Calcium Aluminate Research Articles

Development of new calibrating material for luminescence spectrometer from Eu3+ doped aluminum sodium calcium borate glass

The calibration standards are formulated to correct emissions spectra and systematically monitor sensitivity fluctuations in luminescence spectrometers. This study outlines the development of luminescence calibration standards utilizing glass doped with lanthanide ions, specifically focusing on Eu3+ ions chosen for their robust emission properties. Glasses composed of aluminum calcium sodium borate doped with Eu3+ ions were prepared using the melt-quenching technique, with varying compositions of 20Al2O3–20CaO–20Na2O–(40–x)B2O3–xEu2O3 (where x = 0.0, 0.5, 1.0, 3.0, 5.0, and 7.0 mol%). The intense red emission around 615 nm through the 5D0 to 7F2 transition of Eu3+ was detected. To ensure measurement reliability, this study conducted measurements under four different stimulations: ultraviolet–visible light (photoluminescence), X–ray (radioluminescence), proton (protonluminescence), and electron (cathodoluminescence), verifying consistent peak positions. The findings from this study validate the potential of aluminum sodium calcium borate glasses doped with Eu3+, particularly those containing 3.0 mol% of Eu2O3, as effective calibration materials for luminescence spectrometers. This highlights their capability for accurate and consistent calibration, emphasizing their importance in maintaining measurement precision in the luminescence spectrometer.

Effect of Different Calcium and Magnesium Treatments on the Evolution of Nonmetallic Inclusions in AH36 Ship Plate Steel

Comprehensive thermodynamic calculations and high‐temperature experiments are performed to systematically evaluate the effect of calcium and magnesium additions on the modification and control of inclusions in AH36 ship plate steel. The results show that Al2O3 or MgAl2O4 inclusions are formed under the casting temperature conditions. Calcium treatment modifies the inclusions into calcium aluminate, of which components partially fall into the liquidus region, and the aspect ratio and number density of inclusions became smaller, avoiding nozzle clogging, but the inclusions are easy to gather and grow up, which would affect the steel properties. Magnesium treatment modifies the inclusions into dispersed magnesium‐aluminum spinel with small size. However, the number density and aspect ratio of inclusions increase, as well as the melting points of inclusions are high, which would easily cause nozzle clogging. When calcium–magnesium synergistic treatment, with the increase of magnesium proportion, the inclusions types increased, and the liquidus area of inclusions became narrower until it disappeared. Synergistic treatment with more calcium and less magnesium (Ca2Mg1) is optimal since the inclusions were fine and diffuse, and the corresponding liquidus area of inclusions is wider than the calcium treatment.

Influence of Silica Modulus on the Activation of Amorphous Wollastonitic Hydraulic Binders with Different Alumina Content: Study of Hydration Reaction and Paste Performance.

This study investigates how different sodium silicate SiO2/Na2O MS ratios (0.75, 0.9, and 1.2) affect the hydration behavior of amorphous wollastonitic hydraulic (AWH) binders containing various amounts of Al2O3 content (4, 7, 10, and 12%wt). The effects of and interaction between the MS ratio of the activator and the Al2O3 content of the sample on the hydration reaction and paste performance were investigated. The reaction was followed by calorimetry, and the pastes' compressive strength performances were tested at different curing times (2, 7, and 28 days). The hydrated pastes were characterized by FTIR, thermogravimetry analysis, and X-ray diffraction. The calorimetric results show that a higher Al2O3 cContent and a higher MS ratio result in a longer induction period. In terms of paste performance, an increase of the Al2O3 coupled with an activation with a 1.2 MS ratio results in a lower compressive strength after 28 days of hydration; the results range from 76 to 52 MPa. A decrease of the MS ratio to 0.9 allowed the obtention of a narrower range of results, from 76 to 69 MPa. Even though a decrease of the MS ratio to 0.75 led to higher hydration kinetics and high compressive strength results at early ages, at 28 days of curing, a decrease in compressive strength was observed. This may be a consequence of the fast kinetic of the mixture, since the rapid growth of hydration products may inhibit the dissolution at later ages and increase the porosity of the paste. Moreover, the high Al intake in the hydration product, facilitated by the high sodium content of the activator, promotes the formation of a higher number of calcium aluminate silicate hydrate structures (C-A-S-H) to the detriment of calcium silicate hydrate structures (C-S-H), decreasing the compressive strength of the samples. The TGA results indicate that the samples hydrated with the MS075 solution resulted in a higher number of hydrated products at early ages, while the samples hydrated with the MS09 and MS1.2 solutions exhibit a steady increase with curing time. Hence, an equilibrium in the hydration kinetic promoted by Si saturation-undersaturation appears to be fundamental in this system, which is influenced by both the MS ratio and the Al(OH)4- content in solution. The results of this study suggest that for this type of binder, optimal performance can be achieved by decreasing the MS ratio to 0.9. This composition allows for a controlled kinetic and overall higher compressive strength results in pastes produced with this AWH precursor.

The cementitious properties of alkali-activated municipal solid waste incineration fly ash-phosphorus slag-secondary aluminum dross matrix composites and the mechanism of solidification of heavy metals

Based on the purpose of safe and resourceful disposal of hazardous waste, this paper proposes a new method for the combined treatment of municipal solid waste incineration fly ash (MSWIFA), phosphorus slag (PS), and secondary aluminum dross (SAD). A novel alkali-activated binder was synthesized by orthogonal experimental design, and the strength formation mechanism of the binder and the solidification and stabilization (S/S) mechanism of heavy metals were revealed. The results show that the maximum strength of the sample at 60 d is 22.4 MPa. The addition of SAD will affect the development of the strength of the solidified body and the types of hydration products of the gel. The hydration products of the solidified body are mainly calcium silicate hydrate (C-S-H), calcium aluminosilicate hydrate (C-A-S-H), and calcium alumina (AFt). The solidified body of alkali-activated cementitious material has a good S/S effect on heavy metals, and its solidification efficiency is Zn > Cd > Pb > Cu > Ni > As > Cr. The maximum solidification rates of Zn, Pb, and Cd were 99.97 %, 97.90 %, and 99.68 %, respectively. At the same time, the leaching concentration of various heavy metals meets the threshold requirements stipulated by relevant international norms and has good environmental safety.

Optimization of silty soil solidification agent ratio and mechanism of strength change based on design-expert

ABSTRACT In order to achieve the resource utilization of silty soil, based on the solidification mechanism of existing inorganic solidification agents, coal gangue and fly ash were selected as substrates, and quicklime and sodium silicate were used as activators to study a new type of muddy soil solidification agent. This project adopts mixture experimental design and unconfined compressive strength testing methods, and uses design expert software to analyze each component to obtain independent variable relationship strength prediction formulas. By using scanning electron microscope, Particles (Pores) and Cracks Analysis System, the changes in micro pore structure characteristics of Reinforced soil were obtained. The research results indicate that the relationship between the influence of various variable factors on strength gain is as follows: sodium silicate>calcium oxide>fly ash>coal gangue. As the age increases, the porosity shows a trend of first increasing and then decreasing. It has been revealed that the strength growth of Reinforced soil with curing agents is mainly due to the compaction and filling effects of hydrated calcium silicate, hydrated calcium aluminate, and a small amount of ettringite. This study is expected to provide reference for the solidification of high moisture content muddy soil.

Development of Negative-Temperature Cement Emulsified Asphalt Spraying Materials Based on Spraying Performance and Rheological Parameters.

To develop a cement emulsified asphalt composite (CEAC) that can be sprayed under a plateau negative temperature environment, the effects of the water-solid ratio, calcium aluminate cement substitution rate, emulsified asphalt content, sand-binder ratio, and polyvinyl alcohol (PVA) fiber content on the spraying performance and rheological parameters of CEAC were explored through the controlled variable method. Additionally, the correlation between the spraying performance and rheological parameters of CEAC was established, and the optimal proportion of CEAC was determined. Then, the difference in frost resistance and pore structure between the cement slurry (CS) without emulsified asphalt and CEAC at the optimum proportion was analyzed. The results showed that the optimum proportions for sprayed CEAC were 0.14 water-solid ratio, 0.5 sand-binder ratio, 25% substitution of calcium aluminate cement, 5% emulsified asphalt content, and 1.5% PVA fiber volume mixing. The yield stress and plastic viscosity of CEAC were positively correlated with the build-up thickness, whereas the rebound rate and the latter showed a negative correlation. The spraying performance may be described by the rheological parameters; the ranges of yield stress and plastic viscosity of 2.37-3.95 Pa·s and 77.42-108.58 Pa, respectively, produced the best spray ability. After undergoing an equivalent number of freeze-thaw cycles, CEAC exhibited lower mass and strength loss rates compared to CS, thereby demonstrating superior frost resistance. In addition, the pore structure analysis showed that the difference in capillary and macropore contents was the main reason for the variability in frost resistance between CS and CEAC.

Improvement of the thermionic emission properties of C12A7 electride

Calcium aluminate electride (named as C12A7) has become an active topic as a material for electron emission in the research field of electron sources, especially for electric propulsion, in recent years. Whereas the initially predicted, extremely low work function of 0.6 eV could not be confirmed experimentally at technically relevant surface current densities, the material remains an attractive emitter. Besides C12A7 emitting electrons at lower temperatures compared to LaB6, it appears to be resistant to poisoning and even iodine compatible as only known low work function material. On the other hand, the ceramic electride nature of the emitter introduces challenges related to the thermal, mechanical and electrical properties. Therefore, C12A7 has been investigated experimentally as a candidate material for thermionic emitters in space applications. The aim of this study was to enhance the thermionic emission by material modifications such as surface treatments, electrical contacting methods and doping of the C12A7. The performance improvement was quantified in a thermionic diode configuration, in which the emission current was determined as a function of temperature over multiple heating cycles to observe time dependent effects. The surface treatment such as grinding or polishing affects the emission properties of the C12A7 negatively. In contrary, the doping of the C12A7 lattice as well as the contacting of the back side (heater side) significantly improved the emission as well as the measured current density.

The effects of processing technique on formation temperature of calcium aluminate magnesium (CaO.2MgO.8Al2O3)

This study aims at the synthesis of a ternary phase crystal CaO.2MgO.8Al2O3 (CM2A8) in the Al-rich part of the ternary system CaO-Al2O3-MgO through two techniques: (1) sol–gel citrate and (2) solid-state reaction. Based on the measurement of particle size, density, phase analysis, nature of bounds, and microscopic observation, the effect of the processing technique on the crystal purity, crystallite size, and synthesis temperature of the as-prepared CM2A8 powder was investigated. Phases analysis (XRD patterns) showed in the sol–gel citrate combustion method almost a single-phase material (calcium aluminate magnesium phases) at relatively lower temperatures while in the solid-state method as-prepared CM2A8 powder with a small amount of spinel (MgAl2O4 = MA) and calcium hexaaluminate (CaAl12O19 = CA6) secondary phases. The generated heat through the combustion of the reaction of ammonium nitrate and citrate-based complexes decreases the synthesis temperature of nanocrystalline CM2A8, and the CM2A8 phase is formed at a temperature of 1400 °C. While growth mechanism in the solid-state reaction method adheres to the two-dimensional nucleation theory and a thick hexagonal flake known as CM2A8 is produced at a temperature of 1700 °C. In comparison with the crystals synthesized by the solid-state reaction method, the powder density of the nanocrystals synthesized by a sol–gel combustion method exhibits higher values (3.54 g.cm−3 and 3.65 g.cm−3, respectively). Peak intensities in the 400–1000 cm−1 range, according to FTIR measurements, correspond to metal–oxygen–metal (M–O–M) bonds (vibrations of Al–O stretching in Mg–O–Al and Ca–O–Al), and they grow as the temperature rises from 200 °C to 1400 °C, indicating that CM2A8 was the crystal that was formed. The morphological analysis (FESEM) revealed that most of the agglomerate particles synthesized by the sol–gel citrate combustion remained within the range of 50–83 nm, while the particles synthesized by the had particles as 1 μm. The specific surface area synthesized CM2A8 via the sol–gel method is in the range of 10–24 m2/g. The main advantages of the sol–gel citrate process are the high purity of the product, the narrow particle size distribution, and the achievement of uniform nanostructure at low temperatures.

Characterization and utilization capabilities of industrial wastes for green bricks production

BackgroundThe goal of this study is to develop a feasible and sustainable solution to manage the use of industrial wastes of ground granulated blast-furnace steel slag (GGBS) activated by cement kiln dust (CKD) and quicklime (QL). Using activated GGBS in the manufacture of stabilized green bricks is still uncommon in Egypt in such applications. Five clay-based mixtures, each with varying replacement ratios (5–10, wt.%) of CKD and QL, were studied. Laboratory tests were conducted on cylindrical specimens made from these mixtures, which were left to cure for periods of up to 60 days. The raw materials and lab-made specimens were analyzed using particle size analysis, differential thermal analysis, X-ray fluorescence, and X-ray diffraction techniques. The physical and mechanical properties of the cured specimens were also determined and evaluated according to standard specifications. Furthermore, the durability of the cured specimens was evaluated against collapsibility in water.ResuItsIt has been observed that adding QL and CKD to the stabilized green specimens of different mixes can enhance their engineering properties with curing age increasing. This is due to the pozzolanic reaction, which fills the pore structure with calcium silicate hydrates and calcium aluminate hydrates gel. The ratio of QL and CKD used significantly affected the engineering properties of the specimens. The study found that using 20% GGBS and 5% QL led to an increase in compressive strength (266 kg/cm2) at the density of (2.15 g/cm3), while also water absorption was reduced (8%) to give superior results. When GGBS and CKD were combined, a higher content of CKD (10 wt.%) gave better results compared to (5 wt.%) CKD. Furthermore, the physical and mechanical properties of the tested specimens (MD 1, MD II, MD III and MD IV) met the acceptable limits of dry compressive strength (30–70 kg/cm2), water absorption (8–15%), and density (1.7–2 gm/cm3), as specified by the Egyptian standard specifications for buildings used compressed earth blocks.ConclusionThe CKD and QL act as alkali activators for GGBS and can be utilized in masonry construction.

Effect of calcium treatment on inclusions in 38CrMoAl high aluminum steel

Abstract Three parts of the experiment were mainly carried out in this research: the effect of Ca on inclusions in 38CrMoAl high aluminum steel under atmospheric pressure, the effect of pressure on the solubility of Ca in pure iron under pressurized conditions, and the effect of Ca on inclusions in 38CrMoAl high aluminum steel under pressurized conditions. The results indicated that Ca can significantly transform the inclusions such as Al2O3 and MgO·Al2O3 with high melting points into calcium aluminate inclusions with low melting points. It was found that the pressure condition can significantly improve the solubility of Ca in pure iron and molten steel, which provided reliable data reference and guidance for popularizing Ca treatment of steel under pressure conditions in the future. Finally, the mechanism of inclusion transformation after Ca treatment was put forward. In this study, the theoretical calculation of thermodynamics was closely compared with the experimental data. It was proposed that to modify the inclusions in high aluminum steel into calcium aluminate inclusions with low melting points, it is necessary to accurately control Ca in the target region.

Enhanced prediction of cement raw meal oxides by near-infrared spectroscopy using machine learning combined with chemometric techniques.

The component analysis of raw meal is critical to the quality of cement. In recent years, near-infrared (NIR) has been emerged as an innovative and efficient analytical method to determine the oxide content of cement raw meal. This study aims to utilize NIR spectroscopy combined with machine learning and chemometrics to improve the prediction of oxide content in cement raw meal. The Savitzky-Golay convolution smoothing method is applied to eliminate noise interference for the analysis of calcium carbonate ( ), silicon dioxide ( ), aluminum oxide ( ), and ferric oxide ( ) in cement raw materials. Different wavelength selection techniques are used to perform a comprehensive analysis of the model, comparing the performance of several wavelength selection techniques. The back-propagation neural network regression model based on particle swarm optimization algorithm was also applied to optimize the extracted and screened feature wavelengths, and the model prediction performance was checked and evaluated using and RMSE. In conclusion, the results indicate that NIR spectroscopy in combination with ML and chemometrics has great potential to effectively improve the prediction performance of oxide content in raw materials and highlight the importance of modeling and wavelength selection techniques. By enabling more accurate and efficient determination of oxide content in raw materials, NIR spectroscopy coupled with meta-modeling has the potential to revolutionize quality assurance practices in cement manufacturing.

Study of the Performance of Emulsified Asphalt Shotcrete in High-Altitude Permafrost Regions

To improve the performance of shotcrete in high-altitude and low-temperature environments, emulsified asphalt shotcrete (EASC), which can be used in negative-temperature environments, was prepared by using low-freezing-point emulsified asphalt, calcium aluminate cement, and sodium pyrophosphate as modified materials. The effect of emulsified asphalt on the performance of shotcrete was investigated through concrete spraying and indoor tests. Then, the modification mechanism of emulsified asphalt with respect to EASC was analyzed by combining scanning electron microscopy images and the pore structure characteristics of EASC. The results showed that in a negative-temperature environment, the incorporation of emulsified asphalt delayed the formation of the peak of the cement hydration exotherm, slowed the rate of the cement hydration exotherm, reduced the thermal perturbation of permafrost by EASC, increased the cohesion of the concrete, improved the bond strength between EASC and permafrost, and reduced the rate of rebound. The mechanical strength of the studied EASC decreased upon increasing the amount of emulsified asphalt in the admixture, and its resistance to cracking gradually improved. A content of less than 5% emulsified asphalt could improve the internal pore structure of EASC, thus improving its durability. Increasing the content of emulsified asphalt affected the hydration process of the cement, and the volume content of the capillary pores and macropores increased, which reduced the durability of the EASC.

Impact of trivalent Yttrium on the structural and optical properties of CaAl2O4: New frontier in supercapacitor positive electrode

In this work, trivalent Yttrium doped calcium aluminate (CaAl2O4:x% Y3+) were synthesized for the first time. Through Photoluminescence (PL) spectroscopy and Commission Internationale de l’Eclairage (CIE), CaAl2O4:0.1 % Y3+ has demonstrated to be a potential high emitting phosphor material amongst other high concentration Y3+ doped samples, emitting a vibrant blue – pink hue where others are emitting a transiting hue from blue to green within a white vertex region. FTIR and UV–Vis have confirmed the prepared material and the presence of Y dopant. The SEM showed insignificant morphological change and the presence of pores, which were quantified using BJH and DFT methods to be micro – and meso–pores. Moreover, CaAl2O4 is also being reported as a positive electrode in supercapacitors for the first time. The analysis shows that it has superior performance within 1 M KOH electrolyte, with a specific capacity of 47.71 mA h g−1 at 1 A g−1 and a maximum power of 39.68 kW kg−1. Trasatti's method showed a surface (138 Fg-1) and diffusion (695 Fg-1) contribution ratio of 17:83 (%) of the total stored energy. It has a capacity retention and columbic efficiency of 100 % at the end of 10 000 cycles, which was achieved via utilization of all micropores reaction sites. The EIS showed a small solution resistance of 0.75 Ω, indicating high ionic conductivity and a phase angle of – 50 °. Thus, these results show that CaAl2O4 is a potential candidate for photoluminescence and energy storage application.

In situ concrete sewer performance: comparison of Portland cement, calcium sulfoaluminate cement, and calcium aluminate cement

In situ concrete sewer performance: comparison of Portland cement, calcium sulfoaluminate cement, and calcium aluminate cement

Pozzolanic activity of FCC catalyst waste slag (CWS) for cement and geopolymer production

Catalyst waste slag (CWS) is generated in large amounts when fabricating the catalyst required in the fluid cracking catalyst (FCC) process used for oil refining. Currently, CWS is landfilled. This paper characterizes the CWS and measures its pozzolanic activity. It determines whether the CWS can be used as partial Portland cement (PC) replacement for the first time in the literature. CWS is primarily composed of Al2O3 and CaO. It contains a negligible quantity of heavy metals that can be immobilised in a matrix. The raw CWS is totally amorphous and extremely reactive which results in flash set. Calcination is an effective method to control the reactivity of CWS. Reactivity increased when CWS was calcined between 300 and 600 °C and it peaked at 500 °C, but this caused flash set. Calcination at 800 °C lowers reactivity (as the highly disordered aluminium phases achieve a greater order) which allows for proper handling. Temperatures over 800 °C caused partial crystallization significantly lowering reactivity.The 800°C-calcined CWS reached high mechanical index (6.25), comparable to other pozzolans such as fly ash and red mud, and greater than alum sludge. CWS combines lime profusely and develops more abundant cementing hydrates than similar pozzolans such as calcined alum sludge. The pozzolanic reaction of the 800°C-calcined CWS provides abundant cementing minerals including AFt and AFm phases, calcium aluminium carbonate hydrates and calcium aluminium hydrates.The high reactivity of CWS and its prolific production of cementing phases in pozzolanic reactions indicate that it can be used as a supplementary cementitious material in PC and lime systems; and that it can be used as a precursor to produce low-carbon and geopolymer cements. CWS constitutes a reactive aluminium source which, in a PC system, participates in hydration reactions and can enhance the properties of the resultant materials.

СИНТЕЗ И СВОЙСТВА КАЛЬЦИЕВО-АЛЮМОФЕРРИТОВОГО ЦЕМЕНТА С ИСПОЛЬЗОВАНИЕМ ТЕХНОГЕННЫХ МАТЕРИАЛОВ

The article discusses the production of calcium-aluminoferrite clinker (cement) from a three-component mixture (by sin-tering), where 56.2-57.4 wt.% of the mixture consists of aluminum– and iron-containing man-made waste. It was found that the use of man-made waste as a component of the raw material mixture leads to a decrease in the amount of waste generat-ed by 4.9-5.4%, based on the production of 300,000 tons of calcium-alumoferrite cement per year. The results of qualitative and quantitative X–ray phase analysis of the clinkers obtained are presented, which indicate the formation of calcium aluminates (CA,C3A,C12A7), calcium aluminoferrite(Ca2(Al,Fe)2O5) and calcium silicate (α-, β-C2S) as the main clinker phases in all samples. Clinker phases of aluminate and calcium aluminoferrite are formed not in pure form, but with the introduction of impurity elements (Mg2+, Ti4+). Determination of the hydration activity of CAFC showed that the quantitative ratio of clinker phases CA:Ca2(Al,Fe)2O5 = 38.8:33.8 (CAFC I) and CA:Ca2(Al,Fe)2O5 = 27.6:23.9 (CAFC II) leads to an increase in the strength of cement stone in the initial periods of hardening by 48 and 32 MPa, and in later periods (28 days) - to an increase in strength by 28 and 8 MPa, respectively.

ВЛИЯНИЕ ПЛАСТИФИКАТОРА НА ПРОЦЕССЫ ПЕРЕКРИСТАЛЛИЗАЦИИ ПРИ ТВЕРДЕНИИ ДВЕНАДЦАТИКАЛЬЦИЕВОГО СЕМИАЛЮМИНАТА КАЛЬЦИЯ

The mechanism of structure formation during hydration of duodecalcium semialuminate in the presence of plasticizer is considered. The purpose of the study was to determine the influence of polycarboxylate-based plasticizer on the formation and morphology of the hydrate phases formed. The object of the study was the mineral duodecalcium semialuminate 12CaO-7Al2O3 of stable α-form, having cubic syngony and plasticizer on polycarboxylate basis. The structure of cement stone was studied using X-ray phase and electron microscopic analysis. The mechanism of structure formation during hydration of duodecalcium semialuminate 12CaO∙7Al2O3 in the presence of plasticizer is presented, which consists in the formation of finely dispersed poorly crystallized hexagonal crystals of calcium hydroaluminate. The presence of superplasticizer in the composition of hydrated calcium aluminate slows down the nucleation and growth of crystalline hydrates due to the film formed on the surface of the interface between liquid and solid phases, creating a structural and mechanical barrier, which leads to slower saturation of the liquid phase, but promotes the formation of a greater number of crystallization centers and simultaneous growth of small crystals of both hexagonal and cubic habitus.

Enhancing glass-forming ability and mechanical properties of barium-calcium-aluminate glasses through ZnO inclusion

Calcium aluminate (CA) glasses have garnered attention in the field of infrared photonics due to their low phonon energy. Nonetheless, the poor glass-forming ability (GFA) and strong crystallization tendency have hindered their utilization in various technological applications. Therefore, we demonstrate here that the substitution of ZnO for CaO enhances the GFA of 29Al2O3–(66X)CaO–5BaO–(X)ZnO (X = 0,7,10,15,20,25) glasses and improves their mechanical properties. The structural characterization using Raman, 27Al MAS-NMR spectroscopy and MD simulations reveal that, Zn2+ ions adopt tetrahedral coordination and contribute as network formers along with Al3+ ions. Notably, MD simulations indicate a preference of ZnO4 units for the CaO6 sites to convert non-bridging oxygens to bridging oxygens. The decrease in glass transition temperature and the increase in elastic modulus is noticed which correlated with the structural changes in the studied glasses. These findings provide valuable insights into the design and development of stable multicomponent CA glasses for photonic applications.

Recovery and reuse of phosphogypsum: Effect of ternary cementitious materials on the performance of phosphogypsum pavement base layers

In this paper, the performance of a new type of phosphogypsum (PG) pavement material is studied under the joint action of ternary cementitious materials (cement, mineral powder, and fly ash), CaCl2 and gravel. The experimental results of mechanical properties and durability of the material system, including compressive strength, splitting strength, dry and wet cycle, freeze-thaw cycle, etc., confirm that the material system can meet the design standards for road base material design standards for highways and primary highway sub-base. The test results of SEM, XRD, EDS, contact angle, and solubility of trace elements show that the material system does not cause secondary pollution to the environment, and its strength mainly comes from the C-S-H gel and calcium alumina (AFt) generated by the reaction of the reactive substances in the cementitious materials with PG in an alkaline environment. Finally, the optimal ratio of modified PG: mineral powder: cement: fly ash: gravel: water: CaCl2 was 50:8:3:0:39:11:0.22, and its 7d compressive strength, splitting strength, loss of strength in dry and wet cycles, loss of strength in freezing and thawing cycles, and water absorption were 6.41 MPa, 6.84 MPa, 3.01%, 16.22%, and 8.87%, respectively.

Mechanical, durability and microstructural characterization of cost-effective polyethylene fiber-reinforced geopolymer concrete

Portland cement is widely used in the construction industry. Its production contributes to carbon dioxide emissions, urging the need for sustainable alternatives. The present study aims to evaluate the strength, durability, microstructural properties, and cost-effectivity of geopolymer (GP) concrete containing polyethylene (PE) fibers, with fly ash (FA), ground-granulated blast furnace slag (GGBFS), and calcium magnesium carbonate (CaMg(CO3)2 known as dolomite) as binders. PE fiber used has an ultra-high molecular weight. Six different mixtures were produced with FA, GGBFS, dolomite, and/or PE fiber. The control mix used only FA as a binder without PE fiber. Fresh and mechanical properties, including slump value, compressive strength, and split tensile strength, were determined, and non-destructive tests, such as electrical resistivity and ultrasonic pulse velocity, were conducted. The durability of GP was evaluated through initial surface absorption and capillary suction absorption tests at different curing ages. Microstructural and mineralogical characteristics were analyzed using scanning electron microscopy (SEM), X-ray diffraction (XRD), and Fourier-transform infrared spectroscopy (FTIR). The results revealed that the addition of PE fibers and CaMg(CO3)2 reduced the workability of GP by 30.22% in comparison with that of PE fiber along with GGBFS. Compared to the reference mix at 28 days, incorporating 20% GGBFS resulted in the highest improvement of 76.89% and 104.86% in compressive and split tensile strength, respectively. GP sample with 20% GGBFS replacement of FA presented the highest reduction of 44.4–41.63% for initial and secondary rate of absorption. SEM analysis showed that the addition of GGBFS and CaMg(CO3)2 to fiber-reinforced FA-based geopolymer mixes developed a denser and more homogenous matrix with improved mechanical behavior due to the co-existence of C−S−H and aluminosilicate gel. PE fibers improve the toughness properties by helping to absorb energy and bridging cracks. The development of a stronger matrix was characterized by C−S−H, calcium aluminate oxide (carbonate) hydroxide (C4AHx) and quartz. A one-way ANOVA analysis and cost analysis demonstrate the cost-effectiveness of partially replacing FA with CaMg(CO3)2 and GGBFS in PE fiber-reinforced GP concrete.