper tailings in the preparation of low-calcium Portland cement clinker and carbonation-hardening mechanism

This study presents a strategy for decreasing cement-production-induced CO2 emissions and achieving comprehensive utilization of copper tailings (CTs). This is realized by preparing Portland cement clinkers dominated by calcium silicate minerals with a low Ca/Si ratio through the adjustment of the siliceous (CTs) to calcareous (limestone) material ratio. Differential scanning calorimeter (DSC), quantify X-ray diffraction (QXRD), scanning electron microscopy (SEM), 29Si nuclear magnetic resonance (NMR), and thermogravimetric (TG) analyses were employed to systematically characterize the thermodynamic behavior and mineral composition changes during the formation of the low-calcium Portland cement clinker, and to analyze their mechanical properties, carbonation products, and microstructural evolution under accelerated carbonation conditions (high pressures and CO2 concentration). CTs used as siliceous raw materials enabled the preparation of the low-calcium Portland cement clinkers with wollastonite (CS), belite (C2S), and rankinite (C3S2) as the main mineral phases at 1200 °C. The Ca/Si ratio and calcination temperature markedly influenced the clinker minerals. For a Ca/Si ratio of ≤1.0, CS was the main clinker mineral. When the Ca/Si ratio was between 1.0 and 1.4, the clinker comprised the C2S–C3S2 system, with the C3S2 content increasing as the calcination temperature increased. The prepared clinker achieved a compressive strength of over 100 MPa after carbonation when calcined at 1200°C with a Ca/Si ratio of 1.4. Carbonation of several low-calcium-content silicate minerals produced CaCO3, mainly as spherical vaterite crystals, while silica in the system formed silica gel, which formed a reticulated structure with CaCO3.

Experimental and Numerical Analysis of the Quasi-Static and Dynamic Behavior of Silicate Materials

Experimental and Numerical Analysis of the Quasi-Static and Dynamic Behavior of Silicate Materials

Potential of copper tailings as supplementary siliceous materials in the preparation of autoclaved aerated concrete

The storage of copper tailings (CT) not only consumes considerable land resources but also tends to cause a series of ecological and environmental issues. To achieve the circular economy and green industry development, CT is utilized as a supplementary siliceous material of autoclaved aerated concrete (AAC) in this study. The effects of substitution rate of CT for quartz sand are evaluated though the flow and gas-foaming properties of fresh slurry, and the physical and mechanical properties of AAC products. Meanwhile, the relationship between the macroscopic properties and hydration products is analyzed by multiple microscopic tests, including the Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), scanning electron microscopy (SEM) and thermogravimetric analysis (TGA). The experimental results shows that the bulk density, compressive strength and thermal conductivity of AAC incorporating CT show a trend of first decreasing and then increasing as the substitution rate of CT for quartz sand increases from 0 to 50 wt%, while the specific strength continues to decrease. When the substitution rate of CT for quartz sand is less than 40 wt%, the performances of AAC can meet the specifications of B05 A2.5 level according to Chinese national standards. These findings are closely related to the characteristics of air pore structure and the ordering, quantity and morphology of hydration products. With increasing the substitution rate of CT for quartz sand, the ordering of tobermorite gradually decreases, and its morphology transforms from plate-like to grass-like and then to needle-like, which can reduce the mechanical properties of AAC.

Hydrated silicate ionic liquids: Ionic liquids for silicate material synthesis

The development of Hydrated Silicate Ionic Liquids, which are hypo-hydrated room temperature melts of alkali silicates, has created new opportunities for synthesizing porous silicates. Their discovery also allows to reinterpret the role of an ionic liquid for zeolite synthesis and offer unique opportunities to study crystallization in situ. The reduced complexity of HSILs renders them excellent model systems yielding a large space of zeolite phases and framework compositions, and even allowing computer simulations. This work summarizes the impact of alkalinity, hydration, and cation type on silicate speciation and provides physicochemical data spanning relevant temperatures and compositions for zeolite formation. The data is meant as a reference point to further accommodate and verify (computational) models.

Preparation of C-S-H seeds from waste glass powder and its effect on early performance of cement paste

This study investigates the hydrothermal synthesis of calcium silicate hydrate (C-S-H) seeds using nano-size glass powder (NGP) derived from siliceous raw materials and CaO as the calcareous precursor. The influence of varying NGP concentrations on the particle size, microstructure, and phase composition of the C-S-H seeds was systematically analyzed. The synthesized C-S-H seeds were subsequently employed as additives to evaluate their effects on the early hydration process and compressive strength development of cement paste. The results indicate that increasing the NGP concentration from 0.2 mol/L to 0.8 mol/L leads to an exponential increase in the median particle size of the C-S-H seeds from 147 nm to 1328 nm and a corresponding morphological transformation from flocculent to granular structures. Additionally, the purity of the C-S-H sample decreased from 74.8% to 54.5% as the NGP concentration increased. The addition of C-S-H seeds can increase the 12h compressive strength of cement pastes by 15.5%–53.5%. This improvement is due to the accelerated early hydration kinetics induced by the C-S-H seeds, which act as nucleation sites, thereby increasing the nucleation and growth rates by 31.4% and 53.2%, respectively.

Semi-quantitative μLIBS mapping of germanium diffusion between metal and silicate during planetary core–mantle segregation

Understanding the distribution of elements between the cores and mantles of planetary bodies is essential for elucidating the geological and geochemical processes operating during their formation. Because the semi-metallic element Ge shows complex siderophile, chalcophile, and lithophile properties, it is particularly significant for investigating core–mantle segregation and ore deposit formation. Recent advancements in in situ microanalysis techniques, such as μLIBS, have enabled high-resolution elemental mapping of Ge and other trace elements.This study explores the application of μLIBS imaging to investigate the high-temperature/high-pressure distribution of Ge between metallic and silicate matrices analogous to planetary cores and mantles. By cross-calibrating the μLIBS intensities with electron microprobe profile analyses carried out on piston cylinder experimental samples, we produced semi-quantitative Ge maps from which we extracted Ge concentration profiles to assess Ge diffusion from the silicate to the metal. We determined, for the first time, the diffusion coefficient of Ge between metal and silicate to be D(Ge)metal = 4.03E−13 ± 3.6E−14 m2/s at 1 GPa and 1350 °C. Our results demonstrate the capability and efficiency of μLIBS for providing detailed, high-resolution (15 μm) trace element concentration data at few ppm levels, offering a time- and cost-effective alternative to conventional techniques.These findings bring insights on planetesimal differentiation and on chemical exchanges between metal and silicate phases in a magma ocean and between two different metal phases occurring at the bottom of the magma ocean during planetesimal formation.

Depth profiling of implanted D in silicates: Contribution of solar wind protons to water in the Moon and terrestrial planets

The solar wind protons implanted in silicate material and combined with oxygen are considered crucial for forming OH/H O on the Moon and other airless bodies. This process may also have contributed to hydrogen delivery to planetary interiors through the accretion of micrometre-sized dust and planetesimals during early stages of the Solar System. This paper experimentally investigates the depth distribution of solar wind protons in silicate materials and explores the mechanisms that influence this profile. We simulated solar wind irradiation by implanting 3 keV D ions in three typical silicates (olivine, pyroxene, and plagioclase) at a fluence of sim 1.4 × 10 ions/cm . Fourier transform infrared spectroscopy was used to analyse chemical bond changes, while transmission electron microscopy (TEM) characterised microstructural modifications. Nanoscale secondary ion mass spectrometry (NanoSIMS) was employed to measure the D/ O ratio and determine the depth distribution of implanted deuterium. The newly produced OD band (at 2400–2800 cm –1 ) in the infrared spectrum reveals the formation of O–D bonds in the irradiated silicates. The TEM and NanoSIMS results suggest that over 73<!PCT!> of the implanted D accumulated in fully amorphous rims with a depth of 70 nm, while 25<!PCT!> extended inwards to sim 190 nanometres, resulting in partial amorphisation. The distribution of these deuterium particles is governed by the collision processes of the implanted particles, which involve factors such as initial energy loss, cascade collisions, and channelling effects. Furthermore, up to 2<!PCT!> of the total implanted D penetrated the intact lattice via diffusion, reaching depths ranging from hundreds of nanometres to several micrometres. Our results suggest that implanted solar wind protons can be retained in silicate interiors, which may significantly affect the hydrogen isotopic composition in extraterrestrial samples and imply an important source of hydrogen during the formation of terrestrial planets.

Stability of Supramolecular β-Cyclodextrin-Pyrene Complexes in A Silicate Hydrogel Matrix

In order to use the β-cyclodextrin-pyrene complex as a fluorescent receptor center, its stability in the solid phase of a water-soluble silicate gel was investigated. For this purpose, a technique for obtaining a silicate matrix with a high content of supramolecular complexes was developed and the temperature stability of the resulting material was investigated. Optimal conditions for working with complexes in the silica gel matrix have been identified. Comparative studies of the fluorescence spectra of complexes in liquid and solid phases were carried out by the method of fluorescence spectroscopy. As a result of the work done, it was possible to determine the main patterns of behavior of the supramolecular complex in the silicate hydrogel matrix and to conclude about the influence of the matrix structure on its stability.

Lithic production and the use of siliceous raw material in the Neolithic of Istria, Croatia

This article contains the results of the lithic analysis of assemblages from the Neolithic sites of Kargadur and Vižula in southern Istria, Croatia. The assemblages have been analysed in terms of reduction strategies and typology, with a special focus on raw material analysis and petrographic analysis. During the Early Neolithic, and especially the Middle Neolithic, raw materials circulated the Istrian peninsula, as evidenced by the presence of obsidian and other non-local (exogenous) chert at several sites. Obsidian is certainly an exotic material in this region, and items found at Kargadur come from the Aeolian islands. With these results we have tried to gain a better understanding of lithic production of the period, the approach of the Neolithic people to raw materials and the scope of the distribution network of high-quality chert.

On the issue of functional use of pics during the Early Neolithic: a case study from the LBK site in Wólka Wojnowska (S Poland)

Picks are extremely rare artefacts associated with flint inventories of the Linear Band Pottery culture (hereinafter: LBK). Previously, only three such artefacts attributed to this culture have been found in the drainage basins of the Vistula and Oder Rivers. The contexts of discovery of picks dated to slightly later times indicated that they should be linked with mining activities of early agricultural societies. The presented collection from Wólka Wojnowska is one of the most numerous typological series of LBK picks found at a single site within the entire range of the LBK. The results of traceological and chemical SEM-EDX analyses of residues preserved on their surfaces indicate that these tools were used in processing hematite in order to produce ochre. The obtained data considerably broaden the scope of the functions of picks used during the Early Neolithic and allow us to question the interpretation that they were only employed in mining for siliceous materials.

Effects of chemical etching on surface structure and tribological behavior of silicate substrates

Abstract This study investigated the effect of chemical etching on the surface structure and tribological behavior of silicate substrates. Silicate surfaces were etched using a mixture of nitric acid (HNO3) and ammonium bifluoride (NH4HF2) for durations ranging from 1 to 60 min. The etched surfaces were characterized using optical microscopy, scanning electron microscopy, surface profilometry, water contact angle measurements, and UV–vis spectroscopy to evaluate the changes in surface morphology, roughness, wettability, and optical properties. Tribological performance was assessed using reciprocating ball-on-plate friction tests. The results showed that increasing the etching time resulted in the formation of microscale surface features, increased surface roughness, enhanced hydrophilicity, and reduced optical transmittance. The average friction coefficient decreased with an increase in the etching time up to 30 min, beyond which a slight increase was observed. The 1-minute etched specimen exhibited the best wear resistance with the narrowest wear track and the least material removal. The improved tribological performance was attributed to the formation of a stable transfer film, reduced real contact area, and entrapment of wear debris. This study highlights the potential of chemical etching as a technique to tailor the surface structure and tribological properties of silicate materials for various applications.

Synthesis of Effective Silicate Materials Based on Waste from the Energy Industry

Synthesis of Effective Silicate Materials Based on Waste from the Energy Industry

A New Strategy to Inhibit Scar Formation by Accelerating Normal Healing Using Silicate Bioactive Materials.

Inspired by the scar-free wound healing in infants, an anti-scar strategy is proposed by accelerating wound healing using silicate bioactive materials. Bioglass/alginate composite hydrogels are applied, which significantly inhibit scar formation in rabbit ear scar models. The underlining mechanisms include stimulation of Integrin Subunit Alpha 2 expression in dermal fibroblasts to accelerate wound healing, and induction of apoptosis of hypertrophic scar fibroblasts by directly stimulating the N-Acylsphingosine Amidohydrolase 2 expression in hypertrophic scar fibroblasts, and indirectly upregulating the secretion of Cathepsin K in dermal fibroblasts. Considering specific functions of the bioactive silicate materials, two scar treatment regimes are tested. For severe scars, a regenerative intervention is applied by surgical removal of the scar followed by the treatment with bioactive hydrogels to reduce the formation of scars by activating dermal fibroblasts. For mild scars, the bioactive dressing is applied on the formed scar and reduces scar by inducing scar fibroblasts apoptosis.

The Effect of Time Intervals on Bond Strength of Two Different Glass Silicate Materials Bonded to Resin Composite Using Self-etch Adhesives

The Effect of Time Intervals on Bond Strength of Two Different Glass Silicate Materials Bonded to Resin Composite Using Self-etch Adhesives

Characterization of hybrid silicate materials based on ceramic glazes and waste London underground dust

In “London Underground” stations, a high concentration of dust particles containing organic and inorganic matter of varying chemical composition. “London underground dust” is created from train wheels and brakes grinding against steel tracks and collected in filtration systems. The experiment will focus on using “London Underground Dust” to colour the ceramic facing tiles intended for re-use in newly built London Underground stations. The phase composition, particle size distribution surface area, morphology, and thermal behavior of collected dust were studied by XRD, XRF, SEM-EDS, BET, heating microscopy, STA-MS, UV–VIS spectroscopy. The substrate tiles for glazing experiments were prepared from local London clay. The mixtures of glazes and collected or milled dust were sprayed on the substrate tile's surface, dried and finally fired at 1060 °C. The influence of used materials weight ratio and dust milling time were shown as crucial parameters to obtain optimal final glaze colour.

Long-Term Performance of Mortars with Combined Incorporation of Ladle Furnace Slag and Metakaolin

Ladle furnace slag (LFS) is used as a supplementary cementitious material (SCM) due to its high calcium oxide (CaO) content. Its binding properties are enhanced in the presence of siliceous materials, such as metakaolin (MK), forming a ternary mixture that can directly replace ordinary Portland cement (OPC). However, despite this blend having already been evaluated in alkali-activated mixtures, knowledge about this mixture in situations of direct replacement of OPC by slag is still lacking. This study evaluates the synergistic effects of combining LFS and MK in cementitious mortars. Due to an insufficient hydration reaction observed in the short term, this study focuses on assessing the long-term performance of these mortars. Both the fresh and hardened states at 28 and 180 days are evaluated, and the resulting microstructural characteristics and constituent phases are also examined. After 180 days of curing, the mortar with MK exhibits superior binding activity compared to the results at 28 days. Although the nominal resistance does not show a clear advantage with the application of MK, a significant reduction in the porosity of the mortar is observed. Microstructural analysis indicates that the addition of MK increases the hydration compounds when mixed with LFS. Importantly, the sample containing MK and LFS showed a 42% reduction in cement consumption, highlighting the potential for resource efficiency. Thus, this study contributes to promoting a circular economy between the steelmaking and civil construction sectors.

Reaction mechanism of Ca(OH)2-based carbon storage suitable for the production of building materials

The development of CaCO3 oxyfuel combustion and calcium looping techniques offers opportunities for Ca(OH)2 production with near-zero CO2 emissions. This study investigated the viability of Ca(OH)2-based CO2 storage for use in the production of building materials. To resolve the deficient strength gain of Ca(OH)2 carbonation, siliceous materials, using fly ash as a model compound, were introduced into the raw mixture, and hydrothermal curing was applied to promote the pozzolanic reaction. Two microstructural features, i.e., inner and outer CaCO3 formations, were identified during Ca(OH)2 carbonation via backscattered electron imaging. Inner CaCO3 formation is characterized by Ca(OH)2–CaCO3 conversion within the edge of Ca(OH)2 particles. Outer CaCO3 formation is characterized by the dissolution of Ca(OH)2 and the precipitation of CaCO3 in capillary pores, which generates hollow microstructures. The hollow space can be further filled by Al-tobermorite during hydrothermal curing. The prepared materials are capable of storing up to 16 % CO2 by the mass of the raw mixture. Furthermore, the pore structure influenced by inner and outer CaCO3 formation demonstrates the feasibility of adjusting the material's mechanical and CO2 storing properties by controlling the carbonation and hydrothermal curing schemes.

Influence of cerium addition and redox state on silicate structure and viscosity

AbstractThe viscosities of Ce‐free and Ce‐bearing (∼1.3 mol%, ∼6.5 wt.% Ce2O3) soda lime silicate (window glass) melts were measured with respect to oxidation state. Experiments were performed isothermally using a concentric‐cylinder viscometer on melts equilibrated with successively reducing CO–CO2 gas mixtures within a gas tight vertical tube furnace at 1 atm. Viscosity measurement and sampling were performed at the end of each melt reduction step. Further, viscosities in the glass transition temperature range were estimated using the shift factor method applied to glass transition temperature values determined using differential scanning calorimetry (DSC) measurements on quenched glasses. The Ce speciation at each stepwise melt reduction was probed using Ce L3‐edge X‐ray absorption near‐edge structure (XANES) spectroscopy, while structural information upon Ce addition and reduction was provided by Raman spectroscopy. The viscosities of these materials remain constant at this level of Ce addition and do not vary significantly with redox state at high temperature. Conversely, viscosity values in the glass transition temperature range increase upon both Ce addition and reduction. Our analysis, based on the glass composition analyses obtained via electron probe microanalyzer (EPMA), viscosity calculations, and observations of silicate structural changes, leads to the conclusion that the observed viscosity increase around the glass transition temperature is explained by the high ionic field strength of Ce ions as well as the polymerization behavior of the silicate matrix occurring during reduction of Ce. Because of its low concentration, resulting from its low solubility, Ce redox changes exert only minimal effects on the viscosity of this melt.

Precision Remediation of Mining Soils through On-Site Investigation and Large-Scale Synthesized Ferrosilicate

To seek a restoration plan for the safe use of agricultural land around mining areas, this study focuses on the regions around a mining plant in Huidong County, western Sichuan Province, affected by lead–zinc mining, and the precise remediation of heavy metal pollution through large-scale synthesis of iron silicate. In this study, we investigated heavy metal pollution in the vicinity of the mining area and proposed a treatment strategy using large-scale synthesis of iron silicate to mitigate this pollution. According to field investigation and sampling analysis, the collected soil samples contained excessive Cd, Pb, and Zn. Cd is a heavy metal related to lead–zinc mining. The planting of crops such as loquats and garlic with a high accumulation coefficient for Cd was found inappropriate for the research area. Instead, it was recommended to plant economically important crops like mangoes and peaches which had lower heavy metal accumulation. On the basis of field investigation, the study area was seriously polluted by heavy metals, among which Cd was 4.0 times higher than the standard of agricultural land. In order to accurately passivate excessive Cd, Zn, and Pb, iron silicate material was put into mass production. In situ passivation experiments showed that when the soil water content was between 25% and 20%, adding 4% silicate material could rapidly reduce the content of effective heavy metals in the soil and the heavy metal content of garlic and other cash crops in the research area by about 8%. After conducting a field investigation, it has been determined that the large-scale preparation of iron silicate can accurately repair soil contaminated by heavy metals in the vicinity of mining areas. In conclusion, iron silicate is capable of effectively reducing the pollution of heavy metals on agricultural land and facilitating the safe utilization of such land.