Solid Calcium Research Articles

A novel all-solid-waste binder prepared by salt-alkali synergistic activation system constructed from phosphogypsum, soda residue and calcium carbide slag

Conventional alkali-activated slag materials apply strong industrial alkalis with high cost and potential corrosion risk. Alternatively, this study utilized industrial solid waste phosphogypsum, soda residue, and calcium carbide slag to construct a salt-alkali synergistic activated system. A new salt-alkali synergistic activation effect was formed by the SO42- introduced by PG together with the Cl- and OH- provided by SR and CS, which promoted the hydration reaction. AFt, Friedel's salt, C-(A)-S-H, and other hydration products were generated and congregated, and a new all-solid-waste binder was created with 3d/28d strengths of 17.9/43.9 MPa, meeting the P·O 42.5 cement strength standard requirements. By conducting compressive strength and drying shrinkage tests on mortar and paste specimens with varying ratios, and employing XRD, TG-DTG, FTIR, and SEM-EDS analyses, the mechanical attributes of the binder were systematically assessed, and its hydration process was elucidated.

Effect of different calcination temperatures on clinker and hydration properties of solid waste-based calcium sulfoaluminate cement

Calcium sulfoaluminate (CSA) cement is a promising alternative to Portland cement for reducing CO2 emissions in the cement industry. In this study, solid-waste-based calcium sulfoaluminate cement (SWCSA) was synthesized from steel slag, phosphogypsum, carbide slag, and bauxite. The effects of calcination temperature (1190–1310 °C) on the properties of the SWCSA clinker before and after hydration were studied, and the hydration process was simulated. The main mineral phases of the clinker were C4A3S̅, C2S, and C4AF. During calcination, Fe³⁺ could replace Al3+ in C4A3S̅ to generate C4A3S̅-c. As the calcination temperature increased, the extent of Fe3+ substitution increased, resulting in more C4A3S̅-c, and the amount of C4AF decreased. The element distribution diagram shows the distribution of minor elements in different phases (such as Ti, Mg and K). In terms of physical properties, the SWCSA setting time was prolonged upon increasing the calcination temperature. Furthermore, SWCSA with the best 28 d compressive strength (89.7 MPa) was obtained at a low calcination temperature (1190 °C). During hydration, the initial SWCSA hydration rate was fast, a large amount of ettringite was generated, and the cumulative hydration heat was low. The ratio of the amount of ye'elimite consumed to the initial amount was positively correlated with the compressive strength. In addition, a relationship was observed between AFt/AH3 and the compressive strength. Overall, SWCSA could be prepared at a lower calcination temperature than conventional CSA, offering a new avenue for recycling industrial solid waste via a less-energy-intensive process to obtain high-performance cementitious materials.

One‐Step Construction of 9,10‐Diarylphenanthrenes Using Solid Calcium Carbide as an Alternative of Gaseous Acetylene

AbstractA convenient method for the construction of 9,10‐diarylphenanthrenes through one‐pot multicomponent reactions of iodoarenes, o‐bromobenzoic acids, and calcium carbide is described. A series of target compounds are efficiently synthesized via Csp2−H activation and the simultaneous construction of five C−C bonds. The salient features of this method are the use of inexpensive and easy‐to‐handle solid alkyne source as an alternative of flammable and explosive gaseous acetylene. Meanwhile the use of commercially available substrates, wide functional tolerance, and simple workup procedure are also advantage of this protocol. In addition, the corresponding products can also be synthesized on gram scale.

Synthesis of hydraulic waste-derived belite-rich calcium sulfoaluminate clinker: Feedstock design, component calculation, and clinkering optimization

Solid waste-derived belite-rich calcium sulfoaluminate (BRC) clinker was successfully synthesized, which incorporated incineration bottom ash, recycled concrete powder, and phosphogypsum as the feedstock. The mineral components of BRC clinker were predicted by theoretical formula and thermodynamic modelling, which aligned well with experiments. The effect of clinkering temperature on viscosity, Gibbs free energy, phase equilibrium, and real mineralogy was thoroughly investigated by thermodynamic predictions and experimental characterizations. Optimal clinkering at 1200 °C for 3 h yielded BRC clinker predominantly consisting of 46.3 wt% belite, 22.5 wt% ye'elimite, 16.6 wt% fluorellestadite, and 7.1 wt% brownmillerite. Hydrates AFt and amorphous (AH3 and C–S–H gel) formed the network, playing a crucial role in developing a 60 d paste strength of 42.2 MPa. Utilizing lower temperatures and low-carbon embodied solid wastes for producing this BRC clinker promised to reduce CO2 emissions and preserve natural resources.

Highly Stereoselective Synthesis of 2-Acyl-3-sulfonamidobut-2-enoates Using Solid Calcium Carbide as a Substitute for Gaseous Acetylene.

Multifunctional group compounds, 2-acyl-3-sulfonamidobut-2-enoates, are efficiently constructed using solid calcium carbide as an alkyne source through the simultaneous formation of two bonds in one step. The salient features of this protocol are the use of an inexpensive, abundant, and easy-to-use alkyne source as a substitute for flammable and explosive gaseous acetylene, low-cost catalyst, mild conditions, wide substrate scope, high stereoselectivity, satisfactory yield, and simple manipulation. This method can also be extended to the gram scale.

One-step construction of indolo[2,1-a]isoquinolines using solid calcium carbide as an alternative to gaseous acetylene

An efficient method for the synthesis of indolo[2,1-a]isoquinolines using calcium carbide as an alkyne source, 2-(2-bromophenyl)-1H-indoles as starting materials, and copper as a catalyst is described. The target products are synthesized via Sonogashira cross-coupling/nucleophilic addition tandem reactions. The advantages of this protocol include the use of inexpensive and easy-to-handle solid alkyne source instead of flammable and explosive gaseous acetylene, cheap and readily available raw materials, wide range of substrates, and simple reaction procedure. The method can also be extended to gram scale. In addition, the desired product can also be obtained by one-pot three-component reaction of phenylhydrazine hydrochlorides, o-bromoacetophenones and calcium carbide.

A microcrack-based anisotropic damage model for concrete under mechanical loading and calcium leaching

In underground construction, concrete is always subjected to triaxial stress and calcium ion leaching, which results in anisotropic damage to concrete and reduce the durability of the structure. To capture the anisotropic damage properties of concrete subjected to mechanical-chemical coupling effects and predict the durability of underground concrete structure accurately, a microcrack-based anisotropic damage model is proposed. The mechanical damage, reflecting the density and direction of the microcracks caused by mechanical loading, is defined by a second-order tensor. The degree of chemical damage is defined by the amount of solid calcium phase lost in the concrete. Considering oriented microcrack and the influence of chemical damage on fracture toughness, the anisotropic mechanical damage evolution law of microcrack was established by linear fracture mechanics. A phenomenological chemical model governed by a diffusion law considering the variation of diffusion coefficient with stress induced microcracks is defined to describe the calcium dissolution process. The simulation results are in good agreement with the experimental results. Compared with the traditional elastoplastic damage model, the maximum creep error is only 0.114 ‰.

NiO–Ca9Co12O28 bifunctional phase change catalysts for biomass pyrolysis to hydrogen-rich syngas

In this study, the preparation of hydrogen-rich gases from improved pyrolysis-catalytic reforming system by industrial solid waste calcium carbide slag was investigated in a fixed-bed reaction system. The differences in biomass pyrolysis gas compositions and yields over the bifunctional phase change catalyst NiO–Ca9Co12O28 with different Ni doping ratios, pyrolysis temperatures, and calcium carbide slag doping ratios have been investigated, and a model for the mechanism of the redox reaction over the NiO–Ca9Co12O28 catalyst is proposed at the same time. The results of the study indicated that the maximum hydrogen production is 447.23 mL/gbiomass at 600 °C when the mass ratio of bamboo to calcium carbide slag is 5:9, which is 549.29% higher than that of pyrolysis of bamboo alone. The hydrogen volume concentration increased from 17.93% to 63.78%. This study provides a green and efficient route for high-value conversion of biomass and adsorption-enhanced reforming of solid waste for hydrogen production.

Highly Stable Solid Contact Calcium Ion-Selective Electrodes: Rapid Ion-Electron Transduction Triggered by Lipophilic Anions Participating in Redox Reactions of CunS Nanoflowers.

Solid contact (SC) calcium ion-selective electrodes (Ca2+-ISEs) have been widely applied in the analysis of water quality and body fluids by virtue of the unique advantages of easy operation and rapid response. However, the potential drift during the long-term stability test hinders their further practical applications. Designing novel redox SC layers with large capacitance and high hydrophobicity is a promising approach to stabilize the potential stability, meanwhile, exploring the transduction mechanism is also of great guiding significance for the precise design of SC layer materials. Herein, flower-like copper sulfide (CunS-50) composed of nanosheets is meticulously designed as the redox SC layer by modification with the surfactant (CTAB). The CunS-50-based Ca2+-ISE (CunS-50/Ca2+-ISE) demonstrates a near-Nernstian slope of 28.23 mV/dec for Ca2+ in a wide activity linear range of 10-7 to 10-1 M, with a low detection limit of 3.16 × 10-8 M. CunS-50/Ca2+-ISE possesses an extremely low potential drift of only 1.23 ± 0.13 μV/h in the long-term potential stability test. Notably, X-ray absorption fine-structure (XAFS) spectra and electrochemical experiments are adopted to elucidate the transduction mechanism that the lipophilic anion (TFPB-) participates in the redox reaction of CunS-50 at the solid-solid interface of ion-selective membrane (ISM) and redox inorganic SC layer (CunS-50), thereby promoting the generation of free electrons to accelerate ion-electron transduction. This work provides an in-depth comprehension of the transduction mechanism of the potentiometric response and an effective strategy for designing redox materials of ion-electron transduction triggered by lipophilic anions.

Construction of 3-Methyl-2-Substituted Benzo[b]furans and 3-Methyl-2-Substituted Benzo[b]thiophenes Using Solid Calcium Carbide as a Substitute for Gaseous Acetylene.

A concise method for the facile construction of 3-methyl-2-substituted benzo[b]furans and 3-methyl-2-substituted benzo[b]thiophenes using low-cost, abundant, and easy-to-use solid calcium carbide instead of flammable and explosive gaseous acetylene as an original alkyne source, o-bromophenyl ethers or o-bromophenyl thioethers as substrates through an intramolecular carbanion-yne cyclization in a 5-exo-dig manner, and subsequent double-bond isomerization is described. The simultaneous formation of two C-C bonds is realized in a one-step route. The wide substrate scope, high yield, and simple workup manipulations are also merits of this method. The synthetic strategy can also be suitable for the gram scale.

Bioengineering solutions for expansive soil stabilization using waste materials: An experimental evaluation

Municipal solid waste incineration ash is the outcome/product of bioengineering science. The incineration or burning of municipal solid waste (MSW) reduces the volume of this biomass by 90%, and the residual ash can be used in several applications. In this study, the potential of municipal solid waste incineration (MSWI) ash and calcium carbide residue (CCR) waste for stabilization of expansive soil has been experimentally evaluated. The abnormal shrink–swell characteristics of expansive soils pose several problems for civil engineering structures when these soils are used for construction in their original form. The study presents an experimental set-up to determine the best combination of additives to achieve the most favorable technical characteristics of expansive soil for civil engineering activities. The percentage of expansive soil has been kept fixed at 60% of the total weight of the mix for varying ratios of stabilizing agents. The optimization of the stabilizing materials is based on the highest strength parameters of the mix achieved for a particular ratio of additives and soil. The two stabilizing agents are waste materials, and their disposal through landfilling has become costly due to a scarcity of space and handling mechanisms. The values of strength parameters, unconfined compressive strength (UCS), and split tensile strength (STS) of a treated mix are found to be highest for a unique combination of 60% lime stabilized expansive soil and 20% MSWI ash and an equal quantity (20%) of CCR. The cumulative effect of adding the best mix of additives to soil and curing time depicts an improvement of 526.03% in UCS and 463.41% in STS of the mix compared to one day and 28 days of curing time. There is scope for further study, such as adding some fibers to the finalized mix to reinforce the soil mix.

Preferential formation of uniform spherical vaterite by harnessing vortex flows and integrated CO2 capture and mineralization

The use of calcium bearing resources to facilitate solvent regeneration and CO2 reuse via carbon mineralization offers a low energy pathway for the production of calcium carbonate. However, a crucial challenge is the lack of specificity in the formation of various calcium carbonate polymorphs during carbon mineralization. One of the less explored but highly effective approaches to tune the morphology and crystal structure of specific carbonate phases involves tuning vortex flows. This approach is an alternative to utilizing chemical reagents that need to be regenerated for tuning the morphologies and crystalline structures to direct the formation of specific carbonate phases. In this study, the efficacy of using homogeneous vortex flows in limiting the agglomeration of carbonate particles and directing the formation of metastable vaterite phases is discussed and contrasted with the influence of inhomogeneous conventional feed flow patterns on precipitated calcium carbonate (PCC). Herein, a Taylor-Couette Carbonate Conversion (TC3) reactor is used to direct the formation of spherical vaterite particles with uniform particle size distribution preferentially over calcite and other phases. The formed vortex patterns inside TC3 reactor provide homogeneous reaction spaces conducive to PCC formation, ensuring uniform mixing throughout the process. By increasing the rotational speed and the residence time, higher purity carbonates with more uniform sizes are obtained. Furthermore, preferential vaterite formation is also observed in leachates obtained from alkaline industrial residues such as construction and demolition waste and steel slag. Thus, the proposed approach is effective in harnessing multiple waste streams such as CO2 emissions and alkaline industrial residues to produce calcium carbonate phases such as vaterite with structural and morphological specificity.

<i>In vivo</i> application of prevascularized bone scaffolds: A literature review

BACKGROUND: Despite expanding research, the development of materials for replacing bone defects remains an urgent problem in orthopedics and traumatology. Thus, one of the most important tasks is to create conditions for proper trophicity of the bone implant.
 AIM: To analyze modern approaches to bone scaffold vascularization and evaluate their adequacy in in vivo models.
 MATERIALS AND METHODS: The article presents a literature review dedicated to the methods of vascularization of bone scaffolds. A literature search was performed in PubMed, ScienceDirect, eLibrary, and Google Scholar databases from 2013 to 2023 using keywords, and 271 sources were identified. After exclusion, 95 articles were analyzed, and the results of 38 original studies and one literature review were presented.
 RESULTS: Regardless of the initial vascularization method of scaffolds, bone implants show distinct osteoinductive features and promote advanced bone tissue regeneration. Constructs based on solid polymers and calcium–phosphate compositions also perform osteoconductive functions. Mesenchymal stem cells are used as the main cell type, as well as vessel-type cells, which in cooperation also have a positive effect on bone-defect remodeling. Bone morphogenetic proteins are used for directed differentiation in the osteogenic direction, and vascular endothelial growth factor is used for differentiation in the vascular pathway.
 CONCLUSIONS: At present, no method for vascularization of scaffolds has been approved universally. In addition, no evidence supported the comparative effectiveness of vascularization methods, whereas animal model studies have demonstrated a positive effect of prevascularized patterns on the recovery rate of minor and critical defects.

Solid CaCO3 Formation in Glioblastoma Multiforme and its Treatment with Ultra-Nanoparticulated NPt-Bionanocatalysts.

Glioblastoma multiforme (GBM), the most prevalent form of central nervous system (CNS) cancer, stands as a highly aggressive glioma deemed virtually incurable according to the World Health Organization (WHO) standards, with survival rates typically falling between 6 to 18 months. Despite concerted efforts, advancements in survival rates have been elusive. Recent cutting-edge research has unveiled bionanocatalysts with 1% Pt, demonstrating unparalleled selectivity in cleaving C-C, C-N, and C-O bonds within DNA in malignant cells. The application of these nanoparticles has yielded promising outcomes. The objective of this study is to employ bionanocatalysts for the treatment of Glioblastoma Multiforme (GBM) in a patient, followed by the evaluation of obtained tissues through electronic microscopy. Bionanocatalysts were synthesized using established protocols. These catalysts were then surgically implanted into the GBM tissue through stereotaxic procedures. Subsequently, tissue samples were extracted from the patient and meticulously examined using Scanning Electron Microscopy (SEM). Detailed examination of biopsies via SEM unveiled a complex network of small capillaries branching from a central vessel, accompanied by a significant presence of solid carbonate formations. Remarkably, the patient subjected to this innovative approach exhibited a three-year extension in survival, highlighting the potential efficacy of bionanocatalysts in combating GBM and its metastases. Bionanocatalysts demonstrate promise as a viable treatment option for severe cases of GBM. Additionally, the identification of solid calcium carbonate formations may serve as a diagnostic marker not only for GBM but also for other CNS pathologies.

Investigation of Liquid-Liquid Reaction Phenomena of Aluminum in Calcium Silicate Slag.

To achieve better process control of silicon (Si) alloy production using aluminum as a reductant of calcium silicate (CaO-SiO2) slag, it is necessary to understand the reaction phenomena concerning the behavior of formed phases at the metal-slag interface during conversion. The interfacial interaction behavior of non-agitated melt was investigated using the sessile drop method for varying time and temperature, followed by EPMA phase analysis at the vicinity of the metal-slag interface. The most remarkable features of the reaction were the accumulation of solid calcium aluminate product layers at the Al alloy-slag interface and spontaneous emulsion of Si-alloy droplets in the slag phase. The reduction is strictly limited at 1550 °C due to the slow transfer of calcium aluminates away from the metal-slag interface into the partially liquid bulk slag. Reduction was significantly improved at 1600-1650 °C despite an interfacial layer being present, where the conversion rate is most intense in the first minutes of the liquid-liquid contact. A high mass transfer rate across the interface was shown related to the apparent interfacial tension depression of the wetting droplet along with a significant perturbed interface and emulsion due to Kelvin-Helmholtz instability driven by built-up interfacial charge at the interface. The increased reaction rate observed from 1550 °C to 1600-1650 °C for the non-agitated melt was attributed to the advantageous physical properties of the slag phase, which can be further regulated by the stoichiometry of metal-slag interactions and the composition of the slag.

Numerical modelling on coupled behavior of calcium leaching and chloride transport in cement-based materials by considering ion desorption

Concrete structures serving in water environment with rich chloride ions are subjected to the coupling action of calcium leaching and chloride corrosion. In this paper, a transport model of calcium and chloride ions coupled with the calcium solid-liquid equilibrium equation is proposed to simulate the behavior of calcium leaching and chloride penetration in concrete. In the model, the effect of free chloride ions bound by solid calcium and the release of bound chloride ions caused by the dissolution of solid calcium is considered. Secondly, the model is numerically solved by using the finite difference method of Crank-Nicolson scheme. Then, the experimental data of porosity and calcium silicon ratio, chloride concentration are compared to the calculated results to validate the model. Finally, a numerical simulation is conducted to analyze the evolution of ion concentration, solid calcium content and porosity of cement paste slice exposed to deionized water and accelerated dissolution solution. The results show that, the concentration of calcium ion decreases with corrosion time, while that of chloride ion increases. There are concentration gradient distributions of calcium and chloride ions in the slice. The higher the concentration of accelerated dissolution solution, the larger the porosity of cement paste and the higher the concentration of chloride ions in the paste. It indicates that, the calcium leaching accelerates the chloride penetration into concrete. In addition, the dissolution process of solid calcium, i.e. calcium hydroxide first dissolves followed by C-S-H gel, are presented.

Development of Solid Waste-Based Composite Calcium Ferrite Flux and Its Application in Hot Metal Pre-Dephosphorization.

To enhance the slagging efficiency of the lime-based slag system during the pre-treatment stage of hot metal, a composite calcium ferrite flux based on aluminum industry solid waste was developed in this study. The melting characteristics of the flux and its application in the pre-treatment of hot metal were investigated. The results indicated that the main phases of the composite calcium ferrite were CaFe2O4, Ca2Fe2O5, and Ca2(Fe,Al)2O4. It exhibited high oxidation, high alkalinity, and a low melting point, thereby achieving excellent melting performance. Simulations of various dephosphorization fluxes in the pre-treatment of high-phosphorus hot metal, ordinary hot metal, and kilogram-scale dephosphorization experiment processes were conducted. Under the same experimental conditions, the composite calcium ferrite flux was able to achieve a dephosphorization rate of over 90% and a final phosphorus content of less than 0.02 wt% under high carbon content ([%C] = 3.2 wt%). In the application of hot metal pre-dephosphorization, this flux was able to achieve efficient melting and rapid slagging of lime at a lower temperature, and its slagging time was 50% faster than that of calcium ferrite flux. In addition, this flux enhanced the utilization efficiency of lime during the steelmaking process, effectively prevented the agglomeration of slag, and achieved efficient slag-metal separation. These characteristics were significantly better than the application effect of calcium ferrite flux. This flux has significant implications for the industrial application of deep dephosphorization in the pre-treatment stage of hot metal or the early stage of converter steelmaking.

Effect of Fiber Content on Mechanical Properties of Fiber-Reinforced CGF All-Solid-Waste Binder-Solidified Soil.

In order to realize the resource utilization of solid waste and improve the tensile strength and toughness of soil, CCR-GGBS-FA all-solid-waste binder (CGF) composed of general industrial solid waste calcium carbide residue (CCR), ground granulated blast furnace slag (GGBS) and fly ash (FA) was used instead of cement and combined with polypropylene fiber to strengthen the silty soil taken from Dongying City, China. An unconfined compressive strength test (UCS test) and a uniaxial tensile test (UT test) were carried out on 10 groups of samples with five different fiber contents to uncover the effect of fiber content on tensile and compressive properties, and the reinforcement mechanism was studied using a scanning electron microscopy (SEM) test. The test results show that the unconfined compressive strength, the uniaxial tensile strength, the deformation modulus, the tensile modulus, the fracture energy and the residual strength of fiber-reinforced CGF-solidified soil are significantly improved compared with nonfiber-solidified soil. The compressive strength and the tensile strength of polypropylene-fiber-reinforced CGF-solidified soil reach the maximum value when the fiber content is 0.25%, as the unconfined compressive strength and the tensile strength are 3985.7 kPa and 905.9 kPa, respectively, which are 116.60% and 186.16% higher than those of nonfiber-solidified soil, respectively. The macro-micro tests identify that the hydration products generated by CGF improve the compactness through gelling and filling in solidified soil, and the fiber enhances the resistance to deformation by bridging and forming a three-dimensional network structure. The addition of fiber effectively improves the toughness and stiffness of solidified soil and makes the failure mode of CGF-solidified soil transition from typical brittle failure to plastic failure. The research results can provide a theoretical basis for the application of fiber-reinforced CGF-solidified soil in practical engineering.

Construction of 2‐Methylindoles Using Solid Calcium Carbide as a Substitute for Gaseous Acetylene

AbstractAn efficient method for the construction of 2‐methyl‐1‐sulfonylindoles and 2,3‐dimethyl‐1‐sulfonylindoles using solid calcium carbide as an alkyne source and o‐sulfonamidobenzaldehyde hydrazones or o‐sulfonamidoacetophenone hydrazones as starting materials is described. This protocol has the salient feature of the use of an inexpensive, abundant and easy‐to‐handle solid alkyne source, effectively avoiding the use of flammable and explosive gaseous acetylene as an original alkyne source. Noble‐metal‐free conditions, wide substrate scope, high yield, and simple workup procedures are advantages of this method. The transformation can also be carried out on a gram scale.

Calcium bioaccessibility as affected by strontium. Temperature effect on citrate binding to strontium and calcium alone and in combination

Strontium as a bone health promoter was found to increase the bioaccessibility of essential calcium from solid calcium citrate tetrahydrate in aqueous suspensions. This is unexpected since calcium citrate binds calcium stronger than strontium with ΔH0ass,c = 5.07 kJ⋅mol−1, ΔS0ass,c = 78.0 J⋅mol−1⋅K−1 for 1:1 Ca-Citrate complex formation and ΔH0ass,c = 1.67 kJ⋅mol−1, ΔS0ass,c = 58.3 J⋅mol−1⋅K−1 for 1:1 Sr-Citrate complex formation as determined both electrochemically and by isothermal titration calorimetry. Calcium citrate tetrahydrate has reverse solubility around physiological temperature in contrast to strontium citrate pentahydrate. This difference results in opposite effect of strontium upon calcium ion liberation from calcium citrate suspensions at both low and high temperature compared to physiological temperature, for which strontium was found to stabilize solid calcium citrate tetrahydrate. This effect, confirmed by quantum mechanical calculation and by comparison of spontaneous aqueous supersaturation of calcium citrate and strontium citrate, is suggested to be involved in the positive effect of strontium on bone and teeth health. The conclusions provide a theoretical foundation for the research of molecular mechanisms among calcium, strontium, and citrate ions in relation to bone and teeth health.